Tram Diamond is a classic valve powered transceiver
that has excellent specifications and reflects this in
its rich full audio receive tones and superlative
transmitted studio sounding output audio.
Tram Diamond is a classic valve powered transceiver
that has excellent specifications and reflects this in
its rich full audio receive tones and superlative
transmitted studio sounding output audio.
As much as I would like to talk knowledgeably about
the classic Valve powered CB Radio, the Tram Diamond
D201, I really could not do the radio justice, hence
the story below from Dave Hall N3CVJ.
I had always wanted one since they were released in
the USA in the early days of CB operation on the
government allocated 23 Channels in the 11 Metre Band
at the bottom of 27MHz. Best I could do back then, was
the first Courier Gladiator 40Ch PLL in Aust.
Many radios followed, but my favorite was always the
CPI - Communications Power Inc. CP2000 40CH Base &
Console Freq counter.
When about mid 2007 I was alerted to another radio on
Ebay by a friend who knew I wanted a better UHF 477MHz
CB, but spotted the TRAM D201 going for about $100
In the end after bidding on it, and
getting it for about $170 USD, I had it delivered to
my home in Melbourne Australia for the all up cost of
nearly $500 AUD!! - More than I paid for ANY CPI!!
BUT, it was worth it to me, as it was
in fantastic condition and come complete with original
microphone and complete original service manual with
schematics! Although it was 110VAC input it did not
concern me because I always have had 110 to 240 VAC
transformers around being a mobile Micrographics tech
for a US company - Bell & Howell. (Origin of my
callsign - The BellHopper )
After firing it up and realising it
was only 23 Channels Xtal Locked, I was a bit dismayed
as I had thought it was 40 Ch and had an 02A PLL for
frequency selection. I had confused it with a later
Although the disappointment faded when
I realised it could RX tune to 27,500 on the Manual
Tuning VFO and could be modded to TX as well. Looks
like the RATHOLE and CH#35 are well covered!
After it settled down and got a bit
warmer, I found it was receiving LSB on the USB
setting but it was listening like my CPI CP2000 but
maybe even BETTER! The sound of the audio which can be
adjusted for tone on RX as well as TX was warm and
clear and the QRN seemed much less than usual.
Maybe just conditions but we will see after I have it
tuned up and the RX Mode fixed along with any valves
that may need to be replaced to bring it back to its
The following information was copied
from Dave Halls site below.
In my defense I sincerely apologize, but
put the case forward of so many great stories in a similar
vein that have been lost to the vagaries of time and
forgotten website renewals.
It would be criminal if this valuable
information on the rescue of a few of these great classic
TRAM D201 CB's were lost to the ether and unavailable for
the education of the greater Citizens Band community.
Please follow Dave's Hyperlinked text in
the stories to more information as it is well worthwhile.
And Dave, if your listening and really want
me to remove this, please just ask and I will save it for
my consumption only!
This is the Tram
D-201/201A, A supreme top of the line radio from the
Tram/Diamond corporation. Where the
Browning Golden Eagle was considered the "Cadillac" of
CB radios, the Tram D201 was the "Lincoln Town Car". This
radio was truly at the top of the CB line, and had a price
tag to match. At a retail price of over $750 in 1970's
dollars, this was not the rig for most people, especially
those of us living on paper route money. The D201 was a 23
channel radio, while the D201A was the 40 channel
version. Other than number of channels, they were
virtually identical in appearance and features. The
original D201 was first made in the early 70's and used
primarily tubes, although some oscillator circuits were
solid state. The D201 came loaded with many features.
Besides the usual standard features of Volume, Squelch,
Channel selection, Clarifier, Mode selector, and R.F Gain
& Mic Gain controls, this radio also included a built-in
SWR function with calibration control, and an adjustable
noise limiter. An interesting and innovative feature was
the inclusion of not only a receiver tone control, but
also a separate transmit tone control which allowed the
careful tailoring of the audio characteristics of the
radio to match practically any mike. Also included was a
continuously variable manual receiver tuner. The range of
the manual tuner extended beyond the normal legal channels
and allowed for some interesting operator options
including split frequency operation. Rounding out the
list of features includes a large easy to read S/RF/SWR
meter, a modulation indicator light and a receiver spot.
Some versions of the D201 also came with a VOX which
allowed "hands free" talking. The radio originally shipped
with an un-amplified Astatic
which mated well with the radio.
radio really shined. Transmit audio was, in a word,
awesome. It had that warm "tube sound" that just couldn't
be duplicated or beat by common transistorized radios. The
receiver performance was also exceptional as it had both
great sensitivity and adjacent channel rejection as well.
The D201A was also probably the only 40 channel radio,
that I'm aware of, that still used straight crystal
synthesis, over a PLL circuit. A common modification
involved converting the manual tuner to also operate the
transmitter, allowing for synchronized "sliding" similar
to that found with an external VFO. There were many
other modifications that could be applied as well.
Besides the aforementioned VFO mod, there were also mods
for power, and the clarifier.
Because of the high price
that this radio commanded, there naturally were very few
in my local area.
Storm Queen was rumored to have had one shortly before
her departure from the radio scene. Dennis (not Dennis the
Menace) also had one.
A mint condition D201 still
commands a premium price on the collector's circuit.
Someday, I'm hopeful that I'll be in the right place at
the right time and can pick a decent one up to add to my
collection. That "Someday" occurred recently with the
acquisition of two "needy" D201's from E-Bay. Read about
my restoration project
Back in the 1970's, when
my friends and I first started out in CB radio, we didn't
have a lot of money to spend on equipment, so most of us
worked our way slowly and (sometimes) painfully up from
100 mW Walkie-Talkies, to 1 watt (or more) Walkie-Talkies,
to very modest 23 channel AM mobile rigs, and then
eventually to a SSB rig, in various steps over a few years
time. During that time period, we would peruse the
various radio supply catalogs and admire those fancy,
expensive rigs that everyone dreamed about owning, but
didn't stand a snowball's chance in hell of affording back
then. The Lafayette Telsat SSB-25, SBE Console II,
135, Pierce Simpson Simba,
and others were my most common dream rigs. At the top of
pretty much everyone's dream list though, were the
Browning Golden Eagle, and the
D201. Both of these rigs were at the top of the
premium rig list, and had price tags which were twice what
most other full-featured, dream-worthy rigs had. The fact
that most of us would never see rigs like this only made
them all that much more irresistible and attractive. It's
an unfortunate fact of human nature that the more you
can't have something, the more you seem to want it. Well,
time marched forward, as it invariably does, and I've gone
through quite a few different radios in my time, including
some decent performing (and equally expensive) ham rigs
and Icom 706. And with such radios, the desire to obtain
one of those early dream rigs faded in the process.
However, now that those 30 long years have gone by, and
I'm waxing nostalgic, and revisiting those old classic CB
rigs, I find myself about to realize one of my childhood
dreams, as a once top-of-the-line Tram D201 is about to
fall into my hands. But like many of life's other
pleasures, this one also comes with a catch - it needs
some (maybe a lot of) work to bring it back to its former
glory. This should really come as no surprise as any
electronic device, which survives a 30 year service life,
is going to incur a few battle scars along the way.
Adding to the problem are modifications performed by those
screwdriver "technicians", who often ignore good
engineering practice in the quest to make their rigs
"louder", "stronger", and more frequency agile. Many of
those mods can be detrimental to the life expectancy of
the rig itself. So while I'm excited to finally operate
something I once could only dream about, I'm also
realistic (no not Radio Shack!) about the very real
possibility that the rig may never perform as well as it
once did when new.
The realization of my long
time dream came about totally unexpectedly though. I had
started playing around with the old classic rigs that I
had sitting in my closet, just for fun, and started
extolling the nostalgic appeal of those old vintage tube
rigs to the locals on the channel. The next thing I knew,
at least 2 other people had started buying up old classic
rigs from E-Bay.
especially, had gone totally outer limits buying up Sonar,
and Robyn tube rigs, including a hybridized 40 channel
version, and even some not-so-classic solid state rigs.
But during his buying frenzy, he somehow bid on (and won)
a Tram D201 by mistake (He thought it was an even older
Tram Titan), which needed work. He then found another
D201 to use for parts. But the original rig turned out to
be in worse shape than the supposed "parts" rig and
neither rig is in operating condition. He soon found
himself overwhelmed by the complexity of the Tram's
circuitry. So now I get to put my talents to work in
trying to get at least one of these wonderful old monsters
working again. Me, being the radio optimist that I am, am
not yet ready to condemn the "parts" radio completely and
I will try to get that one working as well. But it's
missing some key parts, and I'll have to find yet another
parts radio (Which I'll also probably want to restore, so
the cycle will never end....) or jury-rig some aftermarket
parts to make them fit.
I was recently at Art's
house to help him with a boat project and while there, I
picked up the two restoration candidates, which I
nicknamed "Bad" and "Ugly". These names came from an
inspiration I got the the other night, when some
skip-talking redneck bonehead kept playing his
overmodulated noise-toy over and over, playing the theme
from the movie: "The Good the Bad and the Ugly", which was
annoying in itself, and forced me to run the squelch
control a bit higher than normal. But like they say,
every cloud has a silver lining, since it gave me the
inspiration for the name of this project. The goal
therefore, is that I will be able to garnish one "Good"
radio from the combination of the "Bad" and the "Ugly".
First let's start by
introducing the 2 rigs:
"Bad", was in somewhat
decent physical shape, a few scratches were the extent of
its exterior defects. It was sold by someone who was in
the process of restoring it, but claimed he had lost
interest. There were a few tubes, the relay, and some
panel lights missing, and the power transformer looked as
though it had caught fire on the bottom, as the insulation
"Ugly" was in a little
rougher physical condition. The top cover had a square
hole cut in the top presumably to accommodate a cooling
fan (I cringe at the mental picture of some yahoo taking a
sawz-all to the top of this classic rig) and there was a
chunk broken off of one of the woodgrained sides. It
contained a fairly complete set of parts, but some of the
circuit boards were blackened, circuits traces lifted,
solder connections showing dull and overheated connections
from excessive current draw (a result of someone's attempt
at a power mod no doubt), as well as many band-aid repairs
and modifications which had been performed over time
trying to keep the rig alive. "Ugly's" power transformer
had similar issues with a burned insulation wrapper, as it
is now completely missing on the bottom, exposing the
windings. When the Art powered up this rig, his room
lights dimmed, and he quickly turned it off. It would
appear that something major is shorted. Hopefully it's
not the power transformer......
Art had taken the relay and
some of the other parts from "Ugly" and transplanted them
into "Bad", and when he powered that rig up, he thought he
had some semblance of receive, but little else. So that's
where I now stand. I will resist the temptation to
immediately power up the rig, and instead work to clean up
the boards, poor connections, switch contacts, and undoing
poorly done modifications first. I began my anxious and
equally daunting task by blowing the insides out with a
blast of compressed air, followed by a manual dusting and
spraying with circuit board cleaner. I also printed out
the service manual and schematic for the radio, and
started to familiarize myself with this unique hybrid
circuitry. It would appear that there were a few
revisions in these D201 radios during their history, and
even my two rigs are different in subtle ways. "Bad" has
a 3 pin grounded A.C. plug, while "Ugly's" plug is only a
2 pin. Adding to the confusion, the D201 schematic that I
have, dated 1975, appears to be for the original
point-point hand wired version, as it does not show the
boundaries and connections of the various circuit boards.
The D201A (40 channel) version, does show the board
divisions, and is otherwise electrically similar. So I'll
have to rely on both schematics to muddle my way through
The next day was spent
cleaning up the low voltage regulator board (called the
"Aux audio" or "BA" board). There were several fractured
solder connections on the Molex plug, as well as blackened
resistors and a tacked-on replacement capacitor. I
replaced the questionable parts and repaired the solder
connections. I also pulled out the other plug-in board and
retouched the solder connections there as well. I also
sprayed more cleaner on the PCB's and went to town
repairing lifted circuit traces, and questionable solder
connections. I also spent some time looking at "Ugly". I
determined that there is a short in the HV power supply,
which would explain the large current draw that Art saw
when he plugged it in. While it seems more likely that
I'll be able to restore "Bad", and may have to take some
parts from "Ugly" to complete the task, I am still hopeful
that I can get both rigs working at some point.
Day 3 started with me
making some further checks of connections, but I wasn't
able to continue on this path for long before I succumbed
to my overwhelming desire to just fire it up and see what
happens. So I placed the radio on my work table and
plugged it in. Turning it on saw the panel lamps light as
well as the tube filaments. So far no smoke, and after a
few more seconds, I started hearing an A.C. hum from the
speaker (at least I have audio). Keying another radio on
the same channel, saw the S meter move and some feedback
erupted from the speaker of the Tram. Great!, I thought,
the receiver's working. But as I would find out, this
project would not bring me satisfaction without a fight.
I tested the power supply voltages and they were all
present and within range, except for the 270V supply which
was running well over 300V. So far, so good. The S meter
was acting somewhat erratic and there was some
intermittent static in the receiver along with it.
Hooking up the signal generator showed that while the
receiver was technically "working", it was not very
sensitive, as I had to put in about 200uV worth of signal
to get anything. Lack of background noise leads me to
believe that one of the later I.F. stages or the detector
may have a problem. To add to the growing list of issues,
the manual tuner does not appear to be working either.
But the worst problem turned out to be SSB receive, or
should I say "no receive", as in it's completely dead. I
tried a quick alignment, and that improved AM receive
slightly, but it's still way down, and still nothing on
SSB. I also swapped a couple of tubes with parts from
"Ugly". I also swapped out the balanced modulator board as
well (since it was plug-in). But so far, nothing helped
the SSB receive. I haven't wired the mike plug yet, so I
didn't try the transmitter, but I did set the final bias.
I plan on trying the transmitter the next time, as it will
help me isolate other problems. If SSB transmits ok, that
reduces my suspect list as parts of the SSB IF are shared
by both transmit and receive. I can also check to see if
the manual tuner works on transmit (another popular mod),
which can further shed light on this problem. I will also
focus on the mode and tuner switches and the relay, and
how the various voltages are switched depending on the
mode it is in. The problems I'm having could be caused by
something as simple as a missing voltage due to a dirty
(or mis-wired) switch. I'm also going to check ripple
voltages on the supplies and replace any filter caps, if
The next night, I wired up
the mic plug and decided to see how the transmit side of
"Bad" was working. Surprisingly, the rig transmitted a
strong 4 watt carrier on AM, with modulation. Switching
the crystal/manual switch to the manual mode did not
change the transmit frequency, which tells me the that VFO
transmit mod had not been performed (or, as I would later
find, not correctly). It also transmitted on SSB,
although it appeared to be distorted or the crystal
oscillator was off frequency. The AM modulation envelope
was also somewhat strange and distorted looking. Attempts
to neutralize the final to remove the spurious emissions
were met with failure, although I was not able to perform
the process per the alignment procedure, so when I revisit
the transmitter later, I'll make a more comprehensive
attempt. Operating the transmitter was done mostly to
determine if the cause of the SSB receive problems could
be traced to the Balanced Modulator board. Since the
transmit and receive share components here, the fact that
SSB transmit worked, pretty much eliminated this component
as the root cause of the receive problem. I then decided
to visit the audio hum issue. Interestingly, when the rig
is first powered on, as the receiver is first warming up,
the audio is crystal clear, then the hum pops in and is
sometime intermittent. The usual initial suspect in a case
like this, is a power supply filter cap. The voltages were
checked for excessive ripple, and where there was a little
more ripple than what I thought it should have, I tacked
another cap across it to reduce the ripple. After the
supplies were corrected, the hum was still present.
Probing the audio output tube socket with the scope showed
a fairly strong A.C. component on the cathode and plate. I
am now wondering if my BRAND NEW 6L6 tube has a
heater-cathode short, which is coupling the A.C. filament
voltage onto the cathode......
Recap of "Bad's" remaining
AM receiver working but weak.
SSB receiver dead.
Manual tuner dead.
Hum on receive audio.
AM TX there, but modulation distorted
(Possibly related to the hum problem).
SSB TX is also working, but in need of an
Day 5 was
a banner day for forward progress on the problems plaguing
"Bad". I had decided to concentrate my efforts to
resolving the receiver hum problem. I had at first
thought that there might be a tube short coupling A.C.
filament voltage onto the cathode of the audio output
tube. But as I progressed down this path, I was able to
determine that the hum was not being introduced in the
final section. I traced the problem back as far as the
volume control. A clue came when the transmitter was
energized and the hum went away. Another clue was that
the hum went away when the squelch was advanced. Swapping
every tube in the audio chain did not resolve the
problem. Becoming frustrated, I decided to take a
different path and look into the weak AM receive. I
noticed that the R.F. front end tuning was not very
responsive, so I swapped out the 6BQ7 front end tube with
the one from "Ugly". Surprise, surprise! Not only did
the AM receive get stronger, but the hum vanished (Huh?).
I would have never guessed that a bad R.F. receiver front
end tube could introduce A.C. hum on the receive audio,
but somehow it did, even with the volume all the way
down. I gave it a quick alignment and discovered that one
of the cans had a cracked slug in it, so I swapped the can
with one from "Ugly". So when I finished the alignment,
the receiver is responsive down to .2uV, which is real
close to what I would expect, and the audio is clean.
Another surprise came when I tried the manual tuner again,
and found that it was now not only working, but the dial
calibration was very close. Sensing the potential for a
hat trick, a Trifecta, or a tick-tack-toe, three in a row,
I optimistically switched to SSB hoping to see it now
working as well. But alas, the SSB receive is still down
for the count. The S meter also has some problems. I was
able to zero the meter (Which seems to drift a whole lot
more than I'd like to see), but I did not have enough
adjustment range to set S9 with 50 uV of input signal. The
meter needle will slam against the glass when I key
another radio, so the meter has enough sensitivity. I am
wondering if there is an AGC problem. But that will have
to wait until the SSB receive is fixed (And who knows, the
problem might be related). At this point, I could probably
throw the rig on the antenna and debut it for the locals.
But I think I'll wait until it's completely fixed first.
Updated remaining issues:
SSB receiver dead.
Align synthesizer and SSB TX.
Align and neutralize the TX final and
Resolve the "S" meter issues.
Parts cannibalized so far from "Ugly":
Resistor from the Aux Audio board.
Balanced modulator board (But may be able
to swap back)
455 Khz I.F. can.
Mic Gain knob.
Over the weekend, even more progress was
made. I went to work on the SSB I.F. section by tracing
signal backwards from the 1st stage. I soon found that a
screen grid bias resistor on the 2nd SSB I.F. amp was
open, which prevented the stage from working. It was odd
for me to see a resistor (especially a 2 watt carbon
resistor) actually open completely up without visible
signs of burning. I think I've only seen this 2 other
times in 30 years. Normally when a resistor opens, it had
very visual signs of excessive current flow (I.E. it's
burned). Replacing that resistor corrected the problem,
and also loaded the +270 volt line back down to about 280V
instead the 315V it had been running at. At this point I
started to hear signals on SSB, but they were very low in
volume. Further checking revealed that there were (2)
2N3904 transistors in the SSB AGC stage which were both
bad. I had to wonder what killed them, and my best guess
was that the +14V supply had jumped up due to the
fractured solder connections I had discovered and
corrected when I first inspected the regulator board.
With the full unregulated 25V applied, the transistors
died a painful death. Once the 2 transistors were
replaced, and with one more alignment, SSB receive was
finally working properly. Now that the receiver was
complete (except for the "S" meter calibration), I set my
sights on the transmitter. I performed the neutralization
procedure and this time was successful. I also aligned the
carrier oscillators and the carrier balance. I was not
able to completely suppress the carrier, so I swapped the
Balanced Modulator board back with the original board, and
this time the alignment went fine. I then turned to the
frequency alignment of the main synthesizer. I went
through all the channels and attempted to set all the
frequencies dead nuts on. After it was all said and done,
I was left with 2 AM and 2 USB crystals which could not be
adjusted on frequency. 3 of the 4 crystals had drifted
low and one was high. Rather than trying to swap with the
crystals from "Ugly", I decided to just change the fixed
capacitors in parallel with the trimmer to give me
additional adjustment range. AM transmit audio still looks
a little strange on the scope, and I'll visit that again
as I begin the final little clean-up checks to finally
finish this radio off. I also swapped the two main tuner
knobs from "Ugly" since they were in better shape. I also
want to revisit the receiver's performance. While the
sensitivity seems "ok", it is not outstanding, which is
something I would expect from such a premium radio. I
still suspect that there is either a tube which is a
little low on gain, or that there may be other parts which
have drifted out of tolerance. Considering all the
current this radio's circuits draw, and all the heat it
generates, caps drying out and resistors changing value is
not out of the question. Add in the fact that the radio's
over 30 years old, and it becomes very likely. It'll be a
painstaking process though, since the sensitivity is
already fairly good. Consequently, without a "perfect
specimen" to compare to, it'll be hard to know which
stages are performing within spec, and which are slacking
a little. I'll probably swap tubes around, measure
voltages and resistor values, and shotgun replace
electrolytic or paper caps. In the process, I also hope
to correct the ills of the "S" meter.
The next day I took a stab at trying to
figure out why the "S" meter could not be set properly.
Not being able to see anything obvious (Like a drifted
resistor value) wrong in the circuit, I dropped the fixed
1M Ohm resistor in series with the S-meter adjustment pot
to a 100K Ohm value. Once that was done, I could easily
set the meter to the proper reading with a 50uV input. But
I can't help but wonder if I had just performed a band-aid
fix which covered up a different problem. Once the
S-meter was set, I then checked the linearity of the
signal scale, and I was a bit disappointed. It's not as
linear as my
Hy-Gain 623. It's linear between S-7 to about +10db
over S-9. But outside of that range, it doesn't track
properly. It's not nearly as bad as my
TRC-451, and many other newer radio designs, but I
just figured that a premium (priced) radio such as the
Tram, would have a better "S" meter. I also swapped the
R.F. Gain pot with the one from "Ugly", since it operated
far smoother and with fewer dead spots. I also bought
some NOS tubes from E-Bay to replace some of the aging
ones in the Tram. Hopefully that will improve the overall
I finally debuted the radio on the air for
the locals. Everyone said that the audio was strong and
the receiver seemed to be ok. I still want to play around
with this radio a bit more. I want to try some different
tubes, and I'm not all that happy with how much the "S"
meter zero drifts, and I may try to modify that a bit.
On-the-air usage has also exposed another
problem; the noise blanker appears to be inoperative.
Further checking into this revealed that one I.C. and two
transistors were bad. After replacement, I was able to
align and observe the gating action of the N.B. circuit.
But I haven't had any pulse type noise to "blank" to
verify if the circuit actually does an effective job.
During the rechecking of the rig, I discovered that the
manual tuner was not working correctly. It would seem
that when the manual tuner is selected, both the xtal
synth and the manual tuner are active, which creates some
interesting frequency mix products in the transmitter. I
suspect that someone tried to perform the transmit VFO
mod, but did not do it correctly. As I suspected, after a
thorough investigation, it was a simple case of "mod gone
horribly wrong". I corrected the problems, and now the
manual tuner works correctly on transmit and receive.
A few weeks later, I changed out all 5 6GH8
tubes with NOS replacements. This has resulted in a
slight improvement in receiver sensitivity, and more
importantly has corrected the earlier issues with the "S"
meter. The meter zero is now stable and it now tracks
signal fairly linearly, as I would expect. The new tubes
also put a little more kick in the transmit audio, as I
now have to back the microphone gain back quite a bit from
the earlier setting.
For the near term, I will enjoy this radio
and hope that it lives up to the expectations that I had
for all these years. As time goes on, I'd like to replace
all the electrolytic and wax paper type caps, as I am sure
they have all drifted with exposure to heat. I also want
to check the value of some of the resistors which carry a
heavy current load, so ensure that they haven't drifted.
Replacement of the rest of the tubes is also a
probability. But all in all, it would appear that I did
manage to make one good radio from the combination of a
"Bad" and an "Ugly" rig.
Total parts replaced:
1 455 Khz I.F. can
1 R.F. Gain pot.
Undid power mod.
Corrected VFO tuner mod.
Fixed numerous solder connections and P.C.
Tracked down and replaced defective parts.
Aligned whole rig.
And here it is, proudly running on my work
table. It'll be an even more challenging project just to
find a space on my operating table for this huge
But what ever became of "Ugly"? Don't
worry, I haven't forgotten about it. In fact, that radio
faired much better than I initially expected. I only had
to steal a small number of parts, mostly cosmetic, and
depending on whether I can obtain a relay and some new
tubes, I should be in good shape to begin restoring "Ugly"
fairly soon. Be sure to look for
to see how that project pans out.
last piece, "I
had a Dream", I told the story of my long time desire
to own a classic
D201, and of my good fortune in finally obtaining, not
one, but two of the rigs, both of which needed some (quite
a lot of) TLC. The story went on to document the process
of bringing back "Bad", the better of the two rigs. Well,
now it's time to set my sights on "Ugly", the worst of the
two rigs. My first look at this radio left me with the
feeling that it was beyond hope and I would probably just
use it as a parts rig. But after having the experience of
the first rig under my belt, and along with some net
scavenged information and some very valuable advice from
others who have hoed this row before, it has given me a
little better perspective and a more optimistic
expectation of what's in store for me when I set out to
complete this project.
the rig as I first looked at it:
was in a bit rougher physical condition than "Bad" was.
It definitely had obvious signs of long term (mis?) use.
This rig obviously did not sit on a shelf for most of its
life, that's for sure. Because these radios generate a
lot of heat (Especially if you try to "soup" them up), one
of the previous owners elected to cut a hole in the top
cover most likely to accommodate a cooling fan, which was
long gone by the time I got it. There was also a fairly
large chunk broken off from one of the woodgrained side
panels. But if the exterior condition appeared to be a
bit rough, this was nothing compared to what was waiting
once the cover was cracked open. At first glance, it
didn't look too bad, as it contained a fairly complete set
of parts, and everything that was there seemed to be in
the right places. But a closer examination underneath
showed that some of the circuit boards were blackened from
long term exposure to heat. A handful of circuit traces
were also lifted, and nearby solder connections showed a
dull, overheated finish most likely occurring from
excessive current draw. Along the way, the rig was
band-aided by "technicians", who had performed "cut and
jump" patches in a valiant attempt to keep the rig
alive. These "repairs" were done rather sloppily and may
have actually contributed to the rig's problems.
The relay was robbed
to bring "Bad" back to life, and both the audio and R.F.
final output tubes looked well used. All of the tubes
were there, but the R.F. front end tube had been swapped
with the defective one in "Bad".
began my task by trying to repair the lifted circuit
traces, and the badly mounted tacked on repair parts.
Along the way I accidentally cracked a 1/2 watt resistor
in half, which was sloppily mounted on the foil side of
the PC board. This disturbed me at first, but it turned
out to be a blessing in disguise. Since I had broken the
resistor, I naturally had to find out what part it was. I
identified the resistor as R403, which was listed on the
schematic as a 2.2K ohm resistor. What I had in my hand
was something like a 39K. Huh? I then instinctively
checked R402, which was the other resistor in the chain
which fed V400's plate and screen grid. As I suspected,
R402's value had been changed as well. The schematic
called for a 47K but instead it was about a 4.7K Ohms.
These changes would result in roughly the same grid
voltage, but a much lower plate voltage. I checked the
other (now working) rig to see what values were in that,
and they matched the schematic. So I replaced both
resistors with the proper values. I wondered why these
parts were changed in the way that they were. Was this a
method to lessen current draw, a performance or
reliability enhancement, or simply the product of a
knucklehead who can't read the resistor color code? I
installed the proper parts from the component side of the
board and repaired their associated PC traces with some
buss wire and super glue. After a night of intensive
surgery, the bottom of the boards look much better.
was the before view of one such section:
the same area after I cleaned it up a bit:
still isn't all that pretty, but it least it's a more
solid connection, and there aren't those little jumpers
dangling in the breeze.
So with that out of
the way, I moved on to other issues.
Art had first tried to fire up the radio, he noticed that
when he turned it on, the lights in his room dimmed, which
is a sure sign of an unusually massive current draw. He
wisely turned it right off. Well, I was able to determine
that there was a dead short on the 425V supply, which
would account for the huge current draw. A check of the
primary fuse showed that someone had replaced it with a 20
amp fuse (it calls for a 3 amp). Ok, time to climb on the
soap box for a second...... What do people think a fuse
is for anyway? One day the rig blows the normal fuse, and
when you replace it, it blows again, so the answer is to
replace it with a big honkin' fuse? Well gee, now the fuse
doesn't blow any more, but what is all this smoke pouring
out of the rig? HELLO!!!!!!!!!!! Sorry, but I have little
tolerance for idiots. Well, a little circuit tracing
revealed that the source of the short was one of the
sections of the multi-section 40 uF C5 filter capacitor.
None of the other sections were shorted, nor were the
sections of the other multi-section cap C624. But C624
had a slightly bulged bottom, which is an indication of
outgassing or other immanent failure. So it looks like
both caps will probably need to be replaced. I hope I can
find NOS multi-ganged caps. As an alternative, I can
probably use some of the caps I'd scavenged from computer
switching power supplies. These are smaller and usually
of a higher value, and I can probably fit them in place
without too much difficulty. I also noticed that the two
47 Ohm resistors between the HV rectifiers and the shorted
cap were burned (think: 20 amp A.C. line fuse). One was
so bad that it was cracked in half. Those were replaced in
short order. The remaining issue was to replace the audio
tube bias resistors on the BA plug-in board. I chose to
use (It was the closest value that I had on hand) an 820
Ohm 7 watt to replace two burned up 2 watt resistors. Yea,
it's a little higher in value than the two originals, but
it shouldn't affect it all that much. If anything, the
tube will draw even less current. If I see problems with
the audio stage, I can always run out and buy the exact
values later. Through the course of checking out the
plug-in circuit boards, I noticed a cap (C427) lifted from
the circuit board. This seemed odd, but the reason it was
lifted became apparent soon enough when I tested the cap
and found it to be shorted. Hmmm, I've found two caps
shorted so far. I'm not sure I like where this is going.
And I still haven't put power to this thing yet. I sure
hope that when I do, that I'm not greeted with a shower of
sparks, or a mushroom cloud full of smoke. Finally, I
replaced two of the diodes in the balanced modulator which
had been previously changed to parts which did not match
the original value. I would think if you were trying to
create something that was balanced, that the parts should
all be of the same type. This might have been the reason
why I could not get sufficient carrier suppression from
this board when it was installed in the other Tram. I also
replaced the balance trimmer cap (C207), as it had become
brittle and snapped during the tuning process.
finally put power to the rig 3 days after starting on this
project. Being somewhat skittish with the burned parts and
shorted caps, I chose to ramp the voltage up slowly with
a Variac. I also replaced the A.C. line fuse with the
proper 3 amp value. I temporarily stole the relay back
from the working Tram to use to test this one. I plugged
it in and started turning up the Variac. I tested voltages
as I brought up the power and they all looked good, at
least the HV short is gone. However, AM receive does not
appear to be working, as I could not hear the signal
generator. SSB receive does seem to be working, at least
the I.F. does, as I can hear a rushing noise. The audio
appears to have some static popping noises as well. I ran
out of time before I could try the transmitter, so I'll
take that up on the next go around.
5, I picked up where I left off, by powering up the
beast. As the rig warmed up and voltage was slowly
increased, I started hearing static popping from the
speaker. Thinking about the bad caps, I started probing
the HV supplies with my scope, to see if the voltages were
spiking due to filter cap breakdown. Sure enough, I
noticed fluctuations on the 410V supply. I then cut the
remaining sections of filter C5 out of the circuit and
subbed in another cap. This time the popping noises
stopped, but there was still a hissing noise which was
constant no matter where the volume was set. Subbing out
the audio driver tube (6GH8) cured that problem. I was
now able to see a clean SSB receive. In fact the SSB
receive was not only working, it was working well, as I
was able to drop well below 1 uV and still hear the
signal. The manual tuner also seems to be working. AM
receive, however, is still totally dead. But this should
be fairly easy to track down. My first area to check will
be the 2nd local oscillator (V301) and then the 455 Khz
I.F. chain. In the meantime, I decided to try the
transmitter, but for some reason the relay would not kick
over. I could hear it trying, but it was acting like there
was not enough voltage across the relay to fully pull it
in. I then pulled the BA board, and I noticed that the
three relay voltage dropping 10K Ohm resistors (R's 611,
612, 613) were all hot to the touch. Well, if the relay
was not energized, there should not be that much current
flowing through the resistors. Suspiciously, there was
another of those .22 uF 450V caps (C639) from the load
side of those resistors to ground. A quick check with the
ohm meter showed that, sure enough, that cap was shorted.
That makes 3 shorted caps found so far. This isn't looking
so good...... At some point, all electrolytic and other
non-disk type capacitors should probably be changed out.
Once C639 was pulled out, the relay could be keyed and the
transmitter could be tried. Both AM and SSB transmit
appeared to be working well, with strong audio. On my
next opportunity, the AM receiver will be gone over and I
should be able to get it working.
Parts tally so far:
4 burned resistors.
3 shorted caps.
2 changed diodes.
2 wrong resistors.
2 bad tubes.
1 bad trimmer cap.
.....and a partridge
in a pear tree.
The next day, I dove
into the AM receiver by tracing signals. I was getting a
signal at V401, but by V400, it was gone. Checking the
voltages on the tube showed the same 250V on the plate
and the screen grid. Replacing the tube cured that
problem, and with it, the AM receiver started coming to
life. I performed an alignment and brought the
sensitivity to where it should be. But there was still a
problem. The "S" meter would not deflect to more than S3
for 50 uV of signal. This was a similar problem to what I
found in the other Tram only worse. The last time, I
cheated and changed a resistor value to allow me to adjust
the meter. This time, the signal voltage was just too weak
and I had to find out what the root cause was. There were
other problems too. There were still occasional pops in
the speaker. I had thought that I fixed this problem when
I replaced the HV filter caps, but the problem resurfaced
again. These pops seemed to increase in intensity when
the rig was on for a while or when under an increased load
(like when the transmitter is operated). There isn't much
in the HV power supply circuit either. There's the
parallel pair of 47 Ohm resistors (R3 & R4). There's a 100
Ohm series resistor (R6) along with the rectifier bridge.
First, I replaced R3 & R4 , with no apparent change. Then,
as an experiment, I jumped out R6 and dropped the voltage
on the VARIAC so that the HV equaled the proper 410V. This
seemed to help, but there still seems to be an occasional
pop. I'm thinking that the rectifier diodes may be
breaking down as the load increases. They were, after all,
subjected to the shock of a dead short, and having to sink
a ton of current that they would not have otherwise. By
lowering the VARIAC, I might have lessened the load enough
to keep the diodes at bay. I will have to wait until I
can get some HV diodes to check that theory.
In the meantime, I
started looking at the transmitter. I aligned the
oscillators, the balanced modulator, and the final
neutralization and output and all looked good except for
the modulation envelope. It seemed to lack enough audio
drive. I thought about the 820 Ohm resistor I had placed
on the BA board to replace the burned 220 Ohm originals.
So just for a test, I swapped out the BA board from the
other (working) Tram. This time the modulation looked
good. So I went back and tacked another 1.3K 5 watt
resistor across the 820 Ohm on the BA board for that
radio, and that did the trick. The modulation looked good
again. I'm sure there is an optimal value to use to set
the proper bias and for optimal D.C. gain, and once I get
everything working, I will dial that value in.
The next night, I
started aligning the crystal synthesizer and, like the
other D201, there were 3 crystals which could not be
netted on frequency. I decided to make a note to revisit
this area later, as I want to cure the rig of all of it's
major ills first before I fine tune the crystal
frequency. So I returned to the AGC/S-meter issue. Both
SSB and AM readings appear to be equally low, and that
should be a clue. After spending what seemed like an
inordinate amount of time looking for parts out of
tolerance and swapping out tubes, I gave up and changed
the value of R428 to a 100K, like on the other Tram, and
adjusted the meter. It bothers me to have to cheat like
that, but with the receiver working properly, and no
obvious problems waving their hands in the breeze, I did
what I needed to do so that I could move on. The next
item on the list was the manual tuner modification. This
Tram, like the other, had the popular manual tuner mod
performed which allows it to function on transmit like a
VFO. Also, like on the other Tram, the mod was performed
incorrectly, allowing the crystal oscillator to run along
with the manual tuner resulting in some strange spurious
transmit products. So now I'm cleaning up that area.
So as it stands now,
the "Ugly" Tram is pretty much functional. I do have some
remaining issues though before I can give it my seal of
Clean up the HV
power supply by installing lower value filter caps or a
higher value dropping resistor to get the HV to run at
the proper level without having to use the VARIAC to
lower the line voltage.
Trace down the
"Popping" noises coming from the HV power supply. May
need new rectifier diodes.
formerly shorted bypass caps with new replacements.
The next few days were
spent taking care of these issues. The "popping" noise
seems to have been caused by poor contact in the Molex
connector on the "BA" board. Cleaning and tightening the
connector fingers seems to have finally solved that
problem. I also picked up some caps and high power
resistors from Art, and have replaced the shorted caps. I
replaced the R3-R4 combination with a single 100 Ohm 10
watt resistor, in order to drop the HV down to the proper
levels with the filter caps that I am using. The values
of the new caps are much higher than the originals, and
should provide better filtering. But they had also caused
the voltage to rise above their nominal value. The new
resistor corrects that. I also went through the
synthesizer and did my best to align the crystals. Some of
the crystals were located in a place where the selector
switch blocked easy access to the solder side of the
board, so I was not able to completely net in all the
frequencies perfectly. But they are all close enough. The
manual tuner was also cleaned up so that it functioned
completely independently from the crystal oscillator.
At this point, it
would appear that I have a completely functional radio.
A pretty good feat considering the less than optimal
condition of the radio when I first started this project,
and of my dubious prognosis and how close this radio came
to simply becoming a parts donor. Of course, I am still
borrowing the relay from the other D201, so at some point
another relay will need to be found so that this radio can
have a fully useful life once again. I'm sure Ebay will
come to the rescue there. While I had to "re-engineer" a
little more on this radio compared to the other D201, and
this radio got the "hand-me-down" parts, it's working
surprisingly well. I plan on returning this radio to Art
at some point, so that he can enjoy it.