In my last piece, "I had a Dream", I told the story of my long time desire to own a classic Tram 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.
Here's the rig as I first looked at it:
"Ugly" 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".
I 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.
Here was the before view of one such section:
Here's the same area after I cleaned it up a bit:
It 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.
When 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.
I 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.
On Day 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 approval:
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.
Replace some formerly shorted bypass caps with new replacements.
Align synthesizer crystals.
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.