Tram D201 no am reception

[klj2497]

I turned it on today and it started to fade as it warmed up i switched to ssb and back to get the rec to come back that works sometimes. i did notice when it came back xtal rec. worked but when i switch to the man rec. its not working but if it cools all the way down both will work for awhile. i wiggle the v400 but there is no pop or static. i noticed some popping in the man mode sometimes when it stops working. also it will stop rec. immediately when i unkey sometimes. the vfo transmits in manual but it would not transmit in manual mode when the man. rec. is out

 

[klj2497]

i wiggled v302 and the man. rec. came back i must have really dirty sockets. i sprayed that electronic cleaner into all of the sockets and used a tooth brush to get into the pin holes. there is residue on the board like something spilled and dried up over the years the old t302 can kinda smelled like old beer. v302B is the rec. man. oscillator.

 

[klj2497]

Kneebiter has the right idea to tap or wiggle components to hear if they pop and/or go out and/or come back. Thankfully now the Tram is working more than not. i think the t302 transformer was the biggest improvement. frequencies come together there and made it hard to diagnose.

 

[klj2497]

i bought some tiny dental floss brushes and scrubbed out those pin holes. no more pop out or in. no fade as of yet

 

[klj2497]

i was studying the block diagram and found the rec. audio goes thru v602 and v603 on the audio board. very interesting as Artie Johnson would say. the meter was not working and the meter uses v602b . so when i cleaned the pin holes the meter began to work.

 

[nomadradio]

Odds are that you will either end up replacing tube sockets with loose contacts or get tired of it and just give up entirely.

Once the spring temper of the contacts is lost, you'll be messing with them more and more frequently. If you don't feel sufficient friction when plugging or unplugging a tube from its socket, this is a clue that it's loose enough to cause intermittent trouble.

We adopted the policy of using the older chassis-mount type sockets as replacements. The sockets built to snap into a circuit board just don't seem to last very long. The spring contacts are shaped differently, and I suspect they are made from a different alloy than what's used in the older sockets. An alloy that just loses its spring temper with age or maybe from temperature cycles.

Maybe. I'm not a metallurgist, and I have never cornered anyone with first-hand design knowledge of tube sockets.

Could be that newer chinese sockets are better. Haven't tried them.

Biggest reason for using the older type socket is the fragile nature of the foil pads under the socket's pins. The solder and foil are all that hold the socket in place. When the foil pads lift, that becomes a structural issue.

We will remove the metal saddle that has the mount holes from a chassis-mount socket. The center hole gets countersunk to accept a #4-40 flat head screw so that the head lays flush with the top of the socket body. A nut under the pc board will secure the socket no matter how degraded the foil pads have become. You have to squeeze the socket pins so they'll pass through the holes in the circuit board, and bend the ends down to pass through the holes.

Thought sure I had shot pics of this process, but I can't find any. Been doing it this way since a decade before obtaining our first digital camera.

Just never got a "round tuit" to document that process.

Probably ought to.

73

 

[klj2497]

Thank You, Nomadradio. That sounds like a good socket replacement. The foil on this tram is really thin and fragile. I cleaned the mode switch again because i noticed it was not smooth, and when i turned it slowely to the right and back the radio rec. came back to life. I cleaned it really good with electronic cleaner. So far the tram is working. no fade or loss of receive. for now. im taking a good look at everything. it is really dirty and some of the sockets have wide pin holes that lost tension.

 

[klj2497]

the trams rec. is improving it works most of the time the radio will lose rec but it is still faint most of the time when it goes. i probed around v400 when i probe r400 i get a reading of .310. when i lose rec it reads .410. The rec eventually returns when i keep touching the r400 or v400 pin 1 or v302 pin 2 it jump starts the rec. somehow, also when i touch a metallic object to the chassis i get a loud pop thru the speakers like a ground is not grounding.

 

[klj2497]

im not ignoring your advice on socket replacement I do not want to change out sockets if i can avoid it this tram has very thin traces. much thinner than the other two trams i had alot of trouble when i replaced the all the old caps and resistors i want to find out for sure what is wrong so i m not changing out good parts. Im not giving up. but i have taken a break.

 

[klj2497]

Everything is working good except for the noise blanker even the limiter works the receive is slow to start up when i first turn it on when it warms up it receives good. I only have a problem at first startup right now.

 

[nomadradio]

Reminds me of the 1962 Chevy I had in high school. The straight six motor began to burn oil, more and more by the week. I really didn't want to tear down the motor, but around the time the oil consumption was being measured in miles per quart, the head gasket blew between two cylinders. Didn't run so well on four, and the smoke cloud it would leave behind it was impressive to say the least.

At that point I had no choice but to pull the motor, tear it down and rebuild it.

I won't criticize an effort to keep it limping along with as little repair as possible. I can sympathize.

But my experience has been that it will be perpetually intermittent until one day when it fades and doesn't come back.

It's your radio to do with as you choose. All I can do is share my experience with the last few hundred of them we have seen. A partial "patch" repair usually becomes a game of "electronic whack-a-mole", running down this failed resistor, then that failed electrolytic cap until all the routine overhaul parts have eventually been changed, one and two at a time.

On the bright side, this is one way to learn electronic troubleshooting.

73

 

[Shockwave]

im using a frequency counter to check the frequencies, the 5.8mhz appears to be steady. at v302 pin 2 im not sure where to measure the 6mhz signal there are some high voltages here. its not faded in awhile so when it fades again i will check the 5.8mhz again, and the 6mhz if i can find it.

If it's still intermittent on AM receive, check that 5.8015 MHz. signal again. Everything you say about how to "jump start" it touching certain pins and switching modes, indicates this crystal oscillator is struggling to maintain oscillation. I'll bet this signal is gone when the AM receiver is out. If you're sure V301 and X300 are good, suspect caps like C311, C312, C326 and C327 or resistor R322 if you don't have 110 volts on pin 1 of V301.

When checking for signals of a known frequency like this, I abandoned the frequency counter long ago in favor of a general coverage receiver with a calibrated digital display. Connect a short piece of coax to the receivers antenna with an insulated probe at the end. The probe end could be a 47 to 56 ohm resistor covered in heat shrink. Just getting the probe close to the signal source will allow you to "hear" the presence of the signal while you check for intermittents. If frequency confirmation is needed, just go to SSB and tune for zero beat. Then you don't have to locate specific test points on the board. Since you don't make any direct connection to the circuit, you also don't load the signal down or shift its frequency at all.

 

[klj2497]

That sounds like a nice gadget to check for a signal. i will check the signal again. it rarely fades anymore. when it does i pull the v400 tube and put it back in to restart it. i may replace the v400 tube socket. i am going to clean the sockets and controls again to be sure that nasty stuff that is dried up on the board isnt in the holes and controls, causing trouble. This radio had something nasty spilled into it many years ago. i have replaced r719 So far I have purchased a resistors and capacitors overhaul kit from ebay and replaced all of them .Also i purchased a tube kit from ebay and replaced all the tubes and i have replaced t302. When i purchased the Tram it did not work It was all patched together. So, i put it back the way it should be, and im still cleaning the gunk.

 

[Shockwave]

Good deal. This problem will not be related to bad connections or tube sockets. In fact, it is the breaking of the connection and starting it again that "bumps" the crystal back into oscillation. Anything from pulling the tube to changing the mode switch will do the same thing.

 

[nomadradio]

Had a 23-channel D201 here that behaved in a similar way. It had one of the small, square 3-pin ceramic filters like those found in the 40-channel version, and four of the round beige 2-pin filters. I replaced those with another of the 3-pin black square ceramic filters. Same setup as found in the D201A.

Can't say for sure they were the cause of the intermittent AM receive in that radio. We'll find out after it gets home and goes back into harness for a while.

Just learned not to trust the old 2-pin ceramic filters when there is any doubt about them.

73