My AM deaf D201

[B C]

I have a Tram D201 from 1976. It has been recapped and the large resistors replaced with flameproof units.
The radio transmits very well and seems to receive SSB fine, but there is no AM receive.
Although I don't think it will have any bearing on the receive, I will mention the two mods which I see have been performed. First the final has been changed to a 6146 from the original 6l6 and the VFO has been opened up to control transmit and variable receive. In tuning around on LSB I can locate AM stations, but when I switch to AM (crystal or VFO) the signal is completely gone. All I can hear on AM is audio hissing.
I have checked all the tubes and they are in great shape. The manual spot feature on channel 9 also works and is shown dead center on the VFO channel 9. I have gone thru the alignment procedures but still no luck receiving signals except for the radio sitting right next to it.

HELP!!!!
B C

[MDYoungblood]

I am by no means an expert especially on Tram tube radios, was hoping one if the tube guys would jump in. You really can't go by having a radio next to it,, most times it is just over powering the 1st IF stage in the receiver. It sounds to me to be possibly the switch or a cap in the receive section is backwards.

I like the tube change over, radio should do a good 50w on SSB, nice mod, the rest of the mods are typical for the D201.

3's

Greg

[B C]

How about all you "tube radio guys", this thing was working OK and then it started downhill. I replaced the electrolytic caps in hopes that they were the cause of the problems the rig was having, but no such luck. An old friend of mine replaced the big resistors with the blue flameproof units a few years ago. The tubes all have been tested and are good and strong.
I sure could use some help on this old boat anchor, it had great ears and talked strong 6 months ago but now it acts like it's ready for the "old radio's home".

B C

[eyecue]

That might be tubes but the demodulator is still solid state diodes. I would be checking d 400- 403.

[B C]

Will do Brad, I'll let you know what I find.

B C

[B C]

I've removed and checked the diodes you spoke of, they are good. What's next?


B C

[TheGman]

The best way to troubleshoot, is to get a signal generator, inject at the antenna connector, and using an o-scope, start tracing back. Easier said than done. I have an HP 606 tube rf generator, but also use a kenwood TS-440s with the rf power turned all the way down as a signal injector too. But.....seeing you said SSB receive is OK, my GUESS is that something in the detector stage has gone south. AM detection is usually done with diodes. Sorry I don't have the 201 schem in front of me, but I bet theres something near the diodes that went bad, since you said the diodes tested good. Best info I can give with the info presented. Hard to fix radio over the phone....... :D :D :D

[201tram]

1st is this a hand wired or or board Version ? Does it have SSb receive, AM and SSb transmitt ?

[B C]

This radio has some hand wiring and also some printed boards. Ye, it does have SSB receive and it transmits on AM and SSB very well, this portion of the radio is very strong.

[201tram]

check the resistors on the 2nd IF section, paying close attention to pin 3 of V401 these are a known trouble spot for the problem you have...

[B C]

I'll give it a shot and let you know, my fingers are crossed.

[TheGman]

So did you find the problem?

[B C]

No sir I have not. Everything that I have checked so far is within spec. I'm obviously open to any and all suggestions other than taking a hammer to it.
I would really like to get it working again and I do keep checking components in the receiver section but so far it's all been dead end.
Any fresh ideas??

B C

[MDYoungblood]

If the radio is a "Keeper" find a Sam's Photofact CB Radio Series (CB-88). It has a lot of tips on what the problem could be and repairs. You'll have to bite the bullet and buy one.

3's

Greg

[nosaj]

I will see if I have that one, I have a stack of them, if so I will scan and upload.

nosaj

[nosaj]

unfortunately I do not have that one.

nosaj

[TheGman]

CB Tricks has schematics for D201's. I just peaked. One suggestion, check AM oscillator crystal X300, 5.8015 mhz. See if that stage is oscillating. No frequency counter? Can use a shortwave radio to dial in that freq and see if there's a carrier or not.

[B C]

I'm back into the 201 again. I reread my earlier posts about the receive, it does receive a little bit on SSB but not on AM. On SSB it is definitely on the channel that my other transmitter is on. If I go one channel up or down on the 201 the SSB signal is gone. I don't think it is peaked properly but I'll handle that after I get the AM receive working. I rechecked the diodes 400 thru 403, all good. I did notice that if I touch the X100 crystal (5.8015) with my finger or with needle nose pliers the background noise jumps up quite a bit but the s meter shows no change. If I remove it the receive goes dead.
That's where I'm at right now, I'm going to check CB Tricks for the schematic to see if that will shed any light on this problem. I'm hoping the schematic shows the polarity of the electrolytics, so I can check my work there .
If you guys have any thoughts and or ideas, let me know...……….that big hammer is in the drawer and I know how to use it!! I hope I won't have to.

B C

[Blue Ox2]

Hey there BC,

You are certainly far more into the repairs of this equipment than I am. I'll pack it up and ship it out to get
workin' proper when it comes to that.

I'm hoping to hear some transmissions this evening and possibly get a buddy of mine
to look this thing over in a week or so.

Best wishes to ya so you'll get this awesome equipment workin' for you again.

73,

Mike

[B C]

Thanks for the good wishes Blue Ox, I can use some luck on this old boat anchor. If I tried to ship this old guy they would have to pick it up with a fork truck and deliver it by semi. Seriously, I am trying to get it listening again and I'll probably stay at it until I get it right or maybe just stumble upon the answer.

B C

[Blue Ox2]

I certainly do hope all works out well for you.

The unit I got has come to life and is singing...….
Praise the Lord this beautiful peice of furniture has
ears and is gettin' out.

73,

Mike

[tramd]

I just saw this as I have not been on here in a while. BC did you get this going yet? If not check R322. It's a 100k 2 watt. Check voltage on V301 pin 1 for about 100VDC on AM and 400VDC on SSB. If voltage is low on Am then R322 is probably bad. If you pull X300 and the voltage falls off then goes back up when you replace it, the crystal is good. V301 could be bad also causing your problem. You can swap it with V302 to check but put V302 back as to not mess up the alignment. Also check R402 47k 1/2 watt. If voltage is below 90 VDC at V400 pin 6 R402 is bad. Hope this helps.

[B C]

Drifter, I really appreciate this info, I set the old Tram aside for awhile as I was getting pretty frustrated with it and with my apparent ineptness. In the near future I'll put that old boat anchor back up here on the bench and check those items you mentioned. I've got my fingers crossed.

B C

[Blue Ox2]

The Tram I have has decided to not transmit properly and I'll be needing to send it off to a good tube radio specialist.

73 folk, Lookin' to learn more in the weeks to come.

Mike

[B C]

Good lu7ck with it Mike, hope you get it back soon without breaking the bank.

B C