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Post by Trans on Feb 28, 2023 14:38:07 GMT -5
I'm restoring a Tram Titan II to look factory new. I have taken the best parts of 3 Trams. The radio looks great, but I get no audio from the speaker or the mic. I have replaced all the capacitors and some resistors. I have checked the tube on an old tube checker and they appear to be good. I get about 4 watts dead key, I can see it receiving on the S meter. I get no sound what so ever from the speaker (new speaker) and I have no modulation. Do you think it might be the audio transformer?
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Feb 28, 2023 19:09:06 GMT -5
I'm restoring a Tram Titan II to look factory new. I have taken the best parts of 3 Trams. The radio looks great, but I get no audio from the speaker or the mic. I have replaced all the capacitors and some resistors. I have checked the tube on an old tube checker and they appear to be good. I get about 4 watts dead key, I can see it receiving on the S meter. I get no sound what so ever from the speaker (new speaker) and I have no modulation. Do you think it might be the audio transformer? The thing is,it could be a whole lot of things in the audio chain. You'd be best off trying to trace audio through the chain and see where it stops. You'll need a scope for this. But it's a better approach than shotgunning parts. |
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Post by 2600 on Mar 2, 2023 1:08:05 GMT -5
An oscilloscope is an unfair advantage in tracking down a missing signal, as in your speaker audio.
A simple multimeter can check for missing DC voltages that are needed to make the tubes do what they do.
But if those measurements are within tolerance, the blockage is in the AC circuit that the signal follows. The audio output transformer has been known to fail in that model, but if it's bad, you'll see a good signal on the grid of the tube, but not on the plate.
Seems to me the T/R relay is not in a socket in that radio. Just making sure the speaker is getting turned on by the receive side of the relay is a logical thing to check.
Checking the resistance of the squelch control would tell you if it has gone bad and caused trouble.
What tools do you have on hand?
73
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Post by Trans on Mar 6, 2023 13:01:12 GMT -5
I have an O'scope and voltmeter. I'll have to get into it an follow the audio chain. I'm hoping it has the right tube. The one I have has a 6GM5, but its hard to tell if its the correct one for this chassis.
Trans
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air1
Ratchet Jaw
Posts: 70
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Post by air1 on Mar 7, 2023 9:58:39 GMT -5
Unless someone has changed the socket, that will be the correct tube. The 6GM5 is a 9 pin tube and the older versions used a 6GK6 as a modulator which is a 7 pin tube. There were quite a few revisions of the Titan II as well as the Titan, and there are schematics and bulletins that reflect the different revisions. If your radio originally came with the 6GM5, it is either revision R3 or R4, and the schematics will be labeled as such. Also in R3 and R4, V10 is a 6HS6. In the earlier versions it was a 6AU6. R3 involved a mod to V10 (the microphone pre amp stage) whether it had a 6AU6 or the 6HS6 to eliminate crackling or sputtering sounds from it into the receiver. R4 was mod to eliminate low receive audio gain due to changes in tube aging or variations of 12AX7 tubes at V9. The easiest way to tell if you have a R3 or R4 version is to check the disk cap that is soldered between pins 7 and 9 of V9, the 12AX7 tube. If it's a .1 it is version R3. If it's a .01 it is an R4 which is the latest version of the Titan II. By the way, the schematics in the SAMS book are from R2.
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