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Tram D201 no am reception

The Tram was working great for a few hours. then when i unkeyed the microphone the receive was gone. I turned it off for awhile and turned it back on and it was receiving again, for about 4 minutes, then it fades away. I read that if you spray air on the board it may cool the bad part to working. i tried that with no luck so far. i think something is getting hot and breaking down. I am confused.
 
a strange thing happened i clamped the neg to the volt meter to the chassis and noticed the rec increased. When i touched the pos probe from the volt meter to v302 pin2 it shocked the receive into working again it faded out after awhile again so i shocked it again into working i dont understand whats happening though.
 
I changed the tube,with no change, so i think it may be c311 a 5pf cap or c312 5pf or maybe r308.
 
i found if i put the volt meter to c311 on the side that goes to v302pin2 and anything else on that trace the receive works great. when i remove the volt meter it fades out after a few minutes if i use a ground wire in place of the volt meter i get no sound but through the volt meter i have sound can anyone explain to me what is going on here
 
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i read the volt meter can act like a resistor i checked r308 a 100k resistor it read 99.4 k ohm
 
I would have a close look at R310, connected to pin 1 of V302. It hides just under the edge of the metal chassis above the rear edge of the circuit board behind V302. It can become intermittent. Usually looks ragged if it's been damaged by a bad tube some time in the last 40-plus years.

73
 
i replaced r308 it did not fix the fade it did bring the v302 pin1 voltage down to 110 volts it was 138v before i replaced the resistor. it should be 130v but its still doing the same fading. there did not appear to be any change in the v302 pin voltages when it fades though
 
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R310 has 260v on one side and 110v on the other it did not appear to change with the fade ill still change it though
 
i figured out how to upload pictures. I realized that my two Trams have different layouts. The one without the square black filter FL401. is the one that fades out.
 

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See the crystal plugged in the socket near the tube on the RX board? That is the mixer crystal that generates the 455 KHz. AM IF signal. The crystal may be weak or something in its oscillator circuit is out of alignment and drops out of oscillation. If you have another Tram, it's worth swapping this crystal to see if that's the issue. It could even be loose or dirty connections in the crystals socket.
 
I found something. i tapped on the yellow resonators they seemed okay then i wiggled t302 and it popped and the receive went out. i can move it and make the rec pop and come and go until it fades out for good and it has to cool off i hope i did not cause a new problem t302 looks soldered in good from the bottom. its not loose
 
Thanks shockwave. i swapped the crystals but no change. I ordered a new t302 transformer. it was popping and going out when i moved it. I am wondering if moving the transformer is flexing the board and causing something else, other than the transformer to cause the fade low/out. i am afraid i may cause more damage every time i try to fix something
 
i found that the cheap 30w soldering irons like you buy at walmart do not get hot enough to quickly melt solder buy a weller or similar
 
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