Tram D201A no USB/LSB receive

[troyota]

Hello, i have a late production D201A. with very low mileage. The resistors are not toast, the BA board looks new, very little darkness on the inside of the top cover. Hey get this, it has a perfectly smooooth and working BLACK channel selector. I did take it apart to clean and lubricate it, and reinstalled it. The rig is a beast on AM, I get superb audio reports. It has a 4-5 watt carrier and will modulate to about 18w on AM. Now on USB/LSB it has no receive, no static. It will modulate on USB/LSB to about 5-6 watts. I have checked the tubes (switched with known good ones) I have put in a known good working BM board, and BA board from another D201A I have. While I had the synthesizer board out I put in a spare good working synthesizer board with a thin gray selector. I have checked all the resistors in the SSB IF chain, all were spot on. I checked all the disc caps for shorts and capacitance value, I have checked all the tube voltages on the receiver board, and some of those were not correct with the schematic. V301 pin 2 reads mv (should be -3v) pin 6 reads 207v (should be 1420V302 pin 7 reads -100 mv (should be -2.5v per schematic). I also have some high voltage on V502 pin 1 = 280v, (should be 130), 3= 245v (should be 40), 6= 274v (should be 135), 7 and 8 have 0v (should be 1.0v and 4.0 v respectively). I thought it would be R519 or R520, but both checked fine. The large PS can caps checked ok, I have ordered some and will replace them when they arrive. I have changed all other elec. caps in the radio except the HV one on the AA board. I am at my wits end on this, I am hoping to get some ideas from you guys. I have all my readings written down. However, I may have made a mistake. If i need to check voltage or resistor values again, please advise.
Thanks

 

[troyota]

My receive HV seems to run about 280v

 

[troyota]

Ok, to keep this updated, Nomad (2600) replied on another forum to this question. his response below.

7 and 8 have 0v (should be 1.0v and 4.0 v respectively

Sounds as if the heater is dark in V502. Bad tube sockets are a common fault. If that one is either loose or oxidized enough to keep the heater from lighting up, those measurements are about what you would see.

And if you can see the heaters glowing in V502, that means I guessed wrong.

73

My response to his post below.

Nomad you were spot on. Thanks so much. I have already replaced 2 tube sockets in this rig. I just ordered more. I gently bent the tubes pins outward a little and the heaters came on. It was still quiet, then I heard a little ping or click and the receive had static. I guess it was the tube finally making contact. With the heaters on all the other voltages that were high are now reading correctly. Anyway, RX is dropping in and out. I am pretty sure it is a tube socket. I did check the solder connections and pins under the relay by pushing around on them gently with a plastic tuning stick and pecking on the relay top. This produced no change is RX coming or going. Now V501 on the other hand I can move the tube around a little in the socket and RX comes back for a bit. When the parts arrive and I get them installed I will report back on the progress. The saga continues!
Thanks!

 

[nomadradio]

Way cool! Shameless plug department. I sell replacement tube socket sets for that radio. One set for the audio board, one for the receiver board. Sounds like you have that in hand, but any other sockets that feel loose now will be causing intermittent dropouts soon enough.

Quirky fact. The 23-channel D201 was shipped via Greyhound bus package service. It was the gentlest package shipper ever was. You had to deliver to the bus station, but it rolled over the the baggage compartment on a hand truck, about 5 inches above sidewalk level. The customer claimed it at the destination bus station. No rough handling at all.

Sometime after 40 channels arrived this service was discontinued and they began using oops, er "UPS". Had trouble with tubes coming out of the sockets in transit. The fix was Loctite. No joke. If you encounter a 40-channel D201A that requires a lot of force to remove a tube, that means it hasn't been pulled out since the factory. The remaining surface contamination will make that socket troublesome later on.

Not hard to see why they went bust.

73