Tram D201 non hand wired rebuilding

[troyota]

Hello,
I have a D201 that I am recapping and going to put in new resistors. The 100K tuneup as Nomad calls it. I have most of the electrolytic caps replaced. I have realized that I did not get the yellow caps located on the boards. I think they are .22mfd, 250v and appear to be paper. I cant remember. Anyway are these a known problem? Should they be replaced too? Another question I have is about pin voltage on the tubes. On pin 6 of V302 I have full voltage 436v. I also have 436v in front of R320. I know R319 and R320 are in series and they drop the voltage to pin 6. When I check the resistance of them I have 22k ohms on each resistor. I am checking them in the circuit. According to the schematic and the parts list this is correct. So is there another reason why voltage would be that high there? Those have been replaced sometime before with what appears to be 5w versions. I intend on replacing them, but it seems they should be working. Just to add I have low tx and rx on SSB. Not sure if they are related.

 

[nomadradio]

The yellow caps are not a failure risk, as a rule. Only the electrolytics.

And all the resistors that overheat and quit.

Tube sockets become a bigger part of the picture every year that goes by.

Pin 6 of V302 only drops to the voltage on the schematic (110 Volts DC) when the VFO is selected, "Man" mode.

The higher reading is correct when the VFO is off, using Xtal mode.

Low SSB receive frequently turns out to be a toasted pair of resistors that feed pin 5 of V500, R503 and R504. They never last very long until the 1-Watt gets upgraded to a 2-Watt and the 2-Watt gets upgraded to a 3 or 5 Watt resistor. Wirewound is okay, it's just a DC circuit with no RF in it.

Same applies to V501, has the equivalent two resistors on pin 5, R507 and R508. Also, R504 and R509 can get damaged by a bad 6BA6 some time in the last 40-plus years.

If C511 did not get changed, this can reduce SSB receive.

And alignment of T500,501 and 502 are important. Simple enough to peak for max noise on the antenna. Turning down the RF Gain will make the peak setting of each coil easier to see on the meter.

Low SSB transmit tends to be the electrolytic caps on the Balanced Modulator board. If you have changed them, double-check the polarity. The pc board is NOT marked in a way to remind you which way each one should be turned.



73

 

[troyota]

Yep that was it. I had checked it in crystal mode. In manual mode I have 114v. So now checking other pin voltages. I am showing -44v am rx and tx on pin 5 of v701, and -31v ssb rx and tx no modulation. In manual or crystal mode. It looks like that should be -.5v

 

[troyota]

Chris, does T500, 501, and 502 just have one slug in them? All the other tall tuning cans have 2 slugs. These only have one in this rig. I have a really slick 201a waiting its turn for the overhaul. I guess I could open it up and see. That is if they are the same. I have double and triple checked the caps I have installed on the BM board, the polarity is correct. I have the BM board, chassis underneath the boards, receiver board, and most of the BA board finished No change yet...stay tuned.

 

[nomadradio]

Bias is normally set in receive mode. Trimpot R708 is set for negative 25 Volts at the junction of R709 and R710. Using pin 5 of V701 works, too. Just don't key the mike with a meter probe still touching V701 pin 5.

R707 is set for negative 35 Volts in either USB or LSB receive mode.

And yeah, the three "five hundred" numbered cans have only one tuning slug each.

Uh, the 40-channel schematic shows 0.5 Volts on pin 8 of V701. The 40-channel radio uses a resistor between pin 8 and ground. The 23-channel radios simply connect pin 8 of the final directly to ground.

Pin 5 should never read 0.5 Volts. Never.

73

 

[troyota]

Ok, thanks. I seen where i got mixed up. I was looking at the 201A schematic. Where the line crosses over pin5 going to pin8 to say .5v, I thought it was pointing to pin 5. Does it matter what mode is used when setting R708? SSB or AM? Oh, what would happen if one was to key the mike while touching pin 5 with a meter probe...not saying I did that or anything...just asking for a friend...

 

[nomadradio]

The 3-foot wire leading from your meter probe is a big feedback antenna. Pin 5 is the input to the final tube. Keying it with a 3-foot antenna wire connected to the tube's input will cause it to oscillate if you key the mike.

Might not cause anything to break.

Bias is set separately in SSB and AM as mentioned above. While receiving.

73

 

[troyota]

I see, I never even thought of creating an antenna with it, makes perfect sense. Sorry about the repetitive R708 question. It was late and I was tired. Looked this morning at the schematic again and it was clearly right there. R708 is the AM setting. Thanks again. Looking over my notes, and voltage readings. I have a couple that may be of concern. V302 pin1 is 121v usually we dont want that one below 130v, correct? My first suspects were R310 and R311, but after checking, R310 is 46.9k and R311 is 6.8k measured in circuit. Now on V301 pin6, I have 173v Whoa! I just rechecked it and that reading is correct. I think I read somewhere that should be at least 85vdc and not much over 100vdc. R307 maybe? Seems like I read somewhere that should be replaced with a 2W resistor, is wirewound ok, or does it need to be a metal oxide? (r307 checked at 109k in circuit)

 

[troyota]

All electrolytic caps and large carbon resistors changed. Still low SSB tx and rx.

 

[KneeBiter]

Did you change the caps on the balance modulator board?

 

[troyota]

yes. I changed them on all of the boards and the ones underneath too. I cleaned the pins on the BM and BA boards. Reflowed the plug ins for the BA board and the Aux audio board, and reflowed the wires at the top of the Aux audio board.

 

[KneeBiter]

I had to rebuild the modulator board on one of my hand wired. I replaced all caps, transistors, and diodes. It fixed my very low output. I was lucky enough to have another radio to swap boards. The board fixed it so I rebuilt it instead of trouble shooting.

 

[troyota]

I have another modulator board, but its from a D201A. and is different, I had thought of that too. I get about 5w swing on SSB, lower channels are less. Doesnt matter if its in crystal or manual. ALC is set for the best swing. looking from the front, from full counter clockwise to about mid way dont change it much. When i get past that i dont get hardly any swing. AM i am getting a 3.5w key with about a 12-15w swing. I am using a handheld d104 m6b. Thanks guys for the ideas.

 

[troyota]

thanks kneebiter and nomad for your suggestions. i think i will set this one aside for a few days.I know the d201 is not known for good ssb. so i guess i can live with it as it is. the AM side does alright. thank you so much.