Receive problem with Tram D201

[cricketsman05]

Hello everyone, I have a 201 that I have been tinkering with for a couple of years now. From all reports the radio sounds great but there is a small problem with the receive. This radio has just received the 100,000 mile tune up from Barkett with all the caps, a load of resistors, relay and some tubes being replaced.

The problem is this. When you first turn the radio on the radio runs great but then after 2-3 minutes at most the am receive drops out. Lets say at first that you had a noise level of 5-6 when it drops out it goes to 1-2 S units. You can still hear the strong stations but the distant stations (11 miles plus) cannot be heard any longer. The radio still talks the same. When the receive drops out it the SSB still works as normal. The receive isn't effected in SSB.

Sometimes keying the mike will bring the receive back for a short while but it will not stay long. Sometimes it will just come back on its own but will not stay long. Banging on the radio has no effect. I've looked around, poked around and can't find anything lose or anything else.

My theory is that something somewhere is heating up and breaking down. Although 2-3 minutes seems a short time for something to heat up.

So there you have it. All in all it is a great radio. I love the old tube stuff. I'm not opposed to another trip to Barkett's but right now my wife really doesn't like old vintage radios. Last trip was pretty costly.

So now I am open to any and all ideas.

Thanks

[cbrown]

Did you call Greg?

[Deleted]

I saw that once on a D201A, and I think a 470K resistor opened. It may not be that resistor, but I would check. It was a 1/2W size. I would measure them out. Greg likely replaced all the power resistor and anything that measured way out. It is possible the one he did not replace, may have gone bad. It happens. I have seen Greg's work, and he is top notch.

[cricketsman05]

Yes, I did call Greg and he said he would be more than glad to look at it. I agree, Greg does excellent work. I have no problem with his work. I highly recommend him. I am simply trying to avoid another trip over there.

This problem was there before the radio was serviced and is still there.

I will try to look at the 470K resistors.

Thanks

[Sandbagger]

I would concur. I have reworked a bunch of D201's and all of them had some amount of resistor value change on those 1 and 2 watt carbon resistors that run pretty warm. On one D201, that had weak AM receive, I had a 100K Ohm resistor on the 2nd oscillator that had changed value to well over 1 meg Ohm and reduced the plate voltage to the tube, and the resulting weak oscillator output, which made the receiver very weak.

As much as I really love Tram radios, and the D201's especially, they were not designed well, in the power supply department. The radio really needs a separate 150V supply section that can feed all the small signal tubes, without having to sink so much current from dropping down from the main 400V supply. That heat is what causes the greatest majority of issues in the D201.

[FIXR]

Since it effects the AM receive only, I would check around tube V301. The 6BK7B, with the crystal next to it. Check for either a loose tube, bad or loose crystal or a bad connection where the large 100 K resistors solder to the board.

Alan

[Deleted]

I only worked on one, and that was enough for me. As good as they sound on the air, they are a horrible designed piece of junk, between the heat problems and the channel selector. I wouldn't take one for free.

[Sandbagger]

Dec 29, 2011 17:39:30 GMT -5 @vinnies said:

I only worked on one, and that was enough for me. As good as they sound on the air, they are a horrible designed piece of junk, between the heat problems and the channel selector. I wouldn't take one for free.

Well, if someone offers you one for free, just take it and give it to me......

[cbrown]

Dec 29, 2011 21:28:00 GMT -5 Sandbagger said:

Well, if someone offers you one for free, just take it and give it to me......

And if they have two...

[gator7]

I will take the other one. ;D

[Deleted]

I will. I promise !

[40sx]

Could it possibly be dirty or pited contacts on the relay. I've worked on many radios that had problematic relays.

Dennis

[cricketsman05]

Jan 3, 2012 8:16:12 GMT -5 40sx said:

Could it possibly be dirty or pited contacts on the relay. I've worked on many radios that had problematic relays.

Dennis

It may be dirty contacts on the radio side, the relay is new and I have tried others that works fine. I believe it is on that board somewhere since keying the mike makes it go and come. I am hoping that I may of found the problem but will not know for sure until I get back home and spend some time with it. I have to drive a truck to pay for all this stuff.

I'll post more later.

Thanks,

73's

[cbrown]

It could be a slightly broken trace on the board, too. Look around the board, especially by the mounting screws.

Good luck, and keep us informed.

[cricketsman05]

I still haven't been able to locate the problem. Radio still transmits great. Everyone I talk to says the radio sounds awesome. Just can't find the receive problem.

Anyway, I notice in the Sam's Photofact CB-88 on page 107 that there is a chart outlining resistance measurements for the tubes in the radio.

Now my question of the day is this. Are these measurements taken with the tubes out of the radio or with the tubes in the radio?

Also, it is my understanding that the tube pin numbers run clockwise from the knockout. Is this correct?

Thanks,

73's

[Sandbagger]

Jan 21, 2012 17:27:38 GMT -5 cricketsman05 said:

I still haven't been able to locate the problem. Radio still transmits great. Everyone I talk to says the radio sounds awesome. Just can't find the receive problem.

Anyway, I notice in the Sam's Photofact CB-88 on page 107 that there is a chart outlining resistance measurements for the tubes in the radio.

Now my question of the day is this. Are these measurements taken with the tubes out of the radio or with the tubes in the radio?

Also, it is my understanding that the tube pin numbers run clockwise from the knockout. Is this correct?

Thanks,

73's

Can't help you there. I've never measured tube resistances, and can't for the life of me figure out how it might help or how you accurately could do it. Obviously the tube only conducts when it is powered, but you can't directly measure resistance on a "hot" tube (300V into a VOM set on resistance won't end well). So if this is to measure the circuit resistance without the tube, it makes more sense, but you're not measuring the tube, only the stuff around it. I've had better luck measuring voltages, and signal tracing.

[cricketsman05]

Signal tracing is a little beyond my expertise at the moment. Although I do have a TEK 2246 but all I know to do with it now is look at AC/DC voltages. How boring is that? lol No signal generator either. It is on the list though but will probably come after the new RC engine. lol Anyway, I guess it makes more sense to measure the resistance with the tube out. I guess they put that chart in there for some kind of reason. Or maybe not. Who knows. Certainly isn't me that is why I asked the question.

Thanks,

73's

[spitfire441]

I have used the resistance charts in the Sams to trouble-shoot tubers...anyway I tried with tubes in and out, I don't think it makes a difference. No power to the radio, your only checking the components around the tube, not the acutual tube circuit. I have found shorted caps this way. Do not power up radio while doing this, and you can leave the tubes in.
Spitfire 441 AA3RE

[cricketsman05]

I checked the voltage on tube V300 6BQ7A the RF amp.

Schematic shows I read

Pin 1: 304 256
Pin 2: 148 105
Pin 3: 157 128
Pin 4: 6.3 0 --- I don't understand this reading, tube is lit up.
Pin 5: Gnd 0
Pin 6: 157 128
Pin 7: .37 .21
Pin 8: 5.56 2.25

I don't understand why the heater voltage would read 0 and the tube still be lit up. I checked it several times and there just wasn't any voltage there.

All of the voltages are lower on all pins for some reasons.

Suggestions please.

Thank you,

73's

I pulled the bottom of the unit and checked all the heater voltages. They all read 6.1 - 6.2, should be 6.3. Close enough, I guess.

[Sandbagger]

Jan 22, 2012 12:03:11 GMT -5 cricketsman05 said:

I checked the voltage on tube V300 6BQ7A the RF amp.

Schematic shows I read

Pin 1: 304 256
Pin 2: 148 105
Pin 3: 157 128
Pin 4: 6.3 0 --- I don't understand this reading, tube is lit up.
Pin 5: Gnd 0
Pin 6: 157 128
Pin 7: .37 .21
Pin 8: 5.56 2.25

I don't understand why the heater voltage would read 0 and the tube still be lit up. I checked it several times and there just wasn't any voltage there.

All of the voltages are lower on all pins for some reasons.

Suggestions please.

Thank you,

73's

I pulled the bottom of the unit and checked all the heater voltages. They all read 6.1 - 6.2, should be 6.3. Close enough, I guess.

Did you switch the meter to AC when you tried to measure the heater voltage? Heater voltages are AC, while the rest are DC.

Also, I looked back over your original description of the problem. You claimed that the receive drops down after a period of time but only on AM,not SSB. Is that correct? If so, that narrows down the problem area to the AM I.F.,since the front end, and first mixer stages are common to both modes and if they're working on SSB, then they're not the problem. I did have a problem in my D201, where AM receive was a bit weak, and the problem turned out to be R322, on the 2nd receive oscillator. It's supposed to be a 100K resistor, but had changed value to over 1 Meg, which caused reduced voltage on the plate of the tube, and reduced oscillator output,and correspondingly weak AM receive.

[FIXR]

I would look around V301, the AM receive oscillator. When the receive drops out, pull the crystal out next to the tube and then reinstall it. If the receive comes right back in, then that could be your problem.

Alan

[cricketsman05]

I didn't switch the meter the first time. When I did switch it all the heater voltages were ok. The SSB works fine RX & TX. Am TX is great. AM receive is weak. It use to go and come some but lately it is out nearly all the time. The only thing I can do to bring it back VERY accasionaly is key the mike and hammer the modulation. Very seldom does it come back now. I will look at the AM I.F. and R322.

Thanks,

73's

[40sx]

Resistance measurments are performed with the tubes in the radio and the radio turned off and un-plugged, just in case.

I'm experiencing "no recieve" problems in one of my D201a radios, just on the crystal side until the radio warms up for about 15 minutes. I believe it may be a BA board problem, I really haven't checked it yet.

Dennis

[cricketsman05]

I swapped the crystal out with two other different cystals and it didn't change the RX any. So unless all 3 cyystals are bad I would say the crystal ins't the problem. I will dig more into it this weekend.

Thanks,

73's

[cricketsman05]

When I arrived home today the first thing I did was turn the radio on. The receive was out. Keyed the mike twice modulating both times and the receive came back in. Left the mike alone for 3 hours now and the receive is still working great. But I am sure that when I key the mike the receive will drop out. That seems kind of weird. I am going to try to get some voltage measurements before I key the mike and the receive drops out.

Thanks,

73's


The radio ran for 5 hours without any problems. RX was great. Until I keyed the mike. Then it drops out.

[Sandbagger]

Jan 27, 2012 16:53:25 GMT -5 cricketsman05 said:

When I arrived home today the first thing I did was turn the radio on. The receive was out. Keyed the mike twice modulating both times and the receive came back in. Left the mike alone for 3 hours now and the receive is still working great. But I am sure that when I key the mike the receive will drop out. That seems kind of weird. I am going to try to get some voltage measurements before I key the mike and the receive drops out.

Thanks,

73's


The radio ran for 5 hours without any problems. RX was great. Until I keyed the mike. Then it drops out.

It sure makes it sound like the relay (or the relay socket).....