Tram D201 low transmit and modulation

[Shockwave]

i swapped out one tube at a time starting with v600 then to v700s then to three, four, and five hundred. When i swapped out v602 and turned it on the meter on the tram went all the way to the right side. I went on swapping out and checking then when i swapped out v401, the meter went back to zero. other than that not much improvement.

The meter change is normal because you changed the meter tubes. There is an adjustment to rezero the meter after changing the tubes. When you say the transmit is low and so is the modulation, do you mean the carrier power is lower too? If so, by how much? This will help us to identify a common problem that could affect both the RF and AF sections. For example, if the problem is both RF and AF, I wouldn't even bother to consider AMC issues yet and would be looking at any resistors that feed B+ to both stages. The Tram likes to kill many of those 2 watt carbon resistors feeding the plate voltage to the tubes. You may want to swap the relay out too because there could be an issue with the transmit B+ being switched through a bad contact on the relay.

 

[klj2497]

i checked the 6.25 frequencies they are okay.

 

[klj2497]

on am the output is about 1 1/4 watts on the watt meter. on sideband it is about 1/2 watt swing.

 

[klj2497]

The v602 voltages are okay but the v600A,and the v601B, voltages are very low or negative voltage im starting at v601 in the schematic and checking the resistors

 

[Shockwave]

I would check the relay. It can cause all 3 of the tubes you mention to have weak or a loss of B+. Does pin 13 on the relay have about 400 volts on it in TX?

 

[klj2497]

Hi, i dont know the relay pin numbers so i swapped out the relay no change checking the voltages both A and B on both tubes were still the same low/no voltages.

 

[klj2497]

i am trying to locate Q600 toQ602, D601, R607-8-9. in the radio. the schematic shows them but they do not appear to be were they should be

 

[Shockwave]

i am trying to locate Q600 toQ602, D601, R607-8-9. in the radio. the schematic shows them but they do not appear to be were they should be

These parts are only used in the first hand wired version of the D201. They are the switching components to operate the VOX. If your radio has a VOX, these parts are buried on a terminal strip in the bottom of the radio.

 

[nomadradio]

One boo-boo Bennie made putting the Tram section of CB Tricks together. Has the VOX (hand-wire) version schematic posted. That's the diagram with your "missing" parts.

Has the 40-channel D201A diagram, but somehow failed to post the 23-channel circuit-board style radio. Most of those (not all) were made in Mexico.

But the 23-channel circuit-board schematic is missing.

He lost interest in updates and fixes before that got fixed.

Can't say I blame him.

73

 

[klj2497]

im learning how to use the equipment. today i hooked up the signal generator using the schematic, to the pin 13 the output of the mod board.i put the signal on 27.115mhz ch 13 and on the radio ch 13. and clip a rf probe to the antenna jack on ac im guessing about how to hook it up. when i key up on ssb it is the the same low signal.but when i unkey i hear the signal loudly in the speaker and then it fades away. i can repeat this on ssb and am the meter at the antenna jack reads with the signal on ssb .135vac and on am its 1.57vac. its .0vac without a signal. i am stumped

 

[Van Lifeson]

The 3-section C5 is wired with two sections in parallel, making it a two-section part, 80uf and 40uf.

We adopted the habit of using a 500-Volt part with two 100 uf sections. The voltage on C5 can spike up to 470 Volts or more when the tubes are cold. Once they warm up and begin to draw B+ current it falls to the 410-Volt range. I'm convinced the 500-Volt part will last longer.

Back in the day, a 450-Volt multi-section filter would have a "surge" rating above the so-called "working" 450-Volt rating. A look at the B+ on C5 with a 'scope shows a sawtooth-shaped 120-Hz ripple waveform. A DC voltmeter will average out the peaks and valleys of this ripple, riding on the 400-plus Volts DC. If the peak value of that ripple waveform pushes past 450 Volts, that's an unhealthy stress on the capacitor. A DC meter reading is only part of the picture.

Rather than try to find the right white/blue wire on S3C, finding that wire at B43 on the audio board is safer. Simply pulling that wire from that hole in the pc board will disable modulation limiting. If that's what's cutting your mike audio, pulling that wire would make a difference.

Too easy to find the wrong lug on S3.

73

Hello, is there a modulation limiter on the hand wired 201? Thanks

 

[Van Lifeson]

The 3-section C5 is wired with two sections in parallel, making it a two-section part, 80uf and 40uf.

We adopted the habit of using a 500-Volt part with two 100 uf sections. The voltage on C5 can spike up to 470 Volts or more when the tubes are cold. Once they warm up and begin to draw B+ current it falls to the 410-Volt range. I'm convinced the 500-Volt part will last longer.

Back in the day, a 450-Volt multi-section filter would have a "surge" rating above the so-called "working" 450-Volt rating. A look at the B+ on C5 with a 'scope shows a sawtooth-shaped 120-Hz ripple waveform. A DC voltmeter will average out the peaks and valleys of this ripple, riding on the 400-plus Volts DC. If the peak value of that ripple waveform pushes past 450 Volts, that's an unhealthy stress on the capacitor. A DC meter reading is only part of the picture.

Rather than try to find the right white/blue wire on S3C, finding that wire at B43 on the audio board is safer. Simply pulling that wire from that hole in the pc board will disable modulation limiting. If that's what's cutting your mike audio, pulling that wire would make a difference.

Too easy to find the wrong lug on S3.

73

Is there a modulation limiter in the hand wired 201?