Traynor Tremolo

[trem]

Not sure how to trouble-shoot this.
I inherited this amp. Everything seems to work, except for the Trem. I replaced the Trem tube (is it V3) and I measured the heater and plate voltages. Those numbers seem to be OK. I do not get any V3 cat voltage regardless of the foot switch or the tremolo knobs positions. I guess this amp has some kind of LDR. I took a picture of it. It is located over in the corner of the chassis behind that aluminum shield. I suppose that could be bad, but I have no idea.
Any of you guys have any idea what I should check in the Trem Circuit to try and get this working.?
Thank You
I have the head and it is marked YGL-3A Mk

Traynor_YGL-3_YGL-3A_MK_III.pdf

http://i111.photobucket.com/albums/n...orygl3a002.jpg
http://i111.photobucket.com/albums/n...orygl3a001.jpg
http://i111.photobucket.com/albums/n...orygl3a003.jpg

[Chuck H]

If you have plate voltage and no cathode voltage the plate voltage should be wrong on V3b. No cathode voltage means the tube isn't doing anything. Check the grounds and components for the V3 cathode circuits.

[g1]

Please list the voltages you read on V3A and V3B. If your cathode voltage is wrong, then the plate voltage should also be wrong. A shorted cathode cap.(C14) could cause a zero volt reading on V3B cathode. Trem problems are commonly the LDR/neon or coupling caps such as the other 4 caps in this trem circuit (hard to read the numbers, C37,12,15,16?).

[trem]

Pin #
1 340
6 270
3 0
8 0
Pin 2 and 7 read Negative 28 & 33 respectively, depending on the position of the foot switch.
4-5 and 9 have heat.

[Chuck H]

Pin 1 is about right at 340V. That's 18V high. Considering any difference in mains voltage that seems right. There's no plate load. So the voltage should read the same as the supply node there. But notice that pin 6 is off by 65V. That's much more. The reason is that there is a plate load on that triode and no voltage is dropping across it because there is very little current. That means the tube isn't working.

The schem shows both cathodes grounded at the same point. But schems sometimes fudge this sort of thing. Still... Look for a fault in the ground lead or connection at the junction of R53, R57 and C14 and the chassis or board connection for that ground.

[trem]

10-4
I will start with that.
Thank You

[trem]

Pin 1 is about right at 340V. That's 18V high. Considering any difference in mains voltage that seems right. There's no plate load. So the voltage should read the same as the supply node there. But notice that pin 6 is off by 65V. That's much more. The reason is that there is a plate load on that triode and no voltage is dropping across it because there is very little current. That means the tube isn't working.

The schem shows both cathodes grounded at the same point. But schems sometimes fudge this sort of thing. Still... Look for a fault in the ground lead or connection at the junction of R53, R57 and C14 and the chassis or board connection for that ground.

At my level of understanding..... your analysis makes sense. There is no cat voltage, so the tube is not working.
I measured both of those resistors in circuit, and they are good.
Checked for continuity between resistors and ground, and from resistors to cathode and that is good.
I did not lift C14 to check its mF value. But I am thinking that even if it is open or shorted, the tube would still have cathode voltage of some kind. Am I wrong.? Should I try replacing C14.?
Even if the LDR were bad, the tube would still have some kind of cat voltage.?
Just trying to figure out where to go from here.......
Thank You

[g1]

You said V3B cathode resistor measured good, so C14 is not shorted. If the bulb side of the LDR were bad, V3A would not work, but you said you have voltage on the plate.
There is a 220K resistor connected to V3B (pin1). You said pin 1 measured 270V. What is the voltage on the other side of that 220K resistor?

[Tom Phillips]

A couple of additional suggestions:
1) Verify that the heater is working in the "Dead" section of V3. I know that you said you changed the tube and measured the heater voltages but we still need to insure that the voltage is getting all the way to the heater inside the tube. Check the tube visually. You should see two separate heaters glowing. A non functioning heater can be caused by a cracked solder joint or a bad tube socket female contact. If the heater isn't on then the tube will not conduct.
2) Make your resistance measurements of the plate and cathode resistors at the top of the tube socket. This insures that the whole path is intact. You are checking for bad or loose tube socket inserts as well as cracked solder joints as in #1.

HTH,
Tom

[Chuck H]

+1
If you were able to measure the resistors in circuit then C14 isn't shorted. When you measured the cathode resistors, did you simply measure across the resistor??? If so then try measuring from the cathode pins to chassis!!! If you don't get a reading there is a fault in the circuit somewhere. If you DO get a reading I'm baffled at how you could have continuity, though not shorted and no cathode voltage.

Also, try measuring plate voltages on V3 from plate to cathode!

EDIT: Sharing a simulpost with Tom... Do check that the filaments are glowing.

[loudthud]

Pin 2 and 7 read Negative 28 & 33 respectively, depending on the position of the foot switch.

Negative voltage on the grids will prevent the tubes from conducting. When the footswitch applies a short to the jack, the voltage on the grids should read closer to zero. Your footswitch should be a simple type with no LEDs. You should be able to measure the short/no short at the jack.

[J M Fahey]

Hey, guys, stop looking for open filaments and shorted cathode capacitors:

Pin 2 and 7 read Negative 28 & 33 respectively,

<-- red light blinking and sirens sounding.
No 12AX* family tube will "work" with such heavy negative voltage.
I guess, (don't have the schematic) that a heavy negative voltage is applied to 1 or 2 grids as a Trem mute method, and shorted to ground when unmuted.
The footswitch *somehow* is not doing its job.

EDIT: sorry Loudthud, just saw yours, answered straight from my email notification.
Well, at least we agree; hope Traynor agrees too

[trem]

Common to all you guys..... continuity and also that the tube is not "on" for one reason or another.
It only took 1 second to measure the heater voltage the first time, so I did it again and it was not there. More pressure on the meter probes brought it back. It seems I have a continuity problem in the heater wires. On their way to the AX7 socket they are old and are stretched pretty tight across the power tube pins and one of the chassis screws. They look a little brittle at Pin 4-5 as well.
Anyway..... it is a job to get them off the power tube socket and get some new heater wires installed. Will report later.
As Always .....Thanks Again

[Chuck H]

Once again I'll request the "slap forehead" emoticon! I guess I just read right past the -V grids when I saw there was no cathode voltage. Sooo... It also seems there is an intermittent fault in the heater wiring. The filament circuit and the switch on the footswitch jack both seem to need repair. And who knows what else after that.

[Tom Phillips]

Ditto on the slap forehead emotion.