Vibro-Champ trem issue

[sluckey]

Question, can I just leave that RED LED in place of the RC? Looks cool.

Absolutely. I like to mount them in a bezel on the front panel. Real eye candy!

[angelodp]

Martin, yes I do have some leaky DC, gotta track it down as it's getting on my Guitar pot, very scratchy.

What's the best method, remove all tubes and check for DC on all the caps?

A

[martin manning]

Ok so when I swapped in the RED LED I forgot to solder in the 1M, now it's in and the LED blinks and it's all working....I have Trem so thanks Steve and Martin. It seems the 10uf cap was blitzo.

Where was this 10u cap?

[angelodp]

Sorry my error, it was 25uf at the Oscillator cathode.

Interesting issue has arisen. Amp plays, all good and Trem, some scratchy on Guitar pot.

V1 pin 3 - now shows less than 1v its .003v on the cathode. I changed out that 25uf cap and checked the
R and its good?? Swapped in a new tube... same. (corrected voltage .003VDC).

Very strange only .003v on cathode of V1? Amp plays.

I also changes the dropping R back to 10k per the schematic.

[Stevem]

Any signs of dc voltage on pin 2?

That will make your guitars volume pot scratchy, and a dc voltage there can only come from a bad tube or a bad tube socket.

Your cathode voltage being that low is a problem also since even with a weak tube you should see .600 volts.

[sluckey]

V1 pin 3 - now shows less than 1v its .003v on the cathode. I changed out that 25uf cap and checked the
R and its good?? Swapped in a new tube... same. (corrected voltage .003VDC).

Is your meter mistakenly set to measure AC volts? What voltage do you measure on V1 pin 8? Or 6V6 pin 8?

[angelodp]

V1 pin 3 - now shows less than 1v its .003v on the cathode. I changed out that 25uf cap and checked the
R and its good?? Swapped in a new tube... same. (corrected voltage .003VDC).

Is your meter mistakenly set to measure AC volts? What voltage do you measure on V1 pin 8? Or 6V6 pin 8?

Meter is set correctly to DC. On V1 pin 8 - 1.6VDC. /. 6V6 pin 8 oscillating 128-150VDC

V1 pin 3 - .003VDC??

Amp works and Trem works??? What is causing that cathode to be so low? Swapped out cap and checked R, all good.

[angelodp]

Any signs of dc voltage on pin 2?

That will make your guitars volume pot scratchy, and a dc voltage there can only come from a bad tube or a bad tube socket.

Your cathode voltage being that low is a problem also since even with a weak tube you should see .600 volts.

I am seeing negative .2 VDC on pin2

I swapped out tubes and still same voltage??

[angelodp]

Grrrr.

Ok, pulled out the 1.5k, measures fine.... replaced it anyway. In goes the 25uf - reflowed all the connections with a bit of flux.....

Finally getting 1.6VDC and all is well in VC land.

I do think that these turrets from AE are not great. I should have gone with the Hoffman turrets.

Anyway.... sounds real good, DC is off my guitar pot, trem works.

Bias is a bit up at 16watts so I'll tackle that next with a 680ohm R

Thanks guys.

[Stevem]

So many times it always boils down to the basics, correct wiring and well flowed solder connections.

I very hot iron is your alli, I keep at work at no less then 650 degrees or more dependent on the tip size I am using.

This allows me to get in and out fast when soldering Semiconductors, yet always get a perfect solder joint.

[sluckey]

Here's an example of how I mount the LED on the front panel.

[angelodp]

Hey Steve, very nice setup. Thanks.

SteveM, yes so true, and I was trying to be extra careful.

One last thing showed up. With the NFB switch engaged, I was getting that squeal thing. Thanks to a previous thread, here, I found the solution easily and swapped the primary wires on the OT, now no squeal and NFB switch works great, also have a RAW pot. I lowered the PD with a 680ohm resistor, down to 13watts....I can live with that. I am there.

Thanks All.

[angelodp]

Steve, quick question. With the RED LED is there any issue with ruggedness and life of component?

If we compare the overall intensity of the Trem with 25uf/4.7k vs Red LED, is the sound equivalent?

Merlin indicates maximum gain and minimum impedance, so I reckon this mod will produce a more pronounced
effect.

A

[sluckey]

Steve, quick question. With the RED LED is there any issue with ruggedness and life of component?

I only have about 10 years experience with the LED in this particular circuit and I'm not rough on my amps. I actually got this idea from the Valve Wizard. I've had no issues. However, I've got about 50 years of experience with LEDs in various military, FAA and industrial equipment. Literally thousands of LEDs. I've never had to replace one. As for general ruggedness and life expectancy, just look how LEDs are taking over the lighting industry. General lighting, indicators, automobiles, even pinball machines! That should speak to general ruggedness and life expectancy.

If we compare the overall intensity of the Trem with 25uf/4.7k vs Red LED, is the sound equivalent?

The LED will produce a much larger trem sine wave than the RC. This usually means a stronger trem effect, but some circuits may not be able to take advantage of the larger trem signal. A side effect of producing a larger sine wave is that you can have a wider speed range before the LFO circuit drops out (quits oscillating). This is more noticeable on the low frequency end, which means you can have a slower speed. I like that. You can easily compare the LED with the RC using a SPDT switch. Use your ears to monitor, but if you have a good meter that can measure voltage of a 5Hz sine wave, then compare the voltage too. Of course, a scope would give you a very good comparison.

[angelodp]

Copy that, thanks for the in depth response.

A