Tremolo Help

[C Moore]

Oh Man -
You are going to hate me.
In my own defense...I got some weird computer virus a while back...I could not open any kind of PDF or schematic. I just got it fixed about a week ago (had to do a restore on my comp two times) which Is why I have come back with this after so long.
Looking back NOW...I see I DO NOT have either of those grounded caps.
Not the pair approaching the power tubes.
Not the pair in the bias circuit.
I hate to ask a stupid question...but I will....Is that why my Trem is so weak.?
I will also scope the power tune grids.

[C Moore]

The Trem is On.
That 130k is jumped/shorted.
With the Intensity on full...I see about 40VAC p to p.
I think my problem is somewhere/somehow in the speed pot.
I get no amplitude unless the speed is almost full on.
If somebody is playing a guitar...Intensity on 10...Speed on 6...there is No Trem.
There is no trem until the speed pot hits about 7-8.
And when it does come on...the speed is REAL fast as you can imagine.
Thanks

[martin manning]

Sounds like the oscillator won't start or run below that speed setting. You can confirm that by scoping the driver stage plate when the speed pot is turned down.

If the oscillator isn't running, one thing you could try is to put a huge bypass cap across the Rk to maximize the gain at low frequencies. Try something approaching 500uF.

[C Moore]

Put the scope on Pin 5 of the oscillator...where that 130k resistor is.
Yes, that is exactly what is happening.
The speed pot has to be at 8-9 before the trem will come on.
I can try a 500 mic cap. If that works I could order one that is a smaller value...10-15 volts I guess.
All I have in that value are 400-550 volt....too big physically.
But if it does work...I guess that is OK.
Do you think there is a "better" solution.? Something like Tubeswell was suggesting.?
One problem is real estate.
I am really squeezed into this chassis. I had to build the bias circuit on the "outside" of the chassis...just to make it fit somewhere.
This is what my build looks like...as far as space available. I would need a trem circuit that I can run with the single 6SL7.
BTW.....did you see my previous post about those caps I left out.?
Thank You

[martin manning]

I don't think that those missing caps would reduce the trem effect, they are more about smoothing the bias voltage, but definitely add them. Did you get much trem effect when the oscillator runs with 40V p-p on the power tube grid?

[C Moore]

Yeah. the trem is fine...just way too fast.
Probably was not real clear.
It will not come on until 8 on the speed pot, but it also dies as you turn the speed down past 8.
So the only trem available is Real Fast.

[martin manning]

So there is enough drive, you just need to get it to run slower. Try that big bypass cap.

[C Moore]

So there is enough drive, you just need to get it to run slower. Try that big bypass cap.

Do not know what to say other than Thank You.
Thank You TAG
and Thank You Martin Manning.
I now have a wonderful 2x6K6 amp head, with beautiful Tremolo.....that I will be lucky to sell for the 250 dollars that I paid Peter Mather for the head box.
Thank You Martin and Tubeswell for sticking with me through all of this.
Cannot tell you HOW relieved I am.
Was really starting to think I had a complete loss on my hands.
I am specially handicapped by the fact that I Do Not play guitar.
Thanks CBASS for helping also.
Anyway.....
Thank You SO MUCH

[martin manning]

Well alright! Bias varying tremolo with separate fixed-bias adjust- first one I've seen ;^). You're welcome, and it was an interesting ride!

[C Moore]

I hate to even ask...but if you guys had built this amp without the trem...and then wanted to add Tremolo to it.....what Trem circuit would you have put into this amp.?
Thanks

[martin manning]

Nothing wrong with the 6SL7 oscillator, and bias-varying term sounds better than the opto-bug thing IMO. BTW, do you have three 120k resistors in the phase shift network? One of them isn't marked in the Joe Piazza Ampeg schematic.

[C Moore]

Oh man.....am I missing a component.?
I believe I built the Trem Circuit as I have it shown on my schem.
There is a 130k, then the caps, another 130k and then a 270k off the grid to ground I believe.
Should I have another 130k in there some where.?
I will have to look ay my board.
Thanks

[C Moore]

Hey Martin -
If I understand you correctly.....Joe shows 2x120k with caps and the Speed Pot in between, and then a grid leak resistor (I guess) but it does not have a value.
THAT resistor is what I have as a 270k... or there abouts.

[tubeswell]

I'd maybe start with all the fixed resistors at 120k or some other 'same' value like 150k or 180k , and then start tweaking. You vary the speed by either varying one or more R or one or more C in the R-C network. But if you start with all of them the same, then you can start to C where u R.

[martin manning]

Hey Martin -
If I understand you correctly.....Joe shows 2x120k with caps and the Speed Pot in between, and then a grid leak resistor (I guess) but it does not have a value.
THAT resistor is what I have as a 270k... or there abouts.

I'm guessing the unlabeled one was supposed to be a 120k like the other two.