tremolo circuit

[J Rindt]

How do i know, or what does it take to make a trem circuit work.?
I basically have a Fender AA1164 Princeton with 6SL7 pre, trem and PI tubes, and 2x 6K6 power tubes.
There is about 320 VDC on the 6K6 plates and 308 on the Screens. I do not hear any effect of the trem circuit.

1. I am using the trem foot-switch to interrupt the ground connection to the trem tube cathode. Is it OK to turn the trem On/Off in that manner.?
2. The B+ for the tremolo is from the screens and is at 308 VDC.
When the trem is "On".....i have 2.2 VDC across the Cat, and 188 on the plate.  When i connect the ground (100k resistor) of the pot. i see B+ variation of about (it is hard to tell with my DMM) 20 Volts. I can kind of see it go from about 170 to 190...back and forth.

What do i need to do to get the Trem to operate properly.?
Thank You

http://el34world.com/charts/Schematics/files/fender/Fender_Princeton-Reverb-AA1164-schematic.pdf

[sluckey]

1. I am using the trem foot-switch to interrupt the ground connection to the trem tube cathode. Is it OK to turn the trem On/Off in that manner.?

WHY??? That'll work but may be slow to start. If you are gonna build a PR circuit, then wire the footswitch according to the PR schematic.

When i connect the ground (100k resistor) of the pot. i see B+ variation of about (it is hard to tell with my DMM) 20 Volts. I can kind of see it go from about 170 to 190...back and forth.

That 100K needs to be permanently connected to ground. The back and forth B+ variation (I'm assuming you mean plate voltage?) is your sign that the oscillator is working. Change the speed pot setting and the plate voltage variation will change also.

Are your 6K6s fixed bias just like the PR? Do you have the tremolo circuit connected to the 6K6 grids just like the PR?

PS... I just realized your trem tube is a 6SL7. You will need to use different value components than the PR's 12AX7 circuit. Look at this Ampeg J12B for a circuit that I know works well with 6V6s, either fixed bias or cathode biased.

     http://sluckeyamps.com/RCA/Ampeg_J12B.pdf

[J Rindt]

Hey Sluckey -
This was a different amp at one time, and the FS was already wired that way...so i just left it on the Cathode. I was not sure if it would "matter", so that is why i asked. I will change it to the Fender schem if it is complicating the trem effect.

The speed pot (i forgot to mention) is only jumpered in at this point. I did not want to hard wire it before i knew it would work. Mostly i was unsure because i am using the octal tubes.
And yes, i am seeing the plate voltage fluctuating.

Yeah...fixed bias at the 6K6 grids, just like the Fender schem. I have a dual 250k Intensity Pot because my bias is also dual so i can adjust Neg Grid Volts for each 6K6.

I will take a look at the Ampeg you suggested.
Thank You

[sluckey]

How much negative voltage is on the grids of the 6K6s? If it's about the same as you would find on 6V6 grids, your trem signal may be too small for a strong trem effect. If you find that's your case, then replace the trem cathode resistor/cap with a 5mm red or yellow LED to increase the trem signal.

I'd love to see a complete schematic of this amp.

[J Rindt]

I wish i knew how to draw a schem on my computer.....Not a computer person at all.
I think i have this amp all drawn out on paper. I will shoot some pictures of my schems and post those.

I am probably running these tubes a little hot.?
They are at about 7.5 Watts.
Across the 1 Ohm cat resistors, in round numbers.....24mA at 315 VDC.
Have about -32 Volts at each 6K6 grid.
Thanks Again

[J Rindt]

How much negative voltage is on the grids of the 6K6s? If it's about the same as you would find on 6V6 grids, your trem signal may be too small for a strong trem effect. If you find that's your case, then replace the trem cathode resistor/cap with a 5mm red or yellow LED to increase the trem signal.

I'd love to see a complete schematic of this amp.

OK...wish i could have gotten back to this sooner.
The only LED i have (i can order the right ones) have about a 1.8V Drop. I have not tried them yet...wanted to see if that is what you are talking about first.
Lets see if my pictures show up.
Like i say, this is pretty much a straight Fender Princeton. I do not have (i can make one) a drawing of the Power Supply.
I took a few gut shots. The reservoir cap is on the main board. the rest of the PS circuit is shown on the other side of the chassis.
The stuff between the trannies is for the Neg Bias Supply.
Thank You
http://imgur.com/uJ8Fmhm
http://i.imgur.com/ZnSmdIt.jpg
http://i.imgur.com/fQTsoGs.jpg
http://i.imgur.com/QKlTCDu.jpg

[sluckey]

The only LED i have (i can order the right ones) have about a 1.8V Drop.

That will work.

[kagliostro]

Ahem ... where is the Tremolo oscillator, is it like on the original schematic ?





Franco

[J Rindt]

Sorry. I am not TRYING to make this hard. 
I had originally used a different circuit from an Ampeg. It was hard to cram it all in this little chassis. So i switched it to the Fender Princeton that uses just one half of a AX7/6SL7.
I did not "bother" to draw that out, because it is available in The Schem Library.
Thank You

http://el34world.com/charts/Schematics/files/fender/Fender_Princeton-Reverb-AA1164-schematic.pdf

[kagliostro]

Based on the improved oscillator by Sluckey I planned this version of LFO that I want to use on a custom AA764 I'm planning



if you prefer this is a shrinked version



and here a shrinked version with LED (strongher signal, but may be too much being used both triodes)



I payed attention on drawing the schematic and the layout, but a revise will be better

Ciao

Franco