Interesting tremolo...but I need some help to show

[m-theory]

I need some help posting a couple of images.  I've got top and bottom pics of a tremolo circuit from an old 6 watt, Garnet-built, Pax amplifier that somebody on another forum posted.  I've never seen a tremolo circuit with so few parts (13 total, including pot w/switch), and thought it worth sharing.  I'm a moron when it comes to posting images, however. 

[foxfire]

well you really just need to get signed up with a host site like Photobucket or imageshack. follow their instructions for loading your pictures. then you just copy the image code and paste it in you post here. that's the simplified version at least. rylan
 

[slacker]

If the images are already posted on another forum you can probably just link to them using the insert picture button .

[m-theory]

[Dragonfly]

You wouldn't happen to know any of the part "values", would you ?

[m-theory]

I'm working on that.  It's not in my hands, so I have to rely upon other eyes. 

[Dragonfly]

I'm working on that.  It's not in my hands, so I have to rely upon other eyes. 

Cool - I can probably get the resistors and make "educated guesses" on the other parts, but verification would definitely help.

I can trace this and do a basic project file tomorrow, so the more info, the better !

[George Giblet]

This is far as I can go without proper value:
http://www.geocities.com/george_giblet/effects/pax_trem_V10.png

Just a Phase Shift Oscillator with some form of voltage controlled resistance device.

There are few important things:
- What are the semiconductors?  The one near the middle of the board could be anything BJT NJFET PJFET
- What is the supply voltage?
- What does the rest of the circuit look like?  It appears the trem circuit  connects to some other circuitry needed for it to work.
   I've drawn one possibility but it could be connected just like the EA Tremollo
- Missing part values.

[Dragonfly]

This is far as I can go without proper value:
http://www.geocities.com/george_giblet/effects/pax_trem_V10.png

Just a Phase Shift Oscillator with some form of voltage controlled resistance device.

There are few important things:
- What are the semiconductors?  The one near the middle of the board could be anything BJT NJFET PJFET
- What is the supply voltage?
- What does the rest of the circuit look like?  It appears the trem circuit  connects to some other circuitry needed for it to work.
   I've drawn one possibility but it could be connected just like the EA Tremollo
- Missing part values.

OK..I guess I won't  do a tracing / project file .

[George Giblet]

> OK..I guess I won't need to do a tracing / project file

I think you should have a go too.
It was little disorientating tracing without knowing what the wires do, and without knowing the type and pinouts of the semi's!

[Dragonfly]

> OK..I guess I won't need to do a tracing / project file

I think you should have a go too.
It was little disorientating tracing without knowing what the wires do, and without knowing the type and pinouts of the semi's!

Honestly, in looking yours over it "seems" correct...at least from what I can gather from the info in the pics. Fairly standard trem type circuit. R7 looks like a 1M ...

[George Giblet]

Thanks for having a look anyway.

> R7 looks like a 1M

Quite possibly, it just doesn't look like the other 1M (unless the other one is 10M).

We'll have to wait and see what m-theory can dig up.

[GREEN FUZ]

I`m confused. There are 8 resistors on the schematic but I can only see 7 in the photos.


I believe R2 might be a 10M and R6 looks like a 26k to me. Mind you my eyes are going funny looking at the lo-res pictures.

[George Giblet]

> I`m confused. There are 8 resistors on the schematic but I can only see 7 in the photos.
See above post.

The circuit on the PCB won't work as is.  It connects to the amp circuit and interracts with it to produce the tremolo.  That part of the circuit isn't available so I've put dummy circuit in there as a possible.  On the schem above the dividing line is AMP and below is Trem PCB.

[letsgocoyote]

Well interesting!

It's funny, I actually saved both of those pictures from HC with the intent of tracing it as well.  great minds think alike!

[m-theory]

A couple more pics...still working on parts codes

[m-theory]

the one top right is 015
22/
25v

[George Giblet]

Thanks for the values.

I removed the old schematic and updated it:
http://www.geocities.com/george_giblet/effects/pax_trem_V11.png

No changes to circuit "shape" only part values have been updated.   The pot resistance is still not known - the value is my guess.  I'm not 100% on how the resistors are wired to the board form the input socket.  I'm assuming a single 47k but the input socket could be wire with 2x47k in parallel.

I'm pretty sure the power amplifier is just an LM380.  The Garnet PAX is on the page below and is a 2.5W amplifier (not 6W). 

http://www.garnetamps.com/stencil.htm

That power would be into say an 8ohm speaker? So perhaps it uses a 15V supply rail (when loaded).  Most likely say a 12.6VAC rms transformer.