Add Reverb/Echo?

[rcrmck]

My dad gave me an old Pritec M-203 PA amplifier that I want to convert to a guitar amp. I've never worked with tubes before, but I've been reading a lot about the conversion here, and other sites. I'm in a planning stage, and I am trying to find out if it is practical or even possible to add a reverb or echo to the amp. I suppose I could just tack in a digital effect, but I want to stay 'vintage tube' I guess.

The amp is really old. My dad says it works just fine. It has 2 microphone inputs and one other input that I'm not sure about. I can't find squat about the amp on the internet. It's labeled 70 watts and has the following tubes:
(2) 7868
(1) 6CA4
(2) 6EU7
(1) 7199

So, what do you think? Is there a way to add either echo or reverb without just slappin' on a pedal?

[Jazz P Bass]

Reverb add on

Yeah. It's possible.
(wasn't there a possum that said that?)
Pull up a Gibson schematic that has reverb & copy it.
Your looking at 1 1/2 12AX7's, a reverb coil for the driver, a reverb tank (that really should match the drive & receive circuit) & a couple of resistors & capacitors.
Time to put on that little striped engineering hat.

[Tubenit]

1 tube reverb

Sure you can add reverb to that. 6EU7 and a 12AX7 is somewhat similar with a different pinout.

Here is some information on adding a one tube reverb:
Adding 1-tube reverb

I have gutted 4 Bogens and rewired them to my liking and adding a one tube reverb to them successfully. Here is a schematic for one of them. However, this type of reverb insertion is somewhat interactive with the volume & you may need to increase the reverb pot as you increase the volume pot.
http://s28.photobucket.com/albums/c2...CBS-Oschem.jpg

Look at the Gibson Scout GA17RVT as an example of what was already mentioned.

With respect, Tubenit

[rcrmck]

That's great!
Like I said, I'm new to tubes, and I'm going to have to trace out a schematic for my starting point, and then work out a schematic for the final product based on what I learned about the conversion so far.

I guess I'll have to buy a reverb tank, but I should still be able to get two preamp stages on one channel with the reverb, using just what's in the chasis now, right?

[Jazz P Bass]

Reverb schematic

Here is a schematic from a Gibson.
Just be aware that the input & output coils on reverb tanks are all different.
Different tanks on the same circuit will sound, well, different.
Accutronics silkscreens a number on there tanks.
The numbers identify I/O coil resistance, decay time, which way it mounts, tank size, number of springs...
They have an excellent tutorial on there web site concerning how to drive & receive a reverb signal.
Goodluck
John G