MX-201 feedback issue

[multivox]

I've got a multivox mx-201 tape echo. It's repeat rate knob(or intensity on the space echo) does not make a difference at all. It will only have 1 repeat whether the setting is 0 or 100%. I'm just wondering what could cause this, I have cleaned the entire machine, very thoroughly, and have ordered a demag and new tape loop. I just feel like this will not work. Do you have any ideas?

heres a schematic Mx201 Mx312 Schematics

[Jazz P Bass]

Here is the schematic.

Good luck reading it.

The Repeat function comes off of the wiper of the Repeat control at Pin 2.
Check the control with a meter to see if it does sweep the wiper up & down (as it is rotated) 50K to ground.

[multivox]

Pot tested our fine. I also replaced the ic near the pot to no avail. Thinking of sending it to orbitelectronix.
Any final ideas?

[Jazz P Bass]

What ic # was that?
I do not recognize '7506P'.

Do you have a guitar signal at pin 3 of that ic?

The signal coupling capacitors (electrolytic) need to be checked that they are passing the signal.

[multivox]

Yea the 7506. Which are the signal caps? The ones near the ic?

[Jazz P Bass]

Look at the schematic & follow the signal.

The 3 7506 opamps on the far left all mix into the first '1/2 1458 opamp (nice of them to label the ic's)
From there the signal leaves at pin 10.
Then down to the 7506 pin 3.
If you have signal at pin 3, the caps are good.

There is a (smudged) note that the Repeat pot goes to PC215, which is in the upper right corner.
I would guess that that is a switch?
Check it.

Note: some opamps have a virtual ground as there inputs, thereby making it impossible to read the inputs.
In that case simply read the signal before the coupling cap or read the opamp output pin.

[multivox]

I have tested pin 3 and am receiving no signal on the 20k ohm setting. I'm going to start testing capacitors now near the IC. would this be a good course of action or do I need to test ALL capacitors. Thanks again for the help!!

[Jazz P Bass]

Are you following the path of the signal?

'No signal on the 20K ohm seting'
But there is signal at other settings?

If not, as I stated, jump to the output pin.

You can check every cap on the board if you like.
I would recommend following the signal through until the signal stops.
This area of the circuit is simply a buffer.
The real 'Repeat' circuit is on page 4.
But you have to find where the signal stops first.

[multivox]

I'm starting to understand.
I found the capacitor 10uf/25 volts is leaking, the one leading to the switches.
So when you say following the signal i'm guessing you mean check all caps before the output of LA5?

[multivox]

Okay, i rephrase.

Unit off.

200K OHM SETTING PIN 3 - 154.5K
20K OHM SETTING PIN 3 - Nothing

[Jazz P Bass]

How can you follow a Vac signal with the unit off?

[multivox]

I'd put it on a nearly impossible level to test this thing while it's on. You have to remove 3 ribbon cables(including one that powers the board) just to remove the top chassis. I have no ideas, So i'd suppose i'm just sending it to orbitelectronix. Thanks a ton anyway dude