Lafayette echo verb

Hi,
I'm trying to repair a Lafayette echo verb.
The main two problems are:
1. There's a strong distortion when I plug a guitar to both instrument and mic inputs.
2. There's strong hum noise while turning up the reverb pot.
I've already replaced the four electrolytic caps, replaced the filtering diode with diode bridge, replaced the four transistors with new ones and nothing seems to make any difference.
Since I can't find the schematics for it I don't know what else should I do.
Any suggestions?

while hunting reverb.com I found this schematic attached with a layfayette for sale perhaps it will help you.

And here is the reverb.com listing

https://reverb.com/item/876447-lafayette-electronics-echo-reverb

Thank you very much!

I've replaced today all the resistors on the board and all the .1 green film caps.
Now the distortion is seems to be gone, but the output is very low.
I've measured the voltage on the collector leg of all the transistors, on Tr1 I have 1.9v, on Tr2 4.9v, on Tr3 4.8v and on Tr 4  1.4v
This is the right voltage I should get according to the schematic?

replacing parts just to replace parts is never a good idea.

II would start with making sure the power supply is in order and go from there.

The Power supply seems to work fine, I measured around 9 ACV from it and 9.3 DCV from the diode.
Between the 1K resistor to the 100 Ohm resistoe I've measured 4.8 DCV, after the 100 Ohm resistor I've measured 4.6 DCV.

If you have a new problem after replacing components it means you made a mistake. Double check all your work.

The hum could be a grounding issue. Check all the ground points visually and with a multimeter then retouch the solder for good measure.

I went thru the whole circuit and everything looks right.
The only thing I've noticed is when I checked the spring tank I found that someone replaced the output transducer.
Now I've measured 730 ohm on the tank input and 743 ohm on the tank output.
Does someone know if this is the right  impedance for this unit?