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Anthony F.
Anthony F., Engineer
Category: Electronic Musical Instruments
Satisfied Customers: 9830
Experience:  Amplifier and keyboard repair.
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Hi Ive got a vox ac15 cc1x in for repair and cant seem to

Customer Question

Hi I've got a vox ac15 cc1x in for repair and can't seem to get the reverb working .ive checked the signal coming directly out of the pan and that's fine but lose it in the circuit.
Submitted: 3 years ago.
Category: Electronic Musical Instruments
Expert:  Anthony F. replied 3 years ago.

Anthony F. :

I assume yours is a newer unit

Anthony F. :

Here is a schematic

Anthony F. :

from 1996 onward

Anthony F. :

hope this helps

Customer : Hi yeah sorry got schematic it is the newer one with the jrc m5201 ic in the reverb return circuit.vx15 type 1-1001-a
Anthony F. :

so what do you have and what dont you have ? on what pins of that ic? voltages ??

Customer :

pin 8 14.95

Customer :

pin 4 15.14v pin 1 11.90

Customer :

if I inject a signal on pin 5 it come through the circuit fine but put into pin 7 nothing comes out

Anthony F. :

Does the unit have a Spring tank?

Customer : Hi Anthony yeah has a spring reverb
Anthony F. :

do you feed audio in to the tank ?do you feed audio out? of it ?

Anthony F. :

measure it what it resistance across the spring?

Customer : I've put audio through and comes out the other end fine into a different amp even on the scope ,until I plug back into circuit signal disappears ,got me baffled .pan reads fine checked the resistances I've even got a spare pan somthing in the return circuit
Anthony F. :

ok so IC 3 pin 7 is where you are loosing it?

Customer : Yeah that's it .even if I take out the ic and scope pin 7 on the board the signal seems gone , I've replaced the cap that's on the input 2n2 and still nothing
Anthony F. :

measure the resistance to ground across that cap

Anthony F. :

in circuit

Customer : Yeah will do I'm back in work in the morn I'll check in then .cheers for ur help .speak to u tomorrow .nite
Anthony F. :

ok let me know this is strange one

Customer : One more thing before I Goto sleep lol .i noticed on ic3 pin 1 connects to ic2 pin 1 and ic1 pin 1 through a 47 ohm resistor .dosnt show that in any of the schematics ?any ideas why they would do that
Anthony F. :

maybe its vcc ? for the ic.s?

Anthony F. :

pin 1 and IC 1 and IC connect to the feed line for audio to the tank

Anthony F. :

there is no connection to ic 3 pin 1

Anthony F. :

pin 1 looks like its switched by trans tr2 in or out of ground

Anthony F. :

pin 8 and pin 4 look like vcc to this chip pos and neg its an op amp

Anthony F. :

Are you sure it doesnt go to pin 2 of of ic 3 ? thats signal ground

Anthony F. :

Is there an R number near it ?