Hello all,
I have been asked to try and repair an old GPS 3500 amplifier.
I have the circuit diagram but I can't find the transformer wiring diagram. Prot_A and Prot-B connect to the transformer thorough some diodes but I don't know why they are connected. The wire to the transformer is open circuit compared to the rest of the windings. Does anyone have a wiring diagram for the transformer or know what it is for? (Yellow wire in the photo)
I have replaced a A78L15 voltage regulator and the zener diodes around. It blew again so I have replaced it now looking for shorts in the circuit.
I have also replaced the NE7115AN current-controlled transconductance amplifier chip too.
The green power LEDs were coming on but now these don't and the relays are not closing.
Peavey GPS 3500
-
j0nsnell
- Member
- Posts: 141
- Joined: Wed Dec 21, 2022 1:33 am
- Location: Jurasic Coast, Great Britain
- Contact:
Re: Peavey GPS 3500
A 78L15 will not blow.
Over current and it shuts down.
Over voltage might upset it but that requires more than 36 - 42 volts.
Transformers go open circuit, meaning no voltages.
Study your schematic, the information is there.
Wires won't have been removed, if they have, refuse the repair if you are not competent to repair it.
Over current and it shuts down.
Over voltage might upset it but that requires more than 36 - 42 volts.
Transformers go open circuit, meaning no voltages.
Study your schematic, the information is there.
Wires won't have been removed, if they have, refuse the repair if you are not competent to repair it.
T
The 78L15 did blow. It literally exploded, I tried to attach a picture but got a HTTP error.
The transformer only outputs 25 Volts so it can't have been over voltage. The 78L15 is rated up to 35 volts. The V/R has a 1N751A zener diode on the ground to raise the output to 20 Volts
The transformer only outputs 25 Volts so it can't have been over voltage. The 78L15 is rated up to 35 volts. The V/R has a 1N751A zener diode on the ground to raise the output to 20 Volts