Need help with Nakamichi AV-1

[AudiHobi]

Hello Experts,

Problem - Acquired the above and found the PCB area around the LM7915, LM7812 are
darken. There are few resistors (2W) nearby that seems to have heated up badly as well.
No sound output but the LED display seems OK, able to select Tuner/CD, etc.

Question - Looking for schematics and what could have cause this to heat up?

 

[(*steve*)]

Some PCB materials darken with temperatures that are not excessive. If there's chatting of the board then that's a different issue.

Have you measured the output voltage of these regulators?

Do you get any audio output? Is there a headphone jack for example?

 

[AudiHobi]

Some PCB materials darken with temperatures that are not excessive. If there's chatting of the board then that's a different issue.

Have you measured the output voltage of these regulators?

Do you get any audio output? Is there a headphone jack for example?

Steve,
- I am not able to measured them as the AV-1 layup is very cramp, full of interconnect wires
Able to take the voltages from a 8pin OP AMp and shows +10v & -7v. W/Out the sch, I am not sure these are the required voltages
- there is no o/p to speakers, There is a H/phone jack but I do not hv a headset
- picture from component view of the burnt area.

 

[(*steve*)]

There some component there which looks to have died, leaving stuff on the PCB.

The PCB looks damaged below it, but it's hard to tell. What does the other side of the PCB look like?

 

[AudiHobi]

PCB copper/solder side looks OK, no visible burnt holes.
This AV has many interconnect wires and 3 x boards on socket making it very challenging to use probes for measurements.
** Key Task -- get hold of the sch and replace the burnt parts of which the p/n are not readable anymore.

 

[bushtech]

https://www.manualslib.com/manual/1355787/Nakamichi-Av-1.html
Havent downloaded it, give it a try

 

[AudiHobi]

bushtech, thks for the link.
Thts the user manual, I am looking for the AV-1 schematics or service manual.
TQ