Yamaha CR800 No Speaker Sound, Headphones work

[YamahaCR800]

I have a 1970s Yamaha CR-800 receiver. I was swapping out speaker wires to connect a 6-channel A/B speaker selector to the stereo and I left the receiver power on while I was doing it. The speakers were working while I was doing the work, then they went silent. I assume I shorted something out with the speaker wire. Headphone jack also does NOT produce sound. Disregard subject title of this thread, the headphones only work on my mixer, not when directly plugged into the stereo receiver. My questions is: Does anyone know the likely culprit? Anything a layman can fix? The main fuse that you unscrew on the back looks intact. Rookie move, I know. How bad is it? Probable equipment and repair cost? Repair advice in the Los Angeles area?

 

[century tek]

The least you did is hopefully you blew some internal fuses. The most you did is probably short an output transistor.

 

[avionic]

Welcome to AK...CR

Do you hear a relay "click" shortly after power on ?

 

[avionic]

Do you have any tools like a multimeter ,soldering iron and hand tools ?

 

[avionic]

Do you know how to read a schematic diagram?

 

[YamahaCR800]

There is no relay "click" when powering on. And there was one prior to this problem. The red light does illuminate on the face of the receiver with power switch on.

I do have a multimeter, soldering iron, and hand tools. I can't claim to be proficient with a soldering iron, but I do enjoy fixing things.

I can't claim a great deal of knowledge about electronics, but I am generally good at figuring things out. Read a schematic? Not sure. Isn't it a lot like a road map?

 

[avionic]

Isn't it a lot like a road map?

Exactly . A road map for electrons.

 

[YamahaCR800]

Exactly . A road map for electrons.

Well I guess I have my work cut out for me. I need to get a schematic for this device and learn how electrons move through it, then learn how to use my multimeter and find magical surgical training with my awkwardly unprofessional soldering iron. I think it might be easier to shoot down the Star Wars Death Star, but I'll go for it! My father wrote a textbook on electricity and magnetism in the 1960s. Maybe I should have read it! If you have a schematic for me that you might share, along with any advice about what you might look at first, I'll do my best to take it from there. I know I'm in over my depth, but nothing ventured nothing gained.

 

[avionic]

http://sportsbil.com/yamaha/cr-800-sm.pdf

 

[avionic]

I will be here. Others may chime in as well.

 

[avionic]

First we need to determine if there is significant DCV ( voltage) on the two amplifier outputs.

 

[avionic]

Page 17 of the manual shows a rough location of various test points in fig. 9. TP-3 is one channel output , TP-4 is the other channel output.

TP-5 and 6 are circuit ground. Connect your multimeter red test lead to TP-3 and your black test lead to TP-5 or 6 or anywhere on the board marked "E" "E" is circuit ground as well.
Set your multimeter for VOLTS DC. Check the voltage at TP-3 then move the red lead to TP-4 and check the voltage.

 

[avionic]

If you don't already have them. I highly recommend that you get a set. Mini-grabber test leads.
https://www.amazon.com/TOTOT-Securi...404459&sr=8-4&keywords=minigrabber+test+leads

 

[avionic]

Yes. To make these voltage measurements. The power must be " on ". ...

 

[YamahaCR800]

THANK YOU!!!! Will report back.