Yamaha CR-420 Dead Tuner

[JB8]

Picked up a CR-420 that initially tested fine across the board - tuner, phono, Aux, etc. But then the tuner stopped working all together - no led's, no signal meter movement, no sound on AM or FM. Now, it didn't just die, it kicked and screamed a bit, I thought it was dead, then it came back to life with lights and beautiful sound, stereo light and all, then, well, it just plain died...

I found a similar thread addressing the same issue with a 620, @avionic said "Suspect C806 47µf/25v, C825 10µf/16v Check the voltage at the base of TR804 ( looking for roughly 13 vdc )". The owner eventually replaced TR803 due to a lack of 12v out and it solved the issues.

I have a great schematic for a 620 that shows all of the voltages, would appreciate a hand pointing to equivalent components in the 420 so I can do some testing and hopeful find the culprit causing the interruption in 12v power.

Lastly as I was initially looking over the circuit board I found C130 had a funky looking solder, so I removed and replaced it. The component didn't test bad but I had a fresh one available so I swapped it in. This repair did not impact the larger issue of no tuner. I also replaced the 3 burnt out dial and signal meter lights with warm white LED's.

Again, any help is much appreciated!

 

[avionic]

Picked up a CR-420 that initially tested fine across the board - tuner, phono, Aux, etc. But then the tuner stopped working all together - no led's, no signal meter movement, no sound on AM or FM. Now, it didn't just die, it kicked and screamed a bit, I thought it was dead, then it came back to life with lights and beautiful sound, stereo light and all, then, well, it just plain died...

Sounds like a solder connection in the power supply. Look over the solder connections for TR505 and 506 and connected passive components. Tapping around on the circuit board around these two transistors may help locate the issue.

 

[JB8]

Thank you, Sir, solders look good for both transistors, no movement, no results from tapping.

I've included a better look at the damage around C130, hesitant to try to clean it more, does it look like it could be a factor here or is the power supply still the lead suspect?

 

[avionic]

Scrub that area off with acetone and a old tooth brush to see how badly those traces are damaged. Could be a broken solder pad or broken PCB trace.

line points to a possibly cold corroded solder connection.

 

[JB8]

Thank you. I removed the cap and cleaned the area with acetone, scrubbing was with a q-tip. I'm getting continuity on the green lines/points but not on the red line.

What do you think, salvageable?

 

[avionic]

What do you think, salvageable?

Oh yeah..

Solder a piece of insulated wire between those two solder connections.

 

[avionic]

I removed the cap

What does the pin end of the cap look like ? corroded ?

 

[avionic]

Or.... scrape off the solder masking with a hobby knife or razor blade in the " green line " area. Tin it with solder. Then solder in a jumper wire " red line " ...

 

[avionic]

Do you have continuity between the blue line ?

 

[JB8]

Working backwards, yes, continuity between the blue line.

I like the plan in post #8, will do.

I included a picture of the pin end of the cap, looks to be some corrosion, as you suspected.



Working on the jumper tonight or over the weekend, will let you know how it goes, thanks, as always @avionic

 

[JB8]

Well it ain't pretty, but that totally fixed it. Works like a champ, thank you, @avionic, you've done it again!

 

[avionic]

Replace that 220µf cap soon. Looks like a little leakage residue on that rubber plug.