Yamaha CR-220 sound dies after a few seconds of sound - Please Help!

W.T. Holt

Active Member
As the title says...

The amp turns on and plays music just fine for about 5 seconds, then the sound fizzles out and eventually stops entirely (takes about a second). My DBT doesn't register any shorts, and the same phenomenon occurs no matter what input is used.

An important (I think) distinction to make is that the power doesn't cut out - just the sound output.

Thoughts on where to start trouble shooting this bizarro problem will be much appreciated!
 
People will suggest cleaning the switches etc... however the rx plays fine for 5 seconds.
Have you opened it up and done a visual inspection for bulging/leaking caps?
Download the service manual. Also, do you have a multimeter for checking power supply is OK.
 
Definitely not an issue with the pots - everything has been cleaned and there is no scratchiness. I do have a MM, haven't checked any circuitry out yet though. I suppose the power supply is a reasonable place to start though!
 
J109 voltage should be about 28V.

Also measure voltage at R707 as shown, expect about 22volts, see pic...

I need to step out for a few hours, I'm sure others will chime in.

do the visual inspection for leaking/bulging caps.

Capture2.JPG
 
Sweet thanks for the direction... caps look good and there are no other obviously damaged components inside. Same behavior through speakers and headphones. I'll probably have a chance to check voltages this afternoon and will check back in.
 
OK so J109 measured ~27V, R707 was at ~6.3V. The voltages do not change as the sound peters out.

Caps all check out visually.

R707 seems out of spec... what does this mean for my amp?

Thanks for the ongoing help!
 
If so. What are you measuring on both ends of R707. If they are both way low.You could possibly have a bad cap in the power supply. The schematic I have is real crappy.I can barely read the voltages and reference designators. If you could measure the voltages on the emitter,base and collector of TR713 that would help narrow down the problem even further.
 
R707 seems out of spec
R707 voltage is not as exspected. Doesn't necessarily mean R707 is out of spec. Now if you have around 27v or more on one side of that resistor and 6.3 volts on the other end . Then yes the resistor could very well be out of tolerance.
 
Candidates are TR713 and D605(unlikely).
Test TR713 with the diode function on your DMM.
You could also measure voltages at TR713 base,
emitter, collector, see pic

Capture3.JPG
 
Avionic and MBZ, Thank you... haven't had a chance to poke around in the amp for the last few days but will do so soon. In reply to the multiple questions posed:

1) Yes I am testing voltages with the common lead on chassis ground.

2) R707 measures 6.3V on both sides.

I believe this means the issue is upstream of the resistor... I'll be testing out TR713 to see if this is truly the cause. If that transistor checks out ok I suppose I should be looking at caps in the power supply? That's what I can infer from the previous replies anyway.
 
The service manual has TR713 E=22.4V, C=-23.7V, B=-23.2V.
You measured E=6.3V (R707 measurement), this is faulty.

Next measure TR713 Collector and Base

If C&B are in the ballpark then TR713 faulty

If Collector voltage is incorrect then check C907 (100/35)
and the 33k resistor next to C907 in the schematic, it has
no designation Rxxx. Failing that, check R761, C735&C736.

If collector voltage OK but base voltage is wrong then
check R761 (4.7k) also C735? (1000uf/35V) and C736? 1/50.
 
f Collector voltage is incorrect then check C907 (100/35)
and the 33k resistor next to C907 in the schematic

The service manual is a bit hard to read so I probably have some of the designations wrong.
C907 should be C807, and the 33k resistor looks like R811, see pic.

Capture5.JPG
 
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