Yamaha CR-640 in protection mode

Hi guys, my cr-640 is in protection mode and I have measured dc offset and left was about +6mV and right was +10mV, but these are highest value, because they ware bouncing around. And if the dc offset is ok, so then my guess is that problem is in relay drive circuit. So what points I need to measure from relay drive circuit?

EDIT: Those dc offset values are wrong.

EDIT: New values, TL -326mV TR 44,2V. So right channel IG02980 is dead?

A dead IG02980 is the most probable cause. When that part fails, it may also damage the emitter resistors, so it would be a good idea to check them.

Cheers,

chazix

I want to know if the tuner is still align before I go further with this. Plan is to test few radio channels after dead IG02980 is taken off and if the protection mode comes off too, is this ok?

Yes, after removing the bad IG02980, the receiver should come out of protection mode, and you should be able to listen to one channel.

chazix

IG02980 was dead, now removed and relay clicks. Tuner is not badly off, low end seems to be only about 0.1Mhz off and high end 0.15Mhz. How I know that right channel driver is ok? There seems to be few sellers on ebay that offer IG02980 but from china, don't know if fakes or not.

There is a procedure for checking the main function of the predriver in the "Ongoing Saga" thread:

http://www.audiokarma.org/forums/showthread.php?t=145244

I don't have any solid suggestions for avoiding fakes. I think it is very unlikely that any original IG02980 parts are available, unless they are parts that have been removed from receivers. You might consider using parts labelled STK0050II. Those will not be original Sanyo parts, but they might be acceptable reproductions.

I just had a CR-640 on the bench with a bad IG02980 myself. What I decided to do was to replace it with an STK0060II, because that part is available from a vendor who has suppled acceptable STK reproductions previously. The part that I got from bdent.com definitely does not perform as well as the original, but it was able to handle full-output testing with a 4 ohm load. The STK0060II has a larger package than the IG02980/STK0050II. There is sufficient room to install it, but new mounting holes had to be drilled in both the part and in the heat sink.

Good luck,

chazix

I measured the voltages from both ig029850 and not looking good.

Left (working channel)
1. +0,247V
2. 0V
3. +0,246V
4. -38,3V
5. Not measured
6. -39,8V
7. +2V
8. -0,43V
9. 0V
10. -0,43V
11. -0,43V
12. -3,1V
13. -3,43V
14. +2,68V
15. +39,9V

Right (Bad channel)

1. +0,1V
2. 0V
3. +0,1V
4. -38,5V
5. Not measured
6. -39,8V
7. +39,8V
8. -0,013V
9. 0V
10. -0,010V
11. -0,013V
12. -0,008V
13. -39,1V
14. +39,8V
15. +39,9V

So driver is dead too.

I think those right channel predriver voltages must have been taken with the power pack removed, but without having taken the steps in the "Ongoing saga". If that is correct, I don't think those voltages necessarily tell you anything about the health of the predriver. Not only is it running without a feedback loop, there is no connection between its + and - outputs, so it is expected that the + output (pin 14) is at the + power supply voltage, and the - output (13) at the - supply voltage.

I know the "Ongoing saga" thread is very difficult to follow, so I'll summarize the predriver test here. It requires a reasonably experienced technician, but my impression is that you are one.

The key is to tack-solder two resistors onto the circuit board, such that they connect the input pins of the power pack (pins 1 and 10, the outermost ones) to the junction of the two emitter resistors. By creating a path from the the absent power pack's inputs to the amplifier output, this completes the overall feedback loop around the amplifier. The resistors should be around 330 ohms. The exact value isn't critical, but use the same value for both.

With the feedback loop completed, if the predriver is OK, it will drive the amplifier output to zero volts DC. If you measure the voltage across the two tacked-in resistors, you should read roughly 2V, and the voltage should be the same for the two resistors.

If that test passes, it is very likely that the predriver's main function is OK. You could even make a listening test, but only with headphones. (Without the power pack, the amplifier can't deliver enough current to drive speakers.)

If you proceed with the repair, don't forget to check the emitter resistors.

Cheers,

chazix

Soldered those two resistors in and voltage across resistor is about 2v, little bit over it in both resistors.

Also emitter resistors are good. Should I test other components before I place new power pack in?

EDIT: Main filter capacitor is also bad, but that was taken off before this thread and now I'm using off board capacitor that is wired to pcb. I haven't been able to find new capacitor that has same kind of terminals. I have also CR-840 and i have been thinking about recapping that so I need filter caps there too and I guess that filter caps have same terminal style as in CR-640.

Good! I don't think you need to do any other testing with the amplifier section. It should work fine with just a new power pack.

chazix