Wrong card on schematic? Kenwood KR-5200

[spxer]

I am working on my son's Kenwood KR-5200. The relay is cycling on and off on occasion. I downloaded the schematic from hifiengine. The schematic there for the KR-5200 show a x00-1170-10 Power Supply card. The KR-5200 on my bench has a x00-1290-10 PS card. They are not the same. Also, although the numbers on the Main Amp card are the same, they do not appear to be the same where I am looking anyway(pin 12). Is the schematic incorrect? Is there another source?

 

[EchoWars]

This help?

 

[spxer]

I believe that schematic is it! That should help immensely, if I knew what I was looking for. There is a 25.3 volt drop across the relay coil. That should keep it closed, assuming it is a 24v coil. I resoldered all the relay points. It may just be time for a new relay, but I find that kind of troubleshooting unfulfilling. Thanks, EchoWars

 

[EchoWars]

Measure the voltage at the base of Qe19. Should be about 1.5V or so. If that's the case, measure the voltage across Re52 (680 ohm resistor). A properly functioning 24V relay coil should have about 37mA through it. That would mean Re52 should have about 25V across it. The collector-to-emitter voltage on Qe19 should be well under 1V.

 

[spxer]

Measure the voltage at the base of Qe19. Should be about 1.5V or so. If that's the case, measure the voltage across Re52 (680 ohm resistor). A properly functioning 24V relay coil should have about 37mA through it. That would mean Re52 should have about 25V across it. The collector-to-emitter voltage on Qe19 should be well under 1V.

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The measurements I get are- base of Qe19, 4.12v to chassis. Voltage across Re52, 7.25v. C to E of Qe19, 72mv. Some very different measurements than you describe, if I made them correctly. I get 23.95 v across the relay coil today, 7.25v across Re52, and 3.5v across Re53. Which is the 35v from the power supply. By the way, the relay has worked properly for the past two days.

 

[EchoWars]

Got a problem with the measurements.

If Re52 is 680 ohms (check it), then your measurements indicate that you only have about 11mA flowing. But if Re53 is 100 ohms (check it), then 3.5V across 100 ohms indicates 35mA (which is what a 24V ice-cube relay should be drawing).

So...it appears that you may have 220 ohm for Re52 and perhaps 100 ohms for Re53. The schematic you had before I posted the one above shows Re52 as 220 ohm, but Re53 as 68 ohm. The one I posted above has Re52 as 680 and Re53 as 100. We need to know what you actually have.

In any event, it appears that Qe19 is turned on, but the relay isn't responding. The saturation voltage on Qe19 is low enough, so that doesn't appear to be an issue. Looking more and more like the relay itself has a problem.

 

[spxer]

Got a problem with the measurements.

If Re52 is 680 ohms (check it), then your measurements indicate that you only have about 11mA flowing. But if Re53 is 100 ohms (check it), then 3.5V across 100 ohms indicates 35mA (which is what a 24V ice-cube relay should be drawing).

So...it appears that you may have 220 ohm for Re52 and perhaps 100 ohms for Re53. The schematic you had before I posted the one above shows Re52 as 220 ohm, but Re53 as 68 ohm. The one I posted above has Re52 as 680 and Re53 as 100. We need to know what you actually have.

In any event, it appears that Qe19 is turned on, but the relay isn't responding. The saturation voltage on Qe19 is low enough, so that doesn't appear to be an issue. Looking more and more like the relay itself has a problem.

You are right on, I believe. Re52 looks like Orange,Orange,Tan which is probably Red,Red, Brn. 220 ohm. Re53 looks like Tan, Blk, Tan, which I take to be Brn, Blk, Brn. 100 ohm. (I know there is no tan. It's what it looks like now.) So, given those values everything seem just fine as is. And as I mentioned it is working fine now. Don't you hate an intermittent problem? I wonder why the schematics do not match. The serial number is 731406. Thanks for walking me through this. Very instructive for me.