Kenwood KR-6600 Power On/off

jforrs

New Member
I got an old kr-6600 from my cousin's barn last year and after some heavy duty cleaning I got it working and sounding great. Then, later last year, it took a while to turn on. This delay got progressively longer until it wouldn't turn on at all. After reading through the forums here, I ended up replacing all the electrolytic capacitors on the power amp board, as well as all electrolytic capacitors and transistors on the Power Amp "A" board. I did the Power amp "A" board because transistor Qk2 was getting really hot. I tested the diodes while I was doing this and they tested fine.

The replacement transistors I used were the following (digi-key p/n):
Qk1: KSA1015GRTACT, PNP, 50V, 150mA
Qk2: 2SC6144SG, NPN Bipolar, 50V, 10A
Qk3,4: 2N5210-ND, NPN, 50V, 100mA
Qk5: KSA1142OSTU-ND, PNP, 180V, 0.1A

Now the relay has no delay when turning on, a slight delay when turning off, and thumps through the speakers on both on and off. Two questions:
1. Did I replace these transistors with the right components?
2. Could the transistors I got be NPN when I ordered PNP? I have heard that counterfeit transistors have been known to make their way over here. How to check?
2. Is there some other component that can also fail that I have missed?

Thanks for all the help, I appreciate any input on this. I did all this work last November and haven't been able to use this since then, so I would like to get this going in the new year. Unfortunately, this also means that I don't remember if sound comes out of it.
 
The original Qk2 was a 2SA733, a PNP.

Your listing seems funny. My schematic says:

Qk1 = 2SC1419 (TO-220 NPN, 50V, 2A, 20W)
Qk2 = 2SA733 (TO-92, PNP, 60V, 100mA, 250mW)
Qk3, Qk4 = 2SC1345 (TO-92, NPN, 55V, 100mA, 200mW)
Qk5 = 2SA885 (TO-126, PNP, 35V, 1A, 1.2W)

The pic on my schematic shows the A885 as a TO-220, but I have the Panasonic data sheet, and IT says an A885 is a TO-126.
 

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Methinks OP reversed qk1 and qk2. 2n5210 is kind of wimpy for relay drive (qk4). Also, the basing of the 2n5210 is different from the original - the base is now the center lead, and usually are labeled, but need to make sure they are in correctly. Symptoms are typical for Qk4 shorted, or in wrong. a better choice for Qk4 would be mpsa05, 2n3904, or KSC945C (make sure the C prefix is used, as that has collector in the center like the original part.
FWIW the pass transistors (qk1 in the schematics posted) always ran very hot and were frequent failure items. Good luck.
 
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Thanks for the help. I definitely had Qk1 and Qk2 confused. I also looked up my original choices again and what I selected as a replacement for Qk5 was not right, either. I have placed another order with DigiKey for the following:

Qk3,4: MPSA05
Qk5: 2SA0963-ND

I went with more replacements for Qk3 and 4 because they're only $0.41 each and they are rated for 60V (original was rated for 55 and my replacements were rated for 50).

Will update when the parts arrive and I get them installed. Thanks for the advice!
 
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