Kenwood KA-5002 - Correct schematic (or compilation of known variants) ?

[david winter]

Hi,

I have an early KA-5002 (serial 250498) which doesn't match the two schematics that I have.
I noticed the following differences :
- A completely different protection board under the chassis: smaller, no ref, only 4 transistors (of which two 2SC1213, one 2SC883 and one 2SA537A). No schematic found.
- The output board is X07-0027-00. At the same time it looks earlier than the X07-0027-01 on the schematic, but contains more parts as seen wjth X07-1020-01.

Anyone has a schematic corresponding to my version ? I planed to upgrade the output board to the X07-0027-01 or X07-1010-01 design but apparently none seem to be close enough to allow this. Thanks.

 

[Semanon]

Board changes that don’t match the schematic are common. It’s rare to see version-based schematic drawings. Early Kenwoods are no different. These changes usually come out in technical service bulletins, if at all.

 

[david winter]

I saw that at least one tech bulletin is on Hifi Engine but their download server is being upgraded.
Right now I'll stick to the existing design, but the board shows more diodes than on the 2-page PDF.
I also found that the 14V zener was open and hope the excess of voltage didn't damage anything.
I replaced it with a 1N4744 testing at 14.0V .
If you know other KA-5002 tech docs than the 2-page PDF I'm interested.
Thanks.

 

[Semanon]

I suspect we have the same schematic. I have the 2 page PDF with the second page noted as “being useful for serial no. 430,001 and above. Is that the one you have?

I also have the SM from HFE.

 

[david winter]

Yes that's the one.
I could not get the protection board to click but finally found the problem : incorrect ECB pcb marking. Will post the explanation to another thread about the protection board so that people can find it more easily.