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My Kenwood KA-9100 Restoration

gort69 said:
Tell us where you live - you seem to be searching for stuff all over the planet
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jajajaa.. yes, in my city there's only no more to five electronic parts shop and nobody can't help me; I live in Barcelona - Catalonia (Spain). Unfortunately this is not America; if someone can help me will be very appreciated. Now I have all parts but I'm missing KSC2690A and the ESRs. Do you know if this is the transistor I'm looking for?

https://www.ebay.es/itm/10x-KSC2690...127488?hash=item2ef643b300:g:g0AAAOxye5BRFW-T
 
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OK - I get it now. All of the sources I would trust (Mouser, Digi-Key, Newark) have none in stock. That's crazy. That's not to say those are the only reliable sources, just the ones I'm familiar with.

I would NOT buy a transistor from a seller on ebay unless I was 100% certain they were selling genuine parts. Many have been burned by counterfeit parts from ebay, including me. Not to mention US $10 is robbery - it's a 60 cent part.

A quick ebay search found one seller I'd trust - Little Diode from the UK. https://www.ebay.com/itm/ON-Semi-KS...047537?hash=item285e9d2031:g:mXYAAOSwVTNbNmVI Ridiculously expensive, however - going from memory - there are only 3 transistors on the KA-9100 that I'd replace with a ksc2690 as a matter of course - one on each amp board and the relay driver on the diode board.

Hopefully someone in your part of the world can help you out with some spares or a reliable local source, or someone can suggest good alternatives

I don't know what you mean by a missing ESR
 
rjsalvi said:
We like 9100s. :D

About the only thing I'll add is that it's generally a good idea to use low ESR (equivalent series resistance) caps in power supplies. Your main filter caps are fine, but you chose Nichicon FG for the PS board. Why use low ESR? Series resistance at the input creates high frequency noise across the cap, and at the output, it can actually cause more ripple. Series resistance can also affect transients. Let's say you're watching a movie, you've got the amp cranked up and suddenly, there's an explosion!...an instantaneous large demand is placed on your power supply, to send the necessary current to your amplifier stage so it can reproduce that explosion with authority and as distortion-free as possible. While that may be a gross example, it illustrates why increased ESR to rapidly changing current demands can affect performance.

Here's an informative video showing various type caps in a circuit, demonstrating the differences in signal integrity due to ESR differences:
Having said all that, the amp will work fine the way it is. :) Good job, Andrew.
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Andrew Page said:
Now for some ESR meter results on some of those old ELNA low leakage caps from the control boards.

10uf 25 volt low leak cap: ESR 7.6 ohms about 5.3 appears to be more acceptable

1uf 50 volt low leak cap: ESR 18 ohms! This rating doesn't come up on my meters chart but appears to be way too high.

10uf 25 volt low leak cap: ESR 6.5 ohms about 5.3 appears to be more acceptable

1uf 50 volt low leak cap: ESR 15 ohms again appears to be another very high reading but not on my chart for this value.

Bigger values all appear to have "mostly" tested really well:

220uf 35 volt standard cap: ESR .31 ohms about .17ohms appears to be acceptable

100uf 35 volt standard cap: ESR .35 ohms about .32 appears to be acceptable

470uf 50 volt standard cap: ESR .10 ohms about .09 appears to be acceptable

47uf 35 volt standard cap: ESR 1.8 OHMS about .68 appears to be acceptable (yes this one a little off)

100uf 35 volt standard cap: ESR .32 ohms about .32 appears to be acceptable (on the money)

220uf 10 volt standard cap: ESR .29 ohms about .6 appears to be acceptable.

This is only a few capacitors and obviously, it's a real mixed bag of results. Some test really well so one would wonder why would you want to change any, some are questionable but then others just tested horribly! Either way, the results are amazing and I'm so glad I finally got around to doing this.
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Dear friends, I'm sorry for my poor english and I'm for my ignorance concerning this matter. I have bought all components necessary to make a full restoration of my Kenwood and now ready to do it but I'm missing a little big detail; the.. ESRs. do you can tell me what are exactly the list of LOW ESR that I have to buy?
 
Screenshot_2020-11-12-18-28-22.png Hello and hi. First time on the forums. Recapping my owned since new ka-9100. Love the beast, great sound but its time. Noticed an oddity on the eq amp board 1410 u/4. C108 wasn't joined properly as per diagram or should I say the leg that ties to the resistor wasn't even soldered. Odd that it still worked all these years. Anyone that has recapped their 9100 noticed this?
 
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Welcome to AK. Consider starting a new thread. It will help future restorers find your specific issue. This is interesting and shouldn’t get buried at the bottom of an old thread.

Sounds like an assembly issue. Obviously it does work without that cap, and that connection is not in the audio or power path for the differential pair. But, it will work better when the cap is connected.

Let us know how it turns out.
 
gort69 said:
Of the two listed, use A. It has the correct dimensions and the correct lug spacing and offset, and is a direct replacement. It is also expensive.

B won't fit the clamps - don't use.

This is a much less expensive alternative but requires some creativity to adapt, as the solder lugs are too close together and aren't offset as required to be a direct replacement..
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what is the length of the original main caps?
 
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