KA-6100 restore

rickl

I'm just a bass player
Subscriber
I really hate to call this thread a restore but I recently picked up a KA-6100 and plan to get it working better.

The thing is dirty. Restaurant or bar setting is my guess. I don't think it has been opened in a long time.

I pulled the cover and checked out. All fuses were not burned out but 2 10A, 1 30A/32V, and a 250mA for the burned out lamps. They should be 4A and a 500mA for the lamp. They were coated in a sticky mess so they have been there for a long time.

Got the SM from HifiEngine and started checking voltages.

I pulled the fuses to check the transformer since too big of fuses can burn up the windings. All is good.
I replaced the fuses with more appropriate size and powered it up on a DBT. No glow and the relay kicked in. +-35 volts on the rails (using the DBT).

put a signal though it and got a crappy sine wave. Note the lower half is larger than the upper half.

I read a few other posts on PS caps so I'll get an order pulled together but I'm encouraged.

I'm missing an input selector knob (shaft might even be bent) and the power switch will need straightening.

More to follow once I dig into this deeper. If anyone has worked on one of these and have suggestions, please share. I think this might be a fun project.
6100-front-left.jpg 6100-fuses.jpg 6100-scope.jpg 6100-front-right.jpg
 
Last edited:
Nice to know the PS is working (even the preamp has +- 24v). I had to clean the face plate. I didn't want to touch it. found a few bent controls. if anyone has a input selector knob, please PM me. Or know what size I need (my guess it is the same size as the balance and tape knobs).

Looks like fresh caps are the next step.
 
Or know what size I need (my guess it is the same size as the balance and tape knobs).
Yes, it is the same size as these two. Also the 6100 has knobs with a cosmetic design unique to itself which has a wider indication notch than the 7100, 8100 or 9100.
 
I pulled a BOM together and replaced a few caps I had on hand. I focused on power supply and coupling caps. I still have the original 6800uF/50v caps in there.

What a difference. Kind of happy about this.

ka-6100-after.jpg

Once I get the part numbers for the PS caps, I'll post the BOM. I think these might work but need to verify lead spacing. I found hopjohn's mounting bracket post from Doug's resto thread.
 
22mV/12mV DC offset and bias adjusted to 20mV per SM.

ka6100-bias-adjust.jpg
 
Last edited:
Here is a list of most of the caps in a 6100. I added hopjohns PS caps. If you plan to re-cap a 6100, I'd verify these caps before placing a mouser order. I had everything except the PS caps in my spare parts bin.

CdXX caps are the phono section, CmXX caps are the pre, amp and PS caps. A few gaps but this should get you close. Note Cm81 is a pretty green bi-polar cap. All others are electrolytic caps unless otherwise noted.

You should be able to copy and paste into Excel and text to column by space.

RefDesg Value Voltage Desc MouserPN
Cd11,12 10uF 25v 647-UFG1H100MDM
Cd25,26 220uF 25v FG 647-UFG1E221MPM
Cd3,4 100uF 10v 647-UFG1A101MEM
Cd7,8 33uF 16v
Cd9,10 470uF 6.3v
Cm11,12 1uF 50v WIMA 505-MKS4B041002CJF00
Cm13,14 4.7uF 25v 647-UKL1E4R7KDDANA
Cm15,16 47uF 16v 667-EEU-FC1C470
Cm17,18 10uF 25v 647-UFG1H100MDM
Cm21~24 1uF 50v WIMA 505-MKS4B041002CJF00
Cm25,26 47uF 16v 667-EEU-FC1C470
Cm27,28 10uF 25v 647-UFG1H100MDM
Cm29,30 .33uF 35v WIMA 505-MKS2C033301C00MI
Cm3,4 220uF 10v 647-UPW1A221MED
Cm41,42 3.3uF 50v WIMA 505-MKS2B043301HJSSD
Cm45,46 47uF 35v 647-UKL1V470KPDANA
Cm47,48 47uF 16v 667-EEU-FC1C470
Cm5,6 100uF 16v 647-UPW1C101MED1TD
Cm53,54 47uF 50v 647-UVR1H470MED
Cm55,56 47uF 16v 667-EEU-FC1C470
Cm61,62 47uF 6.3v
Cm67~70 6800uF 50v 647-UFW1J682MRD
Cm7,8 4.7uF 25v 647-UKL1E4R7KDDANA
Cm71,72 1uF 50v WIMA 505-MKS4B041002CJF00
Cm81 100uF 16v non-polar 647-UES1C101MPM
Cm82 100uF 16v 647-UPW1C101MED1TD
Cm83 10uF 50v 647-UFG1H100MDM
Cm84,85 220uF 35v
Cm86~89 100uF 25v 647-UFG1E101MPM
 
Last edited:
If I can't find what I want at the correct voltage I will jump up to the next (say 10V for a 6.3V cap). New ones are going to be smaller than what's in there so space will not be an issue.

I used all Nichicon Audio Grade except for the non-polar or low leakage caps, used UKL for those. Amp was a Kenwood KA-80, a little newer than a 6100 I think. Some of those caps are running withing a volt or so of their maximum, and since line voltage in the US is higher by a few volts now than when those were made, a higher voltage cap might be a good idea.

Bad caps in the signal path do indeed do bad things to the output -- on the KA-80 there are coupling caps for the tone controls and for the phono input amp, and they were all out of spec on mine.
 
Two questions since I'm new at trying to figure out substitutes or building lists:

1. How do you know where it's appropriate to use low leakage versus audio grade?
2. What happens if you use audio grade where you would put a low leakage cap?
 
I just read the parts list, Kenwood is pretty good about listing type clearly. I think low leakage caps are usually coupling caps, although there are quite a few in my KA-900 and KT-900 that are waiting service.

Non-polars will be used when there is likely to be both positive and negative voltage on either side--- polarized caps don't like reverse voltage much.

Assuming the amplifier design is similar to the KA-80, the caps on the supply rails for the phono and pre-amp sections do not need to be audio grade since they serve the same purpose as the filter caps on the power supply, that is to deliver current above the power supply capability at high demand. Hopefully no audio signal, eh?

As to what happens if you substitute an audio grade cap for a low leakage one, you probably get DC bias where you don't want it, although the difference in leakage between the new audio grade caps I have and the old low leakage ones I tested isn't huge. Around 1% for the new audio grade and 0.5% for the old ones. High ESR and capacitance on the old ones too. Don't remember what the leakage was on the new low leakage caps, I'll record it all next time as I replace caps.
 
Thank you for the info. I had just plopped audio grade caps in for all of them. So would the best way of determining the places audio grade caps would go would be to get the schematic and try and follow the audio through the unit and make every cap you hit audio grade? I'm still learning the differentiation between where the audio path ends and where power supply begins at certain places.
 
If I'm reading my schematic correctly, the audio circuit passes through very few caps. Most are involved with the other circuitry.
 
You are correct, I suspect the 6100 is DC coupled if the tone controls are off.

Do you have a copy of the service manual? There is a parts list in Kenwood manuals and the type of capacitor will be listed. Also, the low leakage caps of that vintage tend to be Elnas in orange although not always. Usually a different color at any rate.

Not easy to tell from the schematic alone.
 
I just took a look at the service manual. They give an OE part number, the voltage and capacitance, but under type, it just has "electrolytic" or "ceramic" or "mylar" but does not call out low leakage or not.
 
I would say then that unless you had some orange Elna low leakage caps in there you are fine with audio grade. Film caps are fine where they fit.
 
Cool. I will open the unit up and physically account for any Elna orange caps. Are low leakage caps denoted in any way on the cap itself?
 
Don't know, other than Elna low leakage of that age are orange. Not the only low leakage caps specified on my amps though.
 
Got the 6100 open. All I see are 3 orange Elna caps in the whole unit. I didn't pop the preamp off the rear of the unit, but shining a flashlight around, I don't see any orange electrolytics. On the amp board, two of the orange caps (Cm41,42) get replaced with Wimas, the other orange cap is Cm82 and I think I'll replace that with a UKL. So only substitution I would be ultimately making from my list I had posted above would be Cm82 becomes UKL1E101KPD1TA.
 
Ok, just completed my KA-6100 with satisfying results thus far. With using the advice of several members, I came up with a cap list I was confident with (And were in stock). Voltages were slightly bumped up in most positions from factory specs. Here's the list:


Cd11,12 10uF 25v UKL1V100KDDANA
Cd25,26 220uF 25v UPW1V221MPD6TA
Cd3,4 100uF 10v UPM1C101MED
Cd7,8 33uF 16v UKA1E330MDD1TD
Cd9,10 470uF 6.3v UKA1C471MPD1TD
Cm11,12 1uF 50v 505MKS4B041002CJF00
Cm13,14 4.7uF 25v UKT1V4R7MDD1TD
Cm15,16 47uF 16v UTT1E470MDD
Cm17,18 10uF 25v UKT1V100MDD1TD
Cm21~24 1uF 50v 505MKS4B041002CJF00
Cm25,26 47uF 16v UTT1E470MDD
Cm27,28 10uF 25v UKT1V100MDD1TD
Cm29,30 .33uF 35v 505MKS2C033301C00MI
Cm3,4 220uF 10v UKA1C221MED
Cm41,42 3.3uF 50v 505MKS2B043301HJSSD
Cm45,46 47uF 35v UPW1H470MED1TD
Cm47,48 47uF 16v UTT1E470MDD
Cm5,6 100uF 16v UPM1E101MED
Cm53,54 47uF 50v UPW1J470MPD1TD
Cm55,56 47uF 16v UTT1E470MDD
Cm61,62 47uF 6.3v UPW1A470MDD
Cm67~70 6800uF 50v UKW1J682MRD
Cm7,8 4.7uF 25v UKL1H4R7KDDANATD
Cm71,72 1uF 50v 505MKS4B041002CJF00
Cm81 100uF 16v non-polar 647-UES1E101MPMTD
Cm82 100uF 25v UKL1V101KPDANA
Cm83 10uF 50v UPW1J100MDD
Cm84,85 220uF 35v UPW1H221MPD
Cm86~89 100uF 25v UPW1V101MPD1TD

I used the original list posted on here as a starting point and then worked up a list from that. So far, the results seem to be a very dynamic sound with clean treble, deep bass, and a very low noise floor. We'll see how it sounds after a few hours of playing..........
 
@rickl I think it was you who said you loved your Bass in another thread? If you already haven't, have a listen to Chris Jones "Moonstruck" album it'll explode your tea bags :D
 
Back
Top Bottom