Kenwood KA-3500 recap

The Glue has been defeated. And I did exaggerate, it was really only about 10 caps.
Progress has been made.
Tone Board, Control board are now both recapped.
10,000/50v Nichicon Gold in place of the OEM 6800/42.
I've only replaced a couple of resistors. No transistors have been replaced.
Kenwood KA-3500 recap 08.jpg
Kenwood KA-3500 recap 11.jpg
 
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HA! Yes, I will be able to put this back together. As long as I get it done quickly, before my memory fades. (Actually, not that bad?)
Kenwood KA-3500 recap 12.jpg
 
Help please - before I put this back together, can you guys\gals please take a quick look at transistor list and tell me if any jump out at you as known problems?
I'd really like to replace any now, before putting it back in service.
Kenwood KA-3500 transistors 01.jpg Kenwood KA-3500 transistors 02.JPG Kenwood KA-3500 transistors 03.JPG
 
Help please - before I put this back together, can you guys\gals please take a quick look at transistor list and tell me if any jump out at you as known problems?
I'd really like to replace any now, before putting it back in service.
View attachment 916414 View attachment 916415 View attachment 916416

well it says 2SC458 and 2SC1000 in the middle of your picture, i´d replace those before puting it together, those are pretty worthless.

or is it just the manual that recommends them as subs for 2SC945? must be a typo in that case :)
who would use those as subs for anything?
 
well it says 2SC458 and 2SC1000 in the middle of your picture, i´d replace those before puting it together, those are pretty worthless.

or is it just the manual that recommends them as subs for 2SC945? must be a typo in that case :)
who would use those as subs for anything?

Thanks, and I think the 733's might be suspect as well.
 
well it says 2SC458 and 2SC1000 in the middle of your picture, i´d replace those before puting it together, those are pretty worthless.

or is it just the manual that recommends them as subs for 2SC945? must be a typo in that case :)
who would use those as subs for anything?

Yeah, I'm sorry, that last pic is the substitution table. And yes, lists 2SC458 and 2SC1000 as subs for the 945.

I've been reading more and more about this amp. I'm pretty sure I'm just going to put it back together and call it good.

Sounds like it's fairly easily damaged and some parts are simply not replaceable.
http://www.diyaudio.com/forums/solid-state/259602-kenwood-ka-3500-my-blooper-3.html
 
getting towards the end. No transistors (other than the two replaced earlier for repair) will be replaced. All electrolytics replaced. All ceramics left alone. Filter caps upgraded.
Not sure why I do this, but cleaned the fuse. And fuse holder.
Kenwood KA-3500 recap 13.jpg Kenwood KA-3500 recap 14.jpg Kenwood KA-3500 recap 15.jpg
 
I think the pictures will suffice. Meaning, you can see my notes, still a few items to get done. And, it's always nice to get good results right out of the gate - no problems found so far. Bias good, sound good (with test speakers and ipod input). Phono is noisy as you would expect with open RCA's.
Kenwood KA-3500 Final 04.jpg
Kenwood KA-3500 RCA 04.jpg
Kenwood KA-3500 Final 01.jpg
Kenwood KA-3500 Final 02.jpg
 
I did decide to clean up the aux\phono\tuner RCA input jacks - cleaned in and out. Sorry, I couldn't figure a way to get a pic of the inside of a RCA input, LOL.
I posted some before\after pics. Well, except I didn't clean the tape inputs at all, I'm lazy and they aren't likely to be used?
Kenwood KA-3500 RCA 06.jpg
Kenwood KA-3500 RCA 01.jpg
Kenwood KA-3500 RCA 02.jpg
Kenwood KA-3500 RCA 03.jpg
Kenwood KA-3500 RCA 05.jpg
 
Dingman

I just read through your post. I've restored a few of these myself. I think the 3500 is a terrific amp. I'm always pleased with the sound it produces, Once one gets the hang of taking this apart to work on it, it's not so bad. I didn't notice if you have checked the dc offset readings. There is no adjustment for these, but if the readings are higher than 50mv, you may need to replace the differential pair Q1-Q4 with matched sets to get the dc offset reading lower. There is also a resistor that can be changed to lower the dc offset reading. Here are some pics of the one I just finished.

IMG_1780.JPG IMG_1779.JPG
 
Those pics show nice caps. I see your 0.47 resistors are all standing up, the one I'm working on has one fully bent over.

But I'll leave it that way, I don't like bending leads more than necessary.

I'm about done with this 3500, waiting on a back-ordered 47\100v cap.

I did do the "Bias Adjustment" as detailed in the service manual, and there are adjustment pots for that. I hit exactly 40mv on both channels. But that's not what you mean?
 
Madfro is referring to the DC offset, not the bias. The DC offset can measured at the speaker terminals +/- right and +/- left with the volume at minimum, speakers disconnected, tone controls off or set to zero. I'm assuming this is a direct coupled amp, and if so you'd look for a reading as close to 0mV for each channel. If the reading is 50mV or higher it might be worth your efforts to gain match the differential transistors in an attempt to lower the offset voltage for better performance.
 
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Madfro is referring to the DC offset, not the bias. The DC offset can measured at the speaker terminals +/- right and +/- left with the volume at minimum, speakers disconnected, tone controls off or set to zero. I'm assuming this is a direct coupled amp, and if so you'd look for a reading as close to 0mV for each channel. If the reading is 50mV or higher it might be worth your efforts to gain match the differential transistors in an attempt to lower the offset voltage for better performance.

Yes, this is a direct coupled amp and there is no speaker protection relay, so checking the DC offset is muy importante. Echowars' thread, here, is a must. Just read his Post #1.
 
Actually, I do have a question. The rectifier looks to be fairly robust (and easily replaced), so what's the opinion on upping the final filters from 6800\42 to 10K\50?
I'm thinking this will be just fine and in fact should be a nice upgrade.
View attachment 910841

Looks isn't everything.... Boosting up filtering capacitance stresses rectifiers. Engineers designed the 3500 with 6800uF
Stick with this value.
FMPOV, you won't get neither better bass rendering or whatever from boosting up filtering capacitance.
 
The original issue on her was that I was getting much higher DC offset on the Right channel - around 52 mV where the left was nice and low, around 4-5 mV if I remember.... I did not look at the bias current though.
 
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