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Recapping and restoring a Harman Kardon 330C

401 and 402 does not make any difference. I am thinking a mismatch on Q401/403 or other such pair... will have to do some debugging. Will update if I find something. In the meantime if you guys can think of something please let me know.

Doug,

Thank you very much for such comprehensive thread on 330C. It is very helpful.
 
Great thread. :lurk:

Wanted to make a comment about the use of D5 and Fader Lube. I am finding that my 330C needed a thorough cleaning of the switches and pots. I was getting an intermittent crackle and loss of the Left channel after acquiring this unit about 2 weeks ago. After spraying the balance pot out twice it cleaned up and I 'thought' I fixed the issue. After a few days and a lot of run time for hours, the problem occurred again in both channels when I depressed the Monitor push button switch. So, I hit that with Fader Lube (worked the switch like crazy) and so far it's performing just great.

I'm debating on doing a full recap although I have ordered all the parts to do it. The 330C just sounds fantastic to my ears. The Contour function gives it a nice extra boost. A really nice sounding receiver and the FM tuner/meter portions work flawlessly! Guess, I was fortunate to find this unit,...:biggrin:
 
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8xlaxx said:
I'm debating on doing a full recap although I have ordered all the parts to do it. The 330C just sounds fantastic to my ears. The Contour function gives it a nice extra boost. A really nice sounding receiver and the FM tuner/meter portions work flawlessly! Guess, I was fortunate to find this unit,...:biggrin:
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I will say again, although it is just my opinion, that a recap does audibly improve the 330C.
 
ENGRF said:
@fuxtor... . It is bugging me OCD :). Will chase it some more next week.
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If you have no tester, you can use a 9 volt battery and a couple resistors. Can't remember off hand but search for a YouTube video for diy transistor tester... The fellow was using some breadboard, but I just used some jumpers instead. Matched a whole pile of differentials for my Hafler DH200. Worked like a charm!
 
Thanks ENate, I might build a set. As far as matching goes, only the diff pair on main amp needs to be matched, correct?
 
Ok, bulit ckt for NPN. I am getting around 1 mV between pairs. It oscillates a bit but settles near around 1mV. Is this sufficient? Hfe 404 for two that I tested.
 
What I do is leave one in place and switch out the other side, then match them based on the readings vs trying to find pairs that zero out the reading. I match to a tenth of a mV but that's probably excessive. Your ability to do that will depend a lot on your meter's capability as well. 1 mV isn't terrible.
 
I looked over the schematic and since this amp section doesn't use a current mirror simply matching the diff pairs should be sufficient as long as the 33k resistors feeding each side are in spec. :)
 
Thanks ENate. I was suspecting those 33K, not sure if these are 1% tolerance or 5. I did see different drop across those between two channels, it could be different current flow due to transistor also. Will check and will also look at those diodes. Now, I can't get it out of my head... Sigh...
 
Just in case if anyone wants to replace the lamps to LEDs, this is what I used. Worked well. I had several lamps including power lamp. All LED now :).

Moderator edit: removed link to ebay auction as that violates AK rules.
 
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Well I am down to 2mv and 18 mv after replacing the transistors. There is still something off with the channel that was 65mV, it is still 16 or so mV higher than the other one. Oh well, I might simulate it one of these days. Bugs me though...
 
ENGRF said:
Well I am down to 2mv and 18 mv after replacing the transistors. There is still something off with the channel that was 65mV, it is still 16 or so mV higher than the other one. Oh well, I might simulate it one of these days. Bugs me though...
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Did you replace the transistors in both channels? If not, that's a potential source of the difference.

If you did replace both channels' transistors, then I'd guess the resistors prior to those transistors were out of sync, value wise, with the other channel.
 
I did change both channels. Diff pair to matched one and the other two as well. In total six KSC1845. It could be the gain resistors or something else down the chain. Actually if rail voltages are off ever so slightly that might add to it as well. I will dig deeper at a later time, will enjoy music for some time before that :). I need to understand this better as HK930 has a very similar architecture, will help me when I work on that.
 
Ok, so I was giving it a listen last night and it seems that in mid position treble is quite muted. I have to crank it all the way up to hear it at a good level. My HK930 is bright at mid position. It appears to be on both channels. Is this how it is designed? Should I have to crank it all the way up? Isn't is supposed to be flat response at mid position for all the controls? Any input is greatly appreciated as always.
 
ENGRF said:
Ok, so I was giving it a listen last night and it seems that in mid position treble is quite muted. I have to crank it all the way up to hear it at a good level. My HK930 is bright at mid position. It appears to be on both channels. Is this how it is designed? Should I have to crank it all the way up? Isn't is supposed to be flat response at mid position for all the controls? Any input is greatly appreciated as always.
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That is not normal behavior. It sounds like your treble pot has a dead spot or a worn spot.
 
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