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Recapping and repairing a Harman Kardon 730 twin power series stereo receiver

IF there's no issues, you can certainly leave them in. The differential input pair, seen in the blue shrink tubing, has known issues, so should be replaced. There are some diodes, etc, that a lot of folks have issues with when trying to set the amp bias. But again, if you're not having these issues, feel free to leave in place. Some folks want full restorations to future proof the work, others just want to get things back and running. Depends on what you're trying to accomplish. Also, remember that with a long running thread like this, what was a good replacement at first, may no longer be available.
 
jheu02 said:
IF there's no issues, you can certainly leave them in. The differential input pair, seen in the blue shrink tubing, has known issues, so should be replaced. There are some diodes, etc, that a lot of folks have issues with when trying to set the amp bias. But again, if you're not having these issues, feel free to leave in place. Some folks want full restorations to future proof the work, others just want to get things back and running. Depends on what you're trying to accomplish. Also, remember that with a long running thread like this, what was a good replacement at first, may no longer be available.
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Thank you for the response. I want to ensure the receiver is in working condition and then replace all electrolytics and all other compoonents that are known to be problematic like the 2SC1400's. If anyone has a more recent Mouser BOM that I could start with I'd would appreciate it since the one posted is pretty old.
 
Do you know if the one you have works at all, or is this an initial inquiry? You might be best served starting your own thread, as you've seen that this one has gotten pretty long. Another thing to consider when trying to bring this unit up, regarding bias, is the old trim pots. At a minimum, as you try to get it working, you should replace the trimmers with sealed cermet pots, like from Bournes and others.

Dirty switches cause all sorts of havoc with this era H/K. When I rebuilt my A-402s, I completely removed the switch board and opened up the switches for a physical cleaning. No substitute. The selector switch (rotary) can also be a bear to clean. If you listen to vinyl, you'll probably want to modify the phono board to bring it closer to RIAA. When done, it sounds very nice.
 
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I'm just doing my homework at this point. It's on it's way and I'll need to go thru it. Did you pull back the spring and remove the clip to completely open up the switches? It appears the switch boards are a PIA to work on.
 
davefr said:
Thank you for the response. I want to ensure the receiver is in working condition and then replace all electrolytics and all other compoonents that are known to be problematic like the 2SC1400's. If anyone has a more recent Mouser BOM that I could start with I'd would appreciate it since the one posted is pretty old.
Click to expand...
You'll want to likely order the small signal transistors if you don't have them (KSA992, KSC1845 do the bulk of the subs there; and whatever you go with for the heat sink and other main amp board subs).

I am nearing a Mouser order for the main amp boards, tone and PS area and have sourced the best (to me, far from an expert) in stock there for these three areas (if you remove the parenthesis you can just plug this into the BOM builder; the quantity follows the part number and the BOM builder will note that.) :

Power supply
647-LLS1H682MELZ 4 (main caps) or 232-50PK4700MEFC18X4 4 (direct fit)
647-UPW1C222MHD1TO 4 (rectifiers)
647-UPW1E471MPD6 2 (rectifier)

Power amp boards
652-3362W-1-102LF 2 (1K pots)
647-UKL1C101MPDANA 4 (100uf 16v, sub for 10)
647-UKA1A102MPD 4 (1000 uf, 10v)
647-UKL1A221MPDANA 2 (220, 6.3 general purpose)

Tone and local rectifier boards
647-UKL1C101MPDANA 2 (Selector top board 2 Capacitor Electrolytic 100 uF 10 V signal)
505-MKS2C041501H00KI 2 (Tone control and local rectifier 2 Capacitor Electrolytic 1.5 uF 35 V signal)
647-UKL1C101MPDANA 2 (Tone control and local rectifier 2 Capacitor Electrolytic 100 uF 10 V signal)
647-UPW1E102MHD1TO 4 (Tone control and local rectifier 4 Capacitor Electrolytic 1000 uF 25 V power)
667-EEA-FC1E220B 4 (Tone control and local rectifier 4 Capacitor Electrolytic 22 uF 16 V signal; NOT MANY OPTIONS EXIST FOR SIGNAL PATH)
647-UPW1E221MPD1TD 2 (Tone control and local rectifier 2 Capacitor Electrolytic 220 uF 6.3 V power)
 
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da_kube said:
You'll want to likely order the small signal transistors if you don't have them (KSA992, KSC1845 do the bulk of the subs there; and whatever you go with for the heat sink and other main amp board subs).

I am nearing a Mouser order for the main amp boards, tone and PS area and have sourced the best (to me, far from an expert) in stock there for these three areas (if you remove the parenthesis you can just plug this into the BOM builder; the quantity follows the part number and the BOM builder will note that.) :

Power supply
647-LLS1H682MELZ 4 (main caps) or 232-50PK4700MEFC18X4 4 (direct fit)
647-UPW1C222MHD1TO 4 (rectifiers)
647-UPW1E471MPD6 2 (rectifier)

Power amp boards
652-3362W-1-102LF 2 (1K pots)
647-UKL1C101MPDANA 4 (100uf 16v, sub for 10)
647-UKA1A102MPD 4 (1000 uf, 10v)
647-UKL1A221MPDANA 2 (220, 6.3 general purpose)

Tone and local rectifier boards
647-UKL1C101MPDANA 2 (Selector top board 2 Capacitor Electrolytic 100 uF 10 V signal)
505-MKS2C041501H00KI 2 (Tone control and local rectifier 2 Capacitor Electrolytic 1.5 uF 35 V signal)
647-UKL1C101MPDANA 2 (Tone control and local rectifier 2 Capacitor Electrolytic 100 uF 10 V signal)
647-UPW1E102MHD1TO 4 (Tone control and local rectifier 4 Capacitor Electrolytic 1000 uF 25 V power)
667-EEA-FC1E220B 4 (Tone control and local rectifier 4 Capacitor Electrolytic 22 uF 16 V signal; NOT MANY OPTIONS EXIST FOR SIGNAL PATH)
647-UPW1E221MPD1TD 2 (Tone control and local rectifier 2 Capacitor Electrolytic 220 uF 6.3 V power)
Click to expand...
Thank you, this is very helpful!
 
dlucy said:
The secondary rectifier board on the 330A, 330B, and 330C tends to show up on my workbench with burned-through or skin-burned-off resistors, but this 730 showed no signs of this problem, so replacements were for the electrolytic caps only.

View attachment 1645948
View attachment 1645949
View attachment 1645943
View attachment 1645944

Just like the prior generation boards, these have no silkscreening, so some reference photos and markings to help reassembly.

View attachment 1645945
View attachment 1645946

and the resulting recapped secondary rectifier board

View attachment 1645947
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Hello @dlucy, I am about to replace the sub rectifier electrolytic capacitors on a HK 730. I noticed that the service manual has C1, C3, C4 listed as 220uF, 16V instead of the 2200uF, 16V that's in the receiver (similar to what you have posted here). Is this a known typo in the service manual for HK 730?
 

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JBL-L26 said:
Hello @dlucy, I am about to replace the sub rectifier electrolytic capacitors on a HK 730. I noticed that the service manual has C1, C3, C4 listed as 220uF, 16V instead of the 2200uF, 16V that's in the receiver (similar to what you have posted here). Is this a known typo in the service manual for HK 730?
Click to expand...

The service manual must be wrong. What is installed in the HK 730 from the factory are 2200uF caps on the sub-rectifier board.
 

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