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  #1  
Old 07-01-2011, 08:31 PM
tube-a-lou tube-a-lou is offline
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Harman/Kardon A500 Tube Amp

Hi all,

Went shopping today and someone had a Harman/Kardon A500
Tube amp, needs to be redone and the gentlemen said he'll sell it me
for $250.00, good deal, I always redo these tube's amps anyway so
what do you think??

Tube
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  #2  
Old 07-01-2011, 08:47 PM
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wildone wildone is offline
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Well I have one, and will be using it as my bench amp. I have the matching tuner too. My A500 has the HK tubes still. I have not done anything with it yet, They say they are nice amps. Like 25w per ch.

Pics?

WO
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  #3  
Old 07-01-2011, 09:42 PM
tube-a-lou tube-a-lou is offline
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Hi,
No pics yet, haven't brought it home, looks to be in good shape, look underneath
it has those huge Sprague black beauty caps on it. the guy told me when he put it
on, one of the can caps started to smoke, so I guess that needs to be replaced and
all the rest!

Tube
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  #4  
Old 07-02-2011, 07:27 AM
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GordonW GordonW is offline
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They're really good, once they've been recapped.

I replaced every coupling cap, and every electrolytic cap (including the cans) on the last one I had on the bench. Total of 24 caps. Be sure and don't forget the little electrolytics in the preamp/phono stage!

It sounded magnificent afterward.

Regards,
Gordon.
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  #5  
Old 07-02-2011, 07:38 AM
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Wardsweb Wardsweb is offline
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Location: San Antonio, Texas
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These really are sweet amps once they have been recapped. Here is mine I used for years before giving it to Kamakiri.




Cap job


More pics and the matching tuner here:
http://wardsweb.org/misc/HK_A500.jpg
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  #6  
Old 07-02-2011, 08:34 AM
buickguy62 buickguy62 is offline
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I've restored a number of these with input from Jim McShane. I replace at a minimum all the electrolytic and coupling caps, the balance pots and the diodes, and liberal use of De-Oxit. I have an Excel spreadsheet that lists the components and sources I use --it's a good place to start--you might have your own preference on component selection. PM me for the spreadsheet if interested, I also have the schematic if you need one. One trick I've found is to use two of the dual 50/50 ufd. 500V JJ can caps from tubesandmore (to replace C29 A&B, and C30 A&B). They are under $10 each (plus the clamps), they fit in the existing holes and allow plenty of room underneath for the additional caps-see pics--that area gets crowded if you put all of the replacement caps under the chassis. See pics.
Tom
Attached Images
File Type: jpg IMG_4162.jpg (72.3 KB, 130 views)
File Type: jpg IMG_4180.jpg (55.9 KB, 132 views)
File Type: jpg caps01.jpg (92.5 KB, 147 views)
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  #7  
Old 07-02-2011, 06:27 PM
tube-a-lou tube-a-lou is offline
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Hi all,
Thanks for all the info, I'm really thinking of getting it maybe I'll try to get
him down a little, how about the power tubes 7355 is there replacements,
would 6V6's be good or 7591, I've read that with a little mod you can use
6L6's??

Tube
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  #8  
Old 07-02-2011, 09:53 PM
Patrice B Patrice B is offline
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7591XYZ are known to be a good (and cheap) replacement. Some mods have to be done however to allow it.
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Scott LK-72A, 222D, LT-110 and 350
Fisher X-100-2, FM200-B and 101-R
Harman Kardon A500
Heathkit's AA-100, AA-32
Eico HF-81 and HFT-90

Stromberg-Carlson ASR-333 and SR-445
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  #9  
Old 07-14-2011, 04:39 PM
tube-a-lou tube-a-lou is offline
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Hi,
Decided not to buy it, I'm going to stick with the Fisher. besides he would not
go down in price, it's odd the knobs are off, the front panel is off, the bottom panel
is off and the light button the the switch is missing, so that's it thanks for all the help
and I'll wait for a better one to appear.

Tube

Tube
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  #10  
Old 07-14-2011, 04:46 PM
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GordonW GordonW is offline
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Quote:
Originally Posted by Patrice B View Post
7591XYZ are known to be a good (and cheap) replacement. Some mods have to be done however to allow it.
Actually, the only mod that is needed, is to snip off the one pin (from the base of the tube itself) that the 7591 (and 7591XYZ) uses, that the 7355 does not. IIRC, that's pin 4. Check with a good tube manual... it'll be the pin that's also connected to the screen grid, in parallel with the "normal" pin that's used for screen in the 7355. You only need one screen grid connection... so that one that's in the unused position on the 7355, can go away safely.

Regards,
Gordon.
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