HK A50K recap.

lechlech

New Member
Hello there folks I recently bought a Harman Kardon A50K and I would love to do a recap my self. I not rich and to send it to a profesional electric is gona cost a ton of money. Can somebody please help me? I need a list of caps to buy and some advice with which caps to replace. Perhaps some foto guidence. I would love to do something like this (picture from buickguy62) not fancy with all the cables just to replace the caps.
best regards Lechu.
 

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Hello and welcome to AK! I have an A500 which is the factory built amplifier. Your A50K is the kit version.

This amplifier has a really lovely phono section. If you are a vinyl fan, this is a very nice sounding amp to delve deep into an LP obsession. However depending upon the size of your space you will want to make sure your speakers are efficient. I have found my HK just does not have a ton of power. It is rated at 25 watts and it feels like it is a quiet 25 watts. Speakers with at least 90DB efficient will sound nice. I have a pair of Snell speakers that pair well with the amp.

I did not do any work on my unit myself, so I cannot help with wisdom about DIY updates. However I would check out this thread: http://audiokarma.org/forums/index....rt-on-just-aquired-harman-kardon-a500.249364/

I have not contacted Jim McShane myself, but I understand if you reach out to him he can help with kits for updating these units. http://www.mcshanedesign.net

Also here is another resource for the HK units: http://shermanr.web.prw.net/Page_02.htm

Good luck with your restore! And please post on any progress. The HK amplifiers are well-built units that have wonderful sounding phono stages. Anything you can add to the knowledge base for the A500/A50K would be appreciated.

Patrick
 
I used to have one of these and have followed these whenever it pops up on sites. I have not
seen a recap list so I'd recommend you start id'ing the caps and writing down the values
(capacitance and voltage) and go from there.

from that pix, the orange caps are film caps either older spragues or orange drops as they
are now called. these come in 400 and 630v versions and will depend on where in the circuit
they are being used. in any case, you will want to replace ALL electrolytic caps with newer
equivalents or the orange drops. this amp was discontinued close to 60 Years ago and will
require the recapping.

you'll need a schematic which is available at hifiengine, free to download after registering.

since it's point-to-point wiring it will be easier than working with PCBs.

good luck

Bob
 
Jim McShane sells a nice kit for these amps: http://www.mcshanedesign.net/
I've done several A500s with his parts and it takes the work out of putting together an order, and he supplies very good stuff.

But It is possible that buickguy has a caps list - he's done a bunch of these amps.

Rich or not, you'll get a lot of satisfaction from getting the amp working and sounding good from your own efforts.
 
Hi there i have rebuilt 3 of these. They are a well made solid amp. Your amp has new coupling caps , which are the orange drops. Those are probably still good and makes me wonder if the power supply caps were also replaced at the time that the orange drops were installed. The original PS caps were the metal can type, except the one covered by a cardboard sleeve to insulate the metal which is carrying high voltage in the voltage doubler circuit. But if your unit doesn't hum and those old can caps have been replaced, you might not need to do any work on the amp, except maybe cleaning the pots and the tube socket pins, and the rca jacks. Sometimes cleaning all those things will yield a surprising performance increase.
 
Jim McShane sells a nice kit for these amps: http://www.mcshanedesign.net/
I've done several A500s with his parts and it takes the work out of putting together an order, and he supplies very good stuff.

But It is possible that buickguy has a caps list - he's done a bunch of these amps.

Rich or not, you'll get a lot of satisfaction from getting the amp working and sounding good from your own efforts.

I totally recommend the Jim McShane recap kit. Great components and well thought out, probably no more expensive than buying the parts individually and paying the individual shipping costs.
Tom
 
I totally recommend the Jim McShane recap kit. Great components and well thought out, probably no more expensive than buying the parts individually and paying the individual shipping costs.
Tom

Agree as well about Jim, I've done 4 of these now and the kit that he puts together will make that puppy sing. On top of that Jim is a great person and easy to work with.

If you want to get migrate away from the 7355 tubes (I did on 2) which are a bit harder to source here's a thread that will address that: http://www.audiokarma.org/forums/in...r-shouldnt-i-get-a-harman-kardon-a500.557563/
 
Agree as well about Jim, I've done 4 of these now and the kit that he puts together will make that puppy sing. On top of that Jim is a great person and easy to work with.

If you want to get migrate away from the 7355 tubes (I did on 2) which are a bit harder to source here's a thread that will address that: http://www.audiokarma.org/forums/in...r-shouldnt-i-get-a-harman-kardon-a500.557563/
Actually the 7355 tubes are not very hard to find and are an excellent tube. They are similar to the 7591 in terms of output and quality and it seem to me that doing a rewire and possible resistor changes are way more work than finding some ouput tubes even if takes awhile.
 
Actually the 7355 tubes are not very hard to find and are an excellent tube. They are similar to the 7591 in terms of output and quality and it seem to me that doing a rewire and possible resistor changes are way more work than finding some ouput tubes even if takes awhile.

Very true, the one I've got now I didn't convert but it's not a difficult job if somebody wants to go that direction. Gordon's instructions were easy to follow for an idiot like me so I guess that made them idiot proof? ;)

With that said, I'm a big fan of the 7355 tube.
 
It is another case where a tube that was produced very late in the tube era and so not a huge amount were stockpiled. Its use was not as prevalent as the 7591 which had gained widespread acceptance since its inception. Thus the the 7355's relative obscurity has kept prices lower than other vintage audio power tubes.
 
Hello and welcome to AK! I have an A500 which is the factory built amplifier. Your A50K is the kit version.

This amplifier has a really lovely phono section. If you are a vinyl fan, this is a very nice sounding amp to delve deep into an LP obsession. However depending upon the size of your space you will want to make sure your speakers are efficient. I have found my HK just does not have a ton of power. It is rated at 25 watts and it feels like it is a quiet 25 watts. Speakers with at least 90DB efficient will sound nice. I have a pair of Snell speakers that pair well with the amp.

I did not do any work on my unit myself, so I cannot help with wisdom about DIY updates. However I would check out this thread: http://audiokarma.org/forums/index....rt-on-just-aquired-harman-kardon-a500.249364/

I have not contacted Jim McShane myself, but I understand if you reach out to him he can help with kits for updating these units. http://www.mcshanedesign.net

Also here is another resource for the HK units: http://shermanr.web.prw.net/Page_02.htm

Good luck with your restore! And please post on any progress. The HK amplifiers are well-built units that have wonderful sounding phono stages. Anything you can add to the knowledge base for the A500/A50K would be appreciated.

Patrick

Hello there, I have speakers Acustic Response Series 707 I hope they will sound good when the recap is finished. I will defenetly consider buying the KIT from McShane.

Hi there i have rebuilt 3 of these. They are a well made solid amp. Your amp has new coupling caps , which are the orange drops. Those are probably still good and makes me wonder if the power supply caps were also replaced at the time that the orange drops were installed. The original PS caps were the metal can type, except the one covered by a cardboard sleeve to insulate the metal which is carrying high voltage in the voltage doubler circuit. But if your unit doesn't hum and those old can caps have been replaced, you might not need to do any work on the amp, except maybe cleaning the pots and the tube socket pins, and the rca jacks. Sometimes cleaning all those things will yield a surprising performance increase.

Hello, I will defenetly clean everything very good thank you for the tip.

Agree as well about Jim, I've done 4 of these now and the kit that he puts together will make that puppy sing. On top of that Jim is a great person and easy to work with.

If you want to get migrate away from the 7355 tubes (I did on 2) which are a bit harder to source here's a thread that will address that: http://www.audiokarma.org/forums/in...r-shouldnt-i-get-a-harman-kardon-a500.557563/

Hello there I think I will stay with 7355 for now. Will changeing the socket tubes and the tubes increse the power of the volume?
 
Here Is two photos of mine amplifier.
 

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Will changeing the socket tubes and the tubes increse the power of the volume

No. And your 7355s could be fine. If not, replacements aren't hard to find. Supply might be low but demand is lower :beerchug:

Yours looks good! There is a guy who makes an aftermarket metal case for these that as really nice. Heavy, reinforced, powdercoated finish. I'll see if he's still on the 'bay
 
No. And your 7355s could be fine. If not, replacements aren't hard to find. Supply might be low but demand is lower

Agreed!

I was able to easily find two quads to have on hand for less than you would think. I averaged about $20 a tube and they tested fine. Certain Bogen and Stromberg Carlson amplifiers also used 7355s so they are out there.
 
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