harman/kardon hk775 amplifier restoration

z-adamson

Addicted Member
Getting the ball rolling on this and to start I will order all the parts first rather than waiting till later.

I have a complete parts list which helps. However, I want to order the right aluminum e-caps for the job rather than just blindly ordering audio grade caps of the right value. I would also like to order transistors. And replace the big filter caps.

I hope to order this week, sooner is better.

So, which caps do I order to replace which caps.
 

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So, the filter caps are 15000uf, 71v. I dont want to use just any cap that fits those specs. What would you recommend?
 
I pick caps by color. You can too.

With such limited information if someone doesn't have a recap list, you need to make one.
Figure out what is in the signal path and use good caps there
Many use film caps to replace anything 4.7 µF or lower
Measure the lead spacing of all caps and duplicate
Measure size of the big caps and get ones that fit.
Use same µF but you can go up in voltage (ConradH recommends 35V minimum for the small ones) unless you know what a change in capacitance will do in the circuit. There are some recap threads that discuss upping the capacitance and what it means. Those guys aren't cap swappers but technically trained knowledgeable repair/rebuilders.


We'll be looking for your list and make comments.
 
Historically I had gone to mouser and got nichicon caps, audio grade, same values. Results were good. However it was said that I should have used low leakage caps in certain spots, low esr in others.

My goal is to select caps with the proper characteristics beyond uf and voltage ratings this time.

I understand this amps runs hot so 105c spec caps will be used.
 
What Blue was getting at (see I didn't use B.S. :D) is it will be helpful if you post a list. If the SM breaks it down by board, all the better. One thing to always do is check what's actually installed vs what's listed in the SM. That will sometimes give you clues as to what to use where...i.e. the orange caps you now know are low-leakage or special in some way like being bipolar.
 
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Here is the list.

Let me state up front that all the caps are black unless specified otherwise.

Power output and protection...4 caps @ 22uf, 100v....1 cap @ 47uf, 10v.....1 cap @ 33uf, 16v....2 caps @ 10uf, 16v - orange

Power output and rectifier...2 caps @ 1000uf, 50v....2 caps @ 1000uf, 80v....1 cap @ 10uf, 16v - orange

Driver.....1 cap @ 10uf, 16v - orange

Power supply....2 caps @ 15000uf, 71v

Pre-driver....2 caps @ 10uf, 16v

Filter switches.....2 caps @ 100uf, 16v - orange......2 caps @ 1uf, 50v - orange

Power level display driver....1 cap @ 1uf, 50v - orange
 
My responses will be imbedded:

Here is the list.

Let me state up front that all the caps are black unless specified otherwise.

Power output and protection...4 caps @ 22uf, 100v....1 cap @ 47uf, 10v.....1 cap @ 33uf, 16v.... use any of the following: Panasonic FM, FR, FC Nichicon HE, PW, PM. 22/100v, 47/25v, 33/25v ... all these are 105C rated

2 caps @ 10uf, 16v - orange Nichicon KL 10/25v look for the 105C rated version, they also come in 85C depending on space available, you could even stick film caps here. I believe Wima has a fairly small profile even for a 10uF cap. Typically film caps get too large for values over about 4.7uF.

Power output and rectifier...2 caps @ 1000uf, 50v....2 caps @ 1000uf, 80v.... same brands as for power board though you may be able to increase the capacitance and I would also increase the voltage rating if you can find the caps. 2200uF is a modest increase and shouldn't tax things, 63V and 100V respectively will give you beefier caps to handle line voltage variations.

1 cap @ 10uf, 16v - orange Nichicon KL 10/25V

Driver.....1 cap @ 10uf, 16v - orange Nichicon KL 10/25V

Power supply....2 caps @ 15000uf, 71v not knowing whether these caps are snap in, screw terminal, solder terminal nor the diameter and length makes it harder to choose here. I've had good success with the following series from United Chemicon: http://www.mouser.com/ProductDetail...GAEpiMZZMvwFf0viD3Y3Xi7NNkeU1cCOHzm9z%2bKVU4=


Pre-driver....2 caps @ 10uf, 16v 10/25v same as power boards though you could also stick KL here to get the total number of that series up to a bulk discount

Filter switches.....2 caps @ 100uf, 16v - orange Nichicon KL 100/25V

.....2 caps @ 1uf, 50v - orange polypropylene film or polyester film. Wima MKP or MKS, Kemet R82 1/50V, you may need to look at 63V and 100V to find some since manufacturers have decreased the number of voltage ratings available. There are other brands available, these are ones I've used. The Panasonic stacked films are good too...ECQ series. Wimas often have short leads however, so make sure you get ones that'll fit properly

Power level display driver....1 cap @ 1uf, 50v - orange Same as above film
 
Power supply....2 caps @ 15000uf, 71v not knowing whether these caps are snap in, screw terminal, solder terminal nor the diameter and length makes it harder to choose here. I've had good success with the following series from United Chemicon: http://www.mouser.com/ProductDetail...GAEpiMZZMvwFf0viD3Y3Xi7NNkeU1cCOHzm9z%2bKVU4=

Moving forward with this project, I have the amp apart and the filter caps are definitely soldered to the board. Does not have the appearance of a screw in or snap in, and perusing the mouser site, there are no offerings other than screw in and snap in. Kinda looks like the snap in version with the 45* bends broken off. Any idea what this could be?

The manual for this amp really sucks. There are many components on the boards that are not listed. Hmmm.
 
When you get one desoldered we'll know for sure. They'll either be snap in or solder lug (straight prongs sort of like a thin screwdriver blade). Take good "before" pics to aid in reassmbly (polarity, etc). Since the manual is poor, I would definitely make a list of the capacitor values and positions and plan on desoldering/installing one part at a time vs a mass desoldering and then parts installation. Any problems with it before you started opening it up? i.e. was it functioning properly or do we need to fix it first before recapping?
 
It was seemingly functional before opening up. I only listened to it for a short time with the hk725 which was a long ways from full health however. I would like to restore to like new condition.

They are definitely solder lug...ie flat head screw driver blade, still no pic, but that is what it is. What is the term for this on mouser? I could have missed it, but I didn't see solder lug on there.
 
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I am contemplating replacement of the output transistors.

They are 2SA1094 and 2SC2564...toshiba. Four each per amp, so 8 each total.

Neither Mouser nor their main competitors have them. A few ebay guys have them, but they want big money for them. Is there a good replacement that is economical and readily available through mouser?
 
It was seemingly functional before opening up. I only listened to it for a short time with the hk725 which was a long ways from full health however. I would like to restore to like new condition.

They are definitely solder lug...ie flat head screw driver blade, still no pic, but that is what it is. What is the term for this on mouser? I could have missed it, but I didn't see solder lug on there.

What are the dimensions of the large cap?
 
Filter cap pics...

52mm diameter, 80mm length, 22mm center to center in the terminals
 

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These are a little long (100mm) and unfortunately only one in stock currently, but would be a good choice when in.

http://www.mouser.com/ProductDetail/Nichicon/LKG1K153MKZ/?qs=sGAEpiMZZMvwFf0viD3Y3TGBqvvFdz90Rzy/6Nc/jdMl79%2bkbKRswQ==

These are screw terminal, but pretty perfect. Just get a thin piece of flat copper, drill a hole for the screw, and make your own tabs. With the way they're mounted, you actually have lots of options.

http://www.mouser.com/ProductDetail/United-Chemi-Con/E36D750MLN183TC79M/?qs=sGAEpiMZZMvwFf0viD3Y3ZyaTCbqW/DTN9TU0mrie7w=

EDIT: Perhaps even using 10 or 12 guage solid copper wire soldered to a ring terminal with silver solder for it's higher melting temp. Then pound flat the end not soldered to make your tab. No drilling required.
 
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Some other items I am trying to replace but not sure what to use.

-Variable resistor.....VR402....part#.....5101 1517475.....150ohms
-Variable resistor.....VR401....part#......5101 1027875.....1kohms

I would like as many turns as I can get to aid in adjustment.

-Cement resistor...R446,447,448,449,450,451,452,453...part# 5723 R33672.....0.33ohms, 3watt x 2 special dual (2 leads on one end, 1 on the other).
 
Some other items I am trying to replace but not sure what to use.

-Variable resistor.....VR402....part#.....5101 1517475.....150ohms
-Variable resistor.....VR401....part#......5101 1027875.....1kohms

I would like as many turns as I can get to aid in adjustment.

-Cement resistor...R446,447,448,449,450,451,452,453...part# 5723 R33672.....0.33ohms, 3watt x 2 special dual (2 leads on one end, 1 on the other).

If you can get a nice picture of how the trimmers are oriented it will help in selection. It's hard to tell from the SM whether you'll need side adjust or top adjust, hence the photos. I'm not having much luck finding 150ohm...you may need to go to 200, again, depends on orientation. VR402 for setting Bias would be better served by a single turn or it will take forever. DC Offset will benefit from multiturn. Haven't yet lookd for the dual resistors. Do you know if they're bad? Most times they're fine.
 
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