Harman Kardon receiver model hk680i (30+ years old): bad caps

[windser]

This 30+ year old Harman Kardon hk680i has a pair of identical caps (C23 & C24) that appear to have both leaked. These two caps sit on a board identified as the “power supply p.c. board.” I want to find equivalent or better new caps and replace these bad original caps.

Here is what I know about those two caps so far:

TK brand
2200uF +50% -10%
16V
85 deg C
“C-340” ?
height: 1”, 25mm
diameter: 5/8”, 16mm
lead spacing: 5/16”, 8mm

My problem is that I don't think I know enough about the original caps to select an optimal replacement. Neither Digikey nor Mouser show any TK brand electrolytic caps. And then there are additional selection attributes presented by Digikey and Mouser. What about tolerance, ripple current, ESR?

I assume can I safely specify slightly higher voltage and slightly higher maximum operating temperature for better longevity.

Is there anything about the context of the circuit in the schematic that would influence the cap selection?

Anyway, any input that would help in selecting a replacement cap would be appreciated.

[rhomanski]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

That looks like the glue they put on them to keep the caps in place. This should be a fine replacement. http://www.mouser.com/ProductDetail/...52bL5DRVH1w%3d .You should replace the resistor and diode and anything else the glue touched. The glue is usually corrosive when it gets old.

[windser]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

Thanks for the input.

I didn't know that could happen with the glue. Nasty stuff.

When I first saw that brownish material, I thought it might be glue rather than cap leakage. But then I spotted the corroded screw (1 of 4 that fasten that circuit board to the receiver frame) just behind and between the two caps and the end of that resistor that appears crumbly so I figured it must be the corrosive cap leakage doing that. I have attached another photo that shows a better view of this corroded screw. The other 3 screws have the usual shiny plated appearance.

I will plan to replace those additional components along with the caps.

Is there a safe way to remove all traces of that glue before adding the new components?

[rhomanski]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

If it's still tan, you can use acetone and a plastic scraper. The black/brownish is usually so hard it flakes off with a plastic scraper. Anything hard will chew up the board so no screwdrivers or knives. You'll have to replace everything it touches. One time I had a part fall into two pieces before I really touched it. It was already eaten through before I desoldered it.

For a scraper check Mouser. I think I saw one there before.

[windser]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

I was able to remove the old glue by carefully scraping with a modified wooden chopstick and then using a cotton swab dipped in acetone to remove glue residue that did not respond to scraping.

In addition to the diode near the corrosive glue shown above, I have found two more identical diodes on another board affected by corrosive glue. So I have three diodes I should replace.

But finding a replacement diode has not been easy.

These diodes are identified as “1SR35-200” in the HK technical manual. But no supplier I checked recognized such an identifier.

After a research effort, it seems that this is equivalent to “1N4003.” Mouser and Digikey recognize this identifier.

It seems Harman Kardon back in the 1980s specified their diodes using a JIS system for identifying part numbers. But these days it seems an EIA/JEDEC system is used.

At this point I am reasonably sure that a “1SR35-200” diode is equivalent to a “1N4003” diode. But the problem is, I never found an unambiguous cross reference that explicitly matched “1SR35-200” with “1N4003.”

If anyone else has had to deal with this diode substitution problem on old electronics and can confirm that I am on the right track, that would be reassuring to know.

Thx

[CapLeaker]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

that old brown goo goes conductive. It will keep moisture. Get rid of all the brown goo anywhere you see it, always. That stuff is bad.
That 1SR35 is just a general purpose 200V diode made by Rohm. Replacing it with a 1n4003 shouldn't matter as it has the same specs. It is not a ultra fast switching, or schottky diode etc. So replacing it with the 1n4003 wont make a difference.

[windser]

Re: Harman Kardon receiver model hk680i (30+ years old): bad caps

. So replacing it with the 1n4003 wont make a difference.

Thanks for the confirmation that 1SR35-200 is equivalent to 1N4003.

Using flashlight and magnifying glass to peer into all the dark crevices of this receiver, I have identified 8 or so additional caps with this dark brown old glue at their bases--with corrosion visible on nearby component leads. I have my work cut out for me.