80v caps--alternative?

[Reeler]

From a novice, if the original design calls for 4 x 15,000uf 80v Capacitors at the input power stage, can these be replaced with any other configuration?

It is becoming increasingly impossible to get caps at 80v. What safe mixture of caps can accommodate the same job?

Thanks.

[Enzo]

The original was probably not rocket science, so some variation woulod likely be OK.

Your circuit shows four 15000uf caps? In parallel? Or two for each polarity? what do you have?

If you can;t find 80v parts, look for 100v parts.

4x15000 would be the same as 3x20000 or the same as 6x10000uf.

[Reeler]

Thank you Enzo,

You should be able to see the caps (in black) at the bottom of this photo. They are all 15,000uf 80v. I believe I should have said 'output' stage instead of input.

I was hoping to get exact matches, in make, power & dimensions - however it is proving impossible; not least because everything seems 'snap-in' these days and the power ratings seem to be geared to 63v.

If I raise the voltage threshold to 100v will I need to consider the ratings of any other components following these caps?

Reeler

[ostripper]

Originally Posted by Reeler

Thank you Enzo,

You should be able to see the caps (in black) at the bottom of this photo. They are all 15,000uf 80v. I believe I should have said 'output' stage instead of input.

I was hoping to get exact matches, in make, power & dimensions - however it is proving impossible; not least because everything seems 'snap-in' these days and the power ratings seem to be geared to 63v.

If I raise the voltage threshold to 100v will I need to consider the ratings of any other components following these caps?

Reeler

@100V, all you will do is have a more reliable amp. You must have 70V rails , most OEM's only derate by 10-15% ... some less (75V rail for a 80v cap). At 100V , you will likely get 10 years or much more from the amp. NOTHING else will change by increasing voltage rating. For size requirements , you could go down in amount of capacitance (10K - 12.6KuF) without any real issues.

A note .... if these caps are bad , the rest can't be far behind. Replace them all.

PS - to clarify , it looks as through you have (+65 -0- -65) to (+72-0- -72 )volt supplies , 2 -15Kuf@80V caps for each voltage "rail". Both amps (6 device BJT output stage) run off this single large power supply.
OS

[Reeler]

Hi OS,

You can tell all that by sitting where you are? That's the point I want to reach in my DIY study.

You are, of course, quite correct!

+73-0--73

Luckily these caps in this amp and her two sister amps are still very good. I am in the throes of rebuilding (component changing) these amps but at the same time I am enthusiasticly gathering in enough parts to build a few more of these amps from scratch.

Its a very steep learning curve for me. You can see some of my fits & starts on this thread --- Japanese to English translation ---

So Ostripper, in light of your knowledge some thousands of miles/kilometers away, I would like you to chaperone me from time to time. I'll keep a spare soldering iron warmed up for you here.. should you feel like popping in for a "Cafe America" sometime. All help from afar is greatly appreciated.

PS there are 12 BJTs (6 of pnp & 6 npn) Maybe that's what you said anyway....I told you I was a novice

Best Regards from the mountains above Barcelona

[ostripper]

No big deal , with classic amps like yours I can fix them with no schematic. If you gave me a full pix , I could most likely tell you it's design (topology). I have only seen that heatpipe thermal solution on a harmon-Kardon , nikko , or luxman amp. I have only repaired about 1200 amps/receivers in the last 25 years , mostly japanese OEM's. I only recently figured out how they REALLY work , so I am sort of a "novice" myself in the DIY arena.

If you have any questions , I would be glad to answer the best I can (still a novice)
PS - with a model # , I could even get the schematic for it .. reverse engineer it in a "snap".
OS

[Reeler]

I think you really should read my thread Japanese to English translation

It is only 3 pages at the moment and from what you have said already I think you might get a spark of delight in wanting to 'wade in' with your rubber boots and 'man kill' plug.

I have the schematics, full build instructions and 2 out of 3 working amps to help me (and the forum) but the Japanese didn't make things easy..... read on in the thread.

From a novice to a "novice" (tongue in cheek --- I've followed some of your postings ) perhaps you can tell me what liquid is used in these pipes? I want to get some made up without breaking open one I have. The liquid is enclosed and doesn't move around.

Incidently [see photos], the fins...which sit either side of the transformer and surround the heat pipes....are they designed to dissipate heat, control magnetic interferance, or both? I have been told variations.

The amps are Luxkit, (Luxman) Z504 or A504, depending where you lived when you bought one.

Reeler

[tauro0221]

Hi,
You can buy them from Mouser they have it. Also you can buy them in EBAY. If you buy from Ebay make sure you buy from good brand name.

Tauro0221

[ostripper]

The old heatpipes used a blend of ammonia and alcohol. Heat pipe - Wikipedia, the free encyclopedia

If the pipe is sealed they should not deteriorate , but they do lose some efficiency with age. Newer heatpipes use sodium and other exotic materials. Your heatpipe evaporates the ammonia/alcohol at the transistors , then it condenses again in the fins ... flows back to the transistors , etc. You should not run this amp in any position besides horizontal. The newer heatpipe solutions (like in a PC) are affected less by position.
This is a drawback to heatpipe cooling. you might want to reapply thermal compound to all transistors and where the pipe interfaces to the aluminum block.

I want the schematics ,I think this amp is similar to my luxman clone (GX) by closely looking at the voltage board.

OS

[Reeler]

Thank you Tauro, I shall have a look into that.

OS, the file is too big to upload on the site. PM me with you email and I'll pass it on.