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4 terminal capacitors

J

Jeddy

Well-Known Member
Hi,
My Amp has been playing up after not being used for a while. I've replaced all the small capacitors which were leaking and the mosfets which has mostly fixed the problem, however I still have a problem while the amp warms up, so I suspect it's the 2 big capacitors which need replacing next.
The amp is a Roksan (20+ years old) and they didn't have any indication of what they were, however Roksan have kindly advised me that the capacitors are 10000mfd 63v (I suspect mfd means micro farad rather than millifarad).

However, the capacitors have 4 terminals.

I'm therefore looking for a couple of 10000 mfd 63v 4 terminal solder terminal caps.

Can anyone point me in the right direction for a replacement. Roksan have advised me that the original caps were specially made for them which is slightly worrying.

Thanks,
Jeddy
 
martin clark said:
What is actually the issue..?
Click to expand...
When I turn the amp on I get quite a bit of noise, crackling etc., it tends to settle down after a while.
Given I've replaced all of the smaller caps and the mosfets and the circuit is relatively simple I'm not sure there's much else of significance there which is likely to go wrong is there?
(Just for clarification this is a power amp. as opposed to a pre-amp or an integrated amp.)
 
BHC T Power. From HiFi Collective. The 63v are 40mm dia x 55mm high.
bhc-t-power-10000uf-63v-350.jpg
 
Sorry to hi-jack the thread, but I've known that these 4 terminal electrolytics exist, but can't get my head around what is inside, how you'd use them, and what the advantage (if any) is? Can anyone explain, for the relatively non-electronic layman?
 
Thanks for the links guys.
The BHC ones have odd spacing on the terminals which may present a problem, however the DNM ones look hopeful, a tad pricey given there is a doubt as to whether they'll fix the problem though, oh well.

No worries Jem, I've been asking myself similar questions. From my perspective I'm simply after a straight swap but like you I am curious. I managed to find a bit of information online, but am still left wondering.
 
JemHayward said:
Sorry to hi-jack the thread, but I've known that these 4 terminal electrolytics exist, but can't get my head around what is inside, how you'd use them, and what the advantage (if any) is? Can anyone explain, for the relatively non-electronic layman?
Click to expand...

It`s a mechanical thing, 4 tags to improve the fixing of a relatively heavy component, from memory of the type used on older Tektronix scopes, three negative terminals and one positive.
 
JemHayward said:
Sorry to hi-jack the thread, but I've known that these 4 terminal electrolytics exist, but can't get my head around what is inside, how you'd use them, and what the advantage (if any) is? Can anyone explain, for the relatively non-electronic layman?
Click to expand...

Good question. I think there are two 'basic' types of 4 pin electrolytic.
First is a normal 2 pin (plus and minus) type with added pins for mechanical stability.
Second is the 'Four pole' type, where the supply plus and minus use one pair of pins and the output from the cap is on the other two pins. Mundorf and Jensen and others make these. (Explanation here: http://jensencapacitors.com/CustomerData/Files/Folders/4-pdf/5_4pole.pdf see fig. 2 and 3 for the differences.)
Not sure if the pin layout prevents incorrect usage? The Jensen and Mundorf have 'square' spacing. But I see that used on ordinary electrolytics too as well as the more common irregular spacing...

It would be important to check what sort are used in the Roksan before ordering replacements...
 
Should of added, is it both channels or one side that is noisy? Was it the problem you replaced the caps and FETs for or started since? Etc...
A squirt of freezer spray and gentle tapping with a tooth pick might locate a faulty joint or component, before doing the big caps.
 
http://www.dnm.co.uk/ALN20S.pdf

These look like Caps designed for a particular PSU configuration. You can't just cut the pins off, as they are all functional.

I would go for standard Low ESR 10,000Mfd 63v Caps in the Roksan.

Do you have a picture of the Roksan Caps, or the specs written on the side?
 
snowman_al said:
Second is the 'Four pole' type, where the supply plus and minus use one pair of pins and the output from the cap is on the other two pins. Mundorf and Jensen and others make these. (Explanation here: http://jensencapacitors.com/CustomerData/Files/Folders/4-pdf/5_4pole.pdf see fig. 2 and 3 for the differences.)
Click to expand...
Ah, that explains it - makes (sort-of) sense, I assume such capacitors wouldn't benefit from small bypass caps in the way larger electrolytics possibly can.
 
JemHayward said:
Sorry to hi-jack the thread, but I've known that these 4 terminal electrolytics exist, but can't get my head around what is inside, how you'd use them, and what the advantage (if any) is? Can anyone explain, for the relatively non-electronic layman?
Click to expand...

No advantages. A sales gimmick that's all. ESR differences between caps of varying constructions would swamp any differences due to the way the last few mm of wiring in the cap is done.
 
My original problem was a big one, as in I blew a woofer twice before working out I had a problem and where the problem was (lent the gear out, while I wasn't using it, some years later it was returned and I found a woofer was blown, I assumed someone had just burned it out, it was only when I replaced the woofer and burt a woofer myself I realised I had a problem. Took the amp to a guy to fix it, he decided that because the 10 or so small caps were leaking it wasn't worth repairing! I replaced the small caps and mosfets and it mostly works, but was noisy when turning on but settled down after a while, but it seems to be getting worse.)
It's mostly the left channel, but I think the right to a degree too, I've not tried removing speaker cable to left to check right on its own.
You may have to spoon feed me a bit with the freezer spray / tooth pick suggestion I'm afraid.
I guessed that because it improves when powered up that it may just be a cap which is starting to break down so struggles from completely discharged - that and there's not much else on the circuit to go wrong, well, as you say bad joints etc..

The caps have Roksan plastered all over them, the only other writing is LW 30199 on the label and 9044 on the top and googling that finds nothing of interest.

I need to check that they are wired into the circuit (i.e. not just supportive), but assuming they are, I'm curious how I can replace them with a standard cap, 2 wires into 4 holes on each channel?

Thanks.
 
I need to get these caps off to see what's going on - but that's one for Monday.
It looks like 2 of the 5(!) terminals have been soldered nicely onto the board and the other 3 terminals have much less solder around them so I'm starting to think they are for support (although there are also 4 'feet' keeping the caps stable. Maybe it is just 2 terminals. It also looks like both terminals are on one side of the cap (12 o'clock and 4 o'clock on the top channel and 3 o'clock and 7 o'clock on the bottom channel) so finding similar is going to be impossible. I have room at the side of the cap but not at the top / bottom - hopefully a replacement cap has long terminals.

43502681422_77c2e5ec11_k.jpg


42832289894_07540b2aad_k.jpg


28662415687_a158d04fea_z.jpg


I've also realised that I only replaced the 4 mosfets attached to the heat sink last time (pretty central but you can only see the terminals to the left of the line of 4 black resistors and not the 4 on the left. Not sure how likely they are to have gone.

Any comments or thoughts most welcome.
Thanks.
 
Very unlikely that any of the mosfets has failed.
I would resolder the input terminals. Direct mounting of phonos without any (or limited) mechanical support is not ideal.
Same comment for the output terminals, but less so.
 
Just to throw the cat among the pigeons, I havent seen one of these before

At roughly 3min 56sec into the video


A picture of the other side of the PCB might be an idea as there no visable circuit traces to follow.
 
Those caps will almost certainly be BHC (now Kemet) in production packaging.

Chances are you can find a drop in replacement with compatible pin configuration from their current range.
 
Barrymagrec said:
It`s a mechanical thing, 4 tags to improve the fixing of a relatively heavy component, from memory of the type used on older Tektronix scopes, three negative terminals and one positive.
Click to expand...

So just a single cap, not two caps in one can like the ones in a Leak Stereo 20 and many guitar amps (and my Verdier preamp)?

PS What is the correct name for the twin caps in one can things? I never know what to search for!
 
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