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Old 25th July 2011, 09:58 AM   #1
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Default pio coupling caps - damaged/used?

I recently replaced some 1uF capacitors in a 6DJ8 SRPP stage with these ones:

1UF 300VDC SELF HEALING PAPER IN OIL CAPACITOR fd1f9 | eBay

I installed them and 120v dc went straight into my power amp! Luckily there are capacitors at the input of my power amp.

I checked with my multimeter, the continuity tester is signalled straight away, it appears there is no capacitance at all in these paper in oils!

Does anyone have some suggestions as to how I can test if they are used/damaged?
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Old 25th July 2011, 10:14 AM   #2
oshifis is offline oshifis  Hungary
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They are feed-through capacitors, meaning the capacitance is between the wires and the metal case.

They are not even PIO. From the datasheet:

MKP technology (dry, self- healing)
Dielectric: polypropylene, metallized
Metal case with synthetic resin terminals

Last edited by oshifis; 25th July 2011 at 10:19 AM.
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Old 25th July 2011, 10:20 AM   #3
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they work in the same way as any axial capacitor, correct?
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Old 25th July 2011, 10:56 AM   #4
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where did you find the datasheet for these capacitors? I've been looking all over the place for it!

OK - so to connect it correctly:

(1) run a flying lead from the pcb hole to the top of the capacitor - it has a washer/nut that can tighten on the lead
(2) the wire from the capacitor (either end) can be soldered to the other hole in the pcb

does the polarity matter?

Last edited by lordearl; 25th July 2011 at 10:59 AM.
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Old 25th July 2011, 11:03 AM   #5
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35$ for one cap

BRB looking for such things in my cellar....
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Old 25th July 2011, 11:15 AM   #6
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No, these are used for de-coupling mainly. The two wires are connected internally--ie, shorted together.

The capacitor is formed between the Case--Thats intended to be grounded, and the wires....

Feedthrough caps are used to pass supplies into a metal box containing sensitive oscillators and such like.....

They aint really intended for audio coupling....
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Old 25th July 2011, 11:20 AM   #7
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The guy selling them prolly doesnt know--Or Care-- exactly What they are....

21 quid is a rip-off in my opinion, for a cap thats not really intended for coupling in audio!

Personally, I would send 'em back and find a proper PIO cap intended for coupling!
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Old 25th July 2011, 11:31 AM   #8
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Darn it...you like and learn!

Another option....I do have some of these:
2PCS 4.7uF 250V B&W Nautilus 800 Customize ClarityCap | eBay

Might be a better choice (although they appear to be for speakers).

The Siemens "paper in oil" (supposedly) might come in handy for something else (god knows what, though!)
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Old 25th July 2011, 11:37 AM   #9
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What value does the circuit call for...?

You've gone up from 1uF to 4.7uF.....

In some cases, a drastic increase in value may cause you issues...
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Old 25th July 2011, 01:03 PM   #10
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Quote:
Originally Posted by Alastair E View Post
What value does the circuit call for...?

You've gone up from 1uF to 4.7uF.....

In some cases, a drastic increase in value may cause you issues...
Schematic attached - we're talking about C4 in the tube output stage. The unit shipped with a 1uF capacitor, however the schematic appears to read 22uF(!). Surely this should be 2.2uF? I think it is actually there to block the DC.

I'll try the 4.7uF and see the result - any other suggestions would be great!
Attached Files
File Type: doc Schematic DAC AD1865_SRPP.doc (89.5 KB, 42 views)

Last edited by lordearl; 25th July 2011 at 01:07 PM.
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