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Old 14th May 2012, 12:45 AM   #1
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Default plessey cap replacement

Hello, first post and all that.

got a sweet pre amp that's just lost one output channel. so i open it up to see if anything obvious is wrong. one of the paper caps has shed its oil.
it's a plessey uk paper capacitor
0.5uf +/- 20%
400v.ac wkg
p54043

Anybody know where these can be acquired? help appreciated

Click the image to open in full size.

tour of insides

Last edited by john townshend; 14th May 2012 at 03:14 AM. Reason: wrong link
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Old 14th May 2012, 02:47 AM   #2
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for the curious amongst you, its an arcadia all triode phono and line pre amp which goes into one of simons 300b systems. i've looked everywhere on the web, i guess a quality equivilant will do, just want my stereo back. i'm stuck on my old cambridge audio. have mercy.
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Old 14th May 2012, 10:07 AM   #3
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Nobody?
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Old 14th May 2012, 12:02 PM   #4
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Plessey stopped making caps decades ago.

Any 0.47uF 20% or better, (non-electrolytic) film will do fine, but check the voltage rating.

400V is safest, but the actual voltage required may be somewhat less.

Just searched Maplin:

http://www.maplin.co.uk/audio-grade-...capacitors-393

will do.

Last edited by cliffforrest; 14th May 2012 at 12:05 PM.
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Old 14th May 2012, 12:41 PM   #5
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cheers for that.
now this thing cost me a small fortune a while back. i want to make sure it sounds as amazing as it did before.
this is the insides
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

i want to make sure that i either have to replace all four to have to make it sound the same, or just the pair? i want to make sure it's got quality bits. i'm not bothered if it costs a few quid to make sure it performs tip top, just want to keep it sounding like it does, well did until last week.
Is there a chance anything else has gone related to this? or is there another component that can fail where this would be a typical symptom? most of the other caps are audio note and a couple of jensens.
does branding make a difference with capacitors?
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Old 14th May 2012, 01:05 PM   #6
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Ah!

You are asking about the "sound" of boutique caps.

This is all a matter of opinion. I don't have one.
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Old 14th May 2012, 01:23 PM   #7
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lol.
all i know is, these caps are linked to the voltage rectifier valve. does that make them less important?
it seems all these jensen, black gate and audio note caps, (after a quick look on the web) are claiming to be quality. then there are these 4 plessey ones which seem to be involved with power supply that apparently are from obsolete stock. so are they some cheapy b make? can't find a thing about them on the web. is the job they are doing less important? i'm no electrician so i've no idea if they make a difference. I just want to put the correct, equivalent caps in so i don't have to go routing in the chassis again after i'm done.i don't want to compromise the sound either. this is why i logged on here. can't beat a forum for good knowledge of specialist subjects. i can't get in touch with simon shilton at arcadia or sjs as he calls himself. I know he hasn't done this for a while, so there's no schematic, no customer service etc..
i'm kind of hoping for, 'these are the same, break out the soldering iron and get to' it answer.
or a,' if you use those you'll ruin it' answer.
is it wise to replace pairs or the 4 off to keep everything right on?
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Old 18th May 2012, 06:18 PM   #8
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I buy long life electrolytic caps. >3000 hours service rating, so I don't have to re-e-cap my amp again as I have my dynakit tube equipment 3 times.
I don't buy boutique caps. I've put about $200 worth in 2 organs, the dynakit preamp and two power amps, a portable radio, a disco mixer, and a PA amp in the last 2 years. I'm mostly buying panasonic, nichicon, rubicon e-caps, but make sure of the life rating, they all sell **** for shops that want every coin out of their repair jobs and don't care if they last more than 90 days. I've seen long life nichicons go over a decade on motor drives in hot burner compartments of industrial food ovens, so long life can be done.
Under 10 uf, you can usually fit in an infinite life (if voltage is overrated) film dielectric cap instead of an electrolytic. Make sure you match the tolerance, 10% caps indicate a frequency sensitive part of the circuit. Experts here recommend polyprophylene dielectric for "best" sound, but I have used a lot of polyester and the result was in every case better than the old dried up electrolytic cap. In the power supply rails, dielectric shouldn't matter much.
I don't do one cap at a time anymore, I replace all the electrolytics on >20 year old gear. Amateurs like us make cold solder joints sometimes, so check the device for better function after every couple of caps so you know where you made your mistake. Mark polarity before you take them out, backwards & they explode. Wear safety glasses, solder splashes coming off. I use stranded wire dipped in flux to remove old solder before bending the lead up with a steel pick and removing. Note you-re in the UK, tin lead solder is a whole lot easier to work with than the ROHS compliant stuff.
I see this is a tube circuit. Make sure all metal is measured at <25 VDC to ground before you touch it, else discharge it with a safe tool. See high voltage for newbies at the top of the tube amp thread. No jewelry, either. Unplug, of course.
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Last edited by indianajo; 18th May 2012 at 06:41 PM.
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Old 18th May 2012, 08:10 PM   #9
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Quote:
Originally Posted by john townshend View Post
lol.
all i know is, these caps are linked to the voltage rectifier valve. does that make them less important?
it seems all these jensen, black gate and audio note caps, (after a quick look on the web) are claiming to be quality. then there are these 4 plessey ones which seem to be involved with power supply that apparently are from obsolete stock. so are they some cheapy b make? can't find a thing about them on the web. is the job they are doing less important? i'm no electrician so i've no idea if they make a difference. I just want to put the correct, equivalent caps in so i don't have to go routing in the chassis again after i'm done.i don't want to compromise the sound either. this is why i logged on here. can't beat a forum for good knowledge of specialist subjects. i can't get in touch with simon shilton at arcadia or sjs as he calls himself. I know he hasn't done this for a while, so there's no schematic, no customer service etc..
i'm kind of hoping for, 'these are the same, break out the soldering iron and get to' it answer.
or a,' if you use those you'll ruin it' answer.
is it wise to replace pairs or the 4 off to keep everything right on?
Why so timid?

Find in a catalogue a 0.5uF 400V, or the nearest value and stick it in. Listen to whether Norah Jones now sounds like Satchmo.

On this basis decide whether to keep it or not. Why are you expecting someone else's ears to be your guide?

Certainly nothing will blow up or be damaged with values from 0.1uF to 1uF and >= 400v.
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Old 19th May 2012, 06:54 PM   #10
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cap replaced. not working.
another cap is leaking voltage. i'm getting 213vdc on the left output. most annoying. so i need to replace even more parts.finding out the hard way that it's live was fun.not.
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