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
tour of insides
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
An externally hosted image should be here but it was not working when we last tested it.
tour of insides
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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-polypropyleneaxial-capacitors-393
will do.
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-polypropyleneaxial-capacitors-393
will do.
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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
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?
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
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
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?
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?
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?
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.
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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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.
A lot of guitar amp people replace all the plate caps and 4th grid caps, too, before they start poking around with a meter. I haven't had to on Hammond organs or dynakit equipment, but those apparently used very premium long life caps.
See this site for a tutorial on fixing tube type guitar amps. www.geofex.com/ampdbug/ampdebug.htm Best I've seen so far. The difference between a guitar amp and a hifi preamp, no power stage bias problems, no push pull AB output stage, tighter tolerance components, different design goals- low distortion instead of maxing out 2nd harmonic distortion. Sounds like Plessey film caps were not as overrated against voltage as the 1968 goodalls and 1961 general instrument paper caps I've encountered in my equipment.
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If you are looking for something similar to the old Plessey caps I suspect the Jensen copper foil paper in oil types are reasonably close. Note that the old Plessey caps were rated for 400VAC so you should replace with a part having a DC rating of 600V unless you are very sure that the voltage across it is well under 400V including the audio signal.
Plessey was a British manufacturer of electronics parts and was quite a large conglomerate at one point. They also owned a number of UK audio company if memory serves.
Plessey was a British manufacturer of electronics parts and was quite a large conglomerate at one point. They also owned a number of UK audio company if memory serves.
well, pre amp mended. 2 caps were duff and the 6sn7gt output valve was gone on one side. so all is well, got some quality polyprop caps and a nos brimar valve and back in service.
now to mend the power amp.
lots of duff caps. ripped it out of the old manky chassis it came in and it now a bit, well, basic looking, lol
3 audion note caps and two black gates are buggered and not available either, so i'm going down the mundorf and clarity cap route i guess. shame about the black gates, they are nice
now to mend the power amp.
lots of duff caps. ripped it out of the old manky chassis it came in and it now a bit, well, basic looking, lol
3 audion note caps and two black gates are buggered and not available either, so i'm going down the mundorf and clarity cap route i guess. shame about the black gates, they are nice
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