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Old 15th Aug 2019, 5:27 pm   #1
Sixer-h
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Default Replacing polarised capacitors (condensers) for Pye Record maker

I could not find any previous threads on this subject, but apologies if I missed them.

I am a novice here, but understand that the older caps will be at risk of leaking or going open circuit with time, and so am looking to replace most of the caps. I attach marked up images of the circuit diagram with the GRAM section in red.

I am trying the source polarised capacitors to replaced the Pye's existing polarised caps (in the GRAM circuit), but when searching for the lower value caps, I can only find bipolar caps. The on-line search engines don't help as they show everything with 'polarised' in the wording, including 'non-polarised'.

The caps I need are 350v (min) 0.1, 0.01, 0.02 and 8.0 uF. Please could anyone provide some advice on sourcing polarised capacitors for my Pye Record Maker, or advise as to whether bipolar caps can be used in some instances ?

The Player also has some (flat) caps of 330, 560, 3300, and 6800 PF, that do not show polarisation markings. Could anyone advise as to whether theses are polarised ?

Thanks
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Old 15th Aug 2019, 5:57 pm   #2
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

No attachments here...!
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Old 15th Aug 2019, 6:25 pm   #3
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

0.1,0.01, 0.02 look at these
https://www.cricklewoodelectronics.c...-to-1000V.html

8ufd look at these https://www.cricklewoodelectronics.c...Capacitor.html

The flat capacitors are very likely to be good ones, only replace if proved faulty.
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Old 16th Aug 2019, 9:59 am   #4
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

I'd be very surprised if any capacitor under 1uF was polarised. They may have markings suggesting this, but which are more likely refer to which foil in the wrap is the "outer" one. In some circuits there may be hum advantages depending on which way round the capacitor is connected since the outer foil can screen the inner one to some extent.
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Old 16th Aug 2019, 12:32 pm   #5
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

It may help to be aware that there is a difference between bipolar caps and nonpolar caps. Bipolar caps (typically used in some speaker crossover networks) are basically polar caps which have been specially made so that they can be used either way round. Nonpolar caps (which most caps are) don't worry about which way round they are anyway.

Low value caps are likely to still be in good order, so no need to replace them unless careful fault tracing shows them to be faulty. Mid value caps may or may not be OK, as it depends on exactly which dielectric they used and how well they were made; leakage current is the usual problem. Larger value caps are likely to be electrolytic and may need replacing.

Do not be tempted to 're-cap' by replacing all of them. This is unnecessary, and can be a quick way to stop something from working.
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Old 16th Aug 2019, 2:41 pm   #6
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

For information, I am sure many forum members will be aware.

According to the Pye manual, the 0.1,0.01 etc are tubular paper, the 8uf electrolytic. The flat capacitors are mica, there is one ceramic C6 220pfd.

The tubular and electrolytic need testing, possibly replacing the others replace only if proved faulty.
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Old 16th Aug 2019, 4:06 pm   #7
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

All of your responses have been very helpful indeed.

Nuvistor, I will test those as you advised (removing them first of course). And I will go to the cricklewood site you have directed me to.

G8HQP Dave, That explains everything. I will only replace dodgy ones.

Herald1360, That explains why I could not find any low value polarised caps. The ones I have taken off to test read OK, but I'm not sure how to tell whether they are leaking.

I'm finding the Vintage site a little difficult to navigate. Did my downloads come through?

Many thanks again for everyone's help, it is much appreciated

Richard
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Old 16th Aug 2019, 5:03 pm   #8
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

I don't think the attachments got through, so for completeness I am trying again !
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Old 16th Aug 2019, 6:50 pm   #9
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Blimey, this is some "big boys toy" should you have the magnetic discs and associated recording head. Also, not too many domestic products have a busbar to keep earth loops at bay. That's the bare wire running the length of the chassis.

Now getting down to the nitty gritty. Other contributors have suggested component sources etc; but I wonder if I may add my two-penneth.

Your only real problems are with ANY Hunts cylindrical capacitors. Those are the brown ones and have a dreadful reputation. They are only a few. The other "change on site" right away are the Plessey electrolytics. They are the yellow ones with a red band at one end. This is the positive connection AND it is important to wire replacements correctly.

The wax coated capacitors have for some a poor reputation but looking at the schematic, I believe that they are not stressed and could be left alone unless, following the above, the record maker doesn't work.
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Old 16th Aug 2019, 10:59 pm   #10
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Many hanks for the advice my Pye's Caps. Yes, this is the second of these machines to come into my possession.
I have the recording head and several magnetic discs, which Poppy records in Bath (worth looking up if you want him to cut you a Wax Cylindrical disc or a million other things that he has built his own bespoke electrical kit for !!) cleaned up and down-loaded onto CD for me, using a BBC deck with his own parallel tracking set up plus wizzardly electronics.
Everything works and I am trying to make sure it stays alive a little longer. I will therefore follow your advice and change the Hunts and yellow Plessey Caps.

Thanks to everyone who got back to me, I'm now clear on what I will do.

Regards,

Richard
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Old 17th Aug 2019, 8:04 am   #11
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

The wax dipped "TCC" paper dielectric capacitors are also very likely to be faulty (low insulation resistance) and should be changed as well.
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Old 18th Aug 2019, 10:34 am   #12
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Thanks Dazzlevsion. I have just looked on line to see what waxed dipped electrolytic Caps look like. I've learnt so much from everyone's responses. Now all ( ! ) I have to do is put this new knowledge into practice, remembering all the time that working on an HV circuit has to be taken very seriously.
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Old 18th Aug 2019, 11:32 am   #13
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Page on capacitors.
https://www.vintage-radio.com/repair...apacitors.html
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Old 18th Aug 2019, 11:49 am   #14
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Quote:
Originally Posted by Sixer-h View Post
Thanks Dazzlevsion. I have just looked on line to see what waxed dipped electrolytic Caps look like.
Those wax dipped capacitors aren’t electrolytic types, but paper. The main difference between capacitors is the dielectric material used.
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Old 18th Aug 2019, 12:07 pm   #15
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Quote:
Originally Posted by Sixer-h View Post
Thanks Dazzlevsion. I have just looked on line to see what waxed dipped electrolytic Caps look like.
As stated in post #4 you are unlikely to find an electrolytic capacitor with a value less than 1uF. I don't think they were ever made.

Below 1uF any vintage capacitor with its value expressed in uF (0.01uF for example) is likely to have a paper dielectric.
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Old 18th Aug 2019, 2:07 pm   #16
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

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Quote:
Originally Posted by Sixer-h View Post
Thanks Dazzlevsion. I have just looked on line to see what waxed dipped electrolytic Caps look like.
As stated in post #4 you are unlikely to find an electrolytic capacitor with a value less than 1uF. I don't think they were ever made.

Below 1uF any vintage capacitor with its value expressed in uF (0.01uF for example) is likely to have a paper dielectric.
Being pedantic, I've seen tantalum electrolytic capacitors down to 0.1uF I think. I've certainly seen them <1uF. The common 'electrolytic capacitor' is the aluminium electrolytic, and I think I've seen 0.47uF ones of those, but they are not at all common.

I will agree that in domestic radios/TVs/audio any capacitor <1uF is unlikely to be electrolytic. And therefore such capacitors are likely to be non-polarised.
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Old 18th Aug 2019, 2:15 pm   #17
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

You're absolutely right. I tried to keep things simple to avoid confusing the OP who didn't seem to know the difference between electrolytic and non-electrolytic capacitors
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Old 18th Aug 2019, 4:49 pm   #18
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

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Originally Posted by Sixer-h View Post

The Player also has some (flat) caps of 330, 560, 3300, and 6800 PF, that do not show polarisation markings. Could anyone advise as to whether theses are polarised ?

Thanks
If you mean like the one at top LH of your first picture, next to the transformer, they will be wax dipped silver mica and are very reliable, so best left alone. As has been said, the ones which are candidates for replacement are waxed paper tubular one and brown Hunts ‘Mouldseals’. Wax paper caps often had a black ring at one end, which signifies the outer foil, but they’e Not ‘polarised’.

A popular replacement type for tubular paper caps are tubular polyester 630V capacitors which cover most eventualities. They abound on internet in a wide range of values, and from traditional component suppliers.

There’s a yellow/red Plessey electrolytic, which I’d be inclined to change.

Whatever you do, don’t change several capacitors without testing after each one, because if you do, and you’ve made an error, you’ll have quite a palaver tracing and rectifying the error.

Good luck in your endeavours.
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Old 18th Aug 2019, 7:12 pm   #19
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Wow - thanks everyone.
OK, I've been on a sharp learning curve on the difference between the various Caps, which I initially found bewildering, but all your advice has been absorbed and I understand the differences now, though why Plessey (and no doubt others) marked the positive end and not the negative end of the polarised Caps is something I'll look out for.
I'll also only change one Cap at a time and check it works before proceeding further, and go for the polyester ones, leaving the big flat silver mica ones alone.

Thanks again

Richard
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Old 19th Aug 2019, 10:28 am   #20
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Default Re: Replacing polarised capacitors (condensers) for Pye Record maker

Marking the negative end of electrolytic capacitors is the norm these days, but it wasn't always so. To be fair, the Plessey red-yellow-black types do mark the negative end (black) as well as the positive end (red). 50 odd years on they're just another of the components with a reputation for (relatively) short lifespans.

Generally, any electrolytic in a metal can will have the can -ve unless it's isolated, which would normally be stated in the markings.
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