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Old 14th Sep 2020, 4:40 pm   #1
yakxx21
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Default R1155 Capacitor replacements

Can somebody advise me the following please :

type of capacitor and where to buy to re stuff the big square 2.5 +1.0+2.5 mfd paper wax caps ? 400 volts DC I think.

Ditto above for the tubular caps under chassis...mainly 0.1 mfd I think

Ditto above for the low capacitance WAX caps all over the place

thank you
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Old 15th Sep 2020, 8:23 am   #2
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Default Re: R1155 Capacitor replacements

For tubular 0.1uF caps, I would buy axial ones, with a voltage rating of 250V or 400V DC. Given the HT is nominally 210V on the R1155, either should be quite adequate for any position in the set.

Radiospares have a 250V offering at £1.29 for 5: https://uk.rs-online.com/web/p/polye...itors/1854151/

Or alternatively a 400V offering at £1.27 for 5: https://uk.rs-online.com/web/p/polye...itors/1854347/

You will need to check physical sizes to see which is most suitable - probably after hollowing one of the originals out to see exactly how much space you really have.

Richard
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Old 15th Sep 2020, 8:25 am   #3
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Default Re: R1155 Capacitor replacements

Not sure what type of caps are the ones you are calling "low capacitance wax caps". They are probably mica or ceramic. In which case they are very unlikely to have failed - unless its some total failure like a lead falling off. Unless you are quite sure they are faulty, I would leave them well alone.

When I restored a R1155 I didn't touch a single one of those caps - there were plenty of other things to occupy my time!!

Richard
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Old 15th Sep 2020, 8:55 am   #4
yakxx21
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Default Re: R1155 Capacitor replacements

Thanks, I will happily leave all those wax ones alone. I assume you feel Vishay poly caps are also good for the big square cans... I couldn't find 2.5mfd only 2.7 but I assume that will be OK..
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Old 15th Sep 2020, 10:09 am   #5
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Default Re: R1155 Capacitor replacements

Capacitors with a paper dielectric will almost certainly need changing. They generally have values from about 0.5uF down to about 0.001uF. Capacitors with lower values that this will be mica or ceramic types and should be left well alone.

Capacitors having values of 1uF or more are generally replaced with electrolytic types assuming they won't reform.
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Old 15th Sep 2020, 10:58 am   #6
yakxx21
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Default Re: R1155 Capacitor replacements

Thanks... I had assumed the Big 4.5 MFD paper wax ones in the R1155 should be replaced by non polarised type ( like the ones I have taken out.....) But you say I should use electrolytic types......this makes things easier ....is there any reason I shouldn't use film types /polyprop types ? although they do seem much more expensive .
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Old 15th Sep 2020, 11:14 am   #7
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Default Re: R1155 Capacitor replacements

Quote:
Originally Posted by trh01uk View Post

Radiospares have a 250V offering at £1.29 for 5: https://uk.rs-online.com/web/p/polye...itors/1854151/

Or alternatively a 400V offering at £1.27 for 5: https://uk.rs-online.com/web/p/polye...itors/1854347/

Richard
Sorry Richard but the price you quote is each rather than for 5. 5 is the minimum quantity that can be ordered.

Hope it’s ok to mention but members of the BVWS can buy capacitors at good prices direct from the BVWS. I have no connection to the aforementioned other than being a very satisfied customer and subscriber.

Peter
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Old 15th Sep 2020, 11:28 am   #8
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Default Re: R1155 Capacitor replacements

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Originally Posted by yakxx21 View Post
Thanks... I had assumed the Big 4.5 MFD paper wax ones in the R1155 should be replaced by non polarised type ( like the ones I have taken out.....) But you say I should use electrolytic types......this makes things easier ....is there any reason I shouldn't use film types /polyprop types ? although they do seem much more expensive .
You can fit non-polarised caps if you wish.

Where caps are specified as having values in uuF (pF) leave well alone.
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Old 15th Sep 2020, 6:12 pm   #9
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Default Re: R1155 Capacitor replacements

Quote:
Originally Posted by Reelman View Post
Quote:
Originally Posted by trh01uk View Post

Radiospares have a 250V offering at £1.29 for 5: https://uk.rs-online.com/web/p/polye...itors/1854151/

Or alternatively a 400V offering at £1.27 for 5: https://uk.rs-online.com/web/p/polye...itors/1854347/

Richard
Sorry Richard but the price you quote is each rather than for 5. 5 is the minimum quantity that can be ordered.

Hope it’s ok to mention but members of the BVWS can buy capacitors at good prices direct from the BVWS. I have no connection to the aforementioned other than being a very satisfied customer and subscriber.

Peter
Peter,

quite right - I should have twigged that the price was suspiciously low!! Particularly when I went to the trouble of buying in such caps from USA some years back to save a small fortune compared to RS/Farnell prices.

Sorry for misleading anyone.

I guess this shocking price shows how out of fashion leaded axial capacitors now are.

Richard
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Old 1st Oct 2020, 11:59 pm   #10
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Default Re: R1155 Capacitor replacements

Hi

I would suggest that you try to get a copy of Pete Holkham's book on R1155 it is a most informative book.

If you cannot borrow one then you will have to buy a copy from Pete Holkham unfortunately he lives in Australia and the postage costs as much as the book itself but as I said it's well worth it

Regards

Bill
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Old 2nd Oct 2020, 8:15 am   #11
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Default Re: R1155 Capacitor replacements

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Hi

I would suggest that you try to get a copy of Pete Holkham's book on R1155 it is a most informative book.

If you cannot borrow one then you will have to buy a copy from Pete Holkham unfortunately he lives in Australia and the postage costs as much as the book itself but as I said it's well worth it

Regards

Bill
The sensible thing is to stop shunting bits of paper around the world, and email over a PDF file. These days, there is every chance the author can provide a PDF - so try asking. He can still charge the same price as for paper if he wants to.

Richard
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Old 2nd Oct 2020, 8:45 am   #12
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Default Re: R1155 Capacitor replacements

You'll need to open the swear box when replacing the metal can paper 0.1uF caps underneath the coil box. You can do it without dismantling the whole assembly, but it's very fiddly. Good luck - I never want to do another one, once was enough. It was also extremely frustrating trying to get the slow-motion dial to work properly. Cheers, Jerry
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Old 2nd Oct 2020, 9:13 am   #13
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Default Re: R1155 Capacitor replacements

Just thinking about these radio's and their original use in Lancaster bombers. Were they ever designed to be serviced? Their construction suggests probably not since failures would normally be expected to be fixed fairly quickly. I heard somewhere that their expected life was only months since Lancasters themselves were heavy casualties of the war.
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Old 2nd Oct 2020, 9:16 am   #14
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Default Re: R1155 Capacitor replacements

The caps can be replaced by re stuffing with 0.1uF SMD's rated at 500 Volts or at least one person has done. Slip in the tube very easily.
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Old 2nd Oct 2020, 10:37 am   #15
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Default Re: R1155 Capacitor replacements

Quote:
Originally Posted by cathoderay57 View Post
You'll need to open the swear box when replacing the metal can paper 0.1uF caps underneath the coil box. You can do it without dismantling the whole assembly, but it's very fiddly. Good luck - I never want to do another one, once was enough. It was also extremely frustrating trying to get the slow-motion dial to work properly. Cheers, Jerry
And you will need a second, very large, swear box, if you discover the set has rubber wiring. All of it will need to be stripped out and replaced - unless by some freak yours hasn't got rubber insulation that has now crumbled into flakes and dust.

Richard
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Old 2nd Oct 2020, 10:44 am   #16
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Default Re: R1155 Capacitor replacements

Quote:
Originally Posted by Sideband View Post
Just thinking about these radio's and their original use in Lancaster bombers. Were they ever designed to be serviced? Their construction suggests probably not since failures would normally be expected to be fixed fairly quickly. I heard somewhere that their expected life was only months since Lancasters themselves were heavy casualties of the war.
We can be pretty sure that the kind of "fixes" we do in restoration - replacing wiring, resistors and capacitors - was never intended to be done by someone in the RAF. I think they would happily swop valves out, and go through dodgy connections on the wiring/audio harness. The latter is where many of the faults would arise from just wear and tear in the plane - provided of course, the plane didn't crash first, as you say.

Strangely, few documents on RAF servicing of equipment have survived. I do have the odd one in APs, listing things like "spare parts" and so on. The occasional modification instruction turns up too. Many T1154s have a notice on the front panel saying "modification xyz carried out" for instance. So we know such work did take place. Its in severe contrast to the Army kit, for which very extensive document survives in the form of EMERs, telling you just everything including how to rewind transformers! That's possibly due to the fact that Army kit could turn up just about anywhere, a zillion miles from the nearest "service centre", but planes tend not to - they land normally fairly often in a location where all the service kit etc is available.


Richard
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Old 2nd Oct 2020, 2:46 pm   #17
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Default Re: R1155 Capacitor replacements

In the RAF we used to do certain levels of modification, depending on depth of maintenance; at first line (at the aircraft) very rarely - merely black box replacement whereas at second line (workshop level) I recall mods to Tornado main computers being carried out to upgrade memory from 128k to 224k RAM (wow!). Usually the line-replaceable unit (black box) had a mod strike-off plate with instructions as to how to annotate it in the relevant mod leaflet. Deeper levels of mod were done at 3rd Line (30MU Sealand, I think it's still going) or 4th Line (manufacturer). Cheers, Jerry
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Old 3rd Oct 2020, 12:58 am   #18
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Default Re: R1155 Capacitor replacements

Hi

I agree that the wiring can be absolutely awful, just looking at can make it crumble if you are unlucky.

I have restuffed many of the 3 X .1uf caps in the cans and all are quite easy apart from the one in the middle of the coil can but with a lot of patience it can be done.

there are also, i think 3 x .1uf in metal cans that are singular that are again quite easy to restuff but one is a right pig, it is in the BFO can and if it goes faulty will only show when you select BFO, to get to that one the can has to come out, with regard to the 4uf capacitor in the rectangular can, I unsolder the base, take all the innards and fit a 4uf electrolytic inside and then resolder the can up
Cleanup and maybe spray the capacitor can and refit.

There are many more things that go wrong with the R1155 and they can be time consuming but very rewarding in the end.

Good luck

Bill
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