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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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8th Sep 2019, 9:11 pm | #1 |
Triode
Join Date: Feb 2016
Location: Manchester, UK.
Posts: 24
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Roberts RT22 - Capacitors
Hi
I'm really a beginner here. I have quite a few vintage radios mostly working so it's time to embark on some repairs. I have a Roberts RT22 which I dismantled to clean but some of the Mullard (?) capacitors (C20 and C39) ends were in the case, looks like they have started to split/ crack. I have the service manual and these state 100nF for both. RadioCruncher (Graham) said these would now be 0.1uF / 104? I have had a look on Ebay and was just wondering what voltage these should be as there are differing voltages for these, anything from 100V to 630V (it doesn't state in the service manual) The radio is 9v / PP9 - no mains. thanks Simon |
9th Sep 2019, 9:24 am | #2 |
Hexode
Join Date: Jun 2011
Location: Glossop, Derbyshire, UK.
Posts: 487
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Re: Roberts RT22 - Capacitors
This is a late 70's early 80's radio and 25v caps is all it needs try RS for spares and if you have problems I only live in Glossop and am willing to help
Dave
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10th Sep 2019, 8:49 pm | #3 |
Triode
Join Date: Feb 2016
Location: Manchester, UK.
Posts: 24
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Re: Roberts RT22 - Capacitors
Thanks Dave. I've been to Glossop quite a lot recently. You don't offer lessons do you...
I would love to start fault finding and repairing as buying 'repair only' would be so much cheaper and I'm keen to start this as a hobby plus I have loads of stuff here that just doesn't work and really needs to be working, both radios and old computers etc. I've had a look on RS and closest I can find is KEMET 100nF MLCC 50V dc which I am hoping is close enough. Thanks for your help - I really appreciate it. |
10th Sep 2019, 9:34 pm | #4 |
Moderator
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,957
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Re: Roberts RT22 - Capacitors
As a general rule, with transistor gear you only need capacitors rated at the supply voltage plus a bit of headroom, so 12V will be fine in this case. Higher voltage ratings will do no harm. You often can't find low value caps rated below 50V because it costs just as much to make them for lower max voltages.
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11th Sep 2019, 7:56 am | #5 |
Triode
Join Date: Feb 2016
Location: Manchester, UK.
Posts: 24
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Re: Roberts RT22 - Capacitors
Ahh I see Paul, Makes sense. You're right though - I can't find any low voltage caps at all...well not as low as the 12V you mentioned.
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11th Sep 2019, 8:41 am | #6 | |
Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,763
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Re: Roberts RT22 - Capacitors
Quote:
There is a variety of materials used - ceramic disc, mylar etc, some of which I've given listings for below. Looking at the position of C20 and C39 on the diagram of the PCB, I'd have thought that the mylar ones would probably be a good choice, but any would suffice. Capacitors are so cheap that whether you buy them from eBay of say RS, Farnell, Crickelwood ESR electronics or whoever, you'll probably find that they have a minimum order level - maybe five, ten or twenty. 100nF is a useful value to have - they're used extensively. I'm not suggesting that you use any of the suppliers below in preference to the likes of RS, but they're all UK based suppliers with good feedback and the prices shown are post free: Ten Ceramic disc: 50V: https://www.ebay.co.uk/itm/100nF-0-1...U2h8ezmzAPW6gQ 25 Ceramic monolithic: 50V: https://www.ebay.co.uk/itm/Ceramic-C....c100005.m1851 20 Mylar polyester 100V: https://www.ebay.co.uk/itm/100nF-Aud....c100005.m1851 Ten Axial multilayer ceramic 50V: https://www.ebay.co.uk/itm/AVX-50V-0....c100005.m1851 Hope that helps a bit Simon. Best wishes on your endeavours.
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13th Sep 2019, 9:58 pm | #7 |
Triode
Join Date: Feb 2016
Location: Manchester, UK.
Posts: 24
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Re: Roberts RT22 - Capacitors
That's great David, that's really helpful. Call me daft but I thought I would have to buy something similar to the size/shape that are in now but seems not!
I'll go along with your recommendation and start to get a selection of components together will will save me in the long run. Many thanks |