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| Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders. |
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4th Apr 2020, 11:37 am
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#1 |
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Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 465
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Avometer 8 rectifier
My faithful old Avo 8 MkII has ceased, following an accidental short, to work on all AC voltage and current ranges. There's nothing which is obviously "cooked" inside, so I assume it's the bridge rectifier.
I imagine replacements are long gone. Is there, I wonder, a modern component which will serve? Or could I make one up with four suitable diodes? |
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4th Apr 2020, 11:51 am
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#2 |
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Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,106
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Re: Avometer 8 rectifier
You can. Recently someone even dismantled, dremelled and re-stuffed a CuO rectifier with silicon diodes: https://www.vintage-radio.net/forum/...3&postcount=26
Alternatively i have used two Germanium diodes (on an old Avo HR whose westectors had become tired) with good results. One of my Avo 9 Mk.II's has been fitted with 4 Germaniums. It behaves well alongside the other Avo 9, which has the original CuO. There are other discussions on the forum about this which should be accessible on the search facility. Dave Last edited by AC/HL; 4th Apr 2020 at 5:21 pm. Reason: Link added |
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4th Apr 2020, 12:04 pm
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#3 |
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Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 22,869
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Re: Avometer 8 rectifier
Germanium diodes have the advantage of lower threshold voltages than silicon. In lieu of Germanium, Schottky diodes are in current manufacture, also offer low thresholds and very stable operation.
David
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Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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4th Apr 2020, 2:10 pm
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#4 |
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Dekatron
Join Date: Feb 2003
Location: Cottingham, East Yorkshire, UK.
Posts: 5,761
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Re: Avometer 8 rectifier
1N34 germanium diodes are plentiful and cheap.
I've used these as replacement for failed detectors is radios (OA90 etc) and as meter rectifiers (Heathkit though - not AVOs). 10 for £1.94 post free from a UK supplier: https://www.ebay.co.uk/itm/1N34A-Ger...597dd72fcdde8d If you preferred Schottky diodes, you can buy 10 x 1N5817 Schottky Diode £1.99 from a UK supplier post free here: https://www.ebay.co.uk/itm/10-x-1N58...1b37e3e2b2be8f Hope that's helpful.
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David. BVWS Member. G-QRP Club member 1339. |
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4th Apr 2020, 8:56 pm
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#5 |
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Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 465
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Re: Avometer 8 rectifier
Many thanks. Diodes are on order.
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5th Apr 2020, 11:02 am
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#6 |
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Dekatron
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 16,535
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Re: Avometer 8 rectifier
Doesn't the current transformer go a long way towards straightening out any diode non-linearities anyway? Or am I barking up the wrong tree with that idea?
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24th Apr 2020, 9:44 pm
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#7 |
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Hexode
Join Date: Feb 2008
Location: Wrexham, North Wales, UK.
Posts: 465
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Re: Avometer 8 rectifier
Just to finish off this thread, I tried replacing the rectifier, with no result. So I thought, wafer switch? A delicate touch of Servisol didn't help.
It was then that I noticed that the cam was not turning on the shaft... ... it now works. |
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25th Apr 2020, 10:08 am
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#8 | |
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Octode
Join Date: Dec 2017
Location: Morden, Surrey, UK.
Posts: 1,557
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Re: Avometer 8 rectifier
Quote:
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25th Apr 2020, 12:40 pm
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#9 |
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Dekatron
Join Date: Aug 2016
Location: Colchester, Essex, UK.
Posts: 4,106
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Re: Avometer 8 rectifier
Yes, as far as i can tell none of the cam rotors were ever designed with positive location pegs so they are able to 'readjust' themselves out of sync. There is only a crinkle washer under the screw head, but this is usually adequate as long as the screw is suitably nipped up.
Dave |
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