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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment. |
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#1 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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Does anyone have a good picture of the paxolin board in an AR88 at the side under the chassis on which some resistors are mounted. The only specimen around here has a decidedly unoriginal board (ditto output transformer) and I thought I had a good photograph but cannot find it and a web search has produced many front panel photographs and a few under chassis pictures where you can see a vertical board but nothing else.
It is what I would call the "usual" type of AR88 with an engraved front panel. |
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#2 | |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,427
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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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#3 | |
Hexode
Join Date: Nov 2011
Location: Chippenham, Wiltshire, UK.
Posts: 287
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Peter |
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#4 | |
Dekatron
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 12,993
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Lawrence. |
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#5 |
Heptode
Join Date: Mar 2010
Location: Eastham, Wirral, Merseyside, UK.
Posts: 780
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Hi Alan.
don,t know if this may be what you want ,never seen a photo of the audio board so hope this is what you need. gezza123 |
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#6 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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Thanks gezza123 and G3PIJpeter this is indeed the board and I found the labelled diagram of the under chassis showing where all the Rs and Cs very useful indeed.
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#7 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,427
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Those resistors are droppers in the HT negative return used to create negative bias for the AGC, RF gain control and the output valve. They run rather hot, so if you do anything to them, go for physically larger parts to reduce the surface temperature.
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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#8 |
Heptode
Join Date: Feb 2009
Location: Rotherham, South Yorkshire, UK.
Posts: 538
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See if this ok for you.
kEV. |
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#9 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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Regarding the "all yellow tuning scale backgrounds", I've never quite known what this means. Here is a picture of the tuning dials (carefully cropped to remove the not-very-period HP8662 adjacent, which nevertheless will be ideal for aligning it)
The tuning knob is unfortunately not original. Someone had hacked around the tuning drive and added a slow motion drive, so I have repaired the gearbox but not yet found a proper looking knob. |
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#10 |
Heptode
Join Date: May 2015
Location: Chatham, Kent, UK.
Posts: 826
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Hi a tuning knob on ebay now nos not cheep ouch https://www.ebay.co.uk/itm/193340783...Bk9SR87EivnfYQ Mick
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#11 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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That prompted me to look for output transformers but it seems I'm not so lucky there... will have to keep using some random thing from an audio amp, but maybe I'll mount it properly rather than having it float about on its leads which seems to have been the previous repair plan....
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#12 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,427
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Ther's a lot more demand for audio output transformers than for tuning knobs. The transformers are fairly fragile and get destroyed if the 'That capacitor' starts leaking. RCA in their wisdom increased this likelihood by using two capacitors in parallel to add leakage!
Your photo shows an AR88 with the earlier 'all yellow background' tuning scale. The majority of sets have alternating scale backgrounds with every other scale showing yellow scale and text on a black background. There was a release of AR88 spares sometime in the 80's and I picked up a spare set of tuning scales and a main tuning knob for my AR88, amongst a few other parts, all for pennies. They were on a stand at the G-QRP doo in Rochdale. 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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#13 |
Dekatron
Join Date: Aug 2007
Location: W.Butterwick, near Doncaster UK.
Posts: 8,753
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Don't forget that cap from the sound o/put anode to deck. Refit across the primary of o/put tx.
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G8JET BVWS Archivist and Member V.M.A.R.S |
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#14 | |
Octode
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 1,535
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That was probably Colomor Electronics. In the 1990s I was going to their warehouses near Bedford, and one of them had an enormous stack of new AR-88 spares, all still in the original manufacturer's wrapping. A guy called John Reynolds (now passed away) brought the lot I believe. Where it all is now....no idea! Richard |
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#15 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,427
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They were indeed in manufacturer's packaging. Interesting to know a little of their history.
I suppose they're all scattered around now, which is good because the ARs potentially needing them are all scattered around too. Thanks 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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#16 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,230
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That must have been a sight to behold! I recall on visits tio Colomor's outlet on Shepherd's Bush Road how there was always what I recognised as an AR88 output transformer at the side of the counter. There is indeed a scattering of NOS spares around at various events, I was lucky to find a still pale-colour frequency scale for an 'LF recently to replace a very darkened scale, the one on my 'D model is still useably deep yellow fortunately.
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#17 |
Dekatron
Join Date: Jan 2006
Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex.
Posts: 5,599
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One of the gents on here had a couple of pallets worth of original MOD items including AR88 spares a decade or so ago. Perhaps it was from the same stack referred to here? I bought one or two items including an AR88 OP transformer that was mint and still sealed in the original packing. They had been described over the years as "rarer than rocking horse droppings". My technical skills are largely absent but I was intrigued, during a period when there was a sort of sudden, unexpected, demand for 88's, that some people did manage to substitute "ordinary" re-cycled OT's very successfully when it was always claimed that the originals were a make or break for restoration
![]() Dave W Last edited by dave walsh; 26th Mar 2023 at 2:01 pm. |
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#18 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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Thanks to all the helpful info here I can reconstruct the paxolin board (and mount it on standoffs -- I don't have the right terminals, but guess the usual terminal eyes will do), not screwed directly to the chassis like the previous bodge - which required some scraps of paxolin behind it to avoid shorting). I can try an old hifi output transformer as I don't really need the 600 ohm output.
That leaves the question of the various aerovox three-caps-in a can, or maybe more accurately three leak resistors to chassis in a can. They look like the cans are soldered so they should open up with heat from the O-A torch to be restuffed, but the terminal insulators also look decidedly ropey so I guess some kind of solution for them is needed - maybe feedthrough caps? The Mr Carlson video linked shows the caps being soldered directly to chassis but I don't think even my large ERSA iron would do that. Advice would be welcome.... |
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#19 |
Moderator
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,427
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Have a hunt around for rivet-on turret terminals. You can make your own tag boards up and they look fantastic. You just need raw paxolin sheet a drill and a punch to form the rivet. It'll still need to go on standoffs.
David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done |
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#20 |
Tetrode
Join Date: Jan 2012
Location: Amersham, Buckinghamshire, UK.
Posts: 51
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Found the turret terminals. Just the thing - thanks for the pointer!
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