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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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Old 9th Jan 2019, 4:50 pm   #1
HamishBoxer
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Default AR88 Tempted as I am!

Got this 50kG of metal on my bench after it has had a 15 years or so rest.

I remember back then carrying it myself, alas no more and last time running it brought in the new year.

Very tempted as it worked then and no oily caps leaking (oil) to run it gently up on the variac.

It goes of course against what I advise everyone else to do having said that.

I will not ask for a show of hands either way.

No doubt some would say go for it with careful monitoring.

Also, is it 2 neons in series that protect the sound transformer? I have searched quickly to no avail.
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Old 9th Jan 2019, 5:10 pm   #2
G4YVM David
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Default Re: AR88 Tempted as I am!

Let us know how it goes...
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Old 9th Jan 2019, 5:19 pm   #3
M0FYA Andy
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Default Re: AR88 Tempted as I am!

Check the capacitor between the anode of the audio output valve and ground. It has a tendency to go leaky and kill the output transformer.

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Old 9th Jan 2019, 5:28 pm   #4
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Default Re: AR88 Tempted as I am!

Thank you Andy,very good point.

Neons will not save it from that capacitor.
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Old 9th Jan 2019, 5:42 pm   #5
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Default Re: AR88 Tempted as I am!

I believe its 2 Neons in parallel, least that's what I did with mine. This thread reminds me, I must get mine back out for another going over...
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Old 9th Jan 2019, 6:37 pm   #6
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Default Re: AR88 Tempted as I am!

I think the mod was move capacitor from Anode to Ground to become Anode to B+ instead.

Then Neons (2 for more clamping effect) across capacitor might protect it somewhat on very loud AF peaks - or?
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Old 9th Jan 2019, 8:14 pm   #7
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Default Re: AR88 Tempted as I am!

On my 88 "that capacitor" was actually two smaller flat brown cased capacitors in parallel.

I replaced it by a modern 400V-rated MKT type.

Also on mine after a period of disuse I found that one of the big brown ceramic resistors in the bias network went open-circuit. I replaced all of them with new square ceramic 'coffin' resistors for enhanced reliability.
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Old 10th Jan 2019, 12:54 am   #8
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Default Re: AR88 Tempted as I am!

If original, change C117, 118, 119, 122 anyway (as mentioned), then lamp limiter in case things like the C96, 97, 98 block aren't what they were?

Still a marvellous radio, just try and imagine how much it would cost to make now!
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Old 10th Jan 2019, 9:11 am   #9
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Default Re: AR88 Tempted as I am!

Thank you all again.

Yes,how much now indeed to produce.Rough guess £5000.
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Old 12th Jan 2019, 9:32 pm   #10
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Default Re: AR88 Tempted as I am!

I bought an AR88 and thinking I had made a mistake when it came to moving it! Now I have it all working I really like it and it was worth the effort. In the 1940s era it must have been highly regarded.
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Old 12th Jan 2019, 11:42 pm   #11
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Default Re: AR88 Tempted as I am!

Seconded! It must have been an excellent tool for its operators when it came out, as with so many things that have reached the halls of fame it hit a sweet spot of capability by combining various developments of the era rather than having one single outstanding feature. Polystyrene coil formers for low loss and high stability, voltage stabilisation, lots of IF tuned circuits, switching between high-ratio and low-ratio tuning gangs for good bandspread and consistent gain, low-noise RF pentodes with good HF capability and sturdy, low-microphony construction all came together to make it among the outstanding mass-produced performers of the era.

It's always a bit sobering to think that without the catastrophe of WW2, only a few lucky US amateurs might have come to appreciate it, though.
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Old 13th Jan 2019, 1:37 am   #12
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Default Re: AR88 Tempted as I am!

See my rusbriges auction post re the AR88.

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Old 13th Jan 2019, 1:19 pm   #13
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Default Re: AR88 Tempted as I am!

It is still on the workshop bench awaiting a careful check before a variac wake up call.
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Old 13th Jan 2019, 2:22 pm   #14
James Duncan
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Default Re: AR88 Tempted as I am!

I know how you feel
I have three ar88's in my shed, just can not lift them now and too heavy to post, what does one do?, break up for people wanting parts?
same with two R107's I have.again too heavy now for me to handle.
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Old 13th Jan 2019, 3:22 pm   #15
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Default Re: AR88 Tempted as I am!

Do not break up, advertise collection only. Yes, I also have an R107.

I collared a pal who came over to lift with mine.
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Old 14th Jan 2019, 11:40 am   #16
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Default Re: AR88 Tempted as I am!

I bought a sack truck. The modern ones on eBay are a bit flimsy, but I found a good S/H metal one cheaper. Invaluable for us oldies!
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Old 14th Jan 2019, 11:56 am   #17
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Default Re: AR88 Tempted as I am!

Yes Bill, I thought about one of those too. Though you still need to lift on to a bench, possibly an engine hoist is about right.
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Old 16th Jan 2019, 2:00 pm   #18
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Default Re: AR88 Tempted as I am!

Yes, very good radios but need to be younger and fitter than I am to move these around
I need the space for other easier lifted projects
collection only ?? I am in wick north Scotland so quite a journey.
The R107's can be dismantled as built in three modules.
the AR88's are more of a problem but they have to go.
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Old 16th Jan 2019, 2:32 pm   #19
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Default Re: AR88 Tempted as I am!

Try putting them out in the offered bit of the forum.Not sure what or if you are asking for them?
It just could save them from being broke up.

Courier on a pallet I guess could be £50 plus but you never know who might be tempted.
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Old 16th Jan 2019, 3:16 pm   #20
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Default Re: AR88 Tempted as I am!

I agree that, for those of us of pensionable age, an AR88 is a 'two-man lift' - its width is part of the problem that make it difficult to get a decent hold.

I recently transferred my own AR88 (unaided) from a shelf in my workshop to a table in another shed some 30 yards away.

With care, I found that my wheelbarrow could do the move as long as the set was located centrally in it to avoid the risk of tipping. Actually getting the set in and out of the barrow just needed patience (and blankets for mechanical protection). I found that I could pretty readily lift one end of the set at a time so that by finding tables, chairs, stools etc of different heights, I could 'walk' it progressively and safely from its shelf into the barrow, down to the floor, and up again to its new table location.

So far, my back hasn't suffered any ill effects!

Martin
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