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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 28th May 2020, 12:11 am   #1
AdrianH
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Default AR77 radio, a possible project.

Well I will soon be picking up an old RCA AR77 locally to me, the case is missing the back panel so if anyone has pictures of the rear of the radio it would be appreciated. There seems to be a couple of mods done to the radio which is not that unexpected for a radio which is now going on for 80 years old.

I will be able to have a closer look over it after collection and I try to remove the front knobs to separate the chassis from the case.

At worst it will be broken up up for project parts. Wife says it is an ugly looking thing!

Adrian
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Old 28th May 2020, 11:04 am   #2
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Default Re: AR77 radio, a possible project.

Good luck with it, I'm sure it will prove to be a good performer. The AR88 got the limelight in the post-war UK, but the AR77 still represents what would have been a top-notch and expensive amateur-use set in its time. The use of a 6-gang tuning capacitor for main tuning and 9-gang for bandspread shows that the designers wanted it to be a good performer even at the highest HF frequencies, though it does mean that the front-end switching gets involved.

Check that the mains transformer is in good condition electrically before you commit too much other effort to it- it has an unusually high voltage secondary (ISTR 375-0-375) and may be difficult to substitute without various other changes to the circuit. No doubt the likes of Hammond offer something usable, or it could be rewound, but either will be a fair dollop of money.

Don't call it ugly, call it classic '30s modernism!

Colin
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Old 28th May 2020, 12:40 pm   #3
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Default Re: AR77 radio, a possible project.

Many years ago I did read a brief description of the AR-77. The bit from that which that sticks in my memory is this: "The AR-77 is effectively an AR-88 with bandspread".

Al.
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Old 28th May 2020, 12:56 pm   #4
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Default Re: AR77 radio, a possible project.

OK have collected the sorry thing, I will include a few of the pictures I have taken of the unit, it has been damaged, to what extent fully I do not know yet. The seller did power the unit up to provide some pictures, which I think he took his life in his hands doing as the mains cable goes into a Bakelite chock block and the wires attached has crumbling rubber. I do know from one pic that the bulb on the S meter lights. But It will not get powered up again for some time if ever.

Several knobs of the wrong type and unfortunately of the correct type I had to break three as they were seized on and ease-it would not shift.

Underneath you should be able to make out some damage to the main chassis and in fact the top three wafers are broken. The bent bits of metal can always be repaired.
So missing back and base plates, damaged to main wafer switches. The two tuning caps rote as do the scales, the shutters have an issue I can see broken cord so they need to be sorted. The main case has a switch fitted and another hole in it?
The S meter is in a bad way. broken glass and looks as though water made it in there. Some corrosion to the very front parts of the scale assembly, but think they will clean up again.

Did not expect the valves to be marked with JAN or USN?

a few mores mics in another post. Dinner time.

Adrian
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Old 28th May 2020, 1:21 pm   #5
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Default Re: AR77 radio, a possible project.

A few more pictures.

The TX/RX switch is also broken, well the spindle came out of the front !
So could be an interesting project, simple tings first un-bend the bottom of the case and put to one side.


Adrian
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Old 28th May 2020, 3:10 pm   #6
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Default Re: AR77 radio, a possible project.

I have an AR77 in much worse condition than yours. I modified it and used it in conjunction with a Heathkit DX100 for some years.
When I get some help, I will get it unearthed and photographed.

You may wish to have a go with it. The transformers and smoothers were OK when put in the heap.
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Old 28th May 2020, 8:34 pm   #7
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Default Re: Signal equipment..... Lend - Lease Shipments.

Well with nothing else to do today I continued on a bit more with the set, thinking at least if I can get some of the mechanical work sorted, I may consider the components!
Cleaned up the rust on the vertical columns and added some silver paint to protect from further rusting, freed off the dried up grease on the shutter mechanisms and straightened as best I could the flattened bit of chassis underneath.

That is all well and good, saw one of the wax style caps that had split in several ways, so know there will be some cap work to be done. Possible signs of resistors being replaced at some point in the past, doubt if they are all original some some more to do?

Also some of the wire, one can see a black wire there in the pic with the cap and how the end of the insulation is missing, there are quite a few like that. I would say that all that is do-able, what I am not sure about is finding replacement wafers for the three broken ones so if anyone can suggest a specialist forum or supplier of old RCA parts I could go off and try them?

I do not want to have another person break his/her radios up to get this one going, it could be a better prospect possibly to keep another working one going?

Last couple of questions I think on this for tonight, where do you buy the cord from to do the tuning scales?
and
anyone got pictures showing the back and base of unit?

Thanks

Adrian
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Old 29th May 2020, 6:48 am   #8
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Default Re: Signal equipment..... Lend - Lease Shipments.

Hi Adrian,

Looking at the broken wafers, are you sure they are beyond repair, looks to me that they may be repairable being ceramic bodied.

Peter
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Old 29th May 2020, 10:01 am   #9
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Default Re: Signal equipment..... Lend - Lease Shipments.

I was thinking along similar lines. The ceramic wafers are almost certainly specific to the circuit, as they will be used for switching appropriate sections of the main and bandspread capacitors in and out of circuit as well as coil-switching, so it would need either a parts mule set or end-of-rainbow spares. The ceramic switch base, being thick and rigid, might well be a better prospect for gluing than thinner composite wafers. My instinct would be to search a specific ceramic bonding type, possibly one of the cyanoacrylates- there'll be folk here better versed than me in appropriate ways of repairing intricate ceramic things who would be better placed to advise. It's just possible that spares exist in the USA, too, as AR77s seem to crop up on the US Antique Radios Forum and come in for praise.

Good luck with it, Colin
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Old 29th May 2020, 10:30 am   #10
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Default Re: AR77 radio, a possible project.

I’ve got a few ceramic switches that at first glance look similar to yours. When you are ready to send a close up pic I’ll Have a good look at what I’ve got even if all that’s rescuable is the ceramic body and you have to fit your own contacts with 10 BA screws.

Jim
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Old 29th May 2020, 10:36 am   #11
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Default Re: AR77 radio, a possible project.

I tried a search on Ebay.com for AR77 wafers and found a AR77 in pieces unit for some crazy amount. Considering this unit cost me all of £10 I find it very surprising.

With the damage I was going to initially break it up for valve holders the transformer/choke OP transformer etc as a way to build up a parts box, but started to slowly attack the simplest things.

I had not considered glueing ceramics together, so that is a possible way forward, thanks. I will box up the valves for safety and see how to remove the selector rod from down the wafers to then pull out the damaged parts, that way I will be able to see if all bits are still there or if any piece is missing.

Adrian
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Old 29th May 2020, 10:43 am   #12
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Default Re: AR77 radio, a possible project.

Hi Jim, was writing my response during your post. If I am allowed to work on it again today I will post some pictures, very kind of you to offer.

I did look at the circuit and parts list last night there seems to be two types I need to repair/replace. For my first repair/refurbish of the old valve gear I seemed to have picked more of a challenge., I guess doing it in stages is the best way forward.

Adrian
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Old 29th May 2020, 11:28 am   #13
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Default Re: AR77 radio, a possible project.

Adrian,

Many years ago I knew someone who was due to have his equipment confiscated due to illegal behaviour on air. He expected to lose his Collins TCS transmitter so he smashed the ceramic wafer switches and later found they weren’t going to take it leaving him with a repair job. I think he Araldited them and claimed a complete success so yours may well be possible if that is the only course of action available.

Jim
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Old 29th May 2020, 9:30 pm   #14
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Default Re: AR77 radio, a possible project.

I thought I was the only one with mates like that
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Old 29th May 2020, 9:59 pm   #15
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Default Re: AR77 radio, a possible project.

Yes Fred, he had other failings in the fibs department but it was 30 years ago and I've nearly forgotten.

Jim
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Old 29th May 2020, 10:14 pm   #16
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Default Re: AR77 radio, a possible project.

I managed to take the section out with two broken wafers in it, these are not meant to be taken apart, it will be fun trying to get things back together. Attached a couple of pictures if the first wafer (S7), the two mounting holes are as close as I can measure to 39mm apart. I doubt they are mean to be metric though?

I have found a trader on the bay that says he has some at 40mm hole spacing in ceramic as part of some switch assemblies, it would be a case of drilling out the rivits and using small screws and nuts as suggested.

I could still have a go at trying to clean these and bond them, what could I use in the small ultrasonic tub, would soapy water and then a long drying period be OK?

Last time I tried acetone in the tub the outer plastic nearly melted away!

Adrian
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Old 30th May 2020, 7:37 am   #17
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Default Re: AR77 radio, a possible project.

If it was mine I would definately bond back the old wafers. There are some specialist ceramic glues available.
As for cleaning, ultrasonic with soapy water is fine but do rince off with distilled water to remove any trace of soap.
Long drying will be needed as the ceramic is not glazed and will absorb some water.

Peter
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Old 30th May 2020, 9:35 am   #18
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Default Re: AR77 radio, a possible project.

Adrian,

I have three of these wafers all unused which you are welcome to if they'll fit or can be made to do the job.

Sizes:- 39/40 mm mounting hole centres. 30 degrees between each click.
overall size 47.4 mm by 39.2 mm. Main body of centre contacts 14.8 mm diameter.

The contact mounting holes are just too small to take 8 BA but 10 BA are fine. Sorry I don't have any suitable screws.

Hope this helps.

Jim

PS Do you know you can get the manual from VMARS manuals FOC or from the Royal Sigs ws19 group again FOC but with a few restrictions to overcome.
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Old 30th May 2020, 10:30 am   #19
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Default Re: AR77 radio, a possible project.

Hello Jim.

Thanks for the offer but not sure if I could use that style, the ones for the AR77 are double sided with contacts on both sides so need to have a wiper on the rear of the switch as well. I have some coming from abroad, will take some time to arrive and I will also be trying to clean and re-glue the units together again first.

I have a manual, brochure and circuits from the radiomusem site all without restriction, that is I am using for reference.

I am taking a break from it today, must spend some time with the wife, well some time at least

Adrian
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Old 6th Jun 2020, 9:56 am   #20
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Default Re: AR77 radio, a possible project.

Adrian...
Just looking around the Forum looking for inspiration for my next project after the HP8640B and thought this article might help with the AR77.
I don't think mine came with a rear cover.
http://www.radiomuseum.co.uk/AR77overhaul.html
Allan G3PIY
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