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Old 27th Oct 2013, 9:09 pm   #1
David Dunlop
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Default RCAF AR88LF (GR-17) Project

Hello everyone.

This website was suggested to me as great information source for these communication receivers, as it seems the vast majority of this particular model, made by RCA in Montreal, Canada ended up in England during the war. I thought my Mk III 19-Set was a weighty beast until I acquired this set. Yikes!

Electronically, it is in great working order, by main initial concern is to carefully go through it with an initial clean up in mind, as well as a basic familiarization with where everything is located. Lots of dust accumulation inside and I have produced a large quantity of old tobacco juice already from an external soap and water cleaning of the cabinet. Next step will be figuring out a safe way of extracting the chassis from the cabinet on a narrow workbench. May end up being a two person job. The cat loves sitting on it but I suspect won't be of much help with any grunt work!

So far I have found that appear from the basic operating manual printed by RCA for this set, the RCAF produced their own manual and so did the Canadian Army, who also referred to it as a GR-17. Seems likely, the navy also used them in that case.

Cheers for now,

David
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Old 27th Oct 2013, 9:56 pm   #2
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Default Re: RCAF AR88LF (GR-17) Project

Hi,
Have you seen:

http://www.radioblvd.com/ar88.htm

Which is one of the better general resources for these sets. Also, if you so a search on AR88 in this site you will find a lot of information, especially around restoring them.

Kind regards

Robin
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Old 27th Oct 2013, 10:09 pm   #3
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

Hi Robin.

Yes, I ran across that site a little while ago and found it quite interesting. Sent him in the serial number info from my set to add to his records.

My set was apparently in service with the RCAF until the mid-1960's, when they were all declared surplus and sold off. It was reconditioned in Mar. 1957 by a company in Canada called Northwest Industries, who may have painted the two horizontal bars above and below the panel assembly the white colour they are now. I can still see the original nickel plated metal under the paint but do not yet know how RCA mounted these two metal strips to the front of the panel. There is a little bit of vertical movement to them, but none horizontally. Most, if not all photos of the AAR88 family of receivers appear to have the nickel plated metal strips, which leads me to believe the white paint job took place in '57. Of course having said that, strips in every colour of the rainbow will probably start showing up now!

David
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Old 27th Oct 2013, 11:47 pm   #4
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Default Re: RCAF AR88LF (GR-17) Project

Quote:
Originally Posted by David Dunlop View Post
Next step will be figuring out a safe way of extracting the chassis from the cabinet on a narrow workbench.
I found the easiest way to do this is to stand it on the floor on its back face, upon two chocks of wood. After releasing the cover screws, the chassis can be withdrawn vertically and placed straight on the bench.
Enlist a spare pair of hands if possible, as it is still jolly heavy with the cover removed.
The cover tends to catch on top of the mains tx, so protect it with a piece of rag. Probably best to remove the bottom cover first, as the screws can catch, especially if they have been replaced with wood screws!
The chrome go faster strips should gently prise off with a fine screwdriver.
Rob.
p.s. how's the gearbox? Did it get an upgrade in '57?
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Old 28th Oct 2013, 11:37 am   #5
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Default Re: RCAF AR88LF (GR-17) Project

It's a shame that RCA didn't fit it with front panel handles, especially considering its weight. Doing that might have saved a few of the bent spindles, damaged knobs and tuning drives and panel scuffs from handling over the years. Also, face down on handles can make a convenient mode of working on large, heavy objects.

Admittedly, standard fitting of handles on 19" kit seems to have been a post-war thing.
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Old 28th Oct 2013, 11:52 am   #6
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Default Re: RCAF AR88LF (GR-17) Project

I found the best way to remove the chrome strips was to lift one end byprising between the end of the strip and the panel, then once the turned-down piece on the end is clear of the fitment on the panel, slide it sideways and along the entire width of the panel - that way you're only stressing one part of the strip rather than the entire length.
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Old 28th Oct 2013, 10:30 pm   #7
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

Rob: The function of the gearbox is delightfully smooth at the moment. Have yet to take a close look to see if it is original or a replacement at the time of reconditioning. The reconditioning itself is another mystery. It may have been a simple case of checking if anything was out of order and fixing/replacing it. or each set may have received a specific overhaul/replacement of parts, whether needed or not.

G6: Thanks for the suggestion for the trim strips. It will probably be one of the later things I attempt with the set. The close proximity of the panel assembly is a bit of a bother.

Best regards to all,


David
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Old 28th Oct 2013, 11:56 pm   #8
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Default Re: RCAF AR88LF (GR-17) Project

Some guidance: if you're doing stuff with any member of the AR88-series, be aware of the fragile-after-65+years insulation of the output transformer.

I've previously described how to protect the transformer by wiring a couple of NE-2 neons across the primary to provide a 'clamp' against excessive voltage surges that could otherwise overwhelm the aged transformer's insulation.

https://www.vintage-radio.net/forum/...2&postcount=10

NE-2 neon bulbs are cheap. AR88 output-transformers are expensive - if you can actually find a replacement. My $1.50 tweak can save you lots of grief.
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Old 29th Oct 2013, 12:02 pm   #9
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Default Re: RCAF AR88LF (GR-17) Project

Hi,
I'll underwrite G6Tanuki's suggestion. I fitted it to mine and whilst I was setting it up was very surprised and pleased by the number of times the bulbs fired. Obviously reduing a great deal of stress on the O/P transformer.

One thing. Has the loom been replaced. A number of the refurbs that I have seen have had the older cloth covered cabling replaced with PVC or similar.

Kind regards

Robin
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Old 30th Oct 2013, 4:10 pm   #10
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

G6: Good suggestion. I know the previous owner had the set up and running from time to time over the years, but better to be safe than sorry.

Robin: I will know for certain once I pull the chassis free from its cabinet. I have my fingers crossed. However, worst case scenario, the chap who gave me the AR88LF stumbled across a dozen or so spools of cloth loomed wire for sale in a local shop some years back and pounced on them. Turned out the end of each spool had a label identifying it as wire for the Wireless Set No. 19. All were dated in the 1940's. Wouldn't be the first time I rewired a chassis, but it is definitely a chore I prefer to do just once in life!.

David
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Old 30th Oct 2013, 8:53 pm   #11
RobinBirch
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Default Re: RCAF AR88LF (GR-17) Project

Well, the AR88 can be a bit of a monster to work on, there are areas where the deceptively open chassis just isn't the same shape as your soldering iron. But, it is reasonably straight forward with a number of known gotchas such as the tuning drive which are relatively well understood - see numerous discussions in these pages - and once properly set up produces a very very good performance.

Robin
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Old 30th Oct 2013, 10:30 pm   #12
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

While I think of it, here are some photos of the RCA speaker box I have for this receiver. It is a mid production item with black metal grill (rather than earlier nickel plated) and fully enclosed with the speaker cord exiting lower right side.

'Bubba' got into this one at some point and added a phone jack on the lower left front and replaced the original internals. If anyone can provide a template for the back louvered cover and dimensions, it would be a great help.

I also need to know if the two small holes on the right side above the speaker wire port are original or need to be dealt with. Ditto, the four holes on the bottom of the case.

Cheers for now,

David
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Old 31st Oct 2013, 7:29 pm   #13
RobinBirch
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Default Re: RCAF AR88LF (GR-17) Project

I don't know about the ones on the side but the ones underneath look exactly the right size for a part number/ID plate.

Robin
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Old 2nd Nov 2013, 10:50 pm   #14
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

Robin.

I had not thought of something that simple. The RCAF manual I have shows a speaker parts list which contains a Terminal Board, RCA # 80872-15, that I was assuming might have been mounted there. The other key pieces are:

Speaker # 107613-1
Gasket Assembly # 863238-501
Cable # 114074-501

and the Back Cover # 110101-1

David
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Old 10th Nov 2013, 5:23 pm   #15
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

I met up with a fellow AR88LF fan here in town yesterday and he gave me digital copies of the RCA Manual for this set, along with a RCEME Maintenance Manual for the AR88LF. Stapled inside the back cover of this manual, was a 17 March 1945 Technical Memorandum issued by the Director of Signals, identifying two faults which needed to be dealt with since the sets went into service: one regarding proper lube of the tuning drive and the second dealing with a mica condenser (C-119) that was prone to failure, which would result in the burnout of the primary of the output transformer (T-2), under certain circumstances.

Attached is a copy of this memo. It has been transcribed as the original mimeograph was too faded to copy directly. Hope it proves interesting reading.

David
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Old 10th Nov 2013, 8:22 pm   #16
Alistair D
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Default Re: RCAF AR88LF (GR-17) Project

Regarding the output transformer failure, there is a mod that helps the valve and the transformer. It is described at the bottom of page 1.

http://www.qsl.net/w/w2vtm//88/Getti...he%20AR-88.pdf

Al
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Old 13th Nov 2013, 4:59 pm   #17
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

Al: Thanks for that reference.

And while on the topic of transformers in the AR88 series of receivers, somewhere a while ago I ran across a photo of an AR88 chassis that showed some sort of markings on the top of the Power Transformer (T-1). It appeared to be white lettering covering most of the top of the transformer (possibly a decal or silk screened stencil perhaps), but it was difficult to read. I checked several different AR88 manuals on line, but it looks as if RCA utilized generic photographs in all AR88 Model manuals and the photos simply show a plain black Power Transformer. I am now curious as to how commonly a Power transformer was used in the AR88 that had the white markings on the top, and what was actually written on it.

David
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Old 15th Nov 2013, 6:29 pm   #18
David Dunlop
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Default Re: RCAF AR88LF (GR-17) Project

Well, it looks like I was partly right. The photo I had seen was on the Radio Boulevard site, but on closer inspection (attached) it turns out the set in question was a postwar SR88 of 1950's vintage. So, perhaps the T-1 Power Transformer was a plain black box during the wartime production after all.

Interestingly, however, RCA seems to have maintained the wartime tradition of placing a paper label on the top of the R-F Cover plate. Not s very clear shot of it, but it looks as if it refers to the specific receiver model in some way.

David
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Old 16th Nov 2013, 8:11 am   #19
M0SOE_Bruce
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Default Re: RCAF AR88LF (GR-17) Project

Hi David,

Not all the AR88s ended up overseas. This bank of 23 units was located in Vancouver. It was part of the wartime rtty link to Australia. Wonder where they are now.

Bruce
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Old 16th Nov 2013, 10:02 am   #20
RobinBirch
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Default Re: RCAF AR88LF (GR-17) Project

Quote:
Originally Posted by David Dunlop View Post
Well, it looks like I was partly right. The photo I had seen was on the Radio Boulevard site, but on closer inspection (attached) it turns out the set in question was a postwar SR88 of 1950's vintage. So, perhaps the T-1 Power Transformer was a plain black box during the wartime production after all.
Hi,
I have never seen a power transformer marked up like that. All the ones I have worked on are anonymous grey boxes. It probably depends on when they were made and who made the parts. I suspect that the earlier the set the more likely that there will be finishes like this. When they got into full swing then simpler ones would come into the fore, especially if alternative production sources were being used.

I've just checked the label in mine and it's similar with a description of the set and a list of the various patents that apply to it.

Robin
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