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 Post subject: Really old theatre amp.....
PostPosted: Aug Sat 11, 2018 9:21 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6563
Location: Freeport, LI, New York 11520
Hi Guys......

I'm doing some research in order to obtain a schematic and any info on the following....
This unit is a PhotoPhone Type PA-36. The Model number is 4-PA-36-B. Serial number is 1019. It's a five tube affair utilizing the following: VT-24 (1st audio) VT-53 (duo-triode) Two VT-47's (output) and a VT-80 (rectifier). The correct speaker comes with the amp in it's own carrying case. It looks to be an early RCA 10" model. It is electrodynamic.
Also in the mix, which I haven't seen yet, is a PhotoPhone Pre-Grooved Disc Recorder. Type PR-14 Model 4-PR-14-B1. Two speed at 78 and 33 RPM. Serial Number 1023.

OK...With tube compliment I would say this unit is from the late 20' early 30's. I'm familiar with RCA radio chassis's from this era (I restore vintage radios as a business) and this chassis is very typical of RCA's early construction. Going thru my early Riders and RCA Redbooks, no light was shed on where I could find the schematic needed. Googling came close but no cigar.

Now, the question: Would anyone know where I could find this particular schematic? Or, are there other circuits that come close to what I'm looking for?

Appreciate the help!
Tnx and a Hat Tip...
Jim Koehler
Antique Radio Repair Service

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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Sun 12, 2018 3:56 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 380
Location: Olympia, Washington
The late Dick Prather from Portland, Oregon would likely have had the schematic. I believe at one time he had worked for RCA Service Company (theater sound system technician). He had just about every RCA and Western Electric theater and public address system schematic and manuals. He would post on the film-tech.com "Film Handler's Forum" there. Perhaps if you joined there, someone may know what happened with all of Dick's manuals/schematics. Brad Miller is the site owner/moderator there. It's ok to mention I sent you.


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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Sun 12, 2018 10:05 pm 
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Posts: 8737
Location: Beaver Falls, PA. USA
I have quite a few theatre sound manuals, and looked through all of my early RCA stuff, but I don't have that one. If the speaker is in a carrying case, it is part of a portable projector system; RCA made some in 35mm, as well as 16mm. The use of the type 53 would put it around 1932-34.

Documentation on the very early commercial RCA equipment is somewhat difficult to find.

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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Tue 14, 2018 3:10 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 5238
Location: Rochester NY USA
The Rider's PA manual doesn't have any RCA schematics earlier than the late '30s (all octal tubes except for a few transmitting tubes). You could take a schematic for a five tube amp using 6J7, 6N7, 6L6 and just change the pin numbers to match the earlier tubes... of course you'd have different voltages and resistor values.

Here's one:

Attachment:
RCA_MI-4274.pdf [56.54 KiB]
Downloaded 45 times

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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Thu 16, 2018 2:23 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6563
Location: Freeport, LI, New York 11520
@ Ken Layton....

Yes, I've joined that site and posted on there as well. I will mention you in my next post.

Thanks to all for the help....

...Jim

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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Thu 16, 2018 3:37 pm 
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Joined: Jun Wed 08, 2011 2:33 am
Posts: 8452
Location: Ohio 45177
If it is considered a collectable item and you intend to sell it, you best consider carefully whether to replace original components. Cosmetics and cleaning is OK usually. If you must replace caps to make it work, I would consider restuffing to the point of making the rework invisible.


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 Post subject: Re: Really old theatre amp.....
PostPosted: Aug Thu 16, 2018 10:41 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6563
Location: Freeport, LI, New York 11520
The trick is to get it working first. I was never one for the restuffing gig anyway unless space considerations demanded it or when it comes to the Philco boats and their ilk. Unless you're looking at a glass chassis, old components get replaced with new ones. Below board anyway....The top deck of the chassis I try to keep as pristine as possible. Even going as far as restuffing a new transformer in the original shell.

...Jim

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