How to identify old tube amp chassis ?????

[Geor...@nospam.com]

Back in the 1960s I was given several heavy tube amplifier chassis. All
of them worked after replacing a few tubes. After all these years, I
still have them. They were very well made, The transformers were not
shaped like most, but were in square cans with rounded corners.

Another unusual thing, was the three part filter capacitors were plug
in, with an octal base (same as an octal tube). Back then, I had a
little hum so I found a store that had identical replacements.

The tubes were all octal based. Four 6L6 outputs, Two 5U4 recifiers, and
at least 4 more octal tubes. I believe at least one was a 6SN7
(something like that). I dont have them handy to look at right now....

Anyhow, they had awesome sound and were loud. The audio output
transformers were huge.

However, there was no brand name or identification of any sort on them.

50 years later I am still trying to ID them...

I think they were from jukeboxes. But that is just a guess....

I have tried to google different words but not found any matching
pictures. I did note that the Rock-Ola chassis all seem to have those
square transformers though. My guess is that they were made in the late
1940s or 1950s.

Does anyone know of any website that has photos of antique jukebox
chassis, or another means to ID them?

[Eremita Analogico]

Hi,
The output transformers seem to be Acrosound, very good transformers.
Try looking for Williamson amplifiers schemes, depending on the valves
used there could be a similar scheme.
Do you sell one of these chassis? Also without tubes.

[Phil Allison]

** Google Images have lots of pics of " Rockola amplifiers" in various states of repair. Most have square boxed transformers, 6L6G and other octal tubes and electro dynamic speakers.

But none had plug in electros on octal sockets



.... Phil

[peterw...@gmail.com]

Back in the day, RCA made theater amplifiers as you describe, up to and including the potted transformers. These things were massive and usually rack-mounted.

The logos were enameled medallions, so if they were removed, you would have no other indication of the maker.

https://thumbs.worthpoint.com/zoom/images3/1/0410/17/vintage-rca-type-mi-4288-mono-tube_1_b74613f650ed1caef9dc8c6b2b59c8f9.jpg

When theaters started replacing tube systems with solid-state and multi-channel systems, many thousands of these amps got trashed, and a vanishing few found their way into other hands.

Peter Wieck
Melrose Park, PA

[John-Del]

I like the advice that they are either jukebox amps or theater amps. Since you described them as physically large, I think a theater amplifier would make sense. The fact that the electros were easily replaceable seem to indicate that they are specifically built to be serviced quickly and on-site, which again favors both jukebox or theater amp.

We have a resident jukebox expert here (John Roberson?) who might be able to add some thoughts.

In the meantime, can you post pictures of these amps to a hosting site?

[John Robertson]

I know of no jukebox amp that had plug in capacitors. I agree that a
theatre amp is most likely - I too would enjoy seeing photos of these
amps you have!

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
(604)872-5757 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

[Terry Schwartz]

I recall some old intercom/PA amps that had both plug-in capacitors and plug-in relays. Everything was socketed.

Terry

[Phil Allison]

John Robertson wrote:

>
>
> I know of no jukebox amp that had plug in capacitors. I agree that a
> theatre amp is most likely - I too would enjoy seeing photos of these
> amps you have!
>

** The idea of using high voltage, plug-in electros seems quite unsafe.

At the very least, the outside metal case would have to be well insulated so a user would not receive a serious shock if a charged cap was withdrawn from the socket.

Even then, some of the octal pins would be hot while others would be connected to the metal case.

Sounds like some amp builder's ones clever idea that is a bit too clever.



.... Phil

[John-Del]

Using bleeders would reduce any shock potential. A big commercial amp would have plenty of room for them. As long as some novice didn't pull the electro with the amp powered up a loaded cap wouldn't be a problem.

A way of making them safer would be to use longer pins on the ground connections (or deeper socket pins for the B+ connections) so the B+ would break before the ground disconnected in case someone pulled one out of a powered up chassis. The cap would remain charged but the tech wouldn't be connected to the live B+ through the cap.

In any case, I do remember in the old tube/valve TV days when low end TVs that didn't use power transformers did have a hot electro on an isolated phenolic base. Those electros had heavy cardboard sleeves well bonded to the can for safety reasons. Never saw one of those come apart.

[tabb...@gmail.com]

it wouldn't have been any great concern back then though. Expectations have much changed. Bare live bits are frowned on now.


NT

[Phil Allison]

tabb...@gmail.com wrote:
>
> Phil Allison wrote:
> > John Robertson wrote:
> >
> > >
> > >
> > > I know of no jukebox amp that had plug in capacitors. I agree that a
> > > theatre amp is most likely - I too would enjoy seeing photos of these
> > > amps you have!
> > >
> >
> > ** The idea of using high voltage, plug-in electros seems quite unsafe.
> >
> > At the very least, the outside metal case would have to be well
> > insulated so a user would not receive a serious shock if a charged
> > cap was withdrawn from the socket.
> >
> > Even then, some of the octal pins would be hot while others
> > would be connected to the metal case.
> >
> > Sounds like some amp builder's ones clever idea that is a bit too clever.
> >
> >
> >
> >
>

> it wouldn't have been any great concern back then though.
> Expectations have much changed. Bare live bits are frowned on now.
>
>

** Tubes have long been user replaceable items, sold direct to the public. Biggest risk is the glass breaks or you plug it in out of key.

Building an electro with octal plug on the end makes it appear just like a tube, so just as safe. So it has to be.


.... Phil

[tabb...@gmail.com]

On Saturday, 3 November 2018 06:10:09 UTC, Phil Allison wrote:

now there's a non sequitur


NT

[John-Del]

Well, I'm sure he's being sarcastic..

Still, a theater amp wouldn't generally be serviced by a novice as common radios and TVs were by consumers. A professional technician would hopefully be aware of the dangers of hot-swapping an electro just as he should be about using any line powered test equipment on a hot chassis without isolation. If it meant getting a theater amp running quickly I guess it made sense.

[tabb...@gmail.com]

On Saturday, 3 November 2018 11:38:28 UTC, John-Del wrote:

I've used 2 lots of cinema equipment from the 1930s. The small setup was reasonably safe, the full size one was another matter. Safety was not high on the list of concerns of whoever designed it, and it was top quality equipment (Kalee). If you opened the side of the thing and caught a glimpse of the carbon arc you wouldn't be seeing anything for a while. There was no latch, let alone a lock or interlock. Needless to say one needed to open the thing regularly to do the job.

There was also no easy way to check if the extractor fan was removing the arc combustion products, and of course no monitoring or interlock and no other vents etc. There were also zero precautions available for nitrate film. And lots of mercury in the rectifiers. The projection booth was all fireproofed though - but the fire extinguishing equipment totalled a single 1kg chemical extinguisher. A cap that might have killed someone that messed with it without knowing what they were doing would not have raised any concerns.


NT

[John-Del]

Wow. Hopefully, only those trained to service that equipment would have worked on it.

[tabb...@gmail.com]

On Saturday, 3 November 2018 16:58:17 UTC, John-Del wrote:

No-one got any training, and there was no paperwork relating to the equipment/installation. No-one checked what we did. We did all have an electronics background though, so weren't stupid with it. I used to check the extractor fan was running, but it wasn't easy to tell if it was. One other chap never bothered to, and the 3rd guy checked it very occasionally. It was once found to be jammed but they still showed the film, so I guess arcs aren't too bad with CO. There was no CO2, CO or smoke detector, no fire drill etc. Times change.

The kit was so old I don't know if they'd have found anyone else to service it. Kalee projectors live in museums now.
https://www.google.com/search?q=kalee+projector


NT

[Tim R]

On Saturday, November 3, 2018 at 12:10:44 PM UTC-4, tabb...@gmail.com wrote:
vents etc. There were also zero precautions available for nitrate film. And lots of mercury in the rectifiers. The projection booth was all fireproofed though - but the fire extinguishing equipment totalled a single 1kg chemical extinguisher. A cap that might have killed someone that messed with it without knowing what they were doing would not have raised any concerns.
>
>
> NT

We have a projection room in a building, no longer used and now repurposed to a music library. The walls are lined with metal. I've been told it was zinc, but have no way of checking.

[tabb...@gmail.com]

On Monday, 5 November 2018 13:31:58 UTC, Tim R wrote:

> On Saturday, November 3, 2018 at 12:10:44 PM UTC-4, tabby wrote:

> vents etc. There were also zero precautions available for nitrate film. And lots of mercury in the rectifiers. The projection booth was all fireproofed though - but the fire extinguishing equipment totalled a single 1kg chemical extinguisher. A cap that might have killed someone that messed with it without knowing what they were doing would not have raised any concerns.
> >
> >
> > NT
>
> We have a projection room in a building, no longer used and now repurposed to a music library. The walls are lined with metal. I've been told it was zinc, but have no way of checking.

Zinc's appearance is distinctive.


NT

[Sjouke Burry]

Apply a bit of acid. with a bit of zinc it starts bubbling.

[Ken Layton]

Can you post pictures of them?