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

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.

Il 01/11/2018 07:43, snipped-for-privacy@nospam.com ha scritto:

** 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

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.

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

On Thursday, November 1, 2018 at 2:43:59 AM UTC-4, snipped-for-privacy@nospam.com wrote :

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 ind icate 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 t o add some thoughts.

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

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 :-#)#

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

Terry

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outside metal case would have to be well insulated so a user would not receive a serious shock if a charged cap was withdrawn from the socket.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

so a user would not receive a serious shock if a charged cap was withdrawn from the socket.

ected to the metal case.

Using bleeders would reduce any shock potential. A big commercial amp woul d have plenty of room for them. As long as some novice didn't pull the ele ctro 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 connec tions (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 connecte d to the live B+ through the cap.

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

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

NT

** 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

now there's a non sequitur

NT

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ic. Biggest risk is the glass breaks or you plug it in out of key.

e a tube, so just as safe. So it has to be.

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

Still, a theater amp wouldn't generally be serviced by a novice as common r adios 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 ab out using any line powered test equipment on a hot chassis without isolatio n. If it meant getting a theater amp running quickly I guess it made sense .

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blic. Biggest risk is the glass breaks or you plug it in out of key.

ike a tube, so just as safe. So it has to be.

radios and TVs were by consumers. A professional technician would hopeful ly 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 isolat ion. If it meant getting a theater amp running quickly I guess it made sen se.

I've used 2 lots of cinema equipment from the 1930s. The small setup was re asonably 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 equipm ent (Kalee). If you opened the side of the thing and caught a glimpse of th e carbon arc you wouldn't be seeing anything for a while. There was no latc h, let alone a lock or interlock. Needless to say one needed to open the th ing regularly to do the job.

There was also no easy way to check if the extractor fan was removing the a rc combustion products, and of course no monitoring or interlock and no oth er vents etc. There were also zero precautions available for nitrate film. And lots of mercury in the rectifiers. The projection booth was all firepro ofed though - but the fire extinguishing equipment totalled a single 1kg ch emical 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

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oo clever.

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public. Biggest risk is the glass breaks or you plug it in out of key.

like a tube, so just as safe. So it has to be.

on radios and TVs were by consumers. A professional technician would hopef ully be aware of the dangers of hot-swapping an electro just as he should b e about using any line powered test equipment on a hot chassis without isol ation. If it meant getting a theater amp running quickly I guess it made s ense.

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 equi pment (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 la tch, let alone a lock or interlock. Needless to say one needed to open the thing regularly to do the job.

arc combustion products, and of course no monitoring or interlock and no o ther vents etc. There were also zero precautions available for nitrate film . And lots of mercury in the rectifiers. The projection booth was all firep roofed though - but the fire extinguishing equipment totalled a single 1kg chemical extinguisher. A cap that might have killed someone that messed wit h it without knowing what they were doing would not have raised any concern s.

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

ee that a

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too clever.

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e public. Biggest risk is the glass breaks or you plug it in out of key.

st like a tube, so just as safe. So it has to be.

mmon radios and TVs were by consumers. A professional technician would hop efully 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 is olation. If it meant getting a theater amp running quickly I guess it made sense.

s reasonably safe, the full size one was another matter. Safety was not hig h on the list of concerns of whoever designed it, and it was top quality eq uipment (Kalee). If you opened the side of the thing and caught a glimpse o f 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 th e thing regularly to do the job.

he arc combustion products, and of course no monitoring or interlock and no other vents etc. There were also zero precautions available for nitrate fi lm. And lots of mercury in the rectifiers. The projection booth was all fir eproofed though - but the fire extinguishing equipment totalled a single 1k g chemical extinguisher. A cap that might have killed someone that messed w ith it without knowing what they were doing would not have raised any conce rns.

worked on it.

No-one got any training, and there was no paperwork relating to the equipme nt/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 extracto r fan was running, but it wasn't easy to tell if it was. One other chap nev er bothered to, and the 3rd guy checked it very occasionally. It was once f ound to be jammed but they still showed the film, so I guess arcs aren't to o bad with CO. There was no CO2, CO or smoke detector, no fire drill etc. T imes 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.

NT

On Saturday, November 3, 2018 at 12:10:44 PM UTC-4, snipped-for-privacy@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 fireproofe d though - but the fire extinguishing equipment totalled a single 1kg chemi cal extinguisher. A cap that might have killed someone that messed with it without knowing what they were doing would not have raised any concerns.

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.

nd lots of mercury in the rectifiers. The projection booth was all fireproo fed though - but the fire extinguishing equipment totalled a single 1kg che mical extinguisher. A cap that might have killed someone that messed with i t without knowing what they were doing would not have raised any concerns.

d to a music library. The walls are lined with metal. I've been told it w as zinc, but have no way of checking.

Zinc's appearance is distinctive.

NT

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

Can you post pictures of them?