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Discussion Starter #1
I just acquired an old public address amplifier from the 50s.

Right off , have a problem since this thing was built to connect to a 6 volt car battery ! :oops:

I have a photocopy of the schematic that I will add but looking for the best solution as to how to connect/convert to plug into a reg 120V wall socket ?

All help would be appreciated.
 

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A 6VDC wall-wart is my first thought.

Learn how much juice it needs (amps/milliamps/whatever), find the right connection and search for an adapter using those criteria.
 
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"I think"........ there has to be something in there to step up the 6 volts, to around 300 to 400 volts for the tubes to function. I made the mistake of googling "vibrator", that took me down all sorts of paths I didn't intend going. I also learned of something called a "dynamo" which was used on a lot of 6 volt radios to up the voltage. Once upon a time.......even car radios used tubes and were 6 volt powered.

My thinking is, there should be a point where you can tap into the circuit with 120 volts and completely by-pass all that step up mechanism, whatever it may be.
 

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Discussion Starter #5
A 6VDC wall-wart is my first thought.

Learn how much juice it needs (amps/milliamps/whatever), find the right connection and search for an adapter using those criteria.
A 6VDC wall-wart is my first thought.

Learn how much juice it needs (amps/milliamps/whatever), find the right connection and search for an adapter using those criteria.
I was thinking of adding a small power converter inside and adding a reg power cord. The power converters semm to be very cheap but need the right Ma current...
 

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My thinking is, there should be a point where you can tap into the circuit with 120 volts and completely by-pass all that step up mechanism, whatever it may be.
That's what I think too, though it may require a different power transformer.
 

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Discussion Starter #7
I made the mistake of googling "vibrator"
:oops: :oops: :oops:
You`ll have plenty of info on that for certain !!!

My thinking is, there should be a point where you can tap into the circuit with 120 volts and completely by-pass all that step up mechanism, whatever it may be.
I`ll be taking pictures later tonight of the items. Currently making room for these.
 

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Discussion Starter #10
OK, had time to take a few pics.

Here is the PA in question, its in rough shape and an idiot painted it black...

327998


327999


328000


328001
 

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Discussion Starter #11
328002


328003


The first thing to take into consideration, all the transformers are Hammond. Whoever painted the chassis was kind enough to write the numbers on everything...

PT
328004


OT
328005
 

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Discussion Starter #12
You can tell its an old one by the tubes !!!

328006


328007


Here is the 6 volts adapter tube !

328008


and its really a tube !

328009
 

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Discussion Starter #13
The inside is a mess... someone played in here and I have no clue as to what was the end goal ! ...

328010


The OT should be easy to decipher ...
328011


Here is were the PT connects. It connects to the 6V tube socket under this silver filter ...
328012

328013


Looks like I could bypass the 6V tube and set up...

I should maybe write to Hammond with the PT number to verify...
 

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Discussion Starter #15 (Edited)
Thanks for the link and info.

That 8Q7 tube may be an issue as well.
Its a 807 power tube, Hammond made all the transformers for SoundMaster and he made 20,000 amps with these tubes. Replacements should exist ! I hope ! or else this is just good for a full rebuild.
 

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Discussion Starter #16
I took better pics of the schematic and adjusted the contrast to make it darker.

328020

328021

328022
 

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So I'll speak up from whatever experience I have - please take with a grain of salt. If this device was designed to work on a 6V DC power source from a car battery and draws 6 Amps continuous, the easiest way would be to connect it to a power supply that can supply that 6V DC voltage and 6A current (rather than trying to tap into the circuit using a different power supply and risk blowing something up). However, you should get a power supply rated far more than the 6 amp steady-state required, probably more like 10-20 amps (wall-warts won't cut it, they rarely go above 1-2 amp). I have seen some 6vDC - 10000 mA power supplies on Amazon, they look like power supplies for laptops - that MAY work.

The only part I am weary of (and maybe a tube amplifier expert can shed light on this, like nonreverb) is the power-on current draw when you turn the tube amp on. This was designed to be used with a car battery and car batteries have awesome cold-cranking amps (a short but high current peak when you start your car), so if you connect this to any power supply that cannot supply the peak current when you turn it on (when those big capacitors charge up) then you may blow up the power supply. If this circuit was designed to run to a 6V car battery, you may be better off using it with such a battery, though it may be expensive to find one with enough Ampere/Hours to run the amp for any length of time.
 

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OK, I'm hooked on this thread now, it's been too long since I have done this kind of research. To avoid highly embarrassing search results, look for RADIART vibrators: "Until the advent of transistors almost all radios that operated from 6-volt or 12-volt batteries used a vibrator to generate the B+ for the vacuum tubes". So the vibrator provides the B+ plate (anode) voltage - that's the high voltage on the tube. The 6X5GT tube is typically used as a rectifier, so I am assuming the vibrator output is an AC voltage (hence "vibrator") derived from the 6V DC input with step-up voltage from the bulky 126347 transformer?

We need Nonreverb on this thread. Rich, where are you? :)
 
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