AR-88 Power supply current capability?
 

I have a couple of questions about a NOS spare power supply I just bought. It's originally intended for an RCA AR-88 receiver, but I intend on using it for a tube amplifier build.

It's part number 901432-501, so it fits the listing for an AR-88D, according to a manual for those receivers.
It's also has two orange stamps:
SC4881A
£234 (not sure about the pound symbol)

So my questions:
1) The heater and rectifier windings have current ratings on them but the HT winding does not. Does anyone know a rough estimated current handling on the HT winding for these supplies? Or perhaps someone here has measured the mA draw before the filter chokes on a functioning AR-88?

I tried searching but didn't see a proper number.

2) Is it possible to date this transformer? I assume it's from around 1944-1950 but I was wondering if anyone is able to tell me a more exact date.

Thanks!

Re: AR-88 Power supply current capability?
 

Hi Jay, I believe your dating is about right.
From the rewind data I have on these transformers it looks to have an HT current rating of about 100mA

Ed

Re: AR-88 Power supply current capability?
 

According to the AR-88D manual, the vibrator power pack supplies an HT of 300V at 90mA.

Richard

Re: AR-88 Power supply current capability?
 

You may find it's a bit low on HT current raring for much of an audio amplifier. The receiver it's from used a lot of valves, taking a lot of heater current, but the majority of them were running at very low anode currents, and there was just a single-ended 6V6 taking more than a few milliamps.

Also, they had a bit of a reputation for burning out in the original receiver if a fault put the HT demand up at all... and that's why Ed's rewound some at various times.

David

Re: AR-88 Power supply current capability?
 

These transformers give an initial impression of being quite big and heavy- but much of that comes from being potted into an outer steel can, as the others say the HT current rating is actually quite modest. Furthermore, the original design uses a relatively high impedance rectifier (5Y3GT) feeding just 4uF reservoir followed by a 400 ohm first choke, so it will have been specified around relatively modest amplitude charging pulse capability. Don't count on making anyone's ears bleed with it!

The SC number signifies US Signal Corps approval but I don't know what the number itself signifies, whether an inspector, a depot or a specification.

Re: AR-88 Power supply current capability?
 

I use an oil filled Parmeko transformer from an RA17 for a stereo valve amplifier - runs about 6 watts per channel - I can tell you the transformer gets too hot for comfort after about an hour's use - I wouldn't think of trying an AR88 transformer in an audio amp.

Re: AR-88 Power supply current capability?
 

Thanks for the generous replies!

I was going to figure the type of amp to make from the abilities of the power supply. So far it would seem like it could be an oversized (but not overpowered) power supply for a SE EL84 or 6V6 amplifier with 1-2 pre-amp tubes.

Wasn't expecting to use this for a monster amplifier, but a low-wattage SE guitar amp (maybe 6 watts) seems doable.

Re: AR-88 Power supply current capability?
 

90 ma about tops for the AR88 power supply.
Not much use for a valve amp, I have built many of these.
tell me the ht current that you need and also tell me the volts and amps you will need for the heaters.
if you intend to use a valve rectifier ( best option) also tell me about that as will be on a separate Xmer winding.
I have many suitable Xmer's and chokes that would be used in such projects.
Very simple to make your own Ht/Lt power supply
MM0HDW

Re: AR-88 Power supply current capability?
 

If you're not after the highest of fi, go for push-pull output with the valves biassed back towards class B. That way you'll only take higher current on peaks.