UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Reply
 
Thread Tools
Old 29th Dec 2018, 7:28 pm   #1
jaycobie
Diode
 
Join Date: Dec 2018
Location: Reykjavik, Iceland
Posts: 3
Default 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!
Attached Thumbnails
Click image for larger version

Name:	s-l1600.jpg
Views:	89
Size:	61.1 KB
ID:	175378  
jaycobie is offline   Reply With Quote
Old 29th Dec 2018, 8:05 pm   #2
Ed_Dinning
Dekatron
 
Join Date: Jan 2004
Location: Newcastle upon Tyne, Tyne & Wear, UK.
Posts: 5,393
Default 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
Ed_Dinning is offline   Reply With Quote
Old 29th Dec 2018, 8:21 pm   #3
trh01uk
Heptode
 
trh01uk's Avatar
 
Join Date: Nov 2010
Location: Ross-on-Wye, Herefordshire, UK.
Posts: 941
Default 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
trh01uk is online now   Reply With Quote
Old 29th Dec 2018, 8:49 pm   #4
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 11,845
Default 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
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 29th Dec 2018, 10:24 pm   #5
turretslug
Nonode
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 2,690
Default 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.
turretslug is offline   Reply With Quote
Old 29th Dec 2018, 10:27 pm   #6
Sean Williams
Dekatron
 
Sean Williams's Avatar
 
Join Date: Feb 2005
Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW
Posts: 3,339
Default 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.
__________________
Engineers make things work and have spare bits when finished
Sean Williams is offline   Reply With Quote
Old 31st Dec 2018, 3:51 pm   #7
jaycobie
Diode
 
Join Date: Dec 2018
Location: Reykjavik, Iceland
Posts: 3
Default 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.
jaycobie is offline   Reply With Quote
Old 31st Dec 2018, 3:51 pm   #8
James Duncan
Pentode
 
Join Date: May 2010
Location: Wick, Scotland, UK.
Posts: 138
Default 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
James Duncan is offline   Reply With Quote
Old 31st Dec 2018, 7:22 pm   #9
Herald1360
Dekatron
 
Herald1360's Avatar
 
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 13,087
Default 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.
__________________
....__________
....|____||__|__\_____
.=.| _---\__|__|_---_|.
.........O..Chris....O
Herald1360 is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 11:50 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.