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 Identification of radiogram chassis needed
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 Return to top of page · Post #: 1 · Written at 5:34:04 PM on 5 June 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 42

Hi, I restored the stereo 6DX8 PP amplifier chassis of an Australian made radiogram a few years ago, but was not able to identify the maker/model of the radiogram at the time as I just had the 'innards'. If anyone can tell from the two linked photos then that would be much appreciated.

The chassis is stamped 1569. The output and power transformers are marked 4156 0C8 (16K PP; 16Ω secondary) and 3261 0C8 (0-240V; 260-CT-260 ?mA, 6V3 5A), so could be custom A&R. The various identifiable part date-codes seem to indicate a circa 1969 manufacture.

https://www.dalmura.com.au/static/$_57a.jpg
https://www.dalmura.com.au/static/IMGP0875.JPG

Ciao, Tim


 
 Return to top of page · Post #: 2 · Written at 5:54:18 PM on 5 June 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

It looks familiar to me ,but I can't put my finger on it ! I think it's HMV ,, tonight I will Look through my books and see if I can identify it ..I'm sure it's HMV ....pete


 
 Return to top of page · Post #: 3 · Written at 6:06:03 PM on 5 June 2020.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1380

What does it say at the top left corner of the front panel? (it's rather blurry there)

What is the valve line-up?


 
 Return to top of page · Post #: 4 · Written at 7:20:39 PM on 5 June 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 42

Just had to check - LHS top says 'Input RH', and below is 'Input LH', and in between is MICROPHONE and TAPE RECORDER.

Line up is 6AN7, 6N8 and 12AX7.


 
 Return to top of page · Post #: 5 · Written at 10:48:52 PM on 5 June 2020.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 4345

Missing a couple of valves, maybe four. 12AX7 is a double triode so if its stereo where are the out put tubes? Other chassis perhaps?

Some manufactures did like certain valves HMV liked 6M5 as an output valve as well as 6BM8.


 
 Return to top of page · Post #: 6 · Written at 11:41:17 PM on 5 June 2020.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1380

I can see at least 7 valves in the first photo - what valves are in the back part?


 
 Return to top of page · Post #: 7 · Written at 11:58:37 PM on 5 June 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 42

Sorry - the initial post says its a stereo 6DX8 PP amp chassis - so yes a quad of 6DX8 (and a rectifier socket which didn't come with a valve, but was likely a 6V4, and I've restored it with a 6V4).


 
 Return to top of page · Post #: 8 · Written at 4:24:02 AM on 6 June 2020.
Robbbert's avatar
 Location: Sydney, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1380

6DX8 is normally used as a video output valve in TVs, I wouldn't have thought it would have enough power for an audio amp. But I guess the manufacturers will try anything.

Thanks for the valve list.


 
 Return to top of page · Post #: 9 · Written at 8:06:39 AM on 6 June 2020.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 882

I used a 6DX8 as the audio output in my 3" TV set.
It is just a triode pentode meant for linear uses.
I used a 100volt to 8 ohm line tranny for the output.
The wattage output would depend on the working voltages in the chassis.
I wanted about 1 watt to drive a 5" speaker and it walked that in!
They probably had a warehouse full of 6DX8's for TV use, so used it for anything else.

Fred.


 
 Return to top of page · Post #: 10 · Written at 8:24:04 AM on 6 June 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

I looked through my books last night and found nothing with that face plate and chassis so whatever unit it came out of was not a popular model as I have photos of most units from the 60s to early 70s.....


 
 Return to top of page · Post #: 11 · Written at 10:05:57 AM on 6 June 2020.
Trobbins's avatar
 Location: Melbourne, VIC
 Member since 11 July 2012
 Member #: 1179
 Postcount: 42

Yes I looked at all the radiogram photos I could find, and still look around if I notice a radiogram show up on ebay or facebook.

The amp chassis was quite nice to restore and re-purpose, with enough chassis face area to add two input jacks, two dual-gang pots for post PI volume, and two speaker jacks.

The Miniwatt datasheet has an audio class AB PP section, so audio wasn't an uncommon use for 6DX8 and its 4W plate dissipation rating. Datasheet rated audio output was 5.4W for PP in to 17.5kohm load (which was a bit higher than typical 6M5). I got a reasonable 3W clean from 90mVrms input, and configured it to over-drive nicely.


 
 Return to top of page · Post #: 12 · Written at 10:38:37 AM on 6 June 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

One thing worth mentioning is don't target the visual search on a black face plate which is easy to do.
Many units had mostly silver but a hand full of blacks are made.
The 1197 did that ,where 90% that I've seen were silver and few odd black ones about the place so other manufacturers would of also done the same ....


 
 Return to top of page · Post #: 13 · Written at 10:50:40 AM on 6 June 2020.
Ian Robertson's Gravatar
 Location: Belrose, NSW
 Member since 31 December 2015
 Member #: 1844
 Postcount: 1910

It's a GE. I remember that model. Not common. Made in the Enfield factory. Successor model was all solid state.


 
 Return to top of page · Post #: 14 · Written at 11:04:03 AM on 6 June 2020.
Vintage Pete's avatar
 Location: Albury, NSW
 Member since 1 May 2016
 Member #: 1919
 Postcount: 1993

A GE ! That makes sense,They had some odd ones... There is one model that brings big bucks I will get the model and post it here.


 
 Return to top of page · Post #: 15 · Written at 1:10:11 PM on 6 June 2020.
MonochromeTV's avatar
 Location: Melbourne, VIC
 Member since 20 September 2011
 Member #: 1009
 Postcount: 1133

This looks like the one.

Maybe upgrade the 6V4 for a 6CA4.

General Electric RS8V1C Circuit Diagram


 
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