GEC 2015 13" Crystal model - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

FERNSEH · 19th Jun 2017, 12:07 pm

I don't have the circuit diagram to hand in order to determine what type of heater chain voltage dropper is employed. Is a simple resistive dropper or is there a silicon diode inserted in the heater chain? An alternative would be a heater supply transformer if space for one could be found.
I'd imagine the Admiral Playmate was similar in terms of cramped component layout and heat dissipation.

DFWB.

usradcoll1 · 21st Jun 2017, 5:23 pm

Quote:

Originally Posted by FERNSEH

It's an imported CRT, possibly from the USA.

If the data label shows a 836 source number, it's definitely a US product!
Admiral had their CRT's sourced by National Video in Chicago.
When I first saw the set, I thought, Admiral made the set, but seeing the chassis, it's totally different from our sets.
Admiral did have a plant in Australia, maybe it was built there. Many of the sets built there, had US sourced parts.

Focus Diode · 22nd Jun 2017, 12:56 pm

Quote:

Originally Posted by FERNSEH

I don't have the circuit diagram to hand in order to determine what type of heater chain voltage dropper is employed. Is a simple resistive dropper or is there a silicon diode inserted in the heater chain?

Hi David,

It looks conventional to me, at least from a Thorn point of view. Don't have the large screen equivalent circuit to hand to compare.

Cheers
Brian

FERNSEH · 22nd Jun 2017, 4:41 pm

SR2 the diode heater supply dropper will help to the reduce the heat buildup to a certain extent. Pity they didn't reverse it so that the receiver would present a full wave load across the mains supply. Thorn so did with the 980. A negative heater supply can provide bias for the frame output valve.

DFWB.

usradcoll1 · 22nd Jun 2017, 5:46 pm

Quote:

Originally Posted by FERNSEH

I'd imagine the Admiral Playmate was similar in terms of cramped component layout and heat dissipation.

The Admiral Playmate set used a large PC board, using a mix of 9 pin, dual purpose valves and Compactrons with a 450ma heater chain, with a HT of 140 volts. The LOPT was mounted on the upright like the set shown.
I owned one for a few years and it was very reliable and a great performer.
The US version didn't run as hot and wasn't as cramped.

FERNSEH · 22nd Jun 2017, 6:18 pm

Of course the Playmate didn't have the problem of having to operate on two different line standards.

DFWB.

gec2110 · 23rd Jun 2017, 6:41 pm

A blast from the past. A lot of these used to have an overheated cabinet back and crinkled cabinet frame
good picture

19th Jun 2017, 12:07 pm	#21
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: GEC 2015 13" Crystal model I don't have the circuit diagram to hand in order to determine what type of heater chain voltage dropper is employed. Is a simple resistive dropper or is there a silicon diode inserted in the heater chain? An alternative would be a heater supply transformer if space for one could be found. I'd imagine the Admiral Playmate was similar in terms of cramped component layout and heat dissipation. DFWB.

22nd Jun 2017, 4:41 pm	#24
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: GEC 2015 13" Crystal model SR2 the diode heater supply dropper will help to the reduce the heat buildup to a certain extent. Pity they didn't reverse it so that the receiver would present a full wave load across the mains supply. Thorn so did with the 980. A negative heater supply can provide bias for the frame output valve. DFWB.

22nd Jun 2017, 6:18 pm	#26
FERNSEH Dekatron Join Date: Mar 2005 Location: Gateshead, Tyne and Wear, UK. Posts: 7,444	Re: GEC 2015 13" Crystal model Of course the Playmate didn't have the problem of having to operate on two different line standards. DFWB.

23rd Jun 2017, 6:41 pm	#27
gec2110 Retired Dormant Member Join Date: Feb 2008 Location: Croydon, London, UK. Posts: 408	Re: GEC 2015 13" Crystal model A blast from the past. A lot of these used to have an overheated cabinet back and crinkled cabinet frame good picture