Decca 94 radiogram service sheet needed.

[boater sam]

Desperately looking for a service sheet for Decca 94 radiogram. I must get it fixed and sold as fast as possible, it is taking up too much room.

It is not the same as 90,91 or 92, B8A valves front end, 6J5 preamp for the pickups and 6V6 output.

Nice piece, came with 3 pickups and spare stylii too.

[pwdrive]

Not sure if this is any use but according to radiomuseum the Decca 97 uses a B8A valve in the front end, valve line up is given as ECH42, EBF80, 6SL7, 6V6 & EZ40, it's available as a download from UKVRR.

Lawrence.

[boater sam]

Thanks Lawrence, I have missed that one. Hope it is on the DVD.

That's an even stranger valve line up, B8A, B9G and Octal. Wonder why they didn't throw in the odd Loctal just for a bit of variety?

Sam.

[Keithstv]

That valve line up is the same as the Decca Portrola portable radiogram from 1952. Probably a very similar circuit.

Keith

[pwdrive]

Sam, what's the valve line up in the Decca? Should be able to fault find without a schematic if push comes to shove, probably a bog standard superhet.

Lawrence.

[ppppenguin]

Decca Portrola is on Trader 1134. This is on the BVWS CDs.

[boater sam]

Similar, thanks Keith. They all seem to be variations on the same theme made up out of what they had to hand in the factory may be. I can probably piece together enough to get a complete circuit now.

I suppose the big challenge will be the deck thou' it looks to be good. The scale lamps are burnt black so it has seen some use in its life.
Came with a Clix 5A plug, the type with no terminal screws just split pins so its been a while since it was last run.

[boater sam]

Thanks Lawrence and Nick for getting this post in the right box.

[boater sam]

We move on with the Decca 94.
Had the chassis out to check it over. It looks untouched and in fine condition. 

The cotton covered twin cables are in rubber insulation and in good condition, the mains lead has either changed its colour of the earth core or it was always yellow! It will have to be changed eventually.

The 2 coupling caps were changed as a matter of course, resistance checks showed no problems so it was time for the power on the lamp limiter. No problems appeared so full power and a reward of sound, cricket! Very quiet though and distorted. Voltage check on the 6V6 looked OK but cathode resistor high and bypass electrolytic useless. Changing these made little difference. With a heavy heart, swapped the output transformer and performance instantly restored.  Original has shorted turns.

So its either a new one or a rewind, does anyone know what weight of copper wire is likely to be needed to rewind it?

[Yorkie]

If you're going to Golborne Sam, Mike Barker invariably brings a load of  scrappers - often good chassis, speakers, OPT etc, but the cabinet is past it, the back missing and dial cracked.
You've been, so you know the score. It's only a few weeks away, so it might be worth holding off till then.

As to the weight of wire needed for a re-wind, really, it's a bit academic realy, because if you have to buy the wire, the usual supplier is 'Wires&Co' (Scientific Wire Co, as was), and as often as not, the offer 50g or 500G. 50G wouldn't be enough, so for example, 500G of 0.1mm (42 SWG) olf solderable enamelled copper wire is 14,307 Metres per KG. Hence, a 500G reel will be 7,153 Metres long - way over what you'll need. (£11.58 +VAT).

https://wires.co.uk/acatalog/SX_0100_0132.html

Hope that helps a bit.