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Old 27th Nov 2021, 2:10 pm   #1
trobbins
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Default Indicator and diode in EKCO adaptor VS101

E.K.Cole Ltd from Southend-on-Sea made a film projector adaptor with a magnetic head that recorded/replayed audio on to film for Victor projectors. A 2010 thread had some info (https://www.vintage-radio.net/forum/...ad.php?t=54106).

I have a unit and am interested to identify two parts in it that relate to what seems to be a volume indictor. The Mullard indicator is quite small compared to something like an EM80 and has a distinctive blue inner glass coating in the central region, with 8 'pins' in a noval style arrangement of which 4 are cut short and not connected. A diode (I assume) associated with the indicator circuitry is labelled K3-2T and I can't find that type in any early data. Anyone come across those parts?

The product appears to have come to market in 1953 (https://www.dalmura.com.au/static/EKCO-Sound%20info.pdf). My unit appears to be circa 1957-8 given the 'F' year code for about 5 TCC caps. At the moment i don't have any other dating info other than it uses Erie resistors and EGEN pots. The other valves (2x EF86, ECC81, EL84, AZ80) are Mullard labelled and appear original but I can't clarify any datecodes on them.

Tim
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Old 27th Nov 2021, 2:17 pm   #2
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Default Re: Indicator and diode in EKCO adaptor VS101

Hi Tim, indicator was a "magic eye" for battery sets, type DM70, not used much in radios but I might have a spare if needed

Ed
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Old 28th Nov 2021, 4:04 am   #3
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Default Re: Indicator and diode in EKCO adaptor VS101

Thanx Ed, that will kick start preparing a schematic.

The diode marked K3-2T measures 2.7V on a cheap DMM (diode test current about 1.4mA it seems but not tested), which to me suggests a selenium stack with an aged increase in on-voltage.

Not sure if there are any 16mm Victor projector enthusiasts who have or would want one of these items - if not then I may prepare a schematic and mull over the restoration options.
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Old 28th Nov 2021, 9:55 am   #4
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Default Re: Indicator and diode in EKCO adaptor VS101

Hi Tim, not sure about the diode, it seems like an STC number, there were also a series of forward diodes used for bias and offset purposes that went to about 2 volts

Ed
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Old 29th Nov 2021, 10:39 pm   #5
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Default Re: Indicator and diode in EKCO adaptor VS101

The 'diode' has quite a beefy package of a type that could house multiple stacked pancake disks, but not like any package styles shown on the websites covering early UK parts like on http://www.wylie.org.uk/technology/semics/GEC/GEC.htm. The only visible association is the classic red dot like on Mullard parts.

I will try and prepare a schematic soon, which might provide some more insight.
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Old 2nd Dec 2021, 9:09 am   #6
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Default Re: Indicator and diode in EKCO adaptor VS101

I prepared a schematic for the unit - makes it a bit easier to appreciate - in linked info doc.

https://www.dalmura.com.au/static/EK...nd%20VS101.pdf
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Old 2nd Dec 2021, 10:05 am   #7
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Default Re: Indicator and diode in EKCO adaptor VS101

Hi Tim, interesting to see it uses the knobs from a round EKCO, the A22

Ed
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