Atlas battery eliminator, any help sought.

[boater sam]

This eliminator came with an old Cossor radio, for the HT only. Model K12/18?

Made by H Clarke & Co. Manchester. Obviously in desperate need or refurbishment.

I need details of how it should be connected, particularly on the two 2 pin plugs on the right ( 1 is missing ) and what the 12/18 sockets with the wander plug below are for.
I assume the stripy item at the rear is a choke.
The rectifier is odd, it looks like a bridge but the front few fins are shorted together.
I can read the values on the capacitor block ( should really be called a condenser block in deference to its age ) marked as made by Callinders.

                           

[Refugee]

From looking at the components I can see a stack of diodes and a bridge rectifier on a single finned stick.
These will be for grid bias and HT.
Without a reverse engineered circuit diagram I can only guess that the stripy item is a prehistoric capacitor rated in jars.
I would not expect there to be another jumper. The existing one needs to be moved around to get various voltages from the four pins.

[boater sam]

When it came, there was a jumper wire in the 2 sockets under the jumper plug so I think that there should be another.
I can't see any diodes in there, there are few resistors behind the socket panel, otherwise its just the strangely altered selenium stack. I think it predates any silicon or germanium fuses!
The set was prewar but I can't date this unit, maybe as old.

[Crackle]

Maybe part of  the rectifier went open circuit on some plates and the faulty ones have been bridged to bodge it.

Mike

[boater sam]

I did consider that,but its a terrible bodge. I would be surprised if it worked well or at all afterwards.
I'll get the meter on it before I go much further.
It seems to be just HT, the set needs 2 grid bias batteries, and there is only one output cable, 2 core.

[Terry]

I can't see any diodes in there ...

What do you think is between fins of the rectifiers if they aren't diodes?

As Refugee says, there are two distinctly separate rectifiers in there. The section with the most fins will be a half wave rectifier for the HT - the voltage rating of each diode is quite low so several in series are needed for high voltages - and the small section at the end is a low voltage bridge modified for half wave operation.

Their are five connections to a bridge like this: +ve, AC, -ve, AC, +ve so the two end +ve fins would always be connected together anyway and the centre vane is negative. 

Can you trace out the circuit so that we can see what is happening? It won't be possible to provide much help without a circuit. Please include all discernible component values and socket markings.

[boater sam]

Terribly sorry Terry, I am well aware of the construction of a metal air cooled rectifier as a stack of rectifying diodes.

Mods please close my thread.

[pwdrive]

Terry, Sam might have been referring to individual replacement diodes?

Lawrence.

[Ed_Dinning]

Hi Sam, an interesting unit, I have similar ones but not quite like this. There should be stuff about it on the web.
GB was not normally on this units as batteries lasted a long time and did not give the hum the unit would. Batteries were also adjustable in 1.5v taps.

12 or 18mA max perhaps on the HT.

Rectifier would be copper oxide, usually pretty reliable and could be in a voltage doubler configuration.
Normally a single output voltage and a series of resistors to give the different voltages at the sockets, pretty hit and miss as it depended what was being drawn from the socket. Check with DVM will probably show it way too high.
These often used an LF choke, looks like that HF one has been bodged in.

It should restore OK, but bake the transformer in an airing cupboard for a week or 2, then Megger it. I have a few of these that I've restored and the seem to work quite well.


Ed

[boater sam]

Thanks Ed for that constructive post. I was close to giving up on this forum.

To paraphrase an old song,  "There's a fault with my Megger, dear Lisa, dear Lisa"

I'll warm the transformer with a few volts on the thickest winding before it sees any real volts.

I'm thinking that the two 2 pin plugs, one missing, are to select either the upper or lower line of output sockets, but it had a wire link in the lower one when I got it.

Its not vital to fix this but it will be a different challenge than touching up cabinets and fitting valve!
The condenser box will be fun to restore, if the rectifier is dead I will hide some Individual Rectifier Diodes where they can't  be seen.
Sam.