Ekco AC18 HT Unit - using?

[SurreyNick]

Wiring diagram attached (PDF and image).
I'm fairly certain I have drawn it correctly.
I now have the task of working out the values of the various components. Anyone able to offer up suggestions how to approach this?
Nick

  Ekco AC18 wiring diagram.pdf (Size: 294.92 KB / Downloads: 37)
   

[boater sam]

You don't seem to have a reservoir capacitor, I doubt that the one in the block is sufficient. Both 4uf caps are in parallel as a smoothing cap, could this be incorrect and one be the reservoir and one the smoother?
Measuring the paper caps is likely to be a waste of time, they will be way past their best!
The carbon adjustable resistances should be measurable but if they are not altered should be OK anyway.
Transformer and choke will be OK if they are not O/C or shorted turns, voltages should be as designed.
I would be tempted to thoroughly dry out the wound components before applying any mains.

[pwdrive]

Either the wiring is wrong or it's a choke input filter?

Lawrence.

[SurreyNick]

Could have sworn I got the drawing right. But it's easy to make a mistake and I didn't open up the 4+4 Electrolytic. As it only had one neg and two live wires going in I assumed it had to be wired in parallel.
I have attached a few high res pics which show the wiring. Perhaps you can spot where I have gone wrong.
               

[ppppenguin]

You're right, the 2 sections of the cap have been wired in parallel. I suspect that the phamtom fiddler has been at work though it's possible that Ekco used a choke input filter as Lawrence suggested.

[pwdrive]

I agree so far as your capacitor wiring diagram goes, if that black block contains capacitors as suggested earlier then we do not know the values as yet, the one that connects to the input side of the choke looks like it might be a higher value than the others....possibly?...it might be large enough to serve as a reservoir capacitor considering that the rated current draw from that power supply is not a lot.

But, as has been said, maybe someone has connected those two electrolytics in parallel after the unit was manufactured, one can only guess at the moment without the manufactures schematic or another unit of the same type for comparison.

Lawrence.

[ppppenguin]

There's evidence of later soldering on the red wires of the cap. I wonder if that paper case electrolytic is actually original. If the balck block contains caps that makes sense. Perhaps the 4+4uF was added to reduce hum or because a cap in the black block failed.

[SurreyNick]

Ah, now that's an interesting suggestion. I said yesterday that the Ekco Power unit was simpler and that was because it lacked the 4+4 electrolytic. In all other respects it was similar - component wise. The sealed capacitor block in the other Ekco unit also has three capacitors in it - 6+6+1 mfd and there are four wires feeding into the block. I cannot see the arrangement as I haven't deconstructed that unit. But yes, perhaps the 4+4 electrolytic was a later DIY modification or repair.

I have searched and cannot find an original schematic for this unit anywhere. I didn't really want to take the other unit apart, but perhaps I will have to.

[ppppenguin]

That more or less confirms that the 4+4 is a later repair or bodge. If you want to retain originality then you'll almost certainly have to open up the black box and fit new the electrolytics (or plastic film caps) inside. The chances of the old caps being in good condition is very small.

[SurreyNick]

Agreed, and I am happy to do so too.

I still need to establish the value of the other components. The thing is, that simply taking measurements will tell me what they are now, but not necessarily what they should be. And it's the 'should be' value that I really need.
I'm tempted to plug it in and then measure the various output voltages. If these are true to the known spec then measuring the component values is valid.

The BIG QUESTION is. Is it safe to plug in? It has been earthed with the new mains cable, but other than that and the bodge repair it's original. I can't afford an electric shock. I've already had one heart op!

Nick