WEM Copicat Custom

[evilmoisture]

Those croc clips are to connect the 2 wires to the smoothing cap, which I removed at the start to test, I didn't solder them back just in case.
They make this photo a bit more confusing but here the green croc cable is from neg side of cap to black meter probe, and the red is from one side of R27 to red probe. And you are right, now it's showing 350v!

[Techman]

Hmm - 350 volts sounds a bit high - check what it says on the circuit diagram.

[evilmoisture]

yes, it says 285 on the diagram, as far as I can make it out

[Techman]

I can't read that diagram very well - does that say 285 volts?

If there's a lack of current being taken due to a fault then this could cause a 'higher' reading, but I don't think it would be as high as you're finding.

Check that meter on a known good 9 volt battery!

Edit: posts crossed - but still do as above.

[evilmoisture]

For the sake of clarity I soldered those 2 wires back on, here's another pic, says 350v again

[evilmoisture]

My meter reads a fresh 9v battery as 9.3v so it's ok I think?

[Techman]

Yes, the connections look ok.

But, you may have 'busted' your meter and it's reading high, so we really need to rule this out first.

Find a 'known' DC voltage source, such as a battery and take the reading on all the voltage ranges that will read above 9 volts (NOT the lower ones OR any current ranges).

[Techman]

Sorry, posts crossed - that's good.

Is that on the 1000 volt range you're using, too?

[Techman]

Our posts will probably cross while I'm typing this, but It's a shame your meter doesn't have a 600 volt range - not sure if 9 volts will show on that 1000 volt range. If it does and it's correct, then it indicates that the 350 volt reading indicates that there is a lack of current being taken due to a fault.

[evilmoisture]

Yes, was on 1000v.
Something just blew anyway, now I get zero volts. If I measure the transformer wires, (red ones) I get minus 90v. Almost nothing on the green wires which go to the heaters, and now nothing over those 2 big caps...also no spark when I do the screwdriver trick. So I think the smoothing caps have had it, since I soldered the 2 wires back...perhaps those croc clips werent actually connecting them? Confusing...

Edit indeed they did cross...the meter has 1000v / 200v / 20v, battery tested on 20v range but also on 1000v it says 9

Maybe the transformer died? The valves still glow though

[Techman]

Yes, I've got a meter with a 1000 volt range at the back of the cupboard, so I just dug it out to check the resolution on a 9 volt battery and it does read ok, so your meter is ok.

It's very unlikely that the smoothing caps have gone.

Go back and check what you have done - carefully!

[Techman]

You need to use a HIGH AC voltage range to check the HT output from the transformer.

[evilmoisture]

Yes, OK, sorry. With the meter on ACV 200 range I get just under 200v from the red transformer wires. The green ones going to the heaters give about 4.5v.
HOWEVER the transformer just started melting!!! So I unplugged it straight away. Scary enough...arghh!!

There must be a serious short somewhere but I can't see where.

Looks like the cap I replaced has melted too.

[Techman]

Yes, just looked at your picture and your highest AC voltage range is only 200 volts, so no good for this test!

It seems from the 200 volt reading you got (would have thought it would have read an error as higher than 200 volts) maybe indicates that the transformer is ok. It seems that you have a short circuit.

I'm starting to think that someone has fitted the WRONG transformer and although the heater voltage is correct, the HT voltage is far too high out of the tranformer. With this in mind, it's 'just' possible that the smoothing cap has been damaged by too high a voltage (check the working voltage written on the can).

You can't go any further with this until you've disconnected the HT windings from the transformer and measured the voltage with a different meter which has a much higher AC voltage range.

[Techman]

Just to make that last post a bit clearer - The HT leads from the transformer need to be disconnected from the circuit and the voltage which will be 'AC' measured with a meter with at least a 600 volt AC range - which is the usual on cheap meters.

It does seem to look more likely to be an incorrect transformer causing other faults.

[evilmoisture]

The meter also has 750 AC, it was still saying 197ish on that setting too. But yes I agree, I suspect it was the wrong transformer all along. My friend said the reason why they replaced it was because the echo stopped working, in other words the same problem as now. What is strange about that is that they didn't replace C9. He also said it was sounding 'weird', but I don't know what that means.
I'd be reluctant to plug the transformer in again at all, the coil has started popping out of the plastic (!). I'll look into getting a replacement, but yes there must be a short somewhere further along from C9...

[Techman]

I'm going to have to leave for a while, so for the time being, with the power OFF, re-check any connections you've made and with the meter on the 'ohms' range, check that replacement capacitor, it sounds like it's gone short circuit.

You can't do a lot more until you can find the actual voltage from the HT winding on that transformer.

[Techman]

Ah, a 750 volt AC range.

Check the transformer with the HT leads from it disconnected from the circuit. It may be reading lower now because it's burnt out - you'll soon know as it'll start to get very hot and smoke, so be careful!

[Techman]

Just to make the above a bit clearer - The transformer may be just over heating due to a short in the circuit.

When you power it up with its output disconnected from the circuit, it shouldn't get hot at all.

If it starts to over heat when it's disconnected, then it's had it.

[Station X]

Just an observation.

Back in post #14 it was stated that winding 1 (the red wires) of the transformer was 250V.

Where did this info come from?