WEM Copicat Custom

[Alistair D]

Regarding the valve line up things may be even more confusing.

http://www.amp-fix.com/copicat1%5B1%5D.htm

Looking at the picture here of the black and cream version PCB. The 2 valves with pins 4 and 5 joined are the first 2. The third valve does not. This third valve would then be V2 6BR8. That would make the valve line up V1,V3 then V2.

The tracking on the PCB here looks the same but the 3rd valve looks to have been converted to be an ECC83 i.e. pins 4 and 5 are now wired together and the heater wiring connected between pins the join and pin 9.

There is another picture on that site of a 2 valve version PCB that shows a similar conversion of the third valve socket.

Al

[evilmoisture]

Hi Omegaman yes please I'd like a larger version of your schematic if possible, andy.bolus at gmail dot com.
Mine has 3 x ECC883's. C9 goes to pin 1 on V3, I replaced it with a silver mica 200pf 600V.
Will have to order more caps so I'll do everythng you have said and get back to you in a day or 2. Thanks so much!

Looking at my board, all 3 valves have pins 4 and 5 joined together, so I think it's for 3 x ECC83s, right?

[Alistair D]

Yes your board should have 3 ECC83s. Just to be absolutely clear C9 is connected to pin 1 of the 3rd valve which is V2 in the schematic.

Al

[evilmoisture]

Correct

[Omegaman]

Andy,
Email with attachment sent..

[evilmoisture]

Got it, thanks! Will print it out, and I might add the component numbers as per the other schematic. I notice some minor differences like 1k instead of 470 ohms for R4.

[Alistair D]

From the site in Omegaman's MK2 schematic.

http://www.backfromthesixties.co.uk/...icat_MkII.aspx

The resistance of the record head should be around 420 Ohms.

Al

[evilmoisture]

Just measured the record head, I get 430 ohms, so maybe it escaped after all.

[Alistair D]

Good news.

EDIT; Just had a thought. It may be worth de-soldering the head wiring from the PCB and connecting a 470 ohm resistor in it's place until you are happy that the C9 issue is resolved.

Al

[evilmoisture]

Good idea, and also doing that would actually make it a lot easier to get at the board too without worrying about those two wires breaking.

[evilmoisture]

Originally Posted by PJL

- Replace C8, C9 again and C10. C8

Just to check, which value for C10 should I go for? It's different on Howards schematic (470p) and the (.002) one here http://www.vintagehofner.co.uk/brita...opicatmk3.html

[evilmoisture]

I took the liberty of cleaning up Howards schematic and splitting it into 3 files, with the hope that they are higher res but still within the forum limits

[Omegaman]

Originally Posted by evilmoisture

I took the liberty of cleaning up Howards schematic and splitting it into 3 files

[PJL]

Replace C10 with a capacitor of the same value as the one installed.

C8 and T1 form a resonant circuit. If C8 has lost capacitance/ESR, it could result in a heavily distorted RF signal with high voltage peaks.

This is a case where an oscilloscope is almost essential. As the record head looks as if it has survived it might be best to see if you can find a repairer with more test equipment.

[Techman]

So what was the result of the transformer test - or have I missed something?

[evilmoisture]

I haven't tested it yet, will do tomorrow

[mole42uk]

Somewhere in the depths of my memory, ISTR that the replay heads could be switched in and out to give variable amounts of echo. And that those switches were a bit temperamental.

[evilmoisture]

I found one thing, I had added an earth wire from the chassis to the metal switch subchassis (where R19,20,21 also connect), and I think this is wrong, and was causing a short. A previous 'modification' is a length of wire soldered to this subchassis with the 3 resistors soldered to it. I think this is wrong also! These should not be connected to ground at all! Except through the swell pot. See photo.

[evilmoisture]

Looks very different on this photo found on the web

[evilmoisture]

Mine from the same angle. Confusing.