WEM Mk4 Copicat - low volume output

[Bushbaby]

Hi All
I do hope that you are all keeping well.
I finally bought an old solid state Copicat unit. I have cleaned it and sorted issues with it wooden case before touching any of the electronics side. 
Yesterday was the first chance I had to try it and have found that although it is working from an effects perspective, the volume output is very low indeed. Has anyone worked one of these before and could provide a heads up where to start. I really dont want to go too far into replacing components that I dont need to.

I've attached some schematics but they are not great quality.

Many thanks in advance

Rob



       

[Refugee]

I would stop it with a good signal on the input and then take the loop off and play it on a regular tape recorder.
You will then be able to eliminate half of the circuit.
Then switch in the scope and find out what stage has low gain. The EQ circuit on the playback side will not offer much overall gain at low frequencies.

[Bushbaby]

Before I go any further with working on it can anyone confirm if the swell control is also a switch? It is has marking on the cover plate indicating OFF, BUT when I plugged this in the main lamp came on straight away and also the motor powered up too (no switch at all)!
I am planning to have an initial once over i.e. check all the electrolytics (as much as I can) whilst the circuit board is in place. The board looks like its a pain to remove.
I will also take some initial pics of the board - the soldering looks appalling BUT I dont know if this was how it was sent out after being manufactured?? I do have a suspicion that someone has 'dabbled' with it. An indication of this is the fact it has modern mains lead colouring AND it has been connected to earth (I am led to believe that these were never grounded when manufactured). As a hobbyist with little electronics knowledge this might be a very good project for me as a learning exercise!

Best Regards

Rob

[Murphyv310]

The common issue on the copycat is worn heads. You will be able to see a groove cut in the heads where the tape runs. If the wear can be felt by your finger nail then the heads are U/S. Some have been able polish out the wear but this can cause azimuth issues I'd not done properly.

[valves4amps]

Hi Rob, these machines are meant to be on from the start with no mains switch. There are 2 effects the machine can give, echo and a kind of reverb. The swell switch is for the reverb effect. The low volume could due to dried up electrolytic coupling capacitors. Try bridging one at a time with a known good one of similar value to see if any improvement can be had. If this doesn't help then as others have said head gaps and azimuth adjustments may be the cause.

Dave.

[Bushbaby]

Ive taken some pics that will give you an insight to the unit. I have felt the heads I cant say that I can feel any lumps or bumps although at the very bottom of the a couple of head it is possible to feel a wear line(?). I assume that these are BSR type heads as they have an adjustable metal shroud. I have seen replacements for £35 per head but this does seem very expensive??

[Bushbaby]

Pics as indicated

                   

[Murphyv310]

The heads look worn to me!
Remember that if the record head is worn less signal will be put to tape and again if the replay heads are worn they will loose sensitivity.
Other than mechanical faults the Wem Copycat is very reliable (heads excluded) I've done many of these over the years. I'd suggest you try and obtain at least a new record head and one replay head initially and test.

Incidentally my late brother in law was in a big Edinburgh band for many years and his copycat needed new heads every three or four years due to head wear

[Bushbaby]

Thanks Trevor
I'm no expert at all in this area. Do you agree that these are BSR type?

Many thanks

Rob

[Murphyv310]

They might be but when I used to repair them I ordered them from a Wem agent.
Although they could be the same you'd need to check the impedance is the same.