68-12013 questions for the board

[flex5150]

Hi guys .
I recently bought 68-12013 from a fellow over here in Australia. It has a couple of what I would consider unique mods. It "apparently has a parrallel effects loop installed (definately a loop not sure if parallel) its send and return a mounted in the Channel II inputs

Channel I hi is the guitar input channel I low is just a bunch of noise when the guitar is plugged in there. The channel I volume works normally and Channel II seams to do nothing?

Also has an extra preamp valve that I presume runs the loop?

Any help would be greatly appreciated,
Cheers
Flex.

[kdmay]

Wow, some nice vintage mojo there.

I'm not much help on the mods, but my recommendation is to take it to a reputable Marshall tech (I think you're based in Melbourne, as am I so I would recommend Barry M from Barwatt amps) and get the thing taken back to stock specs.

A 12xxx series Marshall plexi is very coveted and I would be restoring her to her former glory!!

[neikeel]

Why not take some clear high resolution pictures of the board, the loop and the input connections?

As long as it does not have a ton of black gloop someone will be able to figure out what has been done to it. It maybe the inputs that do not work are not connected (internally bridged etc).

[Flames1950]

Since this is in the Metropoulos Plexi replicas section of the forum, I'll assume we're talking about this George-built amp from the PlexiReplicas archive?

http://plexireplicas.com/amplifier-arch ... 74.jpg.php

If so, sounds like it got butchered a bit.........

[kdmay]

Since this is in the Metropoulos Plexi replicas section of the forum, I'll assume we're talking about this George-built amp from the PlexiReplicas archive?

http://plexireplicas.com/amplifier-arch ... 74.jpg.php

If so, sounds like it got butchered a bit.........

Yes, I realised after I posted!

Anyway, I contacted the owner as ironically he was selling a cab I wanted, and we came to a deal where I would have a look at the amp and grab the cab.

The amp has had a tube buffered parallel effects loop fitted (hence the extra tube) and the normal channel has been disengaged, so the send and return are the normal channel inputs. I am yet to test the loop, as I've removed it from the circuit for the time being to get back to plexi basics.

Given the normal volume is redundant, the previous owner has had a relay fitted (powered from the FX loop board, which has a rectifier circuit in it), and both volume controls are active/switchable for v2a. Works pretty well to be honest.

So, has it been butchered - I would say, yes sort of. If I was the original owner, I wouldn't have done this to a George built 12xxx series. But this amp will be a gigged, so we are exploring other options. I must admit though, my first instinct it to take it back to stock specs......