Pre-NARB/Park Marshall JTM45 Oddity?

[PayDay]

Hey everyone,
So, I've found myself at a bit a fork in the road. I've been putting feelers out here and there but figured why the hell not pop this up here and see if any of our esteemed members may be able to shed some light!

A few weeks ago, while thumbing through the inter-webs, I happened across what seemed to be a great 'project amp'. It was listed on a popular, digital, trading outpost as spares/repairs due to it's age and condition.

While i'm sure that the turret board has been changed and robbed of parts, i'd love to hear people opinions on this amp!

 

[PaulD]

Looks nothing like any Park or Marshall JTM45 I have ever seen. Every one I've ever seen has had a drop through mains transformer with the terminals inside the chassis. Control layout doesn't look like a Park, they had one of the volume controls between the jack sockets. General build quality looks very sloppy and amateurish, looks more like something home made than a Marshall or a Park to me.

 

[Oatie]

Looks home made for sure. All the RS parts were available at the local Radio Shack UK back in the day, the orange Sprague caps were made in the early 1970s, the orange Sprague caps should be dated, date the pots/manufacture codes as well. Looks like you can re-cap that amp and make it a fun project. I would install some Welwyn 1K 7 watt resistors on the power sockets and some 5K6 swamp's on pin 5 of each power tubes. That Partridge PT will make that amp crank, great score. The HT/standby switch looks like it is coming apart, you may want to check it for replacement. It looks like one of those Japan made switches, the Japan switches have 2 screws holding them together, maybe you just need to tighten the flathead screw(s) on the switch. The Japan switches are not riveted like the Arrow England switches. They sold those Japan switches at Radio Shack UK back in the day.
Cool vintage home made amp from the UK. I bet it sounds good, has the quality carbon film resistors. Check the outside foil on the coupling caps to make sure they were installed in the correct direction.

 

[F-Hole]

Home brew.

 

[ourmaninthenorth]

Is that a Partridge transformer though?

I'd say it's another Douglas, I've seen them as Partridge replacements in early Hiwatt's.

 

[TM1]

I've seen some early Marshall/Park boards like this. The cap-cans I should think need to be replaced, but it looks like it's all there. I don't see any place on there where any parts have been robbed. I think if you replaced the smoothing caps/cans that it would work just fine. Maybe spray some Deoxit D5 into the pots and valve sockets and put some on a Q-Tip and cleaned the jacks, I bet you'll have a nice sounding amp. Hell, if you don't like it I'll take it off your hands...

 

[PaulD]

I've seen some early Marshall/Park boards like this. The cap-cans I should think need to be replaced, but it looks like it's all there. I don't see any place on there where any parts have been robbed. I think if you replaced the smoothing caps/cans that it would work just fine. Maybe spray some Deoxit D5 into the pots and valve sockets and put some on a Q-Tip and cleaned the jacks, I bet you'll have a nice sounding amp. Hell, if you don't like it I'll take it off your hands...

With respect I think it needs a bit more than that doing to it! This is clearly not a Marshall or Park amplifier, aside from the obvious fact that the chassis and control panel are nothing like anything produced by Marshall or Park the wiring and build quality are clearly not the work of a professional.

As well as any components that might need changing the rats nest of wiring needs to be thoroughly checked and preferably completely replaced. There are exposed live terminals on the outside of the chassis, the flimsy piece of bare wire acting as a chassis earth connection is totally inadequate, there are wires that appear to be joined with insulation tape, there are wires routed through holes in the chassis with no grommets. All of these are serious safety concerns and that is just from a quick look at the photo, there may well be other issues.

Those grey capacitors look suspiciously like the moulded plastic RS caps that were commonly available in the 60's / 70's. if so they will almost certainly be electrically leaky and will need replacing.