Marshall JMP Output Selector..

[PapaHett]

The Marshall JMP 50w from 1976 has an output selector on the back of the amp.. The problem is.. that the actual selector that was on it appears to be taken off. And i don't really know what ohm it is set to.. Is there any way, to plug it into a Cab, and not harm the amp? It could be 4, 8 or 16ohm?

 

[MrDan666]

The Marshall JMP 50w from 1976 has an output selector on the back of the amp.. The problem is.. that the actual selector that was on it appears to be taken off. And i don't really know what ohm it is set to.. Is there any way, to plug it into a Cab, and not harm the amp? It could be 4, 8 or 16ohm?

Are you talking about the little plug in impedance selector being missing? or did someone actually remove it completely from the back panel?

 

[PapaHett]

The Impedience Selector is there (Although covered up with yellow paper It's just theres no toggle or anything, same thing goes for the Voltage Selector.

The amp itself is in need of some TLC, i'd say the tubes will need changed, and the power cable looks very shotty. Also, when we powered it up.. There was a weird smell of Solder/Flux.. I dunno if this is a bad thing.

Heres some more new pics of the amp, Showing the chassis:

Do you think Marshall would take the amp on themselves if i we sent it to them? To do the repairs? Or would i have to go to someone local?

Thanks
-Conor D-

 

[MrDan666]

That mains selector looks like a Bulgin cable. It looks extremely badly wired, i wouldnt want a powercable open like that man its dangerous.

Basically under the yellow tape, there should be the impedance and mains voltage selector sockets, but they will need the 2 prong plug connector to select the voltage and impedance. The amp would probably not work without these.. as it breaks the circuit without them.

If you cannot get replacements, then maybe a tech could guide you in the right direction for either installing new ones or they could do it for you? Most amp techs could sort this out for you no problem!

By the way.. Nice amp!!!! I love old Marshalls, especially JMPs!!

 

[MrDan666]

Also i wouldnt fire the amp up unless you have removed any dust or dirt inside the chassis. Dust can cause problems if it gets in touch with any high voltage parts of the circuit!

 

[illini]

The tape over the impedance and voltage selector makes me think that it is hardwired inside the amp. The voltage is probably hardwired to the correct 120 voltage, and the impedance may be able to be figured out by looking at how it is wired. This is of course assuming it has been hard wired.