Can somebody help me identify if my head has been modified

[leadandbass]

Hello, I am new to this forum. Just wondering if anybody out there could help me identfiy if my 1974 JMP Marshall lead and bass 50w head is is authentic condition or if it has been modified from pictures? Any help much appreciated.

 

[glip22]

Looks stock to me. Model #1964 Lead/Bass 59. Nice amp!

 

[311boogieman]

+1 and welcome to Rig-Talk

 

[Sitedrifter]

That is some OEM wiring and parts right there with no mods that I can see.

 

[fusedbrain]

Yeah, looks OK to me.
How does it sound?

 

[leadandbass]

Thank you for the replies!

It sounds really good but *very* different from another 1970 (hand wired) 50W Bass head that I have, so much so that I wondered if it had been modded.. This one sounds more fizzy but in a good way and has a collosal sort of boiling sound break up. It is also very sensitive - it breaks up almost immediately with volume above 1.5 or so even with single coils. I love it.

I was wondering about the red component (I assume a cap) across the channel 1 volume pot?

 

[311boogieman]

That cap is normal.

Clips?

 

[itsme]

Treble pot could be suspect?

 

[glpg80]

One of the speaker output jacks has been replaced and there’s a non standard blue wire on the power switch. There is a replaced mains fuse holder and mains fuse wiring. I also think the pilot light has been replaced at some point in its life a long time ago. Everything else looks good and whatever you do, never let those mini red round caps get taken out of that amp. They are super rare and extremely hard to find.

It is time to replace the two blue electrolytic bias capacitors as they don’t affect the tone and do affect bias stability which can cause bias runaway if left as is. It’s also due to have a recap on the B+ side.

Thanks for the gut shots - beautiful amp!

 

[311boogieman]

Hello, I am new to this forum. Just wondering if anybody out there could help me identfiy if my 1974 JMP Marshall lead and bass 50w head is is authentic condition or if it has been modified from pictures? Any help much appreciated.

This will be my last post here because I'm actually not qualified to answer

But I thought I'd drop these comparison pics for you but as you know, Marshall used a lot of different components back in the day based on availability but it looks like glpg80 and fusebrain have a good handle on the situation

(possible the above have been modded but they look pretty clean)