JMP-1 Service - 230V to 120V Conversion and Battery Upgrade

[@Ancient_West]

I love how your channel feeds the guitarist side of me and the electronics nerd side. I love seeing you jam out and i love seeing you mess with electronics.

[@ebheron]

Thanks to this video I managed to change the voltage on my JMP! Only thing is I live in a 220v region so I converted mine from 110v to 220v, now I don't need to use a step down transformer anymore, great vid and it great help, thanks mate!

[@purgasound]

@@ebheron awesome! I'm glad this helped you out!

[@romaindepla]

I’ll be pleased to see your marshall and Tokai collection !

[@JoelGrindMusic]

awesome, I replaced the battery in my MP-1 a couple months ago and soldered in a battery holder that fits the OG battery type, never thought to use AA, cool idea since those are a lot more common to find on tour.

[@heavyasi1981]

I ordered a used one from Guitar Center a year ago and they shipped it in a 2 foot tall box by 1 1/2 sides with bubble wrap and foam above the preamp, the ear of the preamp was bent just like this one, I was so bummed! I scored though, a friend who owns a music store had one for very good condition so I swooped it up!

[@michaelmitchell5909]

That thing sounds awesome...great job man.

[@doc_matter]

Killer straight to the point videos! Love it. Your so chill to, if I see a new upload I always click!

[@tommyservo9660]

Thanks for linking the schematic.

[@80srocker65]

Cool video great sounding amp

[@danielvought1802]

Whoa 😮 these sound awesome!!

[@KevinDick-h6f]

Many people are not informed that European Voltage and Current in appliances are @ 240 volt.

[@heavyasi1981]

Ha! And I totally have the same obituary shirt! 97 tour???? And mines sleeveless!

[@TheAxe4Ever]

Sounds great! Quick and easy fix. But I gotta say, that Tokai Love Rock sounds and looks incredible. I bet it plays awesome! It might make people angry that I say this, but Tokai makes a Les Paul better than Gibson in my opinion. Tokai…..doing Les Paul’s right!

[@K707OR30]

I’ll never understand why Marshall loves to put cheap electrolytic caps right next to hot components. all the caps are right next to a quad of transistors with no heat sinking in a 1u rack unit. Like that won’t produce any heat. I’d absolutely replace those caps.

[@chrisadams628]

Is it possible to change out transformers on a 100 watt amp to a lower wattage? I have a Marshall MGHDFX100 head, and 100 watts is just too much in a bedroom setting. Also, is it possible to mod it in a way to have switchable power levels like some of the newer 20 watt Marshall heads? The obvious answer is to buy a head at the wattage I'd prefer, but I have a soft spot for the old Marshall MGs.

[@purgasound]

I'm not super familiar with the MG series circuit but they appear to get the output from a TDA7293 100W DMOS amplifier. There is too much going on with the circuit to just swap transformers. To reduce output power you can use a higher impedance load. They deliver maximum clean output power at 4 ohms. If you use an 8 or 16 ohm load you should see a reduction in output power. Cheers!

[@chrisadams628]

@@purgasound That makes sense. I am running it into a 16 ohm Marshall Origin 4x12 So I've got that going for me. Thank you for the thorough reply.

[@jamescassidy4045]

oh man. That's a bit of a shame what happened to the chassis. I'd be pretty chocked if that was my amp. I know you didn't mean to, and had good intentions though. In my opinion, I would have just left the OG battery style in, as it's really not that hard to unscrew the lid, and pop in a new battery. It's one thing if someone is on tour, but even then they don't die that quick. The main inconvenience maybe if someone was constantly on tour, and reliant on programming is the battery style itself, not just unscrewing the lid, so maybe mounting the AA holder would be possible inside? Just a thought! Cool video though, thanks!

[@powermorcillo2703]

Why didn’t you just use a replacement of the original battery? The thing last for ever anyway.

[@purgasound]

I would still have to unsolder the original tacked in battery just to install a button cell battery holder. I'd rather not have to disassemble the unit to change a battery. It is a potential show stopper if the unit is installed in a rack system. I had a battery die on tour, we were doing arenas as a support act. I had the same setup for that unit. It was a 60 second job as opposed to unhooking all the cabling that goes into a rack rig to pull the whole unit out, clear a workspace to disassemble, reassemble, reinstall and rewire. That's a lot of unnecessary extra work and this modification took the same amount of time as it would to replace it with a battery holder. Plus everyone has AA batteries on tour. I don't have whatever battery this was.

[@samizdat113]

I hate it when people say 230 volt. It's 208-230.

[@purgasound]

What country does that hold true? It is my understanding that nominal mains voltage in Europe is 230 volts +10% / -6%. That doesn't go down to 208V. Cheers

[@samizdat113]

@@purgasound I was just yanking your chain about you being annoyed with people saying 115. But here in the US we have 208-230 voltage. Anything in that range is acceptable. I am a refrigeration/HVAC tech and if we have a step down transformer in a piece of equipment we often have to confirm incoming voltage and wire the transformer accordingly. If incoming voltage is below 217 use wires A and B, if voltage is 217 or more use wires C and D.

[@purgasound]

@@samizdat113 hell yeah brother. Much respect to my fellow tradesmen!

[@n0nyabznss]

1. STOP CALLING IT AN AMP. 2. That battery mod you did was beyond stupid and unnecessary considering the original holder allows for replacing the battery.. The coin cell battery would outlast a pair of AA/AAA batteries and it won't leak unlike those batteries. The only thing you did which was useful was converting the PREAMP to US current.

[@purgasound]

Lol but this is, by every definition, an amplifier. It takes a small audio signal and amplifies it to a larger signal. You don't have to like the battery modification. That's fine. I did it because it works best for my setup. The amps I used are wired tightly in an enclosed rack. I don't and won't have the time in the middle of a tour to disassemble every cable and connection and snip wire ties to pull out a rack unit to change a battery. Doesn't matter how infrequent that is. Down time is down time and when you already have a busy crew on tour it makes sense to simplify their jobs wherever possible. Cheers

[@thomasgardner3437]

@nOnabsesstus you sir , give dimwitted twits an even worse name.... 😺