Hi ! Need Help on Express PPIMV Right SCHEMETIC

Express, Liverpool, Rocket, Dirty Little Monster, etc.

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DaveWell
Posts: 249
Joined: Wed Feb 25, 2009 9:59 pm

Hi ! Need Help on Express PPIMV Right SCHEMETIC

Post by DaveWell »

Hi there !
Long time no see !

I plan install a PPIMV on my Express,
Really need the right instruction and Layout Please

I a a Dual pot 250 and the 2.2m resistor and double shield Wire

I know that is a lot information on this , but sorry, I'm a little confuse !!

Help would be Much Appreciate !!!

Thanks to all for you help :)
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Last edited by DaveWell on Sat Sep 14, 2024 12:05 am, edited 1 time in total.
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DaveWell
Posts: 249
Joined: Wed Feb 25, 2009 9:59 pm

Re: Hi ! Need Help on Express PPIMV Right SCHEMETIC

Post by DaveWell »

So, i figure it out,

I will let the 1.5K 2w resistor in place.

it is will help for '' ossilation '' ?

I will post picture of my work for those interested :)
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GlideOn
Posts: 114
Joined: Mon Apr 22, 2024 9:57 pm

Re: Hi ! Need Help on Express PPIMV Right SCHEMETIC

Post by GlideOn »

The Type 2 Master Volume, also known as "LarMar"

Absolutely needs safety bias resistors on wiper and ground lugs of pot. Don't forget them!

If that picture is indeed your amp, your heater wires may contribute to noise with extra wire runs. From what I understand this is normal to practice in Trainwrecks for some reason but in most amps these heater wires are twisted to cancel out hum. In your case I would absolutely use shielded wire to avoid picking up noise from them.

You can also try 1.8M to parallel the 250k pot resistance to have it closer to the 220k resistance the power tube grids normally see, not a huge deal ultimately but it is slightly better engineered than way.

See Robinette's method:
Bassman_MV_Type-2.png
Also, you can still utilize Grid Stoppers or "Swamper Resistors." They only need to be 1/2 watt as it's not a high voltage place.

Ex:
1.5k for 6L6
5.6k for EL34s

Ideally use resistors right at the connection pins of power tubes, I would not install at the Master Volume pot like it says in your diagram.

Use a versatile terminal strip if you need an extra connection; you can either attach to board mount screw, power tube mount screw or if you're clever you can simply float it like I did in mine.
PXL_20240921_123551707.jpg
(pardon my slightly dirty 50 year old amp innards)

It's a little trickier this way as it relies on the Grid Stopper resistors to anchor it all in place, so it gets a bit "handsy" when installing to forewarn you.
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