The PPIMV (Post-PI-Master-Volume) thread.

[CoffeeTones]

Did you, or can you try a different set of power tubes? I'm confident that you have it wired correctly, since you've been around here for a while, but things happen. Re-check connections.

[Roe]

Did you, or can you try a different set of power tubes? I'm confident that you have it wired correctly, since you've been around here for a while, but things happen. Re-check connections.

yes, will try a different set as soon as i'm back to my working bench. I experience the same problem even with wires from the PI disconnected to the pot. and the pot is fine (I've changed it)

[Twistingcrow]

Is it OK to use 1/4w 2.2M resistors on the pot instead of 1/2w or is there a risk?
Thanks!

[Roe]

Is it OK to use 1/4w 2.2M resistors on the pot instead of 1/2w or is there a risk?
Thanks!

no problem at all as long as you don't break the legs

[Twistingcrow]

Is it OK to use 1/4w 2.2M resistors on the pot instead of 1/2w or is there a risk?
Thanks!

no problem at all as long as you don't break the legs

OK, thanks Roe. I actually made the mistake of ordering 1/4w 4.7M resistors instead of 1/2w for my 18w and only realized that when I opened the box, ten days after placing the order... But if they work, then awesome! Good luck with your Twin issue, sorry I can't help...

[Twistingcrow]

The Lar/Mar is installed in the 18w TMB and works flawlessly. God this PPIMV is good, it's unbelievable... Thanks everyone for the help!

[Roe]

Did you, or can you try a different set of power tubes? I'm confident that you have it wired correctly, since you've been around here for a while, but things happen. Re-check connections.

thanks, changing tubes worked solved the problem

[nznat]

Hello my friends, or new friends to be!

I have a Marshall Jimi Hendrix Super100JH full stack that i want to put a PPIMV in it. Has anyone else put the MOD in one of these 1966 hand wired reissues before - point me to the post if you know of it.

What were the results in tone.

The amp has simply amazing tone as it is, amazing, but all my family members are now dead, as the shear volume to get the grind going is friggin loud - i personally love it ofcourse! lol

But it will be nice to get it more quiet and still have the effect of the volumes set to anything past 7 where is sustains and has that holy grail tone come through - any volume it sounds amazing, but you know what i mean.

The amp is stock, except i have a set of brand new vintage NOS Mustard caps in it and i'm using the best tubes i've found so far: Watford Cryogenic KT66 Retro matched quad and Watford ultra high gain 270 preamp tubes. This tube set up made such a huge difference to the tone, beyond anything i've tried before.

ANYHOW:

Questions: A link to a Dual 250K stacked POT
Also, is 250vdc 1/4 watt pot enough, or should i be looking for something higher rated? like 500vdc dual pot?
Will it matter greatly if i use a Linear POT over an Audio pot - reaLLY? AS I HAVE FOUND A 250K lINEAR STACKED POT with 500vdc rating. the only 250K Audio pot i have found is 250vdc.
Also, there is a wire with a resistor between output tubes 4 and 5, and also between output tubes 6 and 7, connected to terminal 5 on each of those sockets - what is that for? I haven't found a reference to that on other forums? It obviously has to get removed in the installation of this PPIMV mod.

Any info is fantastic, love to chat

thanks a whole lot

[riff19]

Hey there,

I'm a complete noob looking to install a post pimv in a JTM45 PCB reissue.

Overwhelmed by the amount of info here. 1. What's the latest consensus for the best method to set these up, tone wise? 2. Is there a kit available somewhere for dummies like myself?

Thanks!

[CoffeeTones]

http://metroamp.com/wiki/index.php/Lar/Mar_PPI-MV" onclick="window.open(this.href);return false;
http://valvestorm.com/Amp%20Mods/LarMar" onclick="window.open(this.href);return false;

[riff19]

Yes, I found those.

So visually, I get where to solder on the pot. What I still don't get is where those wires go to...

1. where Pin 5 of V4 - V7 are located on my amp?
2. what using 5.6k grid resistors on each tube means?
3. it says "notice 220k resistors are removed from the board". How do I find those, and am I supposed to remove them?

Also, it looks like 2 ground wires and 2 coax wires need to be soldered to a single pot post. That's hard to do, yea?

[toner]

1. where Pin 5 of V4 - V7 are located on my amp?
2. what using 5.6k grid resistors on each tube means?
3. it says "notice 220k resistors are removed from the board". How do I find those, and am I supposed to remove them?...

1. From inside the amp, the power tube pins are in clockwise order. Pins 8 and 1 will connect to ground. The middle two power tubes probably have a green wire on pin 5 of one tube and an orange wire on the other tube, with jumpers that lead to pin 5 of the outer tubes (V4 / V5 pin 5's are connected and V6 / V7 pin 5's are connected).

2. The 5.6k resistors go right on pin 5 of each power tube inline with the wires from the PPIMV pot.

3. The 220k resistors are red-red-yellow. One end of each connect to the existing wires that go to pin 5 of the middle power tubes. You need to remove those resistors and the existing wires to pin 5.

[riff19]

Also, I took a picture of a Plexi I bought pre-modded.

I love the way it sounds, but this LarMar looks quite different from the mod in my Plexi...
http://forefrontphotography.com/pics/plex4.jpg


Does anyone know how or why this mod is different? I dig the sound of it..

[CoffeeTones]

Looks like the Type 2 master volume without safety resistors like the LarMar has.

[riff19]

Hey, which are the "safety resistors"?

Also, do I need to buy 5.6k resistors, or will those already be on the pin 5's of my JTM?

In looking at the Plexi picture, it looks like the green & orange wire is still in place. Doesn't this LarMar mod call for that to be removed?