12301 ?

[harddriver]

That's the one... I have two pics from two different angles but it is the amp in your picture.

Is this the other angle pic you mean ?

Looks like an RS or Lemco MICA 47pf on the PI fizzy cap on this 68 pic.

[PLX]

I'm going to say the creme colored board is not 12301.

Yeah, no.. that's supposedly the one with the cream colored board is serial# 12369.. but I'm not buying that.

It's too close of a number to 12301 to have changed boards at the factory.


So you say the first pic I posted is 12301 For sure ?

[PLX]

Looks like an RS or Lemco 47pf on the PI fizzy cap on this 68 pic.

I would have to agree.

[harddriver]

Looks like an RS or Lemco 47pf on the PI fizzy cap on this 68 pic.

I would have to agree.

I forgot to put in the MICA in my comment. So I meant to say RS/Lemco MICA 47pf caps. In that pic of the 68 you posted the PI fizzy cap is not a Lemco Dogbone ceramic cap it does appear to be a mica cap same contruction as the mixer and tonestack caps just smaller.

[PLX]

I forgot to put in the MICA in my comment. So I meant to say RS/Lemco MICA 47pf caps. In that pic of the 68 you posted the PI fizzy cap is not a Lemco Dogbone ceramic cap it does appear to be a mica cap same contruction as the mixer and tonestack caps just smaller.

[PLX]

From another angle.. looks more like this type of cap to me.

[harddriver]

I forgot to put in the MICA in my comment. So I meant to say RS/Lemco MICA 47pf caps. In that pic of the 68 you posted the PI fizzy cap is not a Lemco Dogbone ceramic cap it does appear to be a mica cap same contruction as the mixer and tonestack caps just smaller.

That Lemco is later version similar to a CDE mica and they are epoxy dipped with a hardshell. The micas used in 68 look like a flat piece of cardboard and brown in color that resemble the old ceramic cap texture. The large rectangular 560pf cap under the 470K mixer resistor and tonestack cap are what I am referring to. My point being is that it appears in 68 Marshall was using mica caps in the PI fizzy cap location and didn't start using the Lemco Ceramic dogbones until 1969. So to be more era correct maybe a lemco 47pf might be more era correct than a ceramic for a 68 build. It is my belief and experience that the micas cap do smooth out the tone considerably in the 470K and tonestack positions. I originally used new production ceramics in the 470K mixer position an bright cap in my 69 build and had an NOS RS mica in the tonestack and the amp was a little harsh like my 72. So I made more room and installed one of my last RS 560pf micas in the 470K mixer position and bammo the amp sound like my 68 that has Lemco micas in both locations and a Lemco dogbone 47 pf in the PI fizzy location. That's when I also found that the 80's CDE micas sound like the vintage RS/Lemco micas.

When my 72 was 100% stock it was a bright aggressive and sometimes shrill amp. It had smaller diameter ceramic caps in the 470K mixe and a 47pf dogbone PI but my stock tonestack cap was a Lemco 560pf in the 72. I read that 40 year old ceramics can leak DC and overal be extremely noisy and unpleasant as when they were new. So when I replaced the bias filter caps a couple of years ago, I replaced the 470k mixer cap with an NOS CDE 560pf mica cap and I replaced the original 5000pf Lemco bright cap with an NOSnew Mallory 5000pf ( that I sent you) and the amp immediatley sounded much better less shrill an much more like my 68. In the past on my 72 I had also installed a Sang 100pf on the PI fizzy because John Suher said Ed's amp had a 100pf mica there it was alright but while doing that other work I installed a new NOS 47pf Lemco Dogbone that was there originally.

The amp's been great ever since. I'm just passing on some trial and error past experience and revelations I had over the years tinkering.

[harddriver]

From another angle.. looks more like this type of cap to me.

You are correct my correction and explanation is above. I forgot to insert MICA in my original response. The flat cardboard looking RS/Lemco caps are MICA caps including the PI fizzy cap in those 68 pictures. Marshall didn't start using the cermaic dogbones until 1969.

[harddriver]

From another angle.. looks more like this type of cap to me.

You are correct my correction and explanation is above. I forgot to insert MICA in my original response. The flat cardboard looking RS/Lemco caps are MICA caps including the PI fizzy cap in those 68 pictures. Marshall didn't start using the cermaic dogbones until 1969.

I sent you an NOS CDE 47pf silver mica so you are covered if you want to install a mica in the PI fizzy cap position insteadof ceramic. I've tried both and tend to prefer the 47pf Lemco dogbone but that's not saying the 47pf mica doesn't sound great as well. I am assuming those old Lemco's and RS mica caps are silver mica like the CDE's. I just haven't seen people refer to the Lemco/Rs's as Silver micas, it's always just MICA for some reason, did they use another metal I don't know.

[harddriver]

Is this it ?

I would venture to say that 12301 probably looked pretty similar to this one in the picture.

The only spec in question is what what the cathode resistor on V1B? Is it 820/.68uf or is it 2.7K/.68uf....personally I've used both values and the 820 is gainier.

My 69 spec was 820/.68uf Philips Chicklet cap in those clips I posted of it. I also ran the 820/.68uf initially in my Ed spec 68 but I transitioned to the 2.7K/.68uf as I felt it had better definition and headroom when you push and EP3 echoplex and EQ pedal into it. Both sound killer and the 2.7K/68uf is just a personal preference....