So this is it. As I was saying in the 67ish build post this amp has the perforated paxolin board and when I fired it up, got it tested and biased all seemed fine untill I plugged a guitar into it and found it had DC voltage getting onto the inputs causing loud poping when switching pickups and scratchy volume pots on the guitar just like I had on the 67 build.
There was no DC on the amp pots other than the presence pot so that was good news. I had exactly the same problem with the 1987 I built with a perforated whale brand Tuffnol board. So after going through the traumatic re build with the 67 I thought you know what I'm gonna try a few things here first before going down that road again.
I thought about it allot and the first 69 I built also had a perforated Paxolin board that was beautifully made for me in the US but it was made from Paxolin sourced in the UK.
This amp had similar problems, I didn't know then what I know now and I thought the scratchy pots were down to flux that had gotten inside the pots and on the track and wipers from when I cleaned the joints with flux cleaner because the problem kinda went away after a while. I think what was really happening there was the board eventually dried out from the heat of using it so it wasn't shorting out between the turrets.
It also used to make popping and crackling noises intermittently that I put down to the carbon comps drying out, I never bothered with CC's again...
On top of that it went through a phase of after playing for a half hour or so the sound would completely fade out and maybe after a minute would sort itself out. after allot of playing the amp it settled down and sorted itself out, I'm now almost certain it was the board drying out with the heat from using it.
The 67 Tuffnol board that I Meggered out with 1000vdc (all components removed) as in I meggered each turret to every other turret on the board until the resistance readings rose above 200 meg ohms proved to me that the boards had definitely absorbed moisture. I used to megger cables that had been exposed to water this way. It would often happen before the roof went on in the winter, once the roof is on and everything dries out its all OK again.
So with that I took this amp and the 1987 and hooked them up to a cab each and maxed all the presence and EQ to 10 and cranked both volumes with a jumper lead in place.
It was all fairly noisy and as the day went on it got worse especially the 69 100watt. So I just left it on all day from 9 in the morning to 8 at night. I did this for 5 days in a row, there were all sorts of pops and crackling that came out of them but by the 6th day the 1987 suddenly got quiet. The 100watt was still a bit up and down but by the next day it fell silent.
Both of them on at the same time cranked and all I can now hear is the regular white noise.
So glad I didn't re build them.... Any way I also came across these DC filters made by Lehil that block up to 10vdc for this very purpose so I picked up two of them, they were cheap enough and at least this will guarantee there will be no DC getting in to my effect pedals causing popping and even damage.
I'm sure the amps will continue to improve and sort them selves out with more use but the DC filters are just extra insurance. So I come out of my pedal board plug into the filter behind the amp and run anothet cable fromthere into the front of the amp.