Late 68 Early 69 Superlead.

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revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Wed Jan 17, 2018 1:41 am

Well I have had some good news I think....

Was supposed to have the iorn shipped maybe five weeks back but it didn't happen. I got back in touch and apparently now I should be getting two sets shipped, one for this one and one for a late 67 build.

Apparently there is trouble with the steel manufacturer so it may be a while before I get my hands on the 50w set and the 2203 set.

At least i will be able to get this and the 67 up and running.

Nearly done the 67 chassis so I will start another thread hopefully next week.

revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Wed Jan 17, 2018 4:00 am

A couple of credits I really should mention....

Originally I had a different chassis that I had to drill the front panel out. I was a bit hasty and went about it the wrong way.

The chassis is still quite useable and no one would probably ever notice but I know it's not dead on so I couldn't bring myself to use it for this build. I will definitely use it for something in the future.

Anyways I kinda mucked up the face plate into the bargain so I got in touch with Robert from Valvestorm.
I had got all the chassis, hardware and plates from him great stuff.

So it was getting close to Christmas, I originally had the plates reverse engraved at Modulus amplification in Scotland but there wouldn't be enough time to get the plates to England and then send them off to Scotland and get it all back by Christmas.

So I asked Robert to send the plates to Mojo to be reverse engraved, JMP logo on the front and Superlead 100w and the blurb on the rear.

Robert was really great, he said he would hang on to the chassis till the last minuite if something went wrong with the engraving he could get another set of plates to match the chassis done.

So the plates went to Mojo who did a fantastic job. They knew how desperate I was to get it all for the Christmas break and went the extra mile to get it out.
When the plates were done Robert sent the chassis out.

So I can't give enough praise for Valvestorm and Mojo they went above and beyond to get me sorted.
And as if by the miracle of Christmas it all arrived on the very last postal day..... it was almost biblical.....

Tazin
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Re: Late 68 Early 69 Superlead.

Post by Tazin » Wed Jan 17, 2018 5:06 pm

Robert is a great guy...Very accomodating.

revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Thu Apr 11, 2019 7:31 am

So The last time I posted here I was told the iron for this build was on the way so I was expecting 4 to 5 weeks for shipping but a couple of months later it still hadn't shown up....

I've had a rant in my 67ish build post and explained what happened so I'll leave it at that. Needless to say It did all turn up eventually and it does sound amazing, the quality of the sound of the product was never in question.

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revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Thu Apr 11, 2019 8:53 am

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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. :palm:

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.

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revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Thu Apr 11, 2019 9:46 am

I almost forgot another disaster, I tell you these things so hopefully others may avoid the same mistakes. On this one I was heat shrinking some insulation over the O.T connections to the impedance selector and it heated up the rear panel so much that the rear plexi panel buckled and shrank. It sort of happened after I stopped with the hair drier from the residual heat.

Anyway it was beyond repair so I got another one from Robert at Valve storm who kindly sent it over to Mojo Tone to John for reverse engraving. The first time I got them engraved it was back around Christmas so it was nice and cold. As allot of you will already know there is a layer of adhesive glue on the back of the plates and this time it was the middle of summer so the heat must have made the glue more tacky but either way it didn't work this time round.

I must have driven Robert and John mad with all the panels I asked them to do from me messing them up one way or another. Big thanks to Robert at Valvestorm and John Manning at MojoTone.

So I brought another rear panel and asked Robert to please send it over to John again and begged John To give it another go. So John waited for things to cool off and it worked out just fine and looks great.

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revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Thu Apr 11, 2019 10:34 am

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So how does it sound? It sounds great, no wait it sounds amazing. I should go play a regular production amp some where to put it in perspective. I think I'm becoming complacent about all this awesome Plexi tone... :lol:

It sounds exactly as I expected it to. When I hook it up and plug in I'm usually just trying to run a quick test on something but I can't stop playing and it turns into a couple of hours at least and that leads to pissing off the neighbors. I gotta get this stuff to a studio now so I can crank it all up and get things broken in.

So The specs;

Split cathode
220uf/820r on V1
.68uf/2.7k on V1
.0022uf on the 2nd coupling cap
470k with a 500pf silver mica cap on the mixers
no .68uf cap on V2
33k slope resistor with 500pf silver mica cap on the tone stack
47k negative feed back on the 8ohm tap
3Amp fast recovery diodes in the bridge rectifier
4700pf bright cap on Volume 1 pot

Lower voltage tap on the power transformer.

Filtering;
32/32uf on the pre amp
2x 16/16uf on the screens
2x 50/50uf on the mains
16/32uf for 48uf on the phase inverter

Valves are all NOS and biased at 65% ;

V1 Mullard ECC83
V2 Mullard ECC83
V3 Mullard ECC83
V4 Winged C EL34
V5 Winged C EL34
V6 Winged C EL34
V7 Winged C EL34

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axeman
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Re: Late 68 Early 69 Superlead.

Post by axeman » Thu Apr 11, 2019 7:09 pm

A Master piece. Did you build the cab

revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Fri Apr 12, 2019 5:21 am

Thanks axeman, very kind words. No I didn't build the head shell that came from StoneAge custom cabinets. I believe he copied an original 68 cab. I put the logo on it and I put some of the new Marshall shock absorbing feet on it but the new ones are rubbish, they collapsed with the weight of another amp on top so I ended up putting the rubber feet on it and it looks really good.

But all credit to John Wheeler the cab is built like a tank and is spot on in every way plus John was great to deal with.

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neikeel
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Re: Late 68 Early 69 Superlead.

Post by neikeel » Fri Apr 12, 2019 8:41 pm

Lovely build, the plexi panels are a very nice touch.
Neil

revolver1
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Re: Late 68 Early 69 Superlead.

Post by revolver1 » Sat Apr 13, 2019 4:50 am

Cheers Neikeel.

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