Marshall Silver Jubilee - Tagboard layout with mods

[Turret]

I never did anything with 18watt Marshall yet, but I have few layouts for 67/68/69 Suprleads - both tagboard and vintage correct. Also, few Fenders, Hiwatts, VOX's and others with random stadium of completion

My way to express ADHD and OCD I guess

I'm thinking to do SLO100 layout this way, optocouplers lay down nicely on tagboards

[Turret]

Actually, i would encourage you to start a "DIYLC files" thread in the Marshall Discussion forum here.

I will tomorrow (it's 1am here, and I have to hit the hay badly, working in Ambulance Service tomorrow). I will do the tread with my personal templates for DIYLC, like tagboards, schemo symbols and such

[Bob S]

Many Thanks Torg.
Thanks for sharing.
Melikes.
Bob

[Turret]

I tried a number of different master volume alternatives in that circuit, including traditional and PPIMV. The most transparent one was the bootstrapped MV (see schema). It also uses a tandem pot. For my taste, PPIMV generated a too "grainy" distortion (due to loosing NFB at lower volume levels) and the traditional loosed a lot of treble at lower settings

Pablo

Before I rework my layout, could you have a look on schematic attached? Do I got it right?

[pablogt]

Yep, that looks good.

I did want to be able to balance clean and dirty volume levels. What I did is set up a common bootstrapped master volume and activate a "scale control" when in dirty mode. That is, add a 50k reverse taper variable resistor in series with the tail resistor of the PI. That is sort of a poor man's power scaling. It changes the PI's bias, decreasing the drive on the PA but, at the same time, decreasing the PI's headroom so that the overall "grit" does not change much. The draw back is that the cleans become a little hairy, but that's ok for the high gain channel. Besides, since master volume affects the whole amp, you don't need to use the scale control at very high settings, just to pad a little the high gain channel in order to balance it with the cleans. It works very well.

This really sounds a lot more complicated than it is, and it is very easy to try out on any amp. They call it "power dampening" at Mojave Amplifiers

http://mojaveampworks.com/amplifiers/coyote/

[Richie]

You can see many type amp layouts that Nik posts on his ceriatone amp site. Metro amps also has a few. When you get to 18 watt marshall stuff, a lot of info, amp kits etc can have their own version. Some of those were taken from schems that were not finished or corrected,or layout and part values are wrong. Some aren't really wrong, but the layout is made "their" own, which may not be the best way. Like the old saying, a story gets told, by the time it goes through 10 people the story has changed..

[dcribbs1412]

Thanks torg and pablogt
starting a Jub build soon
very much appreciate the info.

Darin

[Turret]

I'm sorry I didn't finish it yet, I moved on to other fields. I promise I will back on it soon

[Turret]

Alright, enough for today, I'm knocked!

I decided to go back to stock MV, I think most of the overdrive comes from diode clipping network anyway, at least I see it that way. Mains filtering remains modified, and comes from early JCM800 (6 can caps on top of the chassis). I decided to move status lamp to be powered from 6.3v taps

Who's happy for second pair of eyes checkover? Any obvious fuckups?

Thank you

EDIT: Project file revised, one error corrected