Jerry Pre-amp mods

[schmidtz]

I used stock values for all except vibrato channel tone caps. There I used the .022 combo for bass and middle, instead of .1 and .047. The project took about 2 hours.

Here's everything I bought:

Power Supply:
2x 220uf 285v electrolytic
3x 20uf 500v electrolytic
2x 100uf 100v electrolytic

Poly: (here's the orange drops)
4x .1 600v
.1 200v
2x .01 600v
4x .022 600v
2x .047 600v

SilverMica:
2x 250pf
2x 100pf
1x 500pf

Small Electrolytic:
5x 25mfd 25v
1x 5mfd 50v


For all coupling caps, I used orange drops (715). For the power caps I went with Illinois caps. The Atoms are like 3 times the price, so I cheaped out.

Time to go wiggle my switch!

[waldo041]

Atom caps in the filter cap position are well worth the money! also, the 150d's cathode bypass caps are worth the money in that position as well but atoms there can equate to the next step below them. the polyPROPYLENES(715's) will be fine in the power section, but when used as the tone caps in the preamp section will make things a little too sterile, bright and Hi Fi sounding. the 225p's (Polyester/Mylars)in the preamp section is a much better choice.

i don't have much experience with the ultra linears, but i would jerrify the preamp section and just tighten up the stock values with a good quality cap job throughout and match resistors where appropriate. i'd also consider removing the stock master volume and associated circuit, and wire straight from the 2 -220k mix node into the .01uf coupling cap just before the phase inverter and/or splice in a 250k pot just after that .01uf coupling cap, right inbetween it and the phase inverter.

peace,
waldo

[hippieguy1954]

Waldo, What would you do to Jerrify the preamp seeing as it is so different from the non ultra linear preamps? Or is it not that different?

By the way, you joined this forum on my birthday...Month/Day....so that means you have to help me! lol....just kiddin! Peace, Jim

[hippieguy1954]

Time to go wiggle my switch!

Thanks for the list, schmidtz! Hope wiggling your switch works! lol...I have one that is getting pretty loose and will replace it in time. When I start working on this '79 ultra linear preamp, I want to use the best parts possible and try to Jerrify it with a little help from Waldo if possible. Let us know how it sounds after you get the switch working. Oh yea, do you know anyone who has a chassis layout for the 135W ultra linear twin? I've looked everywhere and there doesn't seem to be one available.

[hippieguy1954]

Has anyone tried Joe Martin's 135w twin ultra linear Jerry moded amps?

[Capt Rosebuddy]

Has anyone tried Joe Martin's 135w twin ultra linear Jerry moded amps?

Dunno if mine's a linear but JM's worked on my '71 Twin and it sounds fantastic.

[hippieguy1954]

Cool, love it when some one says thier amp sounds fantastic! Ultra linear twins came out in '75 with 135 watts and the useless push pull master volume. Totally different than '71. Thanks for ther reply!

[schmidtz]

Well, I was debugging, and I noticed that when I flipped the on switch, it would smoke. After some smoke it spit out a little spark, and I got SHOCKED. I mean, like I saw Jerry shocked.

I'm taking it back to Savage. Them taking three weeks is better than me convulsing and foaming at the mouth.

[hippieguy1954]

Was it unpluged?

[schmidtz]

Of course it was plugged in! What, do you think I'm intelligent?

[hippieguy1954]

Of course it was plugged in! What, do you think I'm intelligent?

oooooooooook, well that taught ya a lesson! Did you try it again unplugged? New switch time?

[schmidtz]

Yea, I'm going to replace both the on switch and the standby. Probably going to remove the death cap as well.

[hippieguy1954]

I've decided to sell my ultra linear and get the SMS classic. I'm finally in a position to do it, so I'm goin for the gusto! Or somethin like that.

[schmidtz]

Wow. Three weeks of stupidity.

I had previously said that my standby didn't work. After replacing all the carling switches, removing death cap, checking continuity, and crying, I realized that you flip "on" then "standby". I was doing it the other way around.

Now is the part where I say that I have owned this particular amp for over a year, using it daily. I have never had this confusion previously.
In other news, my buffer, plus the newly capped twin (with changed tone caps), and my E120's have made me love guitar all over.
Now just a few more days until I get my MC250 back from the fix it shop.

Take it easy.

[schmidtz]

Well, I got my MC250 back from the shop... everything was good, except the cut power cord and a couple diodes. The guys at Savage told me that it changed their minds on SS Macs (they had only ever dealt with tube Macs).

Then I realized that Waldo had already answered my master volume removal question.... I'm a noob. THANK YOU WALDO.

So I got it all hooked up (I used the existing Vibrato pedal RCA, and the existing ground through the cathode cap). I just pulled the Vibrato wire from the RCA and electrical taped it. All of this will be reversable.
I made a head, it cost me $25 and a weekend. Next will be the speaker cab.
The shop told me that the Mac does 68 watts per channel, so I'm using just the right, and leaving the left for backup.

So here's my rig now:
Maple fingerboard strat w/ OBEL and UGB>the correct Belden cable(the blue stuff)>SF Twin w/ correct Jerry caps, and Master Volume removed>Mac>E120's.

I think I'm done. The tone is to die for, with earplugs .

I want to put up a vid of the tone, but I don't want to aimlessly noodle, any requests?

As always, thanks everyone!