Peavey Windsor to JCM800 Conversion.

[karpathion]

I got this Windsor as broken a couple of months ago for $50. Spent $7 at radio shack to fix it, and have been playing it ever since. It's not a bad amp, but it was just to fuzz like and muddy than I care for.

Luckily, the Windsor's design is not very far from a 2203/2204, and it's stupid easy to work on. That makes the mod I found by Doug Hammond, a no brainer. For the most part, it turns the Windsor into a JCM800.

I'm starting with the preamp first. I want to make sure it's heading in the right direction before I put more money in a choke and components. 

All the new components are carpon comp resistors, and 150 series caps, execept 1. We'll get to that later.

Below is the mod applied to the schematic. It gives you a very clear picture of what needs to be done. You'll notice a lot of removed or replaced components, as well as a few jumpers. Pay special attention to the section around V2b. I'm starting to think that little, "bad design" is what makes those Marshall's sound the way they do.

[karpathion]

Remember that 1 cap I mentioned? I don't know what happened, but I ended up with a massive 1uF cap. I guess I didn't pay attention to what I was ordering. 


I'm glad there is a big open space right below where this thing goes, it's the only 1uF I have. It's just going to have to work.


Mistake #1

[karpathion]

Next step is pulling the chassis and draining those big nasty caps. I'm not going to show you that. If you don't know how to use 100k resistor with longer leads attached, or where to use it, stay out of it! These things can hurt or kill you.


Now we get to break out the iron and sucker.


Not alot left once you pull out everything that needs to go or be replaced.

[karpathion]

New components are in. Remember that giant capacitor? I had to put an insulator on one lead and bend it down under the cap to hit the solder points, but's in there. Time to bolt her back up.





I also found that one of the 2 el34s I was running was bad. The only replacement I had was a quad of 6l6WXT+. So, I used 2 of them. 

While trying jack the bias up to acceptable levels for the WXT's, I noticed a dead spot in the bias control after about 75%. It wouldn't let the bias go about -45ma. I sprayed contact cleaner in it a few times while turning it back in forth. Took about 4 times, but it goes up to -60ma now. I set it at -54ma like Peavey suggests for 6l6s.

Moment of truth. Time to see how it sounds.

[Snake Aces]

This is gonna be sweet

[karpathion]

Completely different amp already. The gain is so much smoother now, and reacts differently. The Distortion went from a muddy, raspy, Fuzz like feel, to an articulate, just squishy enough, smooth Distortion. It even has more gain on tap to boot.

The voicing of the amp has obviously changed, even though very little was done to the tone stack. It's in that JCM mid crunch arena now. You could probably leave the amp alone with just the preamp mod and be very happy with the amp. I just get the feeling that finishing out the power section mod and and adding the choke will put it right where it should be.

From what I was reading about this mod earlier today, it does duplicate the circuit of a 2203/2204, but some values are changed to make it a Bogner Shiva. You can tell it's about right just by how the tone and gain controls react now. 

I ordered the 5H Hammond 194F choke, and the rest of the components for the power section mod today. Hopefully I'll have it all by this weekend. 

Here is the power section mod schematic.

[Oinkus]

How much is the total cost going to be for parts ? Looks like pretty big improvement , never got a decent sound out of the one at the hoarders studio.

[karpathion]

After the choke, I have about $60 in it. Shipping kills you.

[Oinkus]

Still a decent investment if it opens up when you finish the mods. Never liked any stock Peavey guitar amps without at least some work done to them.

[karpathion]

The kicker is going to be if I choose to upgrade the transformers. I'm still not thoroughly convinced they will make that much difference. The stock transformers barely get warm. I'll have to play with it if a bit before I make that decision.