My Train Wreck progress

gnugear · Post by **gnugear** » Sun Oct 02, 2005 4:36 pm

Well, after 9 months of procrastinating I've finally gotten around to drilling, staking, and populating my boards. I'll tell you, the staking is NOT my thing. My fingers hurt and it was basically a big pain in the ass. I don't know how George does it.

I'm missing some parts so I'll have to place another order before I do more. That's okay though because I thouroughly destroyed my chassis trying to drill oversized holes. I've since bought a step bit so I'm going to do that over again. More pics as I progress

Flames1950 · Post by **Flames1950** » Sun Oct 02, 2005 4:45 pm

Gripe about staking all you want, but those boards look sharp. Very nice.
I can't decide if i want to build a more accurate TrainWreck clone or not. I already know that there's way too much gain on tap for my tastes so I'm not sure if there's any point.

Dai H. · Post by **Dai H.** » Sun Oct 02, 2005 5:22 pm

hey gnu the alu housed wirewound won't dissipate the stated wattage unless it's heatsinked (if it matters).

gnugear · Post by **gnugear** » Sun Oct 02, 2005 6:42 pm

Too much gain? Heresy!!! Sounds like it's going to be perfect.

Hey Dai, what exactly do you mean? I thought that aluminum enclosure was basically a heat sink?

Dai H. · Post by **Dai H.** » Sun Oct 02, 2005 6:51 pm

meaning if the resistor says "25watts" or whatever, that's 25watts WITH heatsinking but less watts if not heatsinked. So if you're dissipating much less than the stated watts then you are okay, but if not... Poof!

Could be. In practice (as in actual equipment), for example my Palmer PDI-03 has a couple of those attached to a big heat sink inside the unit. So does my Power Brake. Or sometimes, those will be attached to the chassis.

Guest · Post by **Guest** » Sun Oct 02, 2005 8:16 pm

It's the same spec as the cheapy cement xicon that's in the original trainwreck. I just got the aluminum one because I thought it looked a little nicer ... hope it's okay.

Billy Batz · Post by **Billy Batz** » Sun Oct 02, 2005 9:28 pm

TWreck guys think Ken used those big cement resistors on purpose since he used a rating 2x higher then was needed.

As far as staking, a drill press helps a lot. After drilling my latest Marshall board it took me 10 minutes to stake all the turrets nice and perfect. They were metro turrets but with the hoffman tool the keystones are just as easy.

Billy Batz · Post by **Billy Batz** » Tue Oct 04, 2005 5:11 pm

Flames1950 wrote:Gripe about staking all you want, but those boards look sharp. Very nice.
I can't decide if i want to build a more accurate TrainWreck clone or not. I already know that there's way too much gain on tap for my tastes so I'm not sure if there's any point.

You know the thing thats supposed to be so amazing about real Expresses is how they go from a total brown sound package to cleaning up amazingly with the volume knob with the cleaned up sound actually as loud as the full volume sound and dynamic as hell. Plud the harmonix. Im curious what you went with for your values through the preamp?

Dai H. · Post by **Dai H.** » Tue Oct 04, 2005 5:42 pm

Anonymous wrote:It's the same spec as the cheapy cement xicon that's in the original trainwreck. I just got the aluminum one because I thought it looked a little nicer ... hope it's okay.

might want to make sure it's rated high enough. I don't know if you remember but "mr.Twistyneck" blew up some of those trying to do the "****** mod" using some of those which were not heatsinked.

Billy Batz · Post by **Billy Batz** » Tue Oct 04, 2005 6:21 pm

He should be fine because 25W is way overkill for that spot. I got away with a 5W resistor there before in my Xpress. Like I said the talk on the Twreck pages was that Ken chose those big 25W cementies specifically for some reason not to do with ratings.

gnugear · Post by **gnugear** » Tue Oct 04, 2005 8:51 pm

Dai H. wrote:
Anonymous wrote:It's the same spec as the cheapy cement xicon that's in the original trainwreck. I just got the aluminum one because I thought it looked a little nicer ... hope it's okay.
might want to make sure it's rated high enough. I don't know if you remember but "mr.Twistyneck" blew up some of those trying to do the "****** mod" using some of those which were not heatsinked.

I do remember that!

Hey Dan, I'm just following the 1A schematic ... I have no clue how it differs from other Wreck circuits. I'm only doing it because I've heard it's one of the more accurate layouts.

Billy Batz · Post by **Billy Batz** » Tue Oct 04, 2005 9:42 pm

I assume you mean A1. Wrecks and Dumbles are like all custom amps. Similar models have a similar layout but can have very different values and some tricks thrown in here and there. Now my wreck was built using a Fender chassis and trannys so itll sound different but my suggestions on the A1 is to use sheilded cable on the stage 2 grid, scale the PI cathode resistor up with the tail resistor so they are 22k and 820R, use a 47k NFB resistor, and use .047u caps for the output couplers. .022 brightens an already bright, thin amp. .1 can be too much. A 100p cap accross the PI plates like a Marshall is a good idea. Also a mod that sounds great and a lot of the super booteek guys use is to add a cut control. Thats a 1M pot in series with a 500p-.0022u cap accross the output couplers on the grid load resistors side. I also prefered a screens voltage of 380v. I used a zener on the CT to get the voltage just right. I had my standby on the CT as well. I think I had 3k3 swamp resistors. That impedance resistor after stage 2 is key to getting the gain and compression right. Use a pot in place of that resistor to find your ideal resistance. Also using a .68u Ck on stage one really EVH's the tone up. So does lowering the slope resistor.

Are those solens your using? Id bet sozos would sound great in an xpress.

gnugear · Post by **gnugear** » Thu Oct 06, 2005 1:03 pm

Yeah, I meant the A1a schematic. I'm starting out with Solens until John introduces his new soZo caps. Hey what's the purpose of that 100pf cap on the phase invertor? I've heard that people add it even though it's not on the original schematic?

Billy Batz · Post by **Billy Batz** » Thu Oct 06, 2005 1:11 pm

My notes about the A1 still arent the same as the A1a. For instance the A1a has normal Fender/Marshall 10k/470R values in the PI. So only use them where they apply.

Both sides of the PI plates are equal but out of phase. When you mix to equal out of phase signals they cancel out. If you had a jumper there youd have zero signal. With a 100p cap there you let only very high freq's through to cancel out. Its similar to having a 100p to ground on the plate of a preamp stage. Actually many of the super booteekers who sell clones of the Xpress use that but I think they and most hobby TW builders use something like 80p. higher then 47p but not all the way to 100p. If you choose not to use that cut control I showed you then I would use 100p. Some people feel it can kill tghe harmonics and clarity atouch. Its very subtle and helsp to prevent oscillation. This circuit has no shortange of brightness and harmonics. In the end you may not need it but its a good place to start.