R30a & R30b in the Liverpool

[fzfwyv]

Are these resistors needed if the PT has a center tap?

-Rich

[gahult]

Yes, they are bleeder resistor for C17a and C17b. With out them you would still have high voltage stored in the caps when you power the amp off in standby.

Gary

[fzfwyv]

Thanks!

[skyboltone]

Yes, they are bleeder resistor for C17a and C17b. With out them you would still have high voltage stored in the caps when you power the amp off in standby.

Gary

Not only that, but if you were to turn on the amp with no tubes installed, the main filter caps will continue to load with voltage right up to the point of failure. We usually look at a cap input filter network delivering around 1.41 times the RMS voltage of the primary. If you don't have bleeders in place, that voltage can easily get to 1.7 or even 2 times the RMS voltage. They don't like that. They will blow up.

[Ron Worley]

Dan-

then why does the Rocket not have these resistors???? I am not looking at the schematic, so this might be a dumb question... perhaps related to the tube rectifier..


Ron

[skyboltone]

Dan-

then why does the Rocket not have these resistors???? I am not looking at the schematic, so this might be a dumb question... perhaps related to the tube rectifier..


Ron

Don't know Ron, haven't spent much time with the Rocket. But if you've got 500V Mallory filter caps at stage one of the supply and a 240VAC primary even using my math you're ok. It's common practice to use some sort of bleeder load in the design of any power supply. Frequently this might be as little as 470K across each PS filter cap though I think 270K is a better value. If you look at the DC with a scope you'll find more ripple without bleeders too. Until you load it anyway. Hard to say what Ken had in mind. It's just common and good practice.

Dan

[gahult]

The Rocket does have them. They are are R31/R32 100K 3w.

see: taylor_schematic_updated_6_345

Gary

[Ron Worley]

The Rocket does have them. They are are R31/R32 100K 3w.

see: taylor_schematic_updated_6_345

Gary

Well, that's true, but real rockets as seen in pictures and on the layout that Tim Hulsey show that they are not in fact on a real Rocket. I think they were put on Matt's Schematic as a matter of practice, but they are not technically accurate.

Ron

[gahult]

We are not building "Real" Trainwrecks. What we are building are Trainwreck clones.
We can't get these[img:900:600]http://img.villagephotos.com/p/2005-10/ ... AC-425.jpg[/img] anymore or a lot of components that were originally used. But, I will put bleeder resistors in for
safety sake as a "good engineering practice" in any build before a VVR, PPIMV or MV. I've been
using bleeders since 1960 and I hope to be around for another 60 years or so.
All that being said "fzfwyv" was asking about the Liverpool, not the Rocket.

Gary

[Ampsterdoom]

We are not building "Real" Trainwrecks. What we are building are Trainwreck clones. Gary

Thank you Gary,

We are a new generation of amp builders with materials and information that Ken Fisher didn't have. In building a Trainwreck amp he could well say the same thing about us. Ken Fishers genius was reportedly his great ears. None of us have those ears nor do we have any idea what he was listening for. We have a good idea of what looks like and even use many of the same parts as a Trainwreck amp and I'm thankful for the guys that make clones. I learn from them and recognize they are good at what they do. I just can't keep my own ideas from jumping into my builds.

I agree with the chassis information. We have set new standards for the Trainwreck tradition but have you really had the true experience until you get a Bud Box and a set of chassis punches and work with that thin soft metal and all the ragged edges? I myself haven't been able to bring myself to use that old rosin core solder and leave big splotches of flux on my circuit boards either. I know the only time I've seen inside a real wreck he used sheet metal screws for fasteners, I'm glad we aren't bound to that part of the history.

Doom

[RJ Guitars]

I found one of those original spec Bud Boxes at the junk salvage place here in town. I had to put a plate over the top and the ends since it was at one point some mad scientists experimental apparatus - full of big holes. But the way cool thing was finding a few pristine pieces of original Vectorbord.

BTW, Vectorbord is not much fun to work with, it's kinda brittle compared to modern G-10. That same day we found the Vectorbord, Zippy and I found some Flea Clips too. I don't know where I put them so I used modern turrets for my almost authentic Liverpool build.

The faceplate is another one of those awesome Lonely Raven laser etched units... a great piece of work!

rj

[gahult]

bleah, some people have all the luck.

chassis and vector board in one place, same time, go figure
nice score.

Gary

[Zippy]

That same day we found the Vectorbord, Zippy and I found some Flea Clips too. I don't know where I put them so I used modern turrets for my almost authentic Liverpool build.

If you wanna flip that board over and do it right, I know where my bag o' clips is.