Search found 233 matches

by Jackie Treehorn
Fri Apr 08, 2005 2:14 am
Forum: Trainwreck Discussion
Topic: Power amp section layout for A1A version schematic
Replies: 4
Views: 2627

Re: Power amp section layout for A1A version schematic

Ahh, I misunderstood and thought we were talking power SUPPLY! Oh well. Maybe someone else will find my previous post interesting...
by Jackie Treehorn
Thu Apr 07, 2005 7:44 pm
Forum: Trainwreck Discussion
Topic: Power amp section layout for A1A version schematic
Replies: 4
Views: 2627

Re: Power amp section layout for A1A version schematic

I finally dug out my power supply layout from my other computer. The values for the resistors in the bias supply are from the A1A schematic and it has been noted that they result in not enough bias voltage. Someone has posted better values somewhere... Sprague Atoms are too large to use in this layo...
by Jackie Treehorn
Sat Mar 12, 2005 6:43 pm
Forum: Trainwreck Discussion
Topic: Trainflex
Replies: 29
Views: 10960

Re: Trainflex

Maybe there's a way to use a 2 pole switch to change the cathode values on the first two stages to go from Komet (2.7k/.68 & 1.5k/22uf) to Express values (1.5k/22 & 2.7k/22) by using two paralleled resistors around 2.8k to 2.9k and using the switch to lift or connect the ground connection to one res...
by Jackie Treehorn
Thu Feb 17, 2005 7:57 am
Forum: Trainwreck Discussion
Topic: To cap or not!!!!!!
Replies: 7
Views: 4494

Re: To cap or not!!!!!!

I've got an 80pf there, too. I think much of it also depends on the choice of capacitors used in other positions. I used 716P's which don't roll off much highs. I would think an amp with Mallory 150's wouldn't require as much high frequency roll off, since the polyester caps seem to drop some highs ...
by Jackie Treehorn
Sun Jan 23, 2005 7:28 pm
Forum: Trainwreck Discussion
Topic: New Build first power up...Bad News
Replies: 17
Views: 5539

Re: New Build first power up...Bad News

The oscillation you're describing may be because the output transformer is reversed, causing a positive feedback loop rather than negative. Try inverting the phase by either reversing the leads from the coupling caps to the output tubes or reversing the leads from the output transformer to the plate...
by Jackie Treehorn
Sat Jan 22, 2005 7:20 pm
Forum: Trainwreck Discussion
Topic: How did you reach stability..?
Replies: 12
Views: 6533

Re: How did you reach stability..?

In trying to obtain stability, it's probably important to identify which parts of the amp should be relatively stable and which parts should be close to the edge so that the stable parts remain so and the crazier sections are unhindered. I don't think the first stage is ever driven into distortion b...
by Jackie Treehorn
Thu Jan 20, 2005 5:13 pm
Forum: Trainwreck Discussion
Topic: How did you reach stability..?
Replies: 12
Views: 6533

Re: How did you reach stability..?

There was a post on the old site by someone who had been in a wreck who had discovered a 33k grid resistor at the end of the shielded wire to the first gain stage. I used one on my build. I also added a small value grid resistor around 1.5k, I think, on the second stage since I was getting some spla...