Rectified b+ too low

[guilds100]

I just fired my express clone and i have a problem. I have 121 volt at the wall, 588v ac into the rectifying bridge and 265v dc coming out with no load attached. Would a problem with the center tap cause that? I'm using toneslut transformers.

[paulster]

Do you have your cap stack connected, or at least the first filter cap? Or are you trying to measure the rectified DC immediately that it exits the diodes and before you've connected the caps?

If you don't have the caps then you've got a waveform that's continually varying between 0V and 400-or-so volts, but your multimeter is going to expect something stable when it's in DC mode.

Your AC voltage looks reasonable, assuming that you're measuring from one end of the winding to the other, rather than between one end and the centre tap.

[dartanion]

Are you checking it in standby mode? This affects what you see post rectifier.

[guilds100]

Thanks for the reply. I think I have it figured out. I forgot to mention that I am forming the caps. I did this 2 weeks ago for the first time on a jtm 45 and thought that the voltage going up slowly was due to the tube rectifier. I was wrong, the slow climb is due to the inline resistor. Also, I was using much higher quality caps then now and after re-reading the instructions found that lower quality caps may take longer to form. I'm now at 315v with a voltage drop across the 100k resistor of 75v for a grand total of ~390v. I should be all set.

[doctord02]

Take this with a grain of salt, but forming new caps is a complete waste of time. It's only useful on older caps that have sat unused for a long time.

[Structo]

I don't know enough about that to say one way or the other but Larry posted this at Metro and I thought it was an interesting thread.
I know what you are saying about older caps benefiting from it.

http://forum.metroamp.com/viewtopic.php ... &sk=t&sd=a

[guilds100]

Thats where I got my info

[guilds100]

double post