Rectifier not giving enough voltage

[Newbietube]

Hi all I'm currently building a bass amp in which I've used a transformer from an old peavey. The problem is that I've hooked up the HT output to a full wave rectier (no center tap) but I'm not getting the desired output voltage. Transformer o/p is 360v so I should be getting around 500v after rectification, but I'm only getting 350v dc. I've tried it with two different rectifers (one a ready made "block" and the other made up of four 1n4007's) and got the same result both times. I thought at first it might be the block breaking down under voltage which why I tried using the 1n4007's,(the "block" is supposed to have PIV of 800v). However I'm now at loggerheads with my project and its holding up any further progress. Anyone got any good ideas or been through this before?
Thanks for reading
Cheers Just

[EWBrown]

The rectified DC voltage should be about 500VDC, with no current loading, as the rectifiers generate the full peak of the AC voltage which is about 1.4X the RMS AC voltage.

This assumes that you have a capacitor-input filter and not a choke input, which would be a lower voltage, as the choke acts reactively against the 100Hz (or 120 Hz) ripple. Which will be twice the AC powerline frequency in your area.

The best configuration for your purpose is to have rectifier +, cap, choke, cap, etc If there is no choke, then a 50 to 100 ohm, 10W wirewound resistor cound be used between the first and second caps..

Under current loading, the DC voltage will drop down towards 360VDC, and that is dependent on the value any resistors or the DC resistance of any chokes after the + side of the rectifier bridge, and the first cap.

HTH

/ed B in NC

[Newbietube]

The rectified DC voltage should be about 500VDC, with no current loading, as the rectifiers generate the full peak of the AC voltage which is about 1.4X the RMS AC voltage.

This assumes that you have a capacitor-input filter and not a choke input, which would be a lower voltage, as the choke acts reactively against the 100Hz (or 120 Hz) ripple. Which will be twice the AC powerline frequency in your area.

The best configuration for your purpose is to have rectifier +, cap, choke, cap, etc If there is no choke, then a 50 to 100 ohm, 10W wirewound resistor cound be used between the first and second caps..

Under current loading, the DC voltage will drop down towards 360VDC, and that is dependent on the value any resistors or the DC resistance of any chokes after the + side of the rectifier bridge, and the first cap.

HTH

/ed B in NC

I've found the problem. Its my fault. I was testing each assembly as I was buliding and tested the O/P of the rectifer without the smoothing caps. I tried the TX with the original psu board from the donor amp and hey presto 500v. It would appear my digital multimeter does'nt like unsmoothed dc and gives a similar dc reading as the input AC. Glad thats sorted as I was worried that I had a duff TX.
Thanks E W Brown for your advice.
Cheers Just