Green Pre ready, PSU/phantom HUM SOLVED!!!

sadly I don't have one, but a friend does !!! :razz:


Meanwhile: can I test with a 9-0-9 Transformer to know if the HUMMING comes from the 15-0+15-0 Transformer?

I tested with a 9-0-9 transfo and it works fine but with the HUM (sligtly less hum but I guess it is because of the less voltage)

I tested the first Toroidal transfo I had on the GREEN : 15-0-15VAC CHECK!! :razz:

Now I put the 15-0-15VAC transfo again in the Green PRE and measure the AC and DC voltage on the OUTPUT of the PSU


VDC(VAC)
48VDC (100VAC)
0VDC (0VAC) (DOH!!!)
13VDC (30VAC)
-13VDC (30VAC)


So now I think my PSU is bad as a...... :shock:

A 9-0-9v transformer will not get you up to + & - 15v dc in the rectification process, so the regulators would not work properly.

I asked about a scope asthis is the easiest way to measure the ripple voltage on the PSU rails.

Peter

the Voltages are from the "right" transformer 15-0-15VAC. I measure them meanwhile I find my friend with the Scope.

Are those values to crazy off?

It is odd that you are getting +-13v from the PSU. What DC voltages are you getting before the regulators?

after the bridge rectifier just when it touches the 1000uF cap I get 50VAC and 22VDC and -22VDC on each 1000uF cap.

after the 7815 and 7915 on the second pair of 1000uF caps I get +-14-15VDC (near) "with my old needle tester" and 30VAC

bump...

Finnally the GREEN PRE is READY  ;D

changed the Voltage Regulators and the noise/buzz from PSU  went from 5% to none...  super clean 

then, after a lot of testing I changed the 10uF of the Phantom to 100uF and PROBLEM SOLVED, silence, no humm/buzz with condensor mics

Now it sound SO GOOD.

thanks.