st-70 info

[jshull]

Hi group
This newbie has a question I have installed the board but I can only get
-49.8 volts at the check points and I can not get a reading if I use the 3 or 4 pin on the preamp socket out, Yellow_Light_Colorz_PDT_14 I have to use the chassis to get my ground for my meter The bias supply has 100mfdx100v caps that had been installed and diode should thay be 47mfd ?
Thanks

[Shannon Parks]

Hi group
This newbie has a question I have installed the board but I can only get
-49.8 volts at the check points and I can not get a reading if I use the 3 or 4 pin on the preamp socket out, Yellow_Light_Colorz_PDT_14 I have to use the chassis to get my ground for my meter The bias supply has 100mfdx100v caps that had been installed and diode should thay be 47mfd ?
Thanks

Hi jshull,

Increasing the 47uF bias caps to 100uF won't cause you any problem.

Assuming you have about -50V on the grids, the EL34s are probably shut off, as far as cathode current, so you won't really have any voltage across the bias 'current sense' resistors. Have you powered up the whole amp to take voltage measurements or are just looking at the bias supply?

Go ahead and take all the voltage measurements from the sheet in the manual and post them.

Shannon