Re: T922 Power Supply Problem

Mlynch001
 

On Sun, Jul 7, 2019 at 07:17 PM, @DC912 wrote:


Thanks Michael.

I removed and tested the transistors out of circuit. All are good.

I also removed the IC, and installed a new replacement IC in a socket. No
change. Same results as above.

Should I test just the 8v circuit on the power supply board out of the scope?
Dave





Dave,

I am certainly not an expert, but if it is possible to operate the LV supply without a load, it would help you to determine if the problem lies with the supply or one of the other boards in that scope. I have restored a couple of T922/935 scopes to operation, but never had any issues with the LV power supply. Have you checked the voltages at the various components in the supply against the schematic? How about VR746? This is a 9.1 Zener that tends to fail quite often. Any of those many diodes failing could cause problems. I have seen several ZENER and other diode failures in older equipment that I have repaired, most recently in my Type 576 Curve tracer. You replaced C738,758,778 along with C722, 742 and 743 ?

--
Michael Lynch
Dardanelle, AR

Join TekScopes@groups.io to automatically receive all group messages.