Re: 485 super weak brightness control


Mlynch001
 

On Wed, Mar 17, 2021 at 08:45 AM, Ondrej Pavelka wrote:


On Tue, 16 Mar 2021, 22:42 Ozan, <ozan_g@erdogan.us> wrote:




I checked the DC recovery diodes in the HV supply as listed in other
thread

(all under the plastic cover and they are ok.
Any other suggestions?
Note that checking the leakage of those diodes is important, just a DVM
diode check doesn't discover problems.
I would second this part of the post. I had a similar failure on a 475 and traced it to a bad restorer diode. The only way that I was able to locate the problem was using a 5 On Tue, 16 Mar 2021, 22:42 Ozan, <ozan_g@erdogan.us> wrote:


I checked the DC recovery diodes in the HV supply as listed in other
thread
(all under the plastic cover and they are ok.
Any other suggestions?
Note that checking the leakage of those diodes is important, just a DVM
diode check doesn't discover problems.

I would second this part of the comment. I had a 475 with a similar failure and symptoms. A simple DMM diode test showed the diode as “good”. When I removed it and tested it on the 576 curve tracer the problem became apparent, as soon as I checked it on the CT, it exhibited a very strange breakdown at higher voltages. So replacing the diode and associated capacitor with a known good diode and capacitor repaired the problem.

--
Michael Lynch
Dardanelle, AR

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