Oscilloscope problem.
 

I have a Hung Chan 6502 20MHz cro that is proving rather difficult to
repair. Apparently it is also known as a Protek 6502.

The fault is that the trace is only just visible with the brightness on
full. This one has me baffled.

Any advice would be greatly appreciated.

Cheers,

Dan

Oscilloscope problem.
 

On 8/26/07 4:13 PM, in article
, "Dan Stephen"
wrote:

I have a Hung Chan 6502 20MHz cro that is proving rather difficult to
repair. Apparently it is also known as a Protek 6502.

The fault is that the trace is only just visible with the brightness on
full. This one has me baffled.

Any advice would be greatly appreciated.

Cheers,

Dan

I'm not at all familiar with that scope, but....... Do you have access to
the crt cathode, aka Z axis, control? Maybe you have a link, jumper, or
other Z axis option mis-set.

Oscilloscope problem.
 

On Aug 26, 6:13 pm, Dan Stephen wrote:
I have a Hung Chan 6502 20MHz cro that is proving rather difficult to
repair. Apparently it is also known as a Protek 6502.

The fault is that the trace is only just visible with the brightness on
full. This one has me baffled.

Any advice would be greatly appreciated.

Cheers,

Dan

Do you have a schematic? Check the various voltages on the CRT. If
you have a high-voltage probe, measure the accelerator voltage -
carefully!

H. R.(Bob) Hofmann

Oscilloscope problem.
 

Dan Stephen wrote in message
...
I have a Hung Chan 6502 20MHz cro that is proving rather difficult to
repair. Apparently it is also known as a Protek 6502.

The fault is that the trace is only just visible with the brightness on
full. This one has me baffled.

Any advice would be greatly appreciated.

Cheers,

Dan

Is the trace equal illumination over the whole trace or is there an X-axis
gradation in the brightness of trace?
Is the trace constant in brightness or wavering?
Did it suddenly emerge as a problem or gradually over time?
Is the trace of the correct geometry, X and Y sense, for a test signal input
? if it is correct then not an EHT problem

I would suspect leakage/failure in something in the blanking/un-blanking
area (eg opto-coupler high R resistor) or a "sub bright" preset failure.

--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/