Electronics > Repair

Hameg HM604-3 problem

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Davey:
There is a problem with this scope of no control of brilliance. I have checked the internet for a circuit, but although there are circuits, they are not the version I want. The scope I have has a switched mode PSU and the circuits I have found have a linear PSU. If someone can point to a link to a circuit, or a known solution, it would be most welcome. Thanks

Zenith:
I can't help with the manual.

I'd guess that most of the circuitry is similar to HM604 scopes with linear power supplies. A common cause of problems with brilliance in scopes is that the pot that controls brilliance is in the centre of a chain of resistors which have a high voltage across them and one of the resistors is open circuit. The resistors have values of several megohms. Check them and if they are bad, replace them with resistors with a suitable high voltage rating, which are available from Farnell etc.

It's also possible that the pot is faulty, but that seems to happen less often.

Wallace Gasiewicz:
https://www.eevblog.com/forum/repair/hameg-303-5-horizontal-axis-troubleshooting/msg5059750/#msg5059750
Perhaps read this

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