CurtPalme.com Home Theater Forum

[thelasernut]

Following my earlier report that my poor old BG808s had started to loose picture if a sudden onscreen highlight ocurred - such as from an explosion in a movie - I had received helpful advice ( thankyou ) to check the 17V rail and Curte suggested bad EHT components - both of which I have not been able to check so far due to lack of space in my very cluttered cinema room - but tonight the feared breakdown finally happened with a bang.

Over the past several weeks sudden picture loss was getting more frequent and I was wondering if scan failure protection was being triggered by the transient brightness signals getting past any filtering due to worn capacitors ?

However - tonight the picture was being lost with lower and lower levels of sudden whites - so I lowered contrast from normal 60 down to 10 while looking for an imagined peak white level which was tripping protection - but the problem rapidly got worse untill picture loss was occuring while the CRT's were warming up and the picture had not reached full size - but following a loud flashover "bang" the EHT did not give a picture any more.

Trying to analyse as these faults developed - the following observations were made -

1) Despite picture loss occuring with SUDDEN bright screens - normal pictures with contrast set to maximum did NOT cause picture loss

2) I wondered if Darbee was agravating the situation by its Contrast Enhancement giving higher levels of "sudden bright whites" - it seemed not

3) At all times the picture was present there was NO loss of Focus or Size as would occur with varying voltage - so EHT was normal and stable

4) The final flashover and loss of EHT suggests an insulation breakdown - although I have not been aware of Ozone smells from the EHT system

I guess I'm going to need some EHT spares if cleaning ( not done for years ) does not resolve any breakdown paths which exist - also I guess the age of the projector means it's probably wise to look for worn or damaged electrolytic capacitors as all CRT's are good and still in unmarked condition

Regards

[deronmoped]

Don't assume that the obvious symptoms will lead to the cause. I have found this out over years and years of fixing things. If you keep looking for the failure in one area and can not find it, look elsewhere.

[Curt Palme]

You need an HV quad and/or splitter. Neither can be tested due to the high voltages, you need to swap them out. It has nothing to do with the input signal or the way the projector is set up.

I have both splitters and quads, but it will be October before I will be in town long enough to sell them.

[Curt Palme]

You need an HV quad and/or splitter. Neither can be tested due to the high voltages, you need to swap them out. It has nothing to do with the input signal or the way the projector is set up.

I have both splitters and quads, but it will be October before I will be in town long enough to sell them.