G05-801 no HV

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Have 2 x G05-801. One is working and one has no HV.

The non-worker has a slightly different HV PCB layout compared to the working one. The working HV (and the rest of the boards of the monitor) seems to compare to "issue 1" of the manual and maybe versions above that.

C902 on the working board is a tantalum capacitor @ 100uF (according to "issue 1 manual" whilst on the non-working board, there is a 22uF capacitor on the parts side and one on the solder side (2 x uF), but there are other differences of the layout as well. I have isolated the problem with the high voltage to the cage since when I swap in the other HV cage it works. I've tried switching the HV doubler between the cages without success as well as the 2 x chassis transistors on the HV cage has also been swapped with the working one.

I've also replaced the 3 electrolytic capacitors, C901 (47uF/50V) was open circuit.

Game board is working, spot killer is off, chatter is there, neck glow is there.

The black and white vector/x-y guide mentions a "preliminary issue of the G05-801 manual, anybody who has scan of that or a link?

The input voltage of +25V is there on the connector of the HV cage but the other voltages are missing (like +90V, +400V and focus voltage) and they are present on the working HV cage.

Measured +25V at base of Q900 (+18V on the working board).

+9V on the anode of ZD900 on both boards.

Ideas of what to troubleshoot next is appreciated! :)
 
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Show the differences in the layout.

Usually no hv on these means a bad voltage doubler. (Which is not an off the shelf part, but someone here did repro them. I think jkoolpe sells them.)
 
Show the differences in the layout.

Usually no hv on these means a bad voltage doubler. (Which is not an off the shelf part, but someone here did repro them. I think jkoolpe sells them.)
I swapped the voltage doubler from the working cage to the non-worker, made no difference (and the working cage is still working).

Atari's The Book and the BW FAQ points to either open Q900, Q902, Q903, R906 or T900 when base of Q900 measures 25V. All of those, except T900, have been swapped with the parts from the working HV unit.

I will take snapshots next time I'm in the workshop of the differences. There's a few components on one of the units that have been soldered to the solder side and don't have a location on the parts side. So it seems one of them is earlier than the "issue 1" but has been "upgraded" to "issue 1".
 
Non-working HV cage/board.
 

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there are a few high voltage diode in the cage, that can give problems of not HV
i have had these D901 and D902 go bad
replaced both and got it all working again.
check P900 pin 1 , 3 & 5 for correct voltages
 
Catching up on old notifications I missed while on vacation over the summer.

Did you ever get this fixed?

Thanks for the HV pics. The non-working one is an Issue 4 layout, vs Issue 5 on the other one. (Note the Issue number is silkscreened on the solder side).

I went back and checked my records, and I have actually never seen an Issue 4 HV. I wonder if they only made their way to Europe. I didn't go through each component, but it looks like they might have been factory-modded, with the changes that eventually became Issue 5.

Regardless, the most likely thing is still the doubler, as that tends to be the common failure in these.
 
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