VR241 Service Manual?

[Rob Jarratt]

> -----Original Message-----
> From: tony duell [mailto:ard at p850ug1.demon.co.uk]
> Sent: 05 June 2016 15:12
> To: rob at jarratt.me.uk; General Discussion: On-Topic and Off-Topic Posts
> <cctalk at classiccmp.org>
> Subject: RE: VR241 Service Manual?
> 
> 
> 
> > Does anyone have a VR241 Service Manual?
> 
> > I have looked on Manx and BitSavers, but there doesn't seem to be one
> > available in those places, and a more general search has failed to
> > turn up anything either.
> 
> It's also not in (for example) the VT240 manuals. The VR201 is, but said
> manuals specifically refer you to a VR241 documentation set.
> 
> What do you need to know? I've reverse-engineered the schematic and can
> send you that, but if you do delve inside (a) Good Luck and (b) be very
> careful. IIRC there is mains where you might not expect it.

The screen basically works, but it won't go black, it is as if the
brightness is turned up, and I get some diagonal lines when the brightness
is turned up a bit more. I want to know how to take it apart to check the
electrolytics. I have partially dismantled it but I am struggling to take it
apart further, for fear of forcing something and then breaking it.


> 
> It's a Hitachi chassis, and it shares some feautures with Hitachi
televisions of
> the period. There is a thick-film hybrid module in the middle of the
deflection
> board. It contains the sync/oscillator IC and the vertical output stage.
The IC,
> output transistors and a few other componets are soldered to the module,
> the resistors are thick film traces.
> 
> The power supply is evil. It's a switcher, and it runs off the _horizontal
> deflection_ oscillator. So for the power supply to run, the horizontal
> oscillator, horizontal output, flyback transformer, etc must all be good.
> There is a little multivibrator on the PSU board to kick the thing into
life when
> you turn it on.
> 

Thankfully the PSU seems OK, but if I can get the whole thing apart I can
check all the capacitors.

Thanks

Rob