[sdiy] Boss DR110 weak display

[Harry Bissell]

Q17 is the bias circuit for the LCD, it should be 1/3 the supply voltage. I checked the online
docs and it seems that the hitachi processor chip is responsible for setting the LCD column pins
to 25% duty cycle, 1/3 Vcc or something like that..

H^) harry 


----- Original Message -----
From: mike schmidt <itsfatmike at gmail.com>
To: Harry Bissell <harrybissell at wowway.com>
Cc: synth-diy at dropmix.xs4all.nl, Gil W. <gil_we at yahoo.com>
Sent: Mon, 25 Jul 2011 10:11:55 -0400 (EDT)
Subject: Re: [sdiy] Boss DR110 weak display

Harry, that was my first thought, but in my glance at the service manual I
didn't see a bias supply circuit.

On Jul 25, 2011 10:07 AM, "Harry Bissell" <harrybissell at wowway.com> wrote:
> "I'm not a doctor, although I play one on TV..."
>
> Is it possible that the LCD bias supply was damaged as part of the battery
leak, and the display is actually OK but the
> setting of the viewing angle is totally wrong (perhaps 'off-screen' so to
speak) ?
>
> H^) harry
>
>
> ----- Original Message -----
> From: Gil W. <gil_we at yahoo.com>
> To: synth-diy at dropmix.xs4all.nl
> Sent: Sun, 24 Jul 2011 03:15:48 -0400 (EDT)
> Subject: [sdiy] Boss DR110 weak display
>
> Hi all.
>
> I've been fixing a DR110 which had battery leakage. Some acid drops here
and there, basically I think it is fixed now as it powers up and all buttons
responds and it sounds and functions as it should with no seen issues.
>
> The only problem is that I can barely see anything on the display. I first
thought that there was nothing displayed at all, but then I noticed that it
does show faint marks, which are seen better as I enlarge the viewing
angle... it looks like it does show the correct data, once viewable.
>
> The power adapter I'm using is 9v/880ma so I see no problem with that... I
also tried batteries - 4 x 1.5v and a 9v. With the 9v battery the display
marks are better seen, but still not fully, and the strength of display
changes with the preset... Inside, the operating voltage as it should - 5.4v
>
> Are the LCD displays (such as in the DR220/TR707 etc) known as tending to
get weak over the years and need replacement ? any idea what could cause
that and what should else be checked ?
>
> Thank you very much for your help!
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> --
> Harry Bissell & Nora Abdullah 4eva
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-- 
Harry Bissell & Nora Abdullah 4eva