Viewsonic P220f still on it but flying in the dark with no schematic.QH07 and QH08 are a complementary pair in the horiz ckt and attached to each other but since removing them and marking them I am having second thoughts of whether I put them back correctly. Anyone have a schematic that they could look at for me. They are BD140 and BD139 transistors. Many thanks
On 11 May 2005 15:44:08 -0700, "gstringe" put finger to keyboard and composed:
I'm not familiar with your monitor, but are you sure this transistor pair is part of the horizontal circuit? I normally see such arrangements in the vertical output of old TV sets. Either way, I expect the BD139 (NPN) to connect to the positive rail, and the BD140 (PNP) to connect to ground or negative rail. Are the two emitters and bases tied together?
Follow the direction of current flow in the external circuit. Current flows from E to C in a PNP transistor, and from C to E in an NPN transistor. Transistor pinouts are BCE in both cases.
- Franc Zabkar
-- Please remove one 's' from my address when replying by email.
Thanks Frank, So far what I see on the pc board is that the parts have a letter designating the circuit they are part of, hence the H for horiz. This goes for all the parts, caps, resistors, coils etc.
I really haven't traced the circuit to look for the power connection as I figured someone with a schematic would be easier but I guess I am getting lazy in old age ;-)
On 12 May 2005 07:27:12 -0700, "gstringe" put finger to keyboard and composed:
Could the transistors be from some kind of horizontal centring circuit?
Can you power up the monitor in the absence of the transistors? If so, then measure the voltages at the pins. That should tell you which way the current flows.
- Franc Zabkar
-- Please remove one 's' from my address when replying by email.
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