Tech: Intermittnet transistor?

Archived from groups: rec.games.pinball (More info?)

Swap the flipper opto board to the other side. Does the problem move?


C.W.H. wrote:
> Hello folks!!
>
> Quick question wpc-s
> flipper completely rebuilt and it sticks up sometimes...
> 6 or 8 flips and up it stays...
> turn off the game and down it goes....
>
> I've been to Marvins and I don't question all that info but does it ~really~
> happen?
>
> Can a transistor be "sometimes" shorted?
>
> Thanks
>
> Chet

Archived from groups: rec.games.pinball (More info?)

C.W.H. wrote:
> Hello folks!!
>
> Quick question wpc-s
> flipper completely rebuilt and it sticks up sometimes...
> 6 or 8 flips and up it stays...
> turn off the game and down it goes....
>
> I've been to Marvins and I don't question all that info but does it ~really~
> happen?
>
> Can a transistor be "sometimes" shorted?

I've never seen that type of failure mode in a transistor. I've seen
transistors fail to an always short, I've seen them fail to an always
open, and I've seen them fail so that they're neither fully shorted nor
open (meta-state). But I haven't seen a failure mode of sometimes
shorted.

(And I've yanked a LOT of transistors!)

I'd put my money on a bad opto first. After all, the flipper needs to
move when there's an _absence_ of light on the receiver; a bad opto (or
dirty or one with a broken solder joint) can easily cause this kind of
symptom.

Swap your flipper opto boards, see if the problem moves with it.

Archived from groups: rec.games.pinball (More info?)

May times i have had a flipper transistor stick once it is activated.
Usually it's a predriver transtistor and not the main driver.

"C.W.H." <84insulation@earthlink.net> wrote in message
news:wMQwe.13954$pa3.11335@newsread2.news.atl.earthlink.net...
> Hello folks!!
>
> Quick question wpc-s
> flipper completely rebuilt and it sticks up sometimes...
> 6 or 8 flips and up it stays...
> turn off the game and down it goes....
>
> I've been to Marvins and I don't question all that info but does it
> ~really~ happen?
>
> Can a transistor be "sometimes" shorted?
>
> Thanks
>
> Chet
>
>
>