You're currently viewing posts by Pinsider mbwalker.
Click here to go back to viewing the entire thread.
Two diodes, if the same, allows for higher current handling capability. Don't know if that was the reason for doing that - I would have thought the manufacture would have just used a single diode rated for higher current.
The pictures do look like someone added it later. Won't hurt anything tho.
Quoted from Grizlyrig:Unless it fails internally and now becomes a two way street instead of one way. This is a problem waiting to happen, you have no way of trusting this hack.
-Mike
Mike,
True - but that's also true of a single diode.
Simplest thing to do is just check the schematic.
Quoted from vid1900:I've seen that when one diode is open, the tech simply installs another along side of it without snipping the old.
Maybe whoever routed the game just did it as cheap insurance (easier to slap in an extra 10 cent diode rather than the hassle of going out for a repair
to replacing a transistor).
cmack - How did you test Q21? I'd be tempted to start with the basics and look for shorted wires, bent mechanicals touching a connector, etc. What else is on the line w/that fuse which is blowing?
So if the 40 pin connector is removed, does that isolate the MPU from the driver? The driver from the solenoids? Sorry - don't know what game this is for.
Quoted from MrBally:Never power up a System 7 (Early Williams SS) with the driver board disconnected from the CPU Board. Unless you like the Essence of Allen-Bradley smell that will eventually cause the high wattage resistors to fall off the Driver Board after the solder melts on the through-holes.
It's OK for 30 seconds -1 minute. If you walk away, it won't be pretty......
I think I may have misquote what cmack was going to do - which sounds like remove AND CHECK the connections, not just remove. Oops..apologies about that.
Quoted from cmack750:....
At this point, I'm comfortable saying I've found the Solonoid that was causing my fuse to blow. ...
Cmack,
Sorry, this thread got lost in my list and missed it!
I don't have a schematic in front of me, and I admit I'm flying by the seat of my pants here.
One other test you could run is to measure the solenoid resistance and see if it's proper.
Also, using a meter only checks the diode at low voltage. It could be breaking down at the high voltage that runs the solenoid. Might be a very long shot, but it is something to consider (but I would think it would be damaged and actually measure bad). Nonetheless, food for thought.
Q17 - and the odd measurement... With the EB reversed biased, you should read ~8K ohm (see the attachment), reversing the leads, you should read the forwarded biased diodes. One catch is you might have to put the multimeter on diode setting to measure the forward biased diodes. Another might be measuring two diodes that's in the transistor. Perhaps the meter struggles with that.
Work will have me tied up and might not be able to check back for a few days. In the end, all the parts in question are rather cheap...might be easier to 'shot gun' it and just replace the diode, transistor and coil.
You're currently viewing posts by Pinsider mbwalker.
Click here to go back to viewing the entire thread.
Wanna join the discussion? Please sign in to reply to this topic.
Great to see you're enjoying Pinside! Did you know Pinside is able to run without any 3rd-party banners or ads, thanks to the support from our visitors? Please consider a donation to Pinside and get anext to your username to show for it! Or better yet, subscribe to Pinside+!
This page was printed from https://pinside.com/pinball/forum/topic/coil-diode-madness?tu=mbwalker and we tried optimising it for printing. Some page elements may have been deliberately hidden.
Scan the QR code on the left to jump to the URL this document was printed from.
