So I pulled down my RFM; pretty-much a full rubber and cleaning job, plus flipper rebuilds.

Everything went well, but now I have a F107 error (upper right flipper channel on the power board) and the LED is out. The fuse is NOT blown.

However, according to the book F107 (normally upper right flipper, but there is none on this game) is wired to the ramp -- and the ramp is working! Further, all the coil tests in diag mode work.

Uh...... how's the ramp working without power?

I can't find an actual fault in game play, operation or when going through the coils in diags... but the credit dot is there, the F107 error is in the diags, F107 shows as "blown" and the LED *is* out. I pulled the playfield and powered it up and the LED remains off, so whatever is going on it has to be on the power board.

What am I missing?

No, that doesn't make sense and the ramp was not molested during the re-rubber and cleaning. The flippers are fine, and the error is on F107, which is the upper right flipper channel -- and which the book says is connected to the ramp. But... the ramp works (both power and hold) as do both flippers! I can't find a fault in game play, but the F107 error is *real* despite the fuse being good -- the LED is off and with the playfield disconnected and removed from the box it's still unlit. The fuse itself is NOT blown, but with no LED the assumption has to be no power to that circuit -- yet there obviously IS power, or the ramp wouldn't work -- but it does.

I did have an EOS switch problem on the right side originally but the diags nailed it (properly so) and it was easily corrected, never mind being on the other (connected flipper) channels. And that channel (right lower flipper) is fine and working properly.

How can you have power on a circuit yet both the "test" and LED for it shows "nil"? That makes no sense at all.

This is very bizarre. Looking at the schematics for the power board all four of the flipper power circuits are fed from one set of contacts on the enable relay, go through their respective fuse holders (4 of them) and then to the connector that goes to the playfield. Nothing fancy there. The LED is tapped from the output side of the fuse holder, goes through a dropping resistor, has a shunt (47k) resistor to ground (presumably to present some load if the LED itself fails) with the drive from the dropping resistor also going to the circuit (comparator and buffer/line driver) that is used by the game to monitor circuit status.

The only way I can see that the LED can both be out and the game think the circuit is dead when it's not (the load, in this case the ramp solenoid) working is if the dropping resistor is open. If the LED (or its ground) fails the monitor still says it's good and if the comparator fails (beyond the LED) the LED is lit but the CPU says its not. I guess the board has to come out to see if it was just an odd coincidence (vibration, etc) that resulted in a bad solder connection or similar on that dropping resistor, as I cannot see any other way that the LED can be out and the game think the channel is dead when it is in fact not. Thus, today's project is born.....

It appears the actual LED *itself* failed! I'm pulling the board now and will update; there's ~1.7V on the output side of the other LEDs dropping resistors in that chain (from the ~68VDC nominal feed for the flipper coils) but close to 58V on the output side of this one, which basically means zero current drain through that resistor (other than the comparator's resistor bridge) -- and voltage is correct everywhere else (including when driving the coil itself.)

Now why the comparator says the fuse is bad when it's not but the LED is out is another question. That's unexpected behavior; let's hope the comparator's channel didn't get toasted by the dead LED and resulting (way high) voltage on the output of that original bridge.....

Interesting.

The LED was definitely bad -- de-soldered it and tested; open both ways on a diode test. Replaced it with all I had handy, which was a high-output one intended for Sega/Stern opto boards; they're all roughly the same (e.g. 20ma max current draw, same drop across the junction, etc) and it both lights (brightly, of course!) *and* the fuse test now says good.

Now here's what I don't get -- the comparator saw over 50V (!!!) with the LED not functioning, which is *wwaaaayyyy* beyond it's Vmax on any of the input pins. It should have been destroyed, but wasn't -- and that's a good thing, given that I really don't enjoy de-soldering and replacing DIP ICs (and these are not socketed.)

If you run into one of these games alleging a fuse is open, it's not, and the controlled circuit is working the likely culprit appears to be the LED itself. If I have some "regular" red LEDs laying around some day I may put the "right" one back in, but since voltages are all in-range now, the LED is lit and the self-test is happy I'm inclined to leave it alone rather than do the de-soldering thing once again.