I've got a problem on my TAF machine where it gives the check F114 and F115 message. I've been through other posts here and the instructions on pinside; but am looking for more feedback before I go and start desoldering/resoldering stuff to the driver board.

Both of the fuses are fine (checked them by removing them). The +12V pad gives 0V. What's weird though is the other voltages are off. The +18V pad is giving around +16V and the +50V pad is giving around +70V. The AC input voltages from the transformer look fine...but the input to the 12V regulator is only in the low 15V range (and I've read conflicting data that says the regulator needs 15V or 17V input to function). The bridge rectifier for the 18V input tests fine (but of course that doesn't mean it works)....and while it's AC input looks fine (13.5 VAC) the output of the bridge is in the low 16V range...and this value floats around +/-0.5V which seems odd since it's connected to a cap that should be evening it out.

So I'm thinking I have one of two problems...either my voltage regulator is bad...or my bridge is bad for the +18V supply. Is seeing +16V on the +18V connection abnormal and not enough to power the regulator? If so, then I'd think the problem is the bridge...but if those values are reasonable, then I'd think it's the regulator. But then there's also the weird +70V reading for the +50V pad...so maybe there's some other weird issue going on.

I should also mention I'm using a replacement Rottendog board which I bought about 5 years ago.

OK, thanks for the info. I looked at some more datasheets for the 7812 voltage regulator and they all seemed to point to supporting input voltages of higher 14 to 15.0 volts for input; which my measurements indicate I'm above. So given that input voltage looks right and the output voltage of the regulator is zero; and I shouldn't try to read into the other voltages being somewhat off (thanks for the tip!)...I'm going to try the voltage regulator theory out and solder in a new one of those.

Did you always see visual signs of that? I took the board out to check the continuity (which all tested fine) and saw no signs of buldging/exploding of the caps near the regulator. All the continuity I checked was from either the solder or the post itself, so that should have verified all traces are fine. This is board is also only 5 years old (but yeah, I know cheap caps can explode in short order), so it's not going to have the same issues as original boards due to aging. Here's a pic of what it looks like.

TAFCapsPic (resized).jpg

I checked the point that Pin_Guy mentioned and it's 0V and no continuity to ground.

I checked those before during my testing. The input to the bottom diode was in the low 16V range (same as the +18V pad measurement like it should be) and then it had about a 0.5V drop across each diode which left it with the low 15 V range at the input to the regulator.

Pin_Guy@, yeah...you did have me test the heat sink that one time. And I checked again...the output of D2 is at around 15.5V and then F115 is at 0V. Ordered a couple regulators and will try to replace those and will report back my results after that's all done.

Pulled F115 and it's still at 0V at the output of the regulator; so I'm sticking with replacing that as the plan.

That was it, swapping out the voltage regulator fixed the problem. Thanks!