(Topic ID: 247058)

F114 and F115 failure w/ bad voltage levels


By narflex

5 days ago



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  • 21 posts
  • 7 Pinsiders participating
  • Latest reply 1 day ago by narflex
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#1 5 days ago

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.

#2 5 days ago

Ok. A little bit confusing, but don't read too much into it. Keep in mind that the unregulated voltages can be quite a bit different. Are you having a particular symptom with the 50VDC coils? If not, then the 70VDC reading can be ignored. My Williams games all measure on the higher side on this unregulated branch.

I would recommend zooming in on the obvious: the missing +12VDC. Don't worry about the other differences in voltage. They can be normal, or they can be entirely unrelated problems. A completely absent supply voltage IS a problem.

I'm not sure if I can give you enough info because I do not have a Rottendog board, but fundamentally it is probably not too much different than a stock board. There is a diagnostic process for the stock board on the repair guides.
See "Check fuse 114/115' section:

http://www.techniek.flipperwinkel.nl/wpc/index2.htm

#3 5 days ago

The fuse clips on RD boards are always suspect.
Make sure that you have consistent power on both fuse clips...not just the fuse casing.
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

#4 4 days 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.

#5 4 days ago

That’s not the likely cause. The small 100uf @ 25V capacitor next to the regulator has probably exploded and ruined a trace on the top side of the board.

I’ve made this repair so many times, I can do it with my eyes closed.

#6 4 days ago
Quoted from snyper2099:

I’ve made this repair so many times, I can do it with my eyes closed.

Until you burn your hand

D0DfIqkV4AAuHyV (resized).jpg
#7 4 days ago
Quoted from snyper2099:

That’s not the likely cause. The small 100uf @ 25V capacitor next to the regulator has probably exploded and ruined a trace on the top side of the board.
I’ve made this repair so many times, I can do it with my eyes closed.

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
#8 4 days ago
rd-pdb (resized).jpg
#9 4 days ago

Board repair:

Fantasy:
fantasy (resized).jpg

VS.

Reality:
real (resized).jpg

#10 4 days ago

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

#11 4 days ago
Quoted from narflex:

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

That point is the output of your voltage regulator so the failure is prior to that point.
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Tracing the problem back from a known bad point to a good point...

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#12 4 days ago

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.

#13 4 days ago
Quoted from narflex:

it had about a 0.5V drop across each diode

Positive lead on anode and negative lead on cathode? Your meter should measure around 0.08V across each diode, .5V seems high but not enough to assume the diode is bad.

Please pull F115 and retest the regulator output to ground.

#14 4 days ago
Quoted from narflex:

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

EEEK...After looking at your picture again, I think I had you measure the heat sinks board mount point.

Is there anyway you can get on the output leg of the voltage regulator to take a measurement? The best test you can perform at this point is to check your voltage on the output pin of the regulator.

#15 4 days ago
Quoted from Pin_Guy:

The best test you can perform at this point is to check your voltage on the output pin of the regulator.

I thought he already checked the in and out of the regulator and found voltage in, but none out. You dont have to get directly on the output pin of the regulator. Fuse F115 clip is the equivalent point. Looks to me like it's just a failed regulator, from what I've read.

#16 4 days ago
Quoted from Pin_Guy:

Board repair:
Fantasy:
[quoted image]
VS.
Reality:
[quoted image]

Wow... no one told her how to hold it for the pic..
So either it was not plugged, or her fingers have burned badly....

#17 4 days ago

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.

#18 3 days ago
Quoted from Pin_Guy:

Positive lead on anode and negative lead on cathode? Your meter should measure around 0.08V across each diode, .5V seems high but not enough to assume the diode is bad.
Please pull F115 and retest the regulator output to ground.

Typical silicon diode is 0.7V, 0.5V is actually about right.
But I agree with pulling the F115 fuse then trying one more time. Just need to rule out that something down the line isn't pulling the 12V to ground.

#19 3 days ago
Quoted from wayout440:

I thought he already checked the in and out of the regulator and found voltage in, but none out. You dont have to get directly on the output pin of the regulator. Fuse F115 clip is the equivalent point

Typically you wouldn't, you would only do this if you suspected a continuity problem with the board itself; the only way to know for sure if the output of the regulator is 0 is to test it at the regulator. After all, I'm sure everyone working on their machines at this level has clip on test leads. amazon.com link »

#20 2 days ago

Didn’t see you don’t have and original driver board... looks like a Rottendog from your pics. Sorry for the confusion.

#21 1 day ago

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

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