Re: Lights dim when flipping flippers :(

OK, got some info gathered, found at least 1 likely bad part, and have
a plan of action here. Let me know if I've done things right
regarding the rectifier board.

First, with the pin on, I tested all the test points. TP 2,3, & 4
were fine, within range. However, TP1 shouldn't read higher than
7.2v, but it read as high as 7.5v. Am I still OK there? Then, on
TP5, I shouldn't have a reading lower than 47.6v, but my reading was
around 45.4. How am I there?

Moving beyond that, I checked all the solder points on the back of the
board, all the pins and connections seem good. This is a -54
rectifier board, so I didn't find any mods done, nor are there any
that can be done according to clay's, I think.

I then went over the fuse clips, sure enough the 15 and 20 amp clips
are darkened, but there is still a connection there. I do plan to
change them, but I doubt that is causing any immediate problems.
Correct me if I'm wrong.

Also, on the back of the board I found 2 areas that were brown/burnt.
The one area is where those 4 3a diodes are that notoriously do get
hot. Despite them getting hot and browning the board, they did test
within the .4 to .6 range. So is there still an immediate need to
replace them

Now, here is where I think I definitely found an issue. Resistor R1.
The area under it is browned/burnt. On the continuity test, I got
nothing. Not being sure if this is normal for a transistor, I tested
continuity on the R2 resistor and there was indeed continuity. Since
this one looks healthy, and looks just like the R1 resistor but
smaller, I assume the R1 should have continuity.

So I pulled out the manual to check the values for the resistors. I
tested R2 first, according to the manual it should have 25 ohms. I
figured I would test this just like I tested the test points, except
the DMM is set to ohms (auto). I put the back lead of my DMM on the
ground and put the red on one end of the resistor, which read zero,
then tried the other end which read 27 ohms. Consider the manual says
25 ohms for R2, I figure R2 is good and I tested it correctly.

Moving onto the suspect R1 resistor, I tried the same thing. Manual
says it should read 600 ohms. However, my test showed just half an
ohm (.500). That along with no continuity tells me this thing is
totally shot. Does anybody know what symptoms I should have if my R1
was bad?

I should also note that this whole dimming issue is definitely
something I can live with, but I'm looking to prevent future issues.
That said, I was playing a game just a few hours ago, hit a ball that
hit the bumper, drop target, and a standup in very quicks succession,
then the game kinda half died on me. The score reset to zero and some
of the PF lights that were lit went off. Flippers were still
working, shot the ball into the kicker and never kicked out, things
were definietly screwy. On top of that, I noticed this thing where I
don't get any scoring sounds at times, often after I hit the captive
ball target I will lose all scoring sounds for a minute and then they
end up coming back.
Have no idea what is up with the sound thing, but the first issue I
described definitely screams of a power issue.

lastly, I noticed these bridge rectifiers use thermal paste. I have
lots of that from working with computers and this stuff looked so old
and dried up. I will definitely get new paste on them, but I'm not
expecting that to fix anything other than hopefully having a little
less heat on the board.
.

Relevant Pages

  • Re: Lights dim when flipping flippers :(
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