WPC Sys 11 Power Supply question

[Guest]

Archived from groups: rec.games.pinball (More info?)

I'm having a problem with a High Speed which continually resets during
gameplay. Testing the power supply shows the 12v supply as being ok,
but the 5v as being low (about 4.7v).

I've replaced the cap at C8 (47mfd, 50v) and found no change.
Switching the BR at BR1 seems to have caused the voltage to drop a
little lower (about 4.5v). A little later I had 0v on the 5v supply.

After some inspection, I found what appeared to be a short on the
traces under BR1. I had a heck of a time soldering on the BR1 with the
lug connectors and ended up using a little too much solder. I removed
the BR1 and cleaned up the mess, then reinstalled it. Again, 0v.

How susceptible are bridge rectifiers to heat damage? I'm beginning to
wonder if I killed the BR when desoldering it.

I've attempted to locate info on testing BRs and couldn't find much
info. The best article I found indicated a diode tester could be used
between the + and ~ leads and should result in a .6 reading. Reversing
should produce a high reading. This isn't the case the BR I have or
the original BR I removed. Is this info accurate?

I'm also planning to replace the cap at C10 (18000mfd, 20v), but would
like to straighten out the BR problem first.

Any suggestions would be appreciated.

Thanks,
Bob

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

hi Bob,


If The 12 v UNREG was OK there was nothing wrong with the BR
1 see TP3 read notes from schematic please point nr.3
BR are not sensible at solder heat but at a short on output one
or two diodes burned fast
you can test easy the BR with a DM taking care for the signs on
the BR +, - , VAC , VAC as You mentioned before ,,,,,,,,each
diode from the BR
you can messure some voltages on schematic the out 5 v is
adjustable from R7 , R8 if you install a proper SR ( a 10 K SR
instead of R7 R8 )you can easy adjut it

may check the output cap C12 or better change it !!!

Marius

" the pinball Doctor from Dracula 's country Romania "

site updated :
http://www.pinball.ro/tvgamecabinets.htm

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

"Bob D" wrote:
> I'm having a problem with a High Speed which continually resets during
> gameplay. Testing the power supply shows the 12v supply as being ok,
> but the 5v as being low (about 4.7v).

You may want to take a brief look at the article on our website about reset
problems- causes and solutions- may be something there that you can quickly
check or something obvious you may have overlooked- it's at:
www.actionpinball.com in our Technical Articles section.

> I've replaced the cap at C8 (47mfd, 50v) and found no change.
> Switching the BR at BR1 seems to have caused the voltage to drop a
> little lower (about 4.5v). A little later I had 0v on the 5v supply.
>
> After some inspection, I found what appeared to be a short on the
> traces under BR1. I had a heck of a time soldering on the BR1 with the
> lug connectors and ended up using a little too much solder. I removed
> the BR1 and cleaned up the mess, then reinstalled it. Again, 0v.

Don't suspect a bad bridge- I've found a few bad components right "out of
the box". Easy and quick to check before installing.

Also, on these old "lug" type rectifiers, it's better/easier to just scrap
them and replace with a standard wire lead rectifier- one of the heavier
duty 35 amp 400 volt units (rather than original 25 amp 200v wimpy unit).

> How susceptible are bridge rectifiers to heat damage? I'm beginning to
> wonder if I killed the BR when desoldering it.

Heat won't really do much to a big bridge like this- it can usually take it.
Could be that handling of the bridge may have worked something loose inside,
or installing backwards can short it out or open it up internally. Or the
work on the circuit board around the bridge may have caused an inadvertent
open circuit- scratch to a trace or something- easy to check continuity
into, and away from, the bridge with an ohmmeter just to be sure.

> I've attempted to locate info on testing BRs and couldn't find much
> info. The best article I found indicated a diode tester could be used
> between the + and ~ leads and should result in a .6 reading. Reversing
> should produce a high reading. This isn't the case the BR I have or
> the original BR I removed. Is this info accurate?

Yes. You can also use an ohmmeter to test. Basically a bridge has 4 diodes
inside it. Start at one of the AC lugs- leave red (pos) lead on that one.
Then test the two DC leads on either side of it. You should get continuity
in one direction (about a 0.700 reading in diode test) and reversing the
leads should show an open circuit (no continuity). Work your way around the
bridge to the other AC lead on the opposite side doing this testing. If you
get continuity between two leads in either direction (swapping leads
red/black) then that is a short. If no continiuty in either direction, then
that diode is open. Bad bridge either way.

May be some more info on this at: www.marvin3m.com/fix.htm Only so much I
can describe here in words and with fingers getting tired from typing...

> I'm also planning to replace the cap at C10 (18000mfd, 20v), but would
> like to straighten out the BR problem first.

Extremely good idea to replace the cap. Original replacements (same values)
are no longer being made, but we use 15,000uF 50v radial cap (both leads on
one end) and tie-wrap this into position on the board, then run jumper leads
from the lugs on the cap, to the appropriate locations on the board. Very
good replacement cap and we do this on all of the old games like this
whenever we run across one with problems or that still has original parts.
Original parts (rectifier and large caps) don't hold up well under old age-
replace to eliminate them as any possible cause of future problems.

> Any suggestions would be appreciated.

I'd get the continuity problems worked out with the bridge first, and
possibly replace the bridge if it's questionable. And install a new C10
cap. Beyond that, you may have a bad IC7(?) which is the IC on the board
that controls the voltage regulation. I have seen one or two of these go
bad on these games recently where the 5.0vdc drops just a bit too low-
barely into the questionable range (4.85 or so) and that's just enough to
put the game into the range of resetting when it feels like it. It's an
LM723- 14 or 16 pin DIP IC. Install a chip socket under it if installing a
new one, to ease in future replacement/troubleshooting.

Ray J.
--
Action Pinball & Amusement, LLC
Salt Lake City, Utah USA
Web: www.actionpinball.com

We're serious about pinball. Anything else is just for fun!

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Ray,

> Yes. You can also use an ohmmeter to test. Basically a bridge has 4 diodes
> inside it. Start at one of the AC lugs- leave red (pos) lead on that one.
> Then test the two DC leads on either side of it. You should get continuity
> in one direction (about a 0.700 reading in diode test) and reversing the
> leads should show an open circuit (no continuity). Work your way around the
> bridge to the other AC lead on the opposite side doing this testing. If you
> get continuity between two leads in either direction (swapping leads
> red/black) then that is a short. If no continiuty in either direction, then
> that diode is open. Bad bridge either way.

Looks like my BR is testing out ok. I've replaced the original with a
35amp 200v. I'll note for next time that I should get a 400v.

> May be some more info on this at: www.marvin3m.com/fix.htm Only so much I
> can describe here in words and with fingers getting tired from typing...

LOL I know what you mean. I have been using the info at
www.marvin3m.com/fix, I love that site

> I'd get the continuity problems worked out with the bridge first, and
> possibly replace the bridge if it's questionable. And install a new C10
> cap. Beyond that, you may have a bad IC7(?) which is the IC on the board
> that controls the voltage regulation. I have seen one or two of these go
> bad on these games recently where the 5.0vdc drops just a bit too low-
> barely into the questionable range (4.85 or so) and that's just enough to
> put the game into the range of resetting when it feels like it. It's an
> LM723- 14 or 16 pin DIP IC. Install a chip socket under it if installing a
> new one, to ease in future replacement/troubleshooting.
>
> Ray J.

I've replaced the cap with a 18000uF 25v radial cap. So far, no
difference.

I started out with 4.7v on the 5v PS and had encountered occasional
reboots. I followed the following steps thus far:

1) Replaced the cap at C8 (used a 47uF 100v) - No difference in output.
2) Replaced the Darlington transistor at Q5 (used a 2N6057).
3) Replaced the BR at BR1 with a 35 amp 200v lug mount. - No output on
5v supply after this step.

4) Removed the BR and checked it based upon the info on your last post.
It tested fine. I had some 35amp 200v lead BRs I bought awhile ago.
I decided to install one of these. This time the machine makes a LOUD
hum when powered up. I've verified the installation (location of +
lines) about 6 times, it's installed correctly. Oddly, I've had
EXACTLY the same problem with others in this batch. They test ok,
though. Put the lug lead BR back in. No hum, but no voltage from the
5v supply.

5) Replaced the cap at C10 (used a 1800uF 25v radial. - No difference,
no output on 5v supply.

6) I've searched for continuity problems going to the BR. I see no
visible damage and continuity between seems good.

I'm stumped. I haven't replaced the MC1723C at IC1 because I haven't
been able to locate a replacement. Is it possible this component
failed as I was working on the board? Any suggestions on where I could
find one of these?

Thanks!
Bob

 

[Guest]

Archived from groups: rec.games.pinball (More info?)

Bob D wrote:
>
> I'm stumped. I haven't replaced the MC1723C at IC1 because I haven't
> been able to locate a replacement. Is it possible this component
> failed as I was working on the board? Any suggestions on where I could
> find one of these?

I don't know that it is your problem, but it shouldn't be too hard
to find...just a 723 voltage regulator, the National Semi part number
would be LM723, other mfr's may have different prefixes.

--Bob

=======================================================================
Bob Ellingson bobe@halted.com
Halted Specialties Co., Inc. http://www.halted.com
3500 Ryder St. (408) 732-1573
Santa Clara, Calif. 95051 USA (408) 732-6428 (FAX)