Re: Gottlieb System 80 Power Supply Voltage dropping with CPU

On Apr 24, 6:08 pm, "Dan Beck" <biscuitbecks@*nospam*cableone.net>
wrote:
"Matt" <sirmisterm...@xxxxxxxxx> wrote in message

news:c17419b9-1fcd-4b12-a7d4-fa3099531939@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx





On Apr 24, 8:45 am, Matt <sirmisterm...@xxxxxxxxx> wrote:
On Apr 24, 8:33 am, Matt <sirmisterm...@xxxxxxxxx> wrote:

On Apr 20, 3:01 pm, "Dan Beck" <biscuitbecks@*nospam*cableone.net>
wrote:

"Steve Charland" <ccharl...@xxxxxxxxxxx> wrote in message

news:7LydnUmzl9N04JbVnZ2dnUVZ_judnZ2d@xxxxxxxxxxxxxx

Matt,
   What's blinking? If it's the tilt relay only (turning off and
on), then
you could have a bad game ROM or just need to reseat it. Make sure
the
notch is up like everything else before plugging the CPU board in..
If the
notch is down, the game ROM is probably toast now and you could
have other
issues on the board.

Steve
System80, not just a job, it's an adventure

Matt wrote:
Dan,

My backbox parts are completely taken off and disconnected, I just
want to get the voltage to stabilize when I hook up the CPU and go
from there.

I did replace parts and, against good advice (and with the same
curiousity that kills cats), I hooked it up again. This time
instead
of blink blink blink bliiiiiinnnkkk (dim) it just continuously
blinked...

In any event, I will be replacing the transistor and rebuilding my
power supply as soon as I get my parts on Tuesday and will report
back.

Some of this might be highly unneceesary, but I'd rather just
eliminate as many variables as possible.

Thanks.

Best,
Matt J.

Steve, I believe Matt is referring to the 5 volt LED on the power
supply
board.

Matt, certainly you want to eliminate variables by replacing old with
new,
and in my opinion I think it is a good idea in the long run, although
Clay
the gospel speaker does not think so... :-)

Please do not forget you have corroded items on your control (cpu)
control
board.  Once you solidify your power supply, when you power up that
control
board with corrosion the possibility exists that you could still see
a
voltage drop, although in my experience it is not common.  I think
while you
are waiting for power supply parts you should complete that control
board.
I remember seeing pictures of that board; it is no small undertaking
what
you have to do to get that board clean, unfortunately!

Once the control board is clean, and your power supply is known to be
solid,
then a systematic approach (i.e., one at a time) to powering up the
boards
in the backbox (as Clay and others have suggested) is a good idea.

Do you own a logic probe?  That is a handy tool.

Regards,
Dan

** Posted fromhttp://www.teranews.com**

Guys,

OK I replaced my Q3 on the power supply with a new one. Replaced CR5
per Dan at Great Plains' instructions, replaced C2 (which had rusty-
looking leads). Also socketed and replaced IC1 voltage regulator with
a new one.

Put the 5ohm 10watt resistor from test points COM to 5V test point. 5V
LED immediately dims to almost nothing. Was instructed by Dan in an
earlier post/thread to test it under a load like that.

Fixed my final corroded part on CPU, Z2, with a nice new socket and
chip. Just for curiousity's sake I powered the board, and it does the
same thing the resistor does: now the  5V LED doesn't even chug or
blink anymore, it just immediately dims.

I am going to swap out those bridge rectifiers for now until I get my
hands on a new C1, although I am fairly positive C1 is relatively new
(based on decent but clearly "aftermarket" soldering job done on it's
leads, which I haven't touched).

Thus far, I have replaced (according to pinrepair or Great Plains'
guidance):

Q3
C2
SCR1
POT1
CR5
R3
CR6
IC1

Any ideas if this rules out anything or changes directions for me?

For now, I am going to go ahead and change out those bridge rectifiers
and get my hands on a C1. I did already have the orange cap in the
cabinet replaced with a better-than-spec computer grade one.

Any ideas where to go after that, if need be?

THANKS GUYS for the help so far. I really appreciate it and am
enjoying this "adventure."

Best,
Matt

Oh and forgot to add: voltage at 5V test point with resistor load and
immediately dim 5V LED is still at around 1.5 V, same as when it would
blink and huff and puff and then dim.

- Matt

And it's Ed not Dan at Great Plains. My mistake!

- Matt

Hi Matt,

thanks for crediting Ed for the 5 ohm, 10 watt resistor idea; I knew it
wasn't mine!  That's a handy trick to know.  Thanks, Ed!

When you say "replace C1", which C1 are you referring to, the one on the
power supply, or the one on the control (cpu) board?  There was some
confusion about that in another, unrelated thread.  Anyway, C1 on the power
supply concerns itself with the 60 VDC rail, which I believe you have NOT
mentioned to be a problem.  C1 on the control board may be giving you boot
up problems, but you are not going to know that until you can get your 5 VDC
sturdy, using Ed's test.

Regards,
Dan

** Posted fromhttp://www.teranews.com**- Hide quoted text -

- Show quoted text -

Dan,

I meant C1 of the PS. The big silver one.

C1 on my CPU is replaced but I am leaving that board alone for now,
not connected until I can get the PS working solid with the big
resistor in place.

I noticed on Google my comments regarding re-measured voltages above
were not displaying. Here are the re-measurements (now that I got the
correct pin count on my chip, I was doing it backwards):


Here were the results of my "Idiot Moment":

OK I was counting the pins upside down. The IC1 is installed
correctly
but I was counting from the other side.

So to revise my measurements (changes in ***stars***):

Transistor case to ground : 1.8v

CR5 is your suggested replacement, Ed.

***Pin 6 of Ic1: 7.1***

***Pin 10: 2.6v***

And as before,

E4: 14.7v

E5: 1.2v

E6: 1.1v

All with 5OHM 10W resistor ON.

So, it was really Pin 13 of IC1 that was experiencing the rising
voltage (starts at 8.1v cold then ultimately creeps up to 14.7vdc
when
the chip is nice and toasty).

As for the parts mentioned above:

Q3 is new and correctly oriented.

IC1 was, as above, correctly oriented.

I checked in the vicinity of POT1, R7 and R14. No shorted traces I
could find.

POT1 was installed like this:

- Three leads (phillips-screw style turning knob)
- Phillips screw slots facing J3 power connector

I assume this is the correct orientation. When looking at it "from
over" the J3 connector, considering the far left leg: between the far
left leg and the middle leg, I get about 150 ohms resistance. Not one
of any of the pot's legs has continuity with ground.


Perhaps I installed this backwards?


Other than that, do those new readings change the focus of this
"investigation"?


Best regards,
Matt J.

.

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