Low Voltage on Stern SDB-100

[Othello]

Novice taking a stab at troubleshooting. Stern Meteor displays are out.
The playfield lamps are fine, the MPU boots, and games do play fine with
no errors. Just no display.

TP2 voltage on SDU-100 shows 85.6-87.9 Volts where there should be 185V
according to schematic. RT1 does not change measured voltage. Replaced
C23 and C26 capacitors with no improvement. TP4 shows 250V. VR1 shows
65V where schematics says it should be 140V. So all the voltages are
different from schematics.

Any thoughts where the fault could be? Easier to just punt and swap in
an Alltek board?

[John Robertson]

Post by Othello
Novice taking a stab at troubleshooting. Stern Meteor displays are out.
The playfield lamps are fine, the MPU boots, and games do play fine with
no errors. Just no display.
TP2 voltage on SDU-100 shows 85.6-87.9 Volts where there should be 185V
according to schematic. RT1 does not change measured voltage. Replaced
C23 and C26 capacitors with no improvement. TP4 shows 250V. VR1 shows
65V where schematics says it should be 140V. So all the voltages are
different from schematics.

Is the voltage being measured with or without any load. My suspect is
that the pass transistor is open - check what the voltages are on the
driver transistor for the pass regulator

Post by Othello
Any thoughts where the fault could be? Easier to just punt and swap in
an Alltek board?

Easier? Yes, certainly easier, and the Alltek boards are very reliable -
I've been selling them for a couple of decades now.

https://flippers.com/catalog_oc/bally-stern-alltek-ultimate-solenoid-driver-board-ultimate-sol-drv

However I find it more fun to fix the board - if you like troubleshooting!

John :-#)#

[Othello]

Post by John Robertson

Post by Othello
Novice taking a stab at troubleshooting. Stern Meteor displays are
out. The playfield lamps are fine, the MPU boots, and games do play
fine with no errors. Just no display.
TP2 voltage on SDU-100 shows 85.6-87.9 Volts where there should be
185V according to schematic. RT1 does not change measured voltage.
Replaced C23 and C26 capacitors with no improvement. TP4 shows 250V.
VR1 shows 65V where schematics says it should be 140V. So all the
voltages are different from schematics.

Is the voltage being measured with or without any load. My suspect is
that the pass transistor is open - check what the voltages are on the
driver transistor for the pass regulator

Post by Othello
Any thoughts where the fault could be? Easier to just punt and swap in
an Alltek board?

Easier? Yes, certainly easier, and the Alltek boards are very reliable -
I've been selling them for a couple of decades now.
https://flippers.com/catalog_oc/bally-stern-alltek-ultimate-solenoid-driver-board-ultimate-sol-drv
However I find it more fun to fix the board - if you like troubleshooting!
John :-#)#

Indeed it was!

Your tip to look at the pass transistor combined with the
troubleshooting videos on YouTube (like Joe's Classic Video Games
channel) led me to Q23. On closer inspection the transistor can had a
puffy ring of what looked like insulator foam around the base.
Definitely blown. The replacement arrived just today. I popped that bad
boy out and installed the new one, and lo and behold, the display
started to work!

That success is making me feel bolder and more confident. Now I can
tackle my next project, a Bally Spectrum. That one has some stuck drop
targets and a worn out playfield but the biggest problem is that
intermittently all solenoids lose power at game start. No kickers, no
bumpers, no flippers. But they often come back if I power cycle the
game. All sounds, lights and displays work.

[Tony]

Post by John Robertson

Post by Othello
Novice taking a stab at troubleshooting. Stern Meteor displays are
out. The playfield lamps are fine, the MPU boots, and games do play
fine with no errors. Just no display.
TP2 voltage on SDU-100 shows 85.6-87.9 Volts where there should be
185V according to schematic. RT1 does not change measured voltage.
Replaced C23 and C26 capacitors with no improvement. TP4 shows 250V.
VR1 shows 65V where schematics says it should be 140V. So all the
voltages are different from schematics.

Is the voltage being measured with or without any load. My suspect is
that the pass transistor is open - check what the voltages are on the
driver transistor for the pass regulator

Post by Othello
Any thoughts where the fault could be? Easier to just punt and swap in
an Alltek board?

Easier? Yes, certainly easier, and the Alltek boards are very reliable -
I've been selling them for a couple of decades now.
https://flippers.com/catalog_oc/bally-stern-alltek-ultimate-solenoid-driver-board-ultimate-sol-drv
However I find it more fun to fix the board - if you like troubleshooting!
John :-#)#

If it wasn't for me busting every pinball machine this newsgroup,
probably wouldn't exist.

[John Robertson]

Post by Tony

Post by John Robertson

Post by Othello
Novice taking a stab at troubleshooting. Stern Meteor displays are
out. The playfield lamps are fine, the MPU boots, and games do play
fine with no errors. Just no display.
TP2 voltage on SDU-100 shows 85.6-87.9 Volts where there should be
185V according to schematic. RT1 does not change measured voltage.
Replaced C23 and C26 capacitors with no improvement. TP4 shows 250V.
VR1 shows 65V where schematics says it should be 140V. So all the
voltages are different from schematics.

Is the voltage being measured with or without any load. My suspect is
that the pass transistor is open - check what the voltages are on the
driver transistor for the pass regulator

Post by Othello
Any thoughts where the fault could be? Easier to just punt and swap
in an Alltek board?

Easier? Yes, certainly easier, and the Alltek boards are very reliable
- I've been selling them for a couple of decades now.
https://flippers.com/catalog_oc/bally-stern-alltek-ultimate-solenoid-
driver-board-ultimate-sol-drv
However I find it more fun to fix the board - if you like
troubleshooting!
John :-#)#

If it wasn't for me busting every pinball machine this newsgroup,
probably wouldn't exist.

Perhaps...

John ;-#)#