(Topic ID: 224860)

Gottlieb Buck Rogers Driver Board keeps blowing CEN-U45 Q29

By cshelden

3 years ago



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  • 6 posts
  • 2 Pinsiders participating
  • Latest reply 3 years ago by cshelden
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#1 3 years ago

First post so here goes, I did search best I could before posting.

First pin to own is this Buck Rogers in amazing cosmetic and mostly mechanical shape. Things I've already done:
*Ground Boards to back plane
*Replaced "the big capacitor" on PS.
*Added LED to PS, MPU +5 -12, add LED to Driver for +5 indication.
*checked for +5 and -12 at MPU, adjusted 5v pot it was at 6v.
*replaced Kicker Transistor TIPS-102 and burned up coil.
*replaced 5 bank drop target coil (#8) and MPS-45 and 2N3055, replaced MPS with a CEN-45 from Mouser.
*All LED (frosted) on playfield and back glass.
*Confirmed proper fuses and function.

Once I did all above things worked fine. Played about 40 games then bam, 5 bank drop target won't reset. It gives about a 1/2 effort like it would come up then stop. I tested by grounding the 2N3055 and the target would pop up. PS felt pretty warm on the heat sink. Let it cool and worked about 4 games then same thing. Found the CEN-U45 was out, replaced and worked fine for about 10 games. BAM out again.

So my question is this, what do I need to look for? is this a voltage issue? I'm stumped. Getting tired of replacing this transistor too!

Fun game family loves it.

#2 3 years ago

Grounding the case only tests the wiring between coil and driver board & doesn't test Q45.
Make sure wiring between Q45 emitter and ground is OK. Original connectors/contacts?

Are you sure the U45's are bad? Could be the corresponding 2N3055 at Q45 - might have lower than normal gain.
Where did you get the 2N3055's? Not Toshiba's by chance?

Not likely but also check resistor R39 for proper value and not shorted.

#3 3 years ago

Components sourced from Mouser. 2N3055G shows ON Semiconductor. U45 reading with + on center pin and - on right shows OPEN where new shows I believe .7. So it's blowing that transistor however the 2N3055 shows good still. I checked the 1/2w and 1/4 watt resistors on each side tested OK. 900 ohm and I believe the 1/4 w were 1k ohm. All wiring and pins original. I did burnish the board pads with a fiber brush. Traces look ok under a magnifying glass. Will pull and take to work tomorrow and double check it all. Perhaps the 2N3055 is low in gain?

When I removed Q45 the board was very dark and showed signs of high heat it's possible I suppose that there was some damage to trace but not seeing anything obvious.

#4 3 years ago

Unlikely for these new On-Semi 2N3055G transistors to be bad. There is a large, bad batch of Toshiba 2N3055's floating around out there - horribly low gain. I bought ~500 of them... unfortunately, nearly all of them are in the Omaha land fill.

Did you check resistor R39 value? He should be about 9.1 ohms.
Hopefully this one isn't 900 ohms. If so - there's your problem.

If R38 is too low - that can be a problem as well. S/B 1K within ~5%.

#5 3 years ago

You may have nailed it. I double checked. R39 is a 9ohm +/- 5% 1/2 w resistor but it testes 12.1 ohm. Well out of spec. R37-38 are 1k and with in spec. So maybe the higher resistance is whacking it out of range. I hate not having parts on hand. I'll order it.

IMG_2272 (resized).jpg
#6 3 years ago

Resistor did not fix the issue. Same as before it will reset a few times then it only pushes the drops 1/2 way up and back down.

GRRR at a loss.

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