Twilight Zone Lamp Issue

[Jonwolf]

Once again, the newb to the list is leaning on the advice of the community ;-)

Issue: I have a set of lamps that keep burning out. If I put incandescent bulbs in the quickly blacken. LEDs last a while before they burn out with a brown burn smudge at the side.

The lamps are locations 41 through to 48 but it's the yellow inserts that do it and not the red.



Any ideas chaps ?


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[Jonwolf]

Some more information: the row of lights do not 'scroll' left to right - they all 'twinkle'. Also, when in play, they all remain on in 'twinkle mode'
The shoot again light spends most of its life 'on' too. I wouldn't mind so much if 'shoot again' was actually active ;-) But it ain't


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[pinballmania]

Run through the single lamp test. Do any of the problem lamps come on when they shouldn't be? If so then you have a transistor short.

 

[Jonwolf]

Thank you - I haven't done a lamp test yet (should have done) - and thanks for the quick delivery of the pair of playfield bolts [emoji106]


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[Jonwolf]

Just run a lamp test - they all work BUT they also light when other single lamps are on:

Eg: Test lamp 11 (camera door panel) and lamp 41 (2 million) lights as well.
Test lamp 21 (lock 2) and lamp 41 (2 million) lights as a well.

Is this supposed to happen ? Similar results with lamps 42,43,44, etc to 48


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[Jonwolf]

So it's a transistor short I guess. Officially out of my depth.... Again ;-)


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[pinballmania]

No. You have a board fault. Short drive transistor.

 

[pinballmania]

Probably q95

 

[chris b]

if its 41 to 48 as per matrix diagram i would suspect q95 transistor to be the cause

 

[chris b]

you beet me too it andy

 

[Jonwolf]

I've taken a look at the manual and located q95 on the power drive assembly. I'll take a look on the machine and report back tomorrow. I'm used to cleaning and repairing playfield stuff but circuit boards are a strange place for me. Thanks for ghe guidance chaps


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[Jonwolf]

I have ordered a couple of replacement transistors - get ready for the cries for help when I start ;-)


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[Jonwolf]

And so the journey begins... I know not a lot about multimeters but have recently become the owner of one. A quick google on testing transistors before checking q95 and off I go !


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[Jonwolf]

Set multimeter to 'diode' Touch black probe to ground braid and red probe to 'tab' on a random transistor and I get an immediate straight reading of '1'.

Do same with q95 And I get a reading of around 750 that then starts to very slowly climb to around 1900 and then fluctuates, never reading '1'.

Interestingly (or not!) I get a reading of '1' for q91,q92,q93,q94,q96,q97 a a q98 but not immediately - they all start at around 1900 but quickly get to '1'

So, q95 is faulty I guess. I have a replacement so is it time to fetch the board out and replace ? I'll be asking for desoldering/soldering advice next ;-)



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[Jonwolf]

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