Whitestar flashers & transistors

[Fubar]

I have issues with the flasher lamps in my LOTR. Mainly that they don't work:

• Q14 - flasher dome near the right slingshot - tranny burned in short-circuit, incandescent lamp proceeded to melt the dome pronto.
• Q32 - inside the balrog - doesn't work, voltmeter also reads a constant 23VDC at the socket. Unplugging the balrog and applying 12V to the LED pins doesn't do anything, so I'm assuming the LED is toast too (why do they use a 12V LED on a 20V circuit??).
• Q26 - inside the ring - haven't done any diagnosis on this one yet, but it doesn't work either. Assuming either the lamp or another burnt tranny. Edit: this one was just the bulb.

I've tested the Q14/Q32 gates when the machine is powered on and that's reading 0V, so I'm assuming it's not an issue with the upstream latch (HCT273).

My question is: are failing transistors common on the whitestar IO board? I seem to remember somewhere a theory that using them for flasher lamps meant they often operated in their inefficient switching range (ramping up/down) which caused early failure.

I've got a 24NF10 to replace Q14, and a TIP102 to replace one of Q32/Q26 (might have to get another one of those). What about the IRL540, is that worth using instead of the 24NF10 for flashers? Basically any replacement part which can handle this application better? I'm trying to wrap my head around all the issues and make sure I get the fix right, because I don't fancy pulling the IO board out more than once.

Thanks!

 

[Moonraker]

What about the IRL540, is that worth using instead of the 24NF10 for flashers? Basically any replacement part which can handle this application better?

The IRL540 (100v 26A) can be used in place of 24NF10 (100v 24A). It's slightly more beefy allowing for 26A rather than 24A.

 

[Fubar]

The IRL540 (100v 26A) can be used in place of 24NF10 (100v 24A). It's slightly more beefy allowing for 26A rather than 24A.

Thanks for the reply Moonraker. I did see something to that effect on the pinwiki whitestar page.

Does the higher amperage really matter for flash lamps though? I would think that t_on/t_off are the more important properties in this application... I need to read some datasheets tonight.

 

[Moonraker]

Does the higher amperage really matter for flash lamps though?

No...

 

[pinballmania]

Bear in mind that transistors connect the flash lamp to ground. So measuring 23v at a socket is perfectly normal. The supply voltage is present at all solenoids and flash lamps.

 

[Fubar]

Bear in mind that transistors connect the flash lamp to ground. So measuring 23v at a socket is perfectly normal. The supply voltage is present at all solenoids and flash lamps.

That is a good point. To clarify, I'm measuring the voltage between the 2 legs of the socket. In the Q14 case at least, I have a replacement LED bulb: if I insert that and switch on the game, it stays on all the time. So I'm pretty sure that transistor at least is fried in closed-circuit, but I agree that for the others it's not a definitive test.

Do these transistors fail often?

 

[pinballmania]

Yes

 

[Bod]

Funnily enough, I've just bought a LOTR and the right flasher was missing. Upon putting a bulb in, it was locked on. I (someone else!) changed the relevant faulty transistor to IRL540 several weeks ago. So far, everything ok.

 

[Fubar]

Apparently that particular flasher failing is very common.

I changed Q14 & Q32 on mine last night and it's working fine now. Someone had previously done a rather messy job so I cleaned it all up. Only broken one left is the balrog and I'm pretty sure that's down to the bulb now...