GI Lamp fuse blowing - eventually ....

[Marty Machine]

Hi All,

I have THE weirdest problem here with an old (79) "Stellar Wars" machine.

My GI Lamp fuse (20Amp slo-blo) seems to always blow out, even though ALL lamps are working correctly.
Actually it's not 'blowing out' as such, it's getting so hot it unsolders itself internally and goes open.

Last week i replaced all the original #44 globes with new #44's (64 globes in total - 32 on backbox, 30 on playfield and 2 in the coin slots). - 64globes x 250mA = 16Amps, so why does this blow my 20A fuse?

The machine has been playing fine ever since i got it last week and changed the globes etc, until one night i left it unattended for 5 mins and returned to see all the GI lamps were gone.
I replaced the 20A fuse and it blew within 1 minute.

I measured AC volts from the tranny, being 6vac +/-, i removed the fuse and tranny wiring and measured the resistance of the globe-side which various from several ohm's to 10's of ohms, but definately no shorts etc.

I'm now toying with the idea of splitting the ac wiring, so the backboard could run via 1 fuse (10A?) and the playfield runs via an additional (10A?) fuse to take the load off the poor 20A.

I've followed the GI pair of 'stapled' wires around the whole playfield and can't find anything that touches them, or anywhere else around the cabinet that might shut/move the wired onto anything else....


Oh, another note, since i ran out of fuses, i used a few clipwires across the fuseholder which gets quite hot, then upgraded to jamming some pointy-nose pliers across the fuseholder which also (suprisingly) gets hot too...i've now resorted to wrapping the dead fuse in alfoil which still gets warm-hot too.
In all above scenario's ALL lamps still work though, and none are dim or missing....

What The ???????

I also discovered last week that a broken wire on the playfield was stopping some of the GI's working, so i soldered an added wire 'across' the break, i thought this might have added more resistance, but it's only 15cm long and wouldn't be resistive anyway.
( the original wire (stapled on the playfield between globe sockets) had been cut thru by removing the playfield all the time, i think it cut's itself on the edge of the main box from what i can see, so i added this new length of wire to close the break and avoid the sharp edge).

Any ideas about this? has anyone experienced this kind of black magic before???

Marty.

[Strangeways]

I've never seen this before.. sounds like there is either DC on the line, or a short somewhere...

Try removing half the globes and see what happens

Maybe remove the headbox GI connector ?

[Marty Machine]

Yep, that's where i'm heading anyway if i proceed to mount 2 fuses to isolate the headbox and playfield circuits.

Sadly the GI fuseholder wiring is hard-wired as 4 pairs of wires, 2 pairs to the headbox and 2 pairs to the playfield, they seem to be near the middle/ends of the wiring loops to compensate for current losses?

Maybe Plan-A will be to add 'connectors'  and go from there.

Thanx,
Marty.

[Strangeways]

Yep, that's where i'm heading anyway if i proceed to mount 2 fuses to isolate the headbox and playfield circuits.

Sadly the GI fuseholder wiring is hard-wired as 4 pairs of wires, 2 pairs to the headbox and 2 pairs to the playfield, they seem to be near the middle/ends of the wiring loops to compensate for current losses?

Maybe Plan-A will be to add 'connectors'  and go from there.

Thanx,
Marty.

I'd start with the easiest option - remove half the lamps.. Interesting fault.

[Marty Machine]

I'm strongly believing the fuseclip might be the culprit, being tarnished & has lossy issues??

ALL 64 lamps were replaced with NEW ones, and ALL lamps work, and NONE are dim or suspect.

the battle continues 
Marty