(Topic ID: 226097)

GTB Bronco reset issue - no flippers or pf GI

By EMDude

3 years ago


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  • 12 posts
  • 2 Pinsiders participating
  • Latest reply 3 years ago by MarkG
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B636D537-774F-49A1-AABA-1BB1FECA5F3C (resized).jpeg
Bronco Ball Return (resized).jpg
Bronco power rail (resized).jpg
Bronco Playfield lights (resized).jpg

#1 3 years ago

I'm getting close on this machine! Goes through start up sequence; motor runs, player unit resets players 1 & 2 then 3 & 4, ball kicks into shooter lane, player 1 lit, ball 1 lit, but no flippers or playfield GI, however kick out holes do eject ball, but nothing else on pf works.

#2 3 years ago

On the GI or 6.3 volt AC side of the schematic there is one switch on the H/Tilt Hold relay that needs to close to get power to the playfield lights:
Bronco Playfield lights (resized).jpg
That switch connects the white-black wire to the white-red wire (not shown). You could also have a bad 10 amp GI fuse or fuse holder.

On the coil or 25 volt AC side there are a few switches that all need to close to get power to most of the playfield solenoids:
Bronco power rail (resized).jpg
Coincidentally, a H/Tilt Hold relay switch is in this circuit too. I'd start by checking that the H/Tilt Hold relay and its switches are working. Then trace the circuit up the right side to see where you're losing power.

Kick out holes work all the time to let the ball drain in case you tilt the game or shut off the power and turn it back on while the ball is in a saucer.

/Mark

#3 3 years ago

Thanks Mark.
GI issue solved (fuse holder).
Repaired broken sw blade on Q relay on flipper circuit. Now cycles thru reset sequence, but no ball eject, dim pf GI and flippers have weak power, then 5A fuse (circuit breaker) blows.

#4 3 years ago
Quoted from EMDude:

dim pf GI and flippers have weak power, then 5A fuse (circuit breaker) blows.

Whoa. Is that new? Which fuse blows? There are at least five fuses in this game. Go back and check what you fixed because that sounds like you have a short where maybe you didn't before.

If the ball isn't kicking out after reset, check the switches in this circuit:
Bronco Ball Return (resized).jpg

#5 3 years ago

Checked my repair against schematic and all looks in order. 5A fuse blowing is main back near xfmr. With power on when I manually close the out hole sw (or when I start a game) I get a momentary bright green arc on the bottom right sw of the ‘O’ relay, then a couple seconds later circuit breaks, wires red/yellow; red/yellow (see photo).

B636D537-774F-49A1-AABA-1BB1FECA5F3C (resized).jpeg
#6 3 years ago
Quoted from EMDude:

5A fuse blowing is main back near xfmr.

I don't have a Bronco. I'm just working with the schematic. Which fuse is back near the transformer? Use the labels in the game or better yet the wire colors to identify it so I can find it on the schematic. If the main 120v circuit breaker is going I'd check the values of all the other fuses in the game against the schematic. I'd expect them to have blown before the main breaker.

Quoted from EMDude:

I get a momentary bright green arc on the bottom right sw of the ‘O’ relay

What switch is it? (wire colors, or better yet, where in the schematic?)

Quoted from EMDude:

wires red/yellow; red/yellow

Which switch connects red-yellow to red-yellow? Seems unlikely that both wires would be the same color.

#7 3 years ago
Quoted from MarkG:

I don't have a Bronco. I'm just working with the schematic. Which fuse is back near the transformer? Use the labels in the game or better yet the wire colors to identify it so I can find it on the schematic.

Label: “Primary Fuse 5 Amp SLO-BLO” shown at the very bottom of the schematic (F23).

#8 3 years ago
Quoted from MarkG:

What switch is it? (wire colors, or better yet, where in the schematic?)

It’s a pair in and a pair out, upon closer inspection looks like Red/Yel and Red/Wht.

#9 3 years ago
Quoted from MarkG:

I'd check the values of all the other fuses in the game against the schematic. I'd expect them to have blown before the main breaker.

3 other fuses (on bottom board): 25V/15A, play board lights: 10A, Lightbox light fuse: 15A.

#10 3 years ago

The problem sure seems to be on the 25V A/C side. Switch stack on AX relay with 2 pair red/yel and red/blk gets hot due to short. Incidentally sw I repaired on “Q” relay also has 2 pair red/yel and wht/red. If I put a piece of paper between contacts, game resets ok, kicks out ball, but again, no flippers (same as before).

#11 3 years ago

Thanks for hanging with me on this Mark!

#12 3 years ago

Have you ever seen this game run?

It sounds like you have a short somewhere between the red-white wire that comes out of that Q relay switch you fixed, and the black wire that runs up the middle of the schematic from the 25v transformer winding. If you measure the resistance between those two with the power off, what do you get?

Finding a short can be tedious. Apart from visual inspections you'll need to try to eliminate parts of the circuit to see if that helps. Here are some things to try:
- Look carefully at switches and their solder tabs on the score motor and relays. Check for mangled or bent tabs, solder blobs, a loose screw or nut that fell from underneath the playfield, etc.
- Check that the Extra Ball adjustment (7I on the schematic) plug is plugged in and not dangling or touching anything else.
- See if disconnecting the jones plugs in the head helps. Try disconnecting the playfield too. (But just one at a time so you can narrow it down.)
- Look for burnt coils. An overheated coil may have developed a short inside between windings.
- Start at the Q relay switch at 13I on the schematic (the one you fixed) and follow the red-white wire up the right side of the schematic. Block off (with a piece of paper) the first switch on each circuit that goes to the left from the red-white wire. So for example block off the L relay switch at 8I first to see if that helps, then the P relay and Motor 3B switches at 7I, etc.

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