(Topic ID: 220816)

Doodle Bug Magnet Resistance?

By zacaj

5 years ago


Topic Heartbeat

Topic Stats

  • 15 posts
  • 6 Pinsiders participating
  • Latest reply 5 years ago by MarkG
  • Topic is favorited by 1 Pinsider

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#1 5 years ago

Does anyone know the proper resistance of the magnet for the doodle bug (in or out of circuit)? Mine works but it is very weak even after cleaning and adjusting all the related contacts.

#2 5 years ago

Does it feel any stronger if you hotwire it with Alligator clip jumper wires?

#3 5 years ago

You, or a prior owner didn't by chance change any of the game circuitry to DC by chance?

#4 5 years ago
Quoted from MrBally:

You, or a prior owner didn't by chance change any of the game circuitry to DC by chance?

It all looks stock as far as I can tell. I didn't really think anything was wrong until I played another one and it went 5-10x faster.

#5 5 years ago

Could it be that the switch under the runway isn't adjusted properly? It could be cutting magnet power too soon, or for too long.

#6 5 years ago

Measured the magnet at 54 ohms. Could anyone confirm if that's right?

119VAC going to the coil, can't see any change when jumping it but its hard to tell.

I had the switch adjusted about as close as I can. If I make it wider the ball just moves even less, or gets nearly stuck on the center. Even with the closest setting, the magnet isn't strong enough to get the ball to the top.

#7 5 years ago

What about mechanical possibilities? Are the ball and track clean and smooth? Are the rebound posts loose? Are the rebound rubbers in good shape? Is the ball the right size? The parts catalog calls for a 7/8" ball. A smaller one would go faster.

#8 5 years ago
Quoted from MarkG:

What about mechanical possibilities? Are the ball and track clean and smooth? Are the rebound posts loose? Are the rebound rubbers in good shape? Is the ball the right size? The parts catalog calls for a 7/8" ball. A smaller one would go faster.

Cleaned the track, new rubbers. Rubbers/posts won't matter though as the ball doesn't hit them. I'll measure the ball tonight...

#9 5 years ago

Any chance the ball is magnetized?

#10 5 years ago
Quoted from zacaj:

Cleaned the track, new rubbers. Rubbers/posts won't matter though as the ball doesn't hit them. I'll measure the ball tonight...

I owned a Love Bug for a couple years and the doodle ball would hit the rubbers on the posts...at least that's what I recall. I was thinking that fresh rubber would help.

#11 5 years ago
Quoted from zacaj:

Measured the magnet at 54 ohms. Could anyone confirm if that's right?
119VAC going to the coil, can't see any change when jumping it but its hard to tell.
I had the switch adjusted about as close as I can. If I make it wider the ball just moves even less, or gets nearly stuck on the center. Even with the closest setting, the magnet isn't strong enough to get the ball to the top.

Parts catalog says the magnet is 20A-8702, which is just the old baseball game magnet, which my notes say I've measured at 48 ohms, so close enough.

Catalog says the ball is 20A-6518, which is also the baseball game ball, which is indeed 7/8" as previously mentioned. If it's not the original ball, the iron content might be too low or something. With 115VAC going to it, that magnet should be plenty strong to fling the ball up to the top of the assembly.

The schematic calls for a 500 ohm 10W resistor in parallel with the magnet, presumably to cut the power a bit. Is that resistor there and correct? If someone substitute a lower-ohm resistor it would cut the power to the magnet.

3 relay switches are in series with the magnet (one on the Doodle Bug relay, two on the pulse relay), are those are clean and well gapped?

#12 5 years ago
Quoted from frobozz:

Catalog says the ball is 20A-6518, which is also the baseball game ball, which is indeed 7/8" as previously mentioned. If it's not the original ball, the iron content might be too low or something. With 115VAC going to it, that magnet should be plenty strong to fling the ball up to the top of the assembly.

Do you know of a good place to buy one with the write iron content/etc? Would any 7/8 ball from a pinball place work?

Quoted from frobozz:

Is that resistor there and correct

Resistor is present and reads correct.

Quoted from frobozz:

3 relay switches are in series with the magnet (one on the Doodle Bug relay, two on the pulse relay), are those are clean and well gapped?

I cleaned them and gapped them as well as I could. I also tried just jumpering one of the pulse relay switches out since all the second one is doing is wasting amperage, but it didn't make a difference

#13 5 years ago
Quoted from zacaj:

I also tried just jumpering one of the pulse relay switches out since all the second one is doing is wasting amperage, but it didn't make a difference

I'm not sure what you mean by "wasting amperage".

I've wondered about the dual Pulse relay switches. Does anyone know why they used two switches in series? I figured that they were there to distribute the wear and tear of frequent arcing and generated heat across two pairs of contacts.

#14 5 years ago
Quoted from MarkG:

I'm not sure what you mean by "wasting amperage".
I've wondered about the dual Pulse relay switches. Does anyone know why they used two switches in series? I figured that they were there to distribute the wear and tear of frequent arcing and generated heat across two pairs of contacts.

That would make sense if they were in parallel (distributing the load), but in series they're just both bearing the full load, and each one as adding resistance as the current goes across it

#15 5 years ago

I was thinking that they'd be unlikely to open at exactly the same time - one would always open just ahead of the other. In series the earlier one would take the brunt of the arcing and heat, sparing the later one since the current would have reduced or stopped by the time it opened. I suppose in parallel the earlier one would escape the damage since all the current would shunt to the later one. Neither theory holds up though unless the order in which the switches open changes periodically.

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