Gottlieb Hot Shot (Gottlieb, 1973) Blowing Fuse Problem

[Tommycanyouhearme]

1973 Hot Shot Blowing Fuse Problem

My Hot Shot Machine keeps blowing the playfield lights fuse while the game is being played. The game keeps playing but the bonus points aren't added at end of ball. This happened before and I thought the problem was solved but it has started again and I am not sure what to check first.
Any thoughts on what to check first would be greatly appreciated!

Thank you,
Tom

 

[pinballdaveh]

does it seem like the fuse blows when the bonus unit is scanning for bonus? bonus does not add because the bonus scan disc is looking for 6v charged rivets on the disc that works off the ball rack lights on the playfield. no rack lights no bonus. wasnt there a problem with the bonus multiplier lights a while ago. does the fuse blow when a certain multiplier light is on ? a full pic of the lights section of the schematic might help solve this. also could post a pic of the gear side of the bonus unit. this is where the short may be happening.

 

[Tommycanyouhearme]

The fuse blows while the ball is still in play. There was a problem with incorrect bonus points at one time. I will check the gear side of the bonus unit for shorts and post pics. soon.
Thank you pinballdaveh!

 

[pinballdaveh]

if the machine is blowing the fuse while the ball is still in play , the bonus unit is almost eliminated from being the short. the drop targets banks are the next units to check. 1st is resistance test , set DMM to a high resistance range , un-plug machine , connect one DMM lead with alligator jumper to frame of drop target bank , use the other lead and probe each wire connection of each set of bank switches. start manually dropping targets and check for readings. this test checks the insulating fish papers of the switches. check switches that show a reading on DMM. repeat the test if your DMM has a diode beep range. 2nd is a voltage test. set DMM for a ac voltage range higher than 24v. keep the one lead connected to the frame and connect the other lead to the transformer secondary output common. plug in and start game. start dropping targets and check for readings. once a reading shows check what target dropped caused the readings. do each test on each bank and post results. also check for bulb sockets, switches , or wires touching the bank frame as a possible short.

 

[Tommycanyouhearme]

I have peen playing the machine without it blowing the fuse for a few days now on 1 player. The problem might only be when the game is set for 2 players.

 

[Tommycanyouhearme]

It appears that it only blows when on 2 players, but may happen when on 3 or 4 players also. I played it for a week on 1 player and it was fine, but when I put it on 2 players the playfield lights fuse blows while in the middle of the game. I have not noticed that any one feature causes it because it is intermittent and I never know when it is going to blow!

 

[pinballdaveh]

could you please post the complete lights portion of the schematic. that would help to isolate the fuse blowing problem.

 

[Tommycanyouhearme]

Hot Shot Lights

Here are the lights portion of the Hot Shot schematics.

Thank you,
Dave

 

[pinballdaveh]

the two fuses that control lites are divided between playfield and head with coin chute. since the playfield fuse is the one keeps blowing that almost isolates the problem to the playfield. that should mean that no matter how many players are playing the results will be the same. the first thing i would try is to isolate the ball rack lites. un-mount the rack cluster , remove all 15 lites , un-solder the common wire and tape end , and re-mount. inspect all the 15 wire connections for possible shorts to frame. play as many 1 player games as possible and see if fuse is still blowing. bonus points should still work and score.

 

[Tommycanyouhearme]

I have not tried to isolate the ball rack lites yet, but I have some new infomation to add before I do. I have put a 10a slow blow fuse in the game and have noticed that instead of blowing the lites dim and the fuse turns red. If I let the ball go and the game resets for to the next ball, the lites come back on full and the fuse stops glowing red. Also it does happen in 1 player mode.

 

[pinballdaveh]

using slo-blow fuses or over-sizing a fuse for a light circuit is NOT a good idea. light bulbs are a resistive load and need fast-blow fuses. coils are an inductive or impedance load. when coils energize a inrush or EMF is created and a slow blow fuse is made to tolerate this without blowing at its amp rating. fast-blow fuses are used on main solenoid/relay line usually 15 amp because each coil might use 1 amp at a time and a combination of coils firing wont be close to adding up to the 15 amp rating. thats why machines like aztec that has 5 score reels per player needs 3 reset relays to pulse 6-7 coils at a time. 20 score reel coils firing at the same time would be too much amp draw. bank reset coils usually use a 1 or 2 amp slow-blow fuse because of the strength of the coil. when a slow-blow fuse is used on a light circuit and a short happens the coil in the fuse almost turns into a heater element and glow red while not allowed to blow thus putting a strain or direct short on the transformer secondary winding used for lighting. too much winding stress will breakdown the windings insulation and short out the winding , and then a new transformer will be needed.

 

[Tommycanyouhearme]

I have the correct fuses now and have tried removing all the bulbs and disconnecting the common wire on the ball rack lites. The fuse is still blowing! Sorry it took so long to get back to you I have been very busy lately.

 

[pinballdaveh]

we now know the problem isnt in the pool lite rack. re-install the 15 lites , re-mount lite rack and re-connect the common wire. on each of the drop target banks there is a row of long bladed switches. these are for scoring when target drops. un-solder the end feed wire(s) off of each of the two lugs , tape and set aside. do this for each bank. doing this should eliminate the chance of the 24v section causing a short to the frame except for the all targets down switch or the behind rubbers score switches. if this eliminates the short after many games have been played , then start re-soldering the wires on one at a time and test for short before soldering the next wire on. if the short returns check which bank had last wire soldered on , that should be the problem area.

 

[Tommycanyouhearme]

I disconnected the four wires on the drop targets long bladed switches, (2 on each side) from the lugs and the fuse still blows.

 

[pinballdaveh]

the next 3 sets of lites to be checked all have the same common feed colored wire , ___ & blk , i cant tell from the schematic , and all use a M/B switch. un-solder the feed wire(s) from the long blade terminal on these switches.1st is the M/B 1C switch on the score motor , this controls the L&R rollover lites , L&R target lites , and pop bumper lite. 2nd is the M/B switch on the LB relay that controls the bonus multiplier lites. 3rd is a M/B switch that controls the #8 rollover lite and the 8 hole lite , i cant make out the relay letter ( check the schematic for correct relay letter , it should be a latch in relay ) some of the last things it could be is the playfield GI lites , the behind rubber switches behind the drop targets , and the all targets down switch on each bank.

 

[Coil_Smoke]

Long Lasting Overload Vs. Short Short ...?

... a 10a slow blow fuse in the game and have noticed that instead of blowing the lites dim and the fuse turns red. If I let the ball go and the game resets for to the next ball, the lites come back on full and the fuse stops glowing red.

It is interesting that the event blowing the fuse is more than a short, short. I think you are saying >>> once the overload starts, the condition continues until the ball drains ? That does point to the closing of a relay or dropping of a target and not some random brief impulse.

 

[pinballdaveh]

the next thing to try is to remove all playfield plastics. turn machine on , with GI lites lit , wiggle each GI bulb in its socket and see if short happens. next is to remove each GI bulb , and using a magnifying glass and flashlight check inside of each socket for a internal short( maybe a bad spring or sliver of metal from someone using a metal scour pad when cleaning playfield). if there was a internal socket short a burnt mark might show up inside the socket. check all GI bulbs for correct part number and do a ohms test on each bulb if possible. with GI bulbs still out start playing machine and see if short still happens. you may even see a spark in a socket just before the fuse blows.

 

[sleepy]

Wouldn't an ohm meter indicate a short when measured across a light bulb and socket as low resistance/zero resistance? Or a good continuity tester used instead to find a short?

TURN POWER OFF AND UNPLUG THE MACHINE BEFORE YOU GO THERE. and THEN SHORT THE CAPACITORS IN THE CIRCUIT UNDER TEST TO GROUND, TO DRAIN ANY REMAINING VOLTAGES.

 

[Coil_Smoke]

I'm wondering about the #2 scoring wheels. Could the overload happen at a certain score? Like something amiss with the carry contacts say 19990 carrying over to 20,000. I'm not 'reel' experienced with multi-player machines...But... How about the circuits that trigger extra credits. Or, is there a match unit? Can you pull the plugs to the scoring section to help isolate this problem?

Hey this just came to mind...Do you have a Variac ? Getting the machine in "Over load mode" you could drop the voltage to limit the current and possible damage while looking for the short circuit. Because the power to lamps and EM stuff is AC you can use a clamp on amp probe to check wires, relays and contacts on score motor/units for unusual power flow.

What else, other than the Slo-Blow, is getting hot while that extra juice is flowing. That power is being dissipated somewhere ...Every one should have a FLIR camera, I wish they weren't like $1500 bucks .

Something, somewhere, is making a nice BIG spark when that faulty circuit is completed. I have found similar problems by operating playfield switches on machines in the dark and looking at all those sparks when relays operate and contacts make/ brake.

P>S> Pardon the morbid fascination. But I would love to see a glowing fuse...C_S

 

[Tommycanyouhearme]

Thank you all for your suggestions, but this machine has worn me out! I have decided to move on and have sold it. I will buy another EM with less headaches. I appreciate all of your help, but I am not very good with electrical problems.

Thanks again,
PinballTom113

 

[pinballdaveh]

so sorry to hear that you sold your machine. i feel it was just a matter of time that your machine would be 100% repaired.

 

[Tommycanyouhearme]

Hot Shot Had Gremlins!

Hi Dave,
I just couldn't spend any more time and effort on that machine. It had a lot of cosmetic issues to go along with the electrical short. I will pick up something in better condition next time. Thank you for all of your help, I really appreciate all the time and knowledge that you share.

Your friend,
Tom