I am working on a 1983 vintage Gottlieb Haunted House Pinball Machine for a friend. I have never worked on a PB machine previously, but have considerable electrical/electronics troubleshooting experience. I'd appreciate help from anyone on this forum who is knowledgeable and willing to offer me advice.

At this point, I have determined that the F4 glass fuse (8A slow-blow) pops whenever one of the main playfield solenoids attempts to fire. (No other fuses get blown). With the F4 fuse replaced, on startup, the game appears to boot up properly and after a few seconds the "spooky music" and flashing lights (attract mode?) seem to indicate it is working properly. When coins are inserted and the credit button is pressed, the pinball is released to the launcher and the associated "knock" can clearly be heard. But once the ball is launched into play, the sound stops, and none of the flippers, targets, or bumpers work. Shutting off power and performing examination of F4 fuse shows that it is blown open again. (All 14 other fuses are fine).

Per the schematic, fuse F4 appears to feed two bridge rectifiers which are working correctly and supplying unregulated 24VDC and 33VDC. To troubleshoot and attempt to isolate the problem to either the sound system or the solenoids, I disconnected the sound and sound PSU boards and the fuse still blew when the ball entered the playfield. Since it did not appear to be sound board related, I reconnected them and then looked more closely at the A2 Power Supply board. I took voltage measurements on all the clearly marked DCV Test Points (TPs). All seemed to be within expected minor variation from the nominal voltages, except for TP2 which is marked 42V, but is clearly measuring 60V. This 42V output appears to be shorted to the 60V (even after disconnecting the J3 connector to assure short wasn't "downstream") and zener diode CR6 has no voltage drop (18V is expected per the schematic to derive the 42V from the 60V). I have a replacement 18V, 1W zener diode (1N4746A) on order and plan to replace it when it arrives. That said, can someone help me in advance to understand where the 42V goes and how it is consumed by this PB machine?

PS I did find the manual on the Internet and so have the schematic, but can't seem to find where the 42V goes in that 50+ page document. Looking at the wiring harnesses, it looks like it goes to the main playfield, but how exactly is it used? Does it somehow drive the solenoids and would the (1.5x too high) 60V there cause the overcurrent situation that is popping fuse F4 during gameplay? Or am I chasing a phantom here and the root issue is somewhere else? (Where next to look?) Thanks in advance to anyone who can help me understand the purpose of the 42V supply and also help me to understand if it could be the cause for the bumpers/solenoids/etc. consuming too much current and blowing the F4 8A fuse.

Thank you Quench so much for pointing me to the relevant schematic page! I really appreciate you taking the time to post that page and highlight the input voltages to the two types of displays used. So it seems that even though these displays appear to be working fine (even though the 42V is actually measuring 60V), this fault does not seem to affect operation (but might ultimately result in long-term pre-mature failure of the credit counter display).

I removed the CR6 18V zener diode from the A2 PSU circuit power and have verified it is indeed bad. (It measured 36 ohms in both directions using my DVM, so was no longer functioning as a diode and instead had become the equivalent of a low value resistor.) Unfortunately I was really hoping this was the reason the F4 fuse was blowing, but based on the schematic and purpose for the 42V, it seems I will need to fix this and continue to hunt for the root issue.

If anyone has thoughts on how to go about isolating the cause of the F4 fuse issue, I'd love to hear them. As noted in the above original post, this fuse feeds the 38V and 24V bridge rectifiers and DC voltages on them are correct. I also believe the sound subsystem (which from the schematic appears to use the 24V bridge rectified output) is OK since "attract mode" sound is working at power up and disconnecting the A7 (sound/speech PSU) and A6 (sound/speech synthesizer) boards has no affect on the fuse blowing when play is attempted.

This leads me to believe that the issue is likely downstream from that 38V supply which goes out pin 5 on connector A12/J8 to the playfields. So my next question is the 38VDC used to energize the solenoids on all three levels of the playfields or does it have some other alternate purpose? If this is the power for the solenoids, can I simply and safely disconnect each level at its cable harness connectors to try to determine which level is causing the F4 fuse issue? Or is there a better/easier troubleshooting procedure someone on this forum with experience troubleshooting this machine can suggest? Also, if I do attempt to isolate as described here and the fuse blows on all 3 levels, then should I be looking elsewhere, possibly the A3 Driver Board or the A8 Pop Bump Driver Board? (It appears from the schematic that these boards simply provide the ground through power transistors for the solenoids and are not "directly" in the 38VDC power source circuit).

Last question: In the manual I see the nominal resistances for all of the various solenoid coils are listed and most should be simple to verify. That said, I see that two parts (A-17875 used for the flippers and A-20095 used for the super flipper) have two resistance values listed, why? For example, A-17875 lists 2.8/40 ohms and 560/1100 turns and #22/31 gauge wire. Can someone help me with the reason for dual values on these two parts?

Thanks in advance to anyone who can help provide valuable troubleshooting assistance on my thinking and the questions listed above.

Thanks so much once again Quench for the excellent information. At this point I am still awaiting the 18V zener diode to replace on the A2 PSU to get the 42V working correctly again. Once that is fixed, I plan to try isolating this issue. With regard to a possibly always "stuck on" solenoid coil, I do not think this is the case since I can power on the system and let it run in attract mode for as long as I like without blowing any fuses. I also do not believe it is the knocker since I clearly hear that and it sounds like it works correctly after putting in a coin and hitting the credit button. And, as noted earlier, the F4 fuse does not blow even though the ball is released to the launcher chute. It is only after it gets shot up into the playfield that the fuse pops (nearly immediately) as evidenced by the loss of the sound since it too is driven from that F4 fused circuit.

I think before I start disconnecting anything, I will do simple resistance measurements of all the solenoid windings to see if any is shorted. Based on your recommendation, I also will double check that those lower amperage fuses (F10 - F15) under the main playfield (and which are in series with the 38V and 24V supplies fused by F4) are all the correct values (2A or 2.5A slow-blow). My previous assumption had been that since they had not blown, the issue was with one of the non-secondary fused solenoids (one of the flippers or kicking targets since they get fed from the power sources directly).

Since I have never seen the game operating correctly, can someone who has the Gottlieb HH or is familiar with it tell me what the control logic does to the solenoids, targets, kickers, etc. when the ball is launched? The reason I ask is that I remember playing some old PB machines that generated a lot of noise/action when the ball first went out the chute and onto the field of play. If the HH does this, then it would theoretically be possible for any of those solenoids (or faulty protection diodes on them) that get momentarily activated to be causing the fuse to blow.

I will post with what I learn once I get the replacement zener diode installed and get the chance to get back to my friend's house to take another look at the machine. Thanks again.

Update: Replaced CR6 (18V zener diode) and now the 42V seems to be working correctly. Unfortunately and as predicted in string above, this had no effect on anything. I checked all of the solenoid resistances and they all seem to be in spec. I also rechecked all the fuses and determined that some of the 2A slow-blow had been replaced with 3A slow-blow. Turned on the main power switch, waited for boot up, then got coin credits and was able to start a new game. Knocker made the expected loud clack and the ball was sent to the launcher chute. At this point I was able to make all of the main playfield flippers work properly using the left and right red flipper buttons and the upper playfield flippers also worked fine using the green flipper buttons. But, THE lower playfield flippers do not operate even though they measure the correct resistance.

Per page 39 of the schematic, the 24V that feeds these lower playfield flippers (which are not operating) are fed from the exact same green flipper switches as the upper playfield (which is working). Upon checking the voltage on these lower playfield flipper solenoids, the 24V is not there. I do not see any fuses in this circuit ... just the U relay and a connector A9J1.

When the game starts up after turning on the power switch and before inserting coins, I see the U relay cycling on and off in sync with the main playfield bumper lights going on and off in sync with the relay. Once the game is started and the front credit switch is pressed, the cycling stops and the relay is energized and the main playfield bumper lights stay on. That said, the lower level bumper light does not ever light at all. Does this sound like a potentially defective U relay? It is buried pretty far back so I am reluctant to try to remove it if this is not the issue. What is the easiest way to get it out if I do need to remove it? Can the relay contacts be fined/cleaned to make them work again or if there is no contact must it be replaced?

Thanks for any advice/suggestions you can offer me here. This seems like such a simple circuit, how can it be so difficult to find the root issue? Can someone verify that there is nothing else in the circuit (not shown on the schematic) and that the lack of 24VDC on the lower playfield flipper solenoids after pressing either of the the green flipper buttons (and seeing the upper playfield flippers working properly) means that either there is either an A9J1 connector or U relay contact issue. What is the purpose of the U relay and why does it only break the 24V to the lower playfield level flippers?

In closing, I have a few other issues (F12 and F13 fuses blowing and a couple stuck main playfield pop up bumpers) , but I think It best to get all the "uncontrolled" power solenoids working before trying to figure those out next.

Thanks Quench, you are a wealth of knowledge. So the Lower Playfield only illuminates and the flippers operate when the ball enters that level and the upper playfield gets disabled when the lower field is in play? If this is how it supposed to work, then I will need to change my troubleshooting approach because the system does not seem to identify when the ball enters the lower level. (The guy who owned the machine and who hasn't played it in many years thought both flippers operated simultaneously like they do on the main field.)

According to the schematic drawing, the U relay is the one (of the three relays) located furthest to the back of the unit on the bottom side of the playfield. I could swear this is the one that I see toggling on/off/on/off at about 2 second intervals (and in sync with the bumper lights on the main playfield) before the front red credit button is depressed and the knock is heard, the attract music stops, the player 1 illuminates with score of 0, and the ball is moved to the launcher to begin play.

Can you confirm I have the correct relay, the one at the farthest back of the three in a row? And then if I manually depress that relay to look like it is energized I should see the 24V appear at the lower playfield solenoid once the green flipper switches are depressed? By the way, I have traced those green flipper colored wires you described to the connector pins and they appear to be good and go where expected.

Here is page 50 from the manual I found online showing Relay U as the one located furthest back. I also scanned page 39 that shows the U Relay in line with the lower PF flippers, but not for the Upper PF. Both appear to get the same 24V from the T Relay. As noted previously, the Upper PF flippers are working (and the Main PF flippers are working also), but the lower level flippers are dead. Simple circuit, but driving me nuts. For instance I see 3 sets of contacts on each (U, T, Q) relay, but the schematic does not provide that detail.LPF Flipper Circuits.pdf

Main PF Underside.pdf

Thanks. Yep, I see that on the schematic ... U relay with normally closed contacts feeding the main PF flippers. So this tells me that since the main playfield is still operational, my issue is that the U relay is not energizing. If it was, then the main PF flippers would cease working (which they do not). So more than likely, this is a signaling issue. So my next step in troubleshooting would appear to be to skip getting those flippers working and move instead to trying to determine which other targets and "controlled" solenoids are not working and then see if there is something they all have in common. Since there are many things not working (and some targets and kicking rails for instance that are), perhaps this is a bad connector contact issue at either the output from the A1 logic control board to the A3 solenoid/relay driver board?

At this point I have completely disconnected the wires to the two frozen and sticking solenoid pop bumper solenoids to prevent them from blowing fuses or burning up. I'll also leave out the F12 (upper PF pop up bumper) and F13 (lower pop up bumper) fuses that are blowing now that the F4 fuse seems to be stabilized. I'll have to use the listing of all the main and upper PF target switches to compile a list of what actually works and what doesn't and then look more closely at the schematic to see if I can find a common thread for what is not working.

Thanks in advance for any suggestions on what typically causes these types of issues on (a nearly 40 year old) HH machine!

Thanks Quench for the excellent suggestion. I do see the self test capabilities listed in Steps 16-20 on page 14 of the manual. Step 18 appears to be the one that displays any closed switches. So I should expect to get the "99" displayed during that test since they all should be open to start. Then, can I get into that test mode, see the "99" and then manually depress a switch and see that switch number gets displayed? If so, can I then step through other switches and the displayed switch number will follow? Or, alternatively, do I need to close the switch before I get into that step 18 of the self test to see it closed?

This should theoretically be a good way to verify the logic control board A1 is seeing all 67 switches. If not, then a pattern may help me to determine which specific pins in the A1J6 connector might not be making proper contact.

Great! This is exactly how I hoped the test capability would work and I was thinking the same regarding any switches not registering properly. If I can see a pattern, it should point me to the bad contact(s) in a row or column in the switch matrix. These all need to work before any controlled solenoids fire. The fact that some targets and solenoids are working and the player 1 score increments when they are hit tells me the logic control is likely good and the issue lies elsewhere. It will be a few days before I can get back to my friend's house and pursue this, but I will post my findings.

Thanks again for making me aware of the switch and lamp self test capabilities.