Gottlieb System 80 abnormal voltages

[Pauly540]

Hi Guys,
I’ve been restoring a Gottlieb Volcano on and off for the last 12 months, most work has been repairing/clear coating the playfield. I'll start a new tread on that soon. 
Over the Xmas break she is finally back together, powers up and plays (thanks Beaky), but all of a sudden I noticed the uncontrolled solenoids started to really smash the ball to a point where I’m going to break some plastics!
A final thing to do was add the sound board (which I haven’t plugged in yet) as the under playfield PSU kept blowing fuses and blew out the 12v regulator on this PSU.



As far as I can tell, only Mars God of War and Volcano used these wooden PSU’s.
So leaving this PSU disconnected I put a multimeter across the main rectifiers.
The 12V rectifier has correct 14VAC in, but has 25VDC out!



It’s the same for the uncontrolled solenoid 38V rectifier. 34VAC in, but 60VCD out, with 60VDC going to the coils. I understand that this is unregulated, but that's a tad high! 
The really weird thing is that if I leave the machine unplugged for 24hrs, disconnect everything going to the lower power board, power up and I get correct 14VCD and 38VDC from these rectifiers.
I then plug everything back in, power up and its back to 25V & 60V. Disconnect everything again, but they still stay at these high outputs until things cool down. I’m trying to rule out any shorts in the back box/Playfield and any caps holding charge.
I installed a new Great Plains A2 PSU which has the added smoothing caps installed (marked in red) eliminating the need of the lower (ORANGE) 12V cap across the rectifier. I have also tried installing a new large lower cap (with the A2 disconnected) and I’m still getting 25VDC.



The A2 outputs are:
TP3 – 5.11V
TP4 – 8.02V
TP6 – 66.2V
TP7 – 47.7V
Which all seem to be close to specs?
The lower power board has transformers B-19548 (Small), C-19552 (Large).




 

Going off this schematic the transformers are wired correctly. I still don’t understand what high tapped means though!




I have all new rectifiers; line cord, line filter, 2.5ASB fuse and reverted to installing the old working ones, but still the same.

If I leave the multimeter across the DC side of the 12V rectifier, machine plugged in, but not switched on, I’m getting 20VDC?? If I put a 24V lamp across these pins (for load) it then drops back down to zero. In my mind, that is earth leakage? 

Could someone with more knowledge than me and a fresh set of eyes/thinking point me in a direction? Would a set of 240V transformers help?
@Boots Thanks for your help so far via PM, thought I’d start a thread including pictures and this wordy explanation.
Any help gratefully appreciated.
Cheers Paul.
PS. All suggested ground mods done. 

[Boots]

They are the 100/110/130 transformers you have there
You need to change your transformers or get a step-down transformer


    B-19548: small 100/115/130 volt transformer.
    C-19552: large 100/115/130 volt transformer.
    B-19550: small 220/240 volt transformer.
    C-19554: large 220/240 volt transformer.
    B-19549: small German 220/240 volt transformer.
    C-19553: large German 220/240 volt transformer.

[Pauly540]

Thanks Chris,

I'll try a step down  and report back.

[The pinballist formally known as Dean Morgan]

They are the 100/110/130 transformers you have there
You need to change your transformers or get a step-down transformer


    B-19548: small 100/115/130 volt transformer.
    C-19552: large 100/115/130 volt transformer.
    B-19550: small 220/240 volt transformer.
    C-19554: large 220/240 volt transformer.
    B-19549: small German 220/240 volt transformer.
    C-19553: large German 220/240 volt transformer.

Not correct Chris, you can wire the two transformers in series as he has done for 240 volt input.  No need for a step down transformer.

[Boots]

Hmmm
That would mean the high current coil voltage would be affected by the mains running through the low current small transformer????
I am sure as you say it would work but wouldn't there be some performance loss with the coils?
Would there be disturbance to the 5v?

[Mr Pinbologist]

They are the 100/110/130 transformers you have there
You need to change your transformers or get a step-down transformer


    B-19548: small 100/115/130 volt transformer.
    C-19552: large 100/115/130 volt transformer.
    B-19550: small 220/240 volt transformer.
    C-19554: large 220/240 volt transformer.
    B-19549: small German 220/240 volt transformer.
    C-19553: large German 220/240 volt transformer.

Not correct Chris, you can wire the two transformers in series as he has done for 240 volt input.  No need for a step down transformer.

+1, i have done this with my Roller Disco which has the American type 130v transformers in it. It had a GINORMOUS step-down transformer in it when i got it. I wanted to piss that off out of the game and wired the primaries of the two transformers in series as shown in Pauly540s pics.

It most certainly CAN be done BUT.. you DO get some flickering of the lamps as the coils fire, which doesn't bother me that much so i live with it. The voltages from the smaller transformer seem unaffected, as the game operates fine and hasn't missed a beat.. no resets or anything like that.

Also being a four flipper game it did weaken the flippers slightly which i remedied by adding a 3300uF capacitor across the bridge rectifier for the coils.. yeah i know its not a real good thing to do but it was justified in this case i thought  as the game plays the way it should having added the cap.

[DSB]

The 12V rectifier has correct 14VAC in, but has 25VDC out!

This suggests to me that the problem is not with the transformers. Sounds to me like a voltage is be introduced from a short, crossed wire or faulty component after the rectifier?

[Pauly540]

The 12V rectifier has correct 14VAC in, but has 25VDC out!

This suggests to me that the problem is not with the transformers. Sounds to me like a voltage is be introduced from a short, crossed wire or faulty component after the rectifier?

You were right 
Always had a short in my mind, but I was going around in circles lifting the Playfield up and down doing constant measurements. Sometimes this 12V/38V was fine, sometimes jumping to 20+V/60V.
So today I started from scratch again. Unplugged everything, de-soldered all the rectifiers and had two multimeters measuring AC & DC at the same time whilst reconnecting. (Unplugging mains each time)
Everything was perfect 14VDC & 40VDC, until getting to the GI. I still have the fuses F1/F2 removed, but when I de-soldered all the GI playfield/Light box main feeds I’m at a point where it is definitely within the GI section somewhere. Keep in mind to GI works perfectly (with fuses in) even with these high readings.
Maybe the 14V + a 6+V GI are giving me the 20+V reading and the excessive 20V + 38V is giving me 60V somehow?
Ran out of time today, so will hopefully find my ‘stupid’ mistake tomorrow.
Thanks for all the pointers, guys.
Cheers, Paul.

[DSB]

So today I started from scratch again. Unplugged everything, de-soldered all the rectifiers and had two multimeters measuring AC & DC at the same time whilst reconnecting. (Unplugging mains each time)

   This was going to be my next suggestion! A pain to do though.

[Pauly540]

Making some progress. There are defiantly no shorts in the head box/Playfield 6VAC GI! I spent hour’s double checking everything. 
I replaced the 38V smoothing capacitor and with both GI fuses removed, again I have 14VCD & 40VDC as per schematic.

Put the head box fuse in and it goes up to 17VDC & 45VCD.
Now put the second PF fuse in and it goes up to 19VDC & 50VDC.

Whilst triggering the un-controlled solenoids this 50V drops down to around 44V and they are not smashing the ball around now, but the 19VDC stays constant.

I still do not understand how the separately tapped AC GI can affect the rest of the machines DC outputs, because the 24VDC (other solenoids) and 6VDC (controlled lamps) readings are spot on. 
Maybe I’m now chasing ghosts in frustration and these are now acceptable readings for this dual 115V transformer configuration?
I only need to get the regulated 12VDC (from separate PSU) to the sound board and I’m almost done.

Any thoughts?

[DSB]

   This may be above my pay scale!

For interest does each transformer input voltage change when the fuses are installed, although even if it does it doesn't explain how a rectifier can have a higher voltage on its output than what is going in. You mentioned Beaky has helped out, Maybe a PM to him for any info on the problem or non problem as you have said.

[Pauly540]

DSB. AC input voltages don’t vary much, just 0.5 – 1 VAC. This is what is starting to make me go insane.  

I know Andrew (Beaky) is always more than helpful on this forum, but I don’t want to impose a PM on him, just because he provided me a service repairing my system/driver boards. (That’s just my way thinking). I put the question out there, because others may have had a similar problem.

After many hours tracing wires/schematic, I have now 100% confirmed that the 6.3VAC tap (Playfield/ Back box GI) when either fuse is installed, affects/increases my rectified DC (solenoids mainly) outputs, this transformer also outputs the 25VAC to rectifiers. Makes absolutely no sense to me.  

At this point, I can only assume I have a defective transformer, or maybe others with this USA/series wired setup, have not noticed that the DC solenoid outputs are higher than required. I’m not dreaming/ghost chasing RMS readings; I really am getting permanent 60VDC to 38VDC solenoids, because it’s smashing the ball around with GI the running, perfect without GI fuses.

If I put my meter inline on each GI fuse clip on Amps, I get around 2A (x 20 #47 bulbs), which should be OK for a 7A rated circuit?

I borrowed   a set of 240V transformers from a ‘Haunted House’ and with these installed everything is perfect, so I’m tending to lean towards (boots)   original reply about 240V transformers.

If anyone has a spare set of working B-19500 – C19544 transformers for sale, please PM me.

I come from an automotive background, so fully understand about bad DC earthing, but still can’t get my head around how this single 6.3VAC tap/circuit can cause havoc on the rest of the machines DC’s rectified side. All my machine earthing is correct, including transformers.

If I can’t source a set of 240V transformers, would I be able to source a high Amp 6.3VAC transformer, taking a 240VAC feed off the AC input and run the GI off that to get me running?  
Or, and please don’t shoot me down for hacking, tap into the controlled playfield 6VDC line for controlled lamps, rated a 7.5A using LED’s instead. Just posing a theory.  
Hope this frustrating post makes some sort of sense.
Cheers, Paul.  

[Retropin]

Just come onto this thread and we need to go back to basics.

Transformer in question is the 6.3VAC and 25VAC output yes?

Firstly, make sure the transformer is wired correctly and that the -ve AC side is taken to COMMON and not ground. Reason for this is that often common can be sitting at 20VAC... your solenoid AC output at 60VAC ( when referenced to ground)... the machine only see the potential difference of the Common and Solenoid AC output... which would be 60v Minus 20V =40V.
Reference to true ground and youll get higher readings... you are only interested in both outputs of the AC windings.

I  don't understand this statement:

it’s smashing the ball around with GI the running, perfect without GI fuses

Are you saying that the GI is running Ok without a fuse installed??..If so - you have a bypass of the fuse somewhere.
Am I reading you right when I say that GI is running without a fuse installed and when you do install a fuse then the coil voltage rises but lamps do not blow?

[Pauly540]

Sorry, I might have worded it better. Please be patient with me, as I'm still new to this. Well, SYS80's.
The transformers are wired correctly as per picture #6 using the commons, not any machines earth's and Yes; I am referring to the 6.3/25V output transformer being my problem. (In my mind)
If I continuity check the transformers casings, they are connected to the machines earth as per earth mounting points screwed down to wooden board. If I remove or add new earth's, it makes no difference. The transformer commons’ don’t read anything to any earth point.
With the two GI fuses removed and ‘NO’ GI lamps powered (because the fuses are out), the 24V/38VDC solenoids fire/push the ball around as the machine was designed. I have two multimeter's running across a rectifier, one reading AC input and the other reading DC output.
Just sticking to the 38V rectifier for example, I have around 38VAC in and around 40VCD out. When the 38V solenoids fire, the AC inputs stay constant and the DC readings jump around from 40-50VDC when energised. I would say that is a normal slight spike, because it settles back down to 40VDC when idle.

Now If I put one GI fuse in (Playfield) the 38VAC is normal, but the DC reading ups to 50VDC. The game still plays well, but they are firing a bit stronger, sometimes it spikes to 60VDC. Everything’s still fine, the machine is still playable.

If I then put the second GI fuse in (Back Box) the 38VAC is normal, but the DC reading ups again, to 60VDC. I dare not put the PF glass in, as the 38V slings are now smashing the ball around and sometimes throwing it out of the machine! Plus it’s denting my new clear coated playfield. 
I think I have seen a spike of 70VDC. No fuses are blowing buy the way.

As per ‘Mr Pinbologist’ comments, yes the GI does flicker when solenoids are fired and going off my EM’s, I thought that was normal. The 6VDC controlled lamps outputs are always spot on.
I even tried temporally running new wires from the 6.3VAC taps to the separate GI circuits (eliminating any shorts within the machines loom), but it’s still the same.

Like I said above, if I install a set of OZ delivered machine 240V transformers from the Haunted House, everything works fine, so I know there is not a problem in the GI lines.
I think I mentioned before, I have be playing with this problem for a few weeks now and can hear the transformers hum pitch change when I put the GI fuses in, so I am adamant that there is some sort of load going on. Could be wrong. 
 
My next step is to get a cheap stepdown transformer, rewire the transformers back to the US 115V spec and see what happens.
Hope that ranting makes some sort of sense!
Cheers, Paul.

[The pinballist formally known as Dean Morgan]

Certainly sounds like the transformer is breaking down under load. Buy a desperate transformer to run the GI from Jaycar and sounds like it would all be fine