Bally Lost World: Solenoid Driver TP2 Voltage Constantly Too High

I've squared away my rectifier board on my Lost World (as of now), so I'm starting to move on to plugging the other boards in individually and verifying their voltages are good one by one. My solenoid driver board is giving me issues. All test points are good, except for TP2. TP2 is supposed to be 190vDC, adjustable by the trimmer pot RT1. Mine, however, tests consistently 240vDC, no matter what the trimmer pot is set at. It is the -22 revision of the board.

I recapped the board (including tantalum cap, upgraded C23 to a 15000uf cap), replaced both bottlecap transistors, reflowed the header pins, did the two suggested jumper mods (jumpered the negative lead of the cap C23 to the trace directly below it and tied TP1 and TP3 together), replaced Q23, replaced one of the diodes near the bottom of the board (CR8 IIRC, but that's not particularly relevant to this problem I don't think), replaced trimmer pot RT1.

I tested essentially everything in the 190vDC circuit, and I found that VR1 (the diode), R56, R35 and R54 all tested bad/out of spec. The fuse never blew.
My readings for Q22:
Red lead on base- c tests .64 and e tests .65
Black lead on base- c tests open, e tests 1.26
Black lead on c- e tests 1.25
Red lead on c- e tests open

My readings for Q23:
Red lead on base- c tests .64 and e tests .65
Black lead on base- c tests open, e tests open
Black lead on c- e tests .52
Red lead on c- e tests 1.03

Tests on Q22/Q23 were done within circuit, with the 4 parts I identified as bad earlier out of circuit (if it makes any difference). It seems to me that these are bad (even the one I just replaced).

Something I did notice is that from both Big Daddy and Marco, the cap that's supposed to be 360uf is sold as a 350uf. I'm assuming the 360uf isn't made anymore. Would this cause issues?

My plan was essentially to just shotgun replace the 6 parts that are bad, as well as the two 0.01uf 500v ceramic disc capacitors in the circuit. Is there anything else I should test or consider before going for this plan of action?

#2 3 years ago

AMS

barakandl

OP
Quoted from Knxwledge:
I've squared away my rectifier board on my Lost World (as of now), so I'm starting to move on to plugging the other boards in individually and verifying their voltages are good one by one. My solenoid driver board is giving me issues. All test points are good, except for TP2. TP2 is supposed to be 190vDC, adjustable by the trimmer pot RT1. Mine, however, tests consistently 240vDC, no matter what the trimmer pot is set at. It is the -22 revision of the board.
I recapped the board (including tantalum cap, upgraded C23 to a 15000uf cap), replaced both bottlecap transistors, reflowed the header pins, did the two suggested jumper mods (jumpered the negative lead of the cap C23 to the trace directly below it and tied TP1 and TP3 together), replaced Q23, replaced one of the diodes near the bottom of the board (CR8 IIRC, but that's not particularly relevant to this problem I don't think), replaced trimmer pot RT1.
I tested essentially everything in the 190vDC circuit, and I found that VR1 (the diode), R56, R35 and R54 all tested bad/out of spec. The fuse never blew.
My readings for Q22:
Red lead on base- c tests .64 and e tests .65
Black lead on base- c tests open, e tests 1.26
Black lead on c- e tests 1.25
Red lead on c- e tests open
My readings for Q23:
Red lead on base- c tests .64 and e tests .65
Black lead on base- c tests open, e tests open
Black lead on c- e tests .52
Red lead on c- e tests 1.03
Tests on Q22/Q23 were done within circuit, with the 4 parts I identified as bad earlier out of circuit (if it makes any difference). It seems to me that these are bad (even the one I just replaced).
Something I did notice is that from both Big Daddy and Marco, the cap that's supposed to be 360uf is sold as a 350uf. I'm assuming the 360uf isn't made anymore. Would this cause issues?
My plan was essentially to just shotgun replace the 6 parts that are bad, as well as the two 0.01uf 500v ceramic disc capacitors in the circuit. Is there anything else I should test or consider before going for this plan of action?

HV in = HV out usually means all three HV transistors are bad.

The 22k and/or 82k 1/2W resistor burn up when the transistors go bad. Can normally glance at a SDB and if you see the 22K or both resistors fried you can pretty much guarantee the HV section transistors are bad. The bally repair guide tells you to replace the 22k resistor if the if the HV transistors are bad, probably because it consistently burns up when the transistors fail.

HV in good but low HV out usually is bad zener diode.

The HV cap should be 150uF at 350v+ So i think you are probaby mixed up V rating with the uF rating. 360uF will be fine too as long as it is rated for over 350vdc.

#3 3 years ago

DNH

Knxwledge

Pinside member

Quoted from barakandl:
HV in = HV out usually means all three HV transistors are bad.
The 22k and/or 82k 1/2W resistor burn up when the transistors go bad. Can normally glance at a SDB and if you see the 22K or both resistors fried you can pretty much guarantee the HV section transistors are bad. The bally repair guide tells you to replace the 22k resistor if the if the HV transistors are bad, probably because it consistently burns up when the transistors fail.
HV in good but low HV out usually is bad zener diode.
The HV cap should be 150uF at 350v+ So i think you are probaby mixed up V rating with the uF rating. 360uF will be fine too as long as it is rated for over 350vdc.

I pulled Q22 Q23 out of circuit and tested them; they tested fine that way. I could pull the other HV transistor out and test it too, but it is new. When you say "HV in = HV out usually means all three HV transistors are bad.", are you referring to 'HV in' as the HV from the transformer rectifier board, and 'HV out' as the HV from the solenoid driver board? If my understanding of the flow of power is correct (and it totally could not be), the 190vDC on the solenoid driver board is fed from the 230vDC on the rectifier board. IIRC (and I'm not sure if it would be smart to reconnect the solenoid driver board to test it again), TP2 on the rectifier board was testing lower than TP2 on the solenoid driver board.

The bad parts I talked about in the previous post don't really have any obvious signs of damage/burning up, they just tested out of spec.

I am having a new issue with F1 blowing on the rectifier board with J1 J3 plugged in, which I think is unrelated to the main problem of *this* thread. I will likely make a new thread about it if I can't figure it out through searching.

#4 3 years ago

GPE

G-P-E

You mention Q21 is new.
Where did you get it and what markings are on the transistor?

#5 3 years ago

AMS

barakandl

OP
Quoted from Knxwledge:
I pulled Q22 Q23 out of circuit and tested them; they tested fine that way. I could pull the other HV transistor out and test it too, but it is new. When you say "HV in = HV out usually means all three HV transistors are bad.", are you referring to 'HV in' as the HV from the transformer rectifier board, and 'HV out' as the HV from the solenoid driver board? If my understanding of the flow of power is correct (and it totally could not be), the 190vDC on the solenoid driver board is fed from the 230vDC on the rectifier board. IIRC (and I'm not sure if it would be smart to reconnect the solenoid driver board to test it again), TP2 on the rectifier board was testing lower than TP2 on the solenoid driver board.
The bad parts I talked about in the previous post don't really have any obvious signs of damage/burning up, they just tested out of spec.
I am having a new issue with F1 blowing on the rectifier board with J1 J3 plugged in, which I think is unrelated to the main problem of *this* thread. I will likely make a new thread about it if I can't figure it out through searching.

HV in = +230v from the transformer bridge. The unregulated voltage.

HV out = the regulated +175vdc for the displays leaving the HV section.

When the HV in is the same voltage as high voltage out and shows no adjustment with the pot, the transistors are bad, pretty much it has to be the transistors. To get that situation and it not be the transistors bad something is really hooked up wrong. Repaired hundreds of these boards. HV section fail mode is very consistent and common.

9/10 all three transistor fail at the same time so replace all three at once. People screw themselves by replacing them one at time and trying the board between each one and they keep frying other transistors. What GPE is hinting at is these can transistors are obsolete and one of the most faked parts is can'd transistors and v-regs. Never buy transistors from dodgy china sources if they are bigger than TO92. MJE3439 and BUX85 can be used if you have trouble sourcing the original and probably obsolete can parts. Get the bux85 version with the metal tab you you can still mount it to the heat sink (cut off middle pin and use tab for the screw hole connection). MJE3439 can have the small to220 heat sinks mounted to them, but honestly my temp measurements show they well within safe temp range naked.

#6 3 years ago

DNH

Knxwledge

Pinside member

Quoted from G-P-E:
You mention Q21 is new.
Where did you get it and what markings are on the transistor?

I'm no stranger to the concept of bootleg parts, especially the 2n3055 bottlecaps for Atari AR2s. I bought it, and Q22 directly from Marco Specialties:
https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=2N3584
https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=2N3440

If you want me to snap a pic of the actual part I received, I can.

#7 3 years ago

DNH

Knxwledge

Pinside member

Q21. Just took it apart and double checked I didnt put it in backwards
20201210_191112 (resized).jpg

#8 3 years ago

GPE

G-P-E

OK -- NTE. So that's OK, they are one of the few reliable sources left.
Markings on part look correct, same as the 2N3584s that I bought direct from NTE, so he should fine.

It is still possible that a new, off the shelf part can be bad. Doesn't happen often but does occasionally.
I did run into another customer that had one fail like this. When he disassembled, he noticed one of the transistor legs touching the heat sink case. Shifted it over, tightened it back down and it started working again.

As I look at the photo... why is the 140V zener hanging with one leg in the air?

#9 3 years ago

DNH

Knxwledge

Pinside member

Quoted from G-P-E:
OK -- NTE. So that's OK, they are one of the few reliable sources left.
Markings on part look correct, same as the 2N3584s that I bought direct from NTE, so he should fine.
It is still possible that a new, off the shelf part can be bad. Doesn't happen often but does occasionally.
I did run into another customer that had one fail like this. When he disassembled, he noticed one of the transistor legs touching the heat sink case. Shifted it over, tightened it back down and it started working again.
As I look at the photo... why is the 140V zener hanging with one leg in the air?

The zener is hanging there because it tested bad (I checked it like a normal diode), and I was going to replace it. I have not run the board with parts hanging like that. Also, the thermal pad I had for the Q21 had to be slightly cut because it didn't line up perfectly. I checked that the case of the transistor isn't shorted to the frame, but would this cause an issue? I did also check that the E and B legs are not touching the heat sink, and they aren't

#10 3 years ago

AMS

barakandl

The resistor next to cr21 looks burnt too.

Is the zener short circuit or open circuit fail? Every time i had a bad zener in this circuit ended up with really low HV output.

#11 3 years ago

DNH

Knxwledge

Pinside member

Quoted from barakandl:
The resistor next to cr21 looks burnt too.
Is the zener short circuit or open circuit fail? Every time i had a bad zener in this circuit ended up with really low HV output.

I think the one you are referring to (the resistor to the left of CR21) was on the chopping block to get replaced. Looking back at the board, I noticed a couple of the resistors I tested that were still within spec also looked burned. Worth replacing those too?

The zener tested open

#12 3 years ago

GPE

G-P-E

OP
Quoted from Knxwledge:
The zener is hanging there because it tested bad (I checked it like a normal diode), and I was going to replace it. I have not run the board with parts hanging like that. Also, the thermal pad I had for the Q21 had to be slightly cut because it didn't line up perfectly. I checked that the case of the transistor isn't shorted to the frame, but would this cause an issue? I did also check that the E and B legs are not touching the heat sink, and they aren't

Thermal pad in photo was for a TO-3 style transistor which is why you had to cut it - that will work fine. TO-3 transistors are bigger than that TO-66 at Q21.
It was the legs of Q21 that I was referring to. I have seen that heat sink twisted just enough to where the transistor leg was barely shorted to heat sink.

Open zener diode results in no biasing of transistor Q23. Since Q23 has a pull down on his base then he will be turned off and unable to vary the voltage on output of Q22. Essentially - Vout will be equal to Vin.

while you're at it, may as well replace other toasty components such as that resistor which measures in spec....for now.

#13 3 years ago

DNH

Knxwledge

Pinside member

Quoted from G-P-E:
Thermal pad in photo was for a TO-3 style transistor which is why you had to cut it - that will work fine. TO-3 transistors are bigger than that TO-66 at Q21.
It was the legs of Q21 that I was referring to. I have seen that heat sink twisted just enough to where the transistor leg was barely shorted to heat sink.
Open zener diode results in no biasing of transistor Q23. Since Q23 has a pull down on his base then he will be turned off and unable to vary the voltage on output of Q22. Essentially - Vout will be equal to Vin.
while you're at it, may as well replace other toasty components such as that resistor which measures in spec....for now.
Ed

Thanks you guys. For now, one last question. In the schema, if a resistor says the ohm value, but doesn't mention the wattage, what is the wattage? 1/4 watt? For example, R55 is listed as 1.2k.

#14 3 years ago

GPE

G-P-E

There is normally a set of notes on the drawing which specifies "All resistors are 1/4W unless otherwise specified".

#15 3 years ago

AMS

barakandl