Atari Centipede Cocktail table game has no power

[jennifer]

White to green, good, anything to black, bad...From what your saying I think, (and from looking at your volt chart) is everything is good until you hook up the interlock then the problem begins (but checked out as good)...Well That would suggest it is either wired incorrectly or something downstream is tripping those fuses...keep the board out of the loop until the end and voltages can be verified...So go back to the your "brick" it's not popping fuses, and aparently checks out fine with no load... This is your jumping off point, whatever you plug into it causes the trouble.

[PL1]

Check out reply 32 for a pic of the underside of the brick. That will show the Bridge rectifier and the big blue cap.

Based on the schematic Mike posted, the cocktail should have a 2 diode full-wave rectifier, not the 4 diode bridge rectifier shown in the upright schematic.

The two types of rectifiers perform similar functions, but are wired to the transformer and C1 differently.

The full-wave rectifier applies a positive to the positive terminal of C1 from whichever diode is forward biased with the negative terminal of C1 tied to the center tap.
- Only one half of the winding is used at a time.
- Orange (ends) to violet (center) = 1/2 of orange to orange
- Think "top pushed up and bottom stays in the middle".

A bridge rectifier applies a positive to to the positive terminal of C1 from whichever diode on the top half is forward biased and applies a negative to the negative terminal of C1 from whichever diode on the bottom half is forward biased.
- Both halves of the winding are used at the same time.
- Think "top pushed up and bottom pushed down".

Correct me if I'm wrong, but it seems like the orange to orange windings for the transformers in the cocktail and upright would be different values for the different types of rectifiers to output the same voltage.   


Scott

[jennifer]

I think you may have something there,Effectively a half wave rectification, that would explain why it is ok, until it has a load...Clever PL1😉

[PL1]

Thanks, Jennifer.   

I agree about the "ok, until it has a load" part of your comment, but disagree about the "Effectively a half wave rectification" part.

A one diode half-wave rectifier would only use the positive part of the waveform -- but that's not the problem here.



In this case, I'm referring to the transformer difference between the two types of rectifiers used to generate the same voltage (V_m) at the load. (R_L)

Full-wave rectifier
- End tap to end tap (A to B) = 2 * V_m
- Voltage at load = V_m.


Bridge rectifier
- End tap to end tap (A to B) = V_m
- Voltage at load = V_m.


If you connect points A and B of the bridge rectifier circuit to points A and B of the full-wave circuit's transformer, you get twice the voltage (2 * V_m) applied to the load.

More details at https://www.elprocus.com/full-wave-bridge-rectifier-versus-center-tapped-full-wave-rectifier/.


Scott

[Mike A]

I have my cab all opened up. If you need pics of anything just let me know. I can leave the cab disassembled until the end of the month.

[bperkins01]

I ended up upgrading wifi yesterday.  The rectifier item is a good catch. 
If the on/off switch + interlock = sends power to pop the fuses - that certainly makes sense.
It doesn't make sense that if you bypass them with jumpers at the power brick - nothing happens.
But again - really hard to do this this remote.

[vapuser]

Good morning all. Scott, thanks for all the technical details of the two types of rectifiers. I had no idea that
there would be a voltage difference. So, if I'm understanding this correctly, by using the bridge rectifier instead
of the full wave rectifier configuration, the circuit is drawing twice the current. Thus, blowing the fuses across
the secondary winding of the transformer. This sounds like why both F2 and F3 fuses are blowing when power is turned
on. I'm glad I saved the full rectifier board. I pulled the brick out of the unit again and I'll reinstall the full
wave rectifier circuit board tonight. Do you think I'll need to replace the two diodes on the board? I already
restored the main fuse holder back to the original component. I agree Jen, it looked funky and I wouldn't have been
able to easily replace that fuse if it ever blew. I included more pics below to show the bypassed switches, the new
fuse holder and the full rectifier circuit board.

bperkins01, your absolutely correct, it doesn't make any sense to me either. By bypassing the switches at both switch
locations or by putting jumpers across J2 at the brick is accomplishing the exact same thing. That one is still stumping
me!  I ordered two 7 amp circuit breakers. As soon as those come in, I'm going to hook them up and go over
that scenario again. This is driving me crazy.

[vapuser]

The pic below is the interlock switch bypassed.

[vapuser]

This pic is the main power switch bypassed.

[vapuser]

This pic is the Full Bridge rectifier board that I will be reinstalling.

[vapuser]

This pic is the bottom view of the Full wave rectifier board.

[vapuser]

Only had time to restore the main fuse holder back to using original component.

[vapuser]

This pic is the solder joint of the bottle cap transistor. First time changing a Transistor component or a rectifier component for that matter.

[jennifer]

Those traces look scary nasty and old to you I would imagine, (I dont know what they got for modern day replacements off hand) But they all do that, it is a age/heat thing and they are still good, Just get in and out (around 700deg.) While soldering them, excessive heat will make the problem worse, and solder pads will fall off...Then you are into patch wires, *not fun, or pretty.

[bperkins01]

On the ARII boards - they all kinda look like that..  Mine does..  agreed..  But it works 

[PL1]

So, if I'm understanding this correctly, by using the bridge rectifier instead of the full wave rectifier configuration, the circuit is drawing twice the current. Thus, blowing the fuses across the secondary winding of the transformer. This sounds like why both F2 and F3 fuses are blowing when power is turned on.

F2 and F3 blowing showed that you wired the bridge across that entire secondary winding (orange to orange) instead of one end to the center tap (orange to violet) which would only blow the fuse on that one orange line.

I haven't found a clear explaination what would happen to the current draw if you use a bridge rectifier in place of a full wave.   

Of course, that doesn't matter because you have the original board and it is easy to replace bad diodes.   

Do you think I'll need to replace the two diodes on the board?

You'll need to test them.




Scott

[vapuser]

Good morning all, Scott, thanks for that video above. Since I have to take the diodes out of the circuit to test, I thought I would just replace them. I also found another video on how to test a diode without a meter. They showed just using a 9 volt battery an LED and a 220 ohm resister. Either way seemed to be simple enough. I'm going to order those parts this morning. Maybe while I'm waiting for parts to come in I'll remove the monitor and take a closer look at the burned out chip. I know I'm going to have to order that part as well eventually. Thanks again for all that research. Have a good day.

[jennifer]

And a cap kit...And a flyback, because that it most likely what welded that regulator like that with leaky high voltage, be carefull working on that thing.

[PL1]

Since I have to take the diodes out of the circuit to test, I thought I would just replace them.

You don't need to desolder/remove the diodes from this board to test them.
- Black lead on the left and red lead on the right = forward biased.



Even if the board was fully installed, removing the "+" connection (lower left hole) or removing F2 and F3 would ensure there is no complete parallel path through other components that could cause misleading multimeter readings.

For circuits where there is no easy disconnect to isolate the diode (i.e. relay with snubber diode at 0:55), you can test it in-circuit using the resistance scale on your meter.




Scott

[vapuser]

Good morning all. I took the time last night to test out the rectifier diodes on the board before replacing them. Please see the pics below to verify that these diodes may be ok. I used the diode setting on my volt ohm meter. With the positive probe of my meter on the cathode of the diode it always read 1, which on my meter is open (no continuity). With the negative probe of the meter on the cathode the reading keep changing. It read anywhere from 002 to 008. Just wondering if that is an acceptable range. I also switched the setting over to ohms, just to see what those readings would be. With the positive probe on the cathode the reading was the same as above for both diodes (no continuity). With the negative probe on the cathode for both diodes the reading was anywhere from .02 to 7.0. That reading keep changing as well. Do you think those readings may be acceptable?

[vapuser]

The pic below is showing the reading of the first diode with the Negative probe on the cathode.

[vapuser]

This pic is showing the positive probe on the cathode of the first diode.

[vapuser]

This pic below is showing the positive probe of the meter on the cathode of the second diode.

[vapuser]

The pic below is showing the negative probe of the meter on the cathode of the second diode.

[vapuser]

From what I've read, I should be getting a forward bias reading of .2 to .7. Typically a .2 reading for the germanium type diodes and .7 reading for the silicon type diodes. It appears that I'm getting a short  reading on the forward bias for both diodes. What I didn't expect to see was a OL (Over limit), (1 on my meter), on the reverse bias for both diodes. From what I gather, both of these diodes are shorted! Back to the store!

[bperkins01]

Your meter is a bit confusing (to me)  - are the 007 and 008 really .007 and .008?
Certainly testing against a good one will tell you for sure.

You have diodes all over that machine to do some checking against.
Hope that's it!
Keep up the good work.

added:
Something killed them - be nice to know what.  (Maybe the old big blue?)
Buy a few extra diodes..  Just in case they pop.
I'd check the resistance across the secondary winding (both orange lines on F2 and F3) with the fuses pulled. 
It should NOT show shorted..  not sure how many ohms you should have... but not shorted.

While I was at it - I'd check for continuity from those same spots against all of the connections on the primary side of the transformer.. just in case.  they should all show open based on the schematic.  right?
Transformer failure is very uncommon..  but not unheard of...

[vapuser]

I'm not crazy about my ohm meter either. Sometimes It doesn't appear to be that accurate. I thought those shorts would have shown a .002 reading, instead of a 002 reading. But I'm pretty much convinced that those diodes are showing a short condition and should be replaced.

Would you or Mike or Scott be able to upload a current full schematic of the power supply? The cocktail table schematic should show the two diode rectifier instead of the half wave rectifier. I feel any further testing of the brick will be more accurate with the correct schematic. Thanks.

[bperkins01]

Pay no attention to the red arrows - I saw this on another thread - but this is the one you have..

[Mike A]

I just emailed you a copy too.

[vapuser]

Thanks, both of you!!

[vapuser]

Good morning all, TGIF! Now that my 7 amp circuit breakers came in, I'll be looking for that short circuit over the weekend. I'm hoping that those rectifier diodes (MR750) come in today or tomorrow as well. I finally found someone who had them. I ordered them from Digikey who actually located them at Rochester Electronics. Rochester Electronics only had one pack of 25 for 5 dollars left. The killer was the $10 dollar S&H charge I had to pay. As was mentioned in an earlier thread, something must have caused those MR750's to short out. Maybe it's a good thing that I'll have a few extra, just in case. I'd like to put this brick back together and come to a determination if any of the windings on the primary or secondary side of the transformer are actually shorted and causing all my problems. Enjoy the weekend.

[bperkins01]

Winding shorts you can test while you wait.  *if* its there - it will be between that winding and one of the others.  Good luck.

[pbj]

Throw that piece of ---steaming pile of meadow muffin--- multimeter away and get something that actually works. 

 

[vapuser]

Good morning all. I'd like to give an update as to where we are currently with this restoration. Originally and currently the game has no life other than the red lights at the two coin slots. We have many good voltages but seem to be missing some 5 volt readings. So to correct that issue, as was suggested, I replaced the 2N3055 (Q3) Transistor and also the LM305 5-volt Linear Voltage Regulator (Q1) on the ARII. I’m anxious to re-test those voltages and continue to move forward.

Problem 2 – As mentioned early on, before joining the forum, I replaced the Big Blue Cap as well as the rectifier circuit. Not having the correct schematic, I replace the full wave rectifier with a half wave rectifier. Now that I have the correct schematic for this cocktail centipede game, I removed the have wave rectifier and ordered two MR750 diodes to replace the shorted out diodes on the original full wave rectifier circuit board.

Problem 3 - Additional Short Circuit problem – F2 and F3 (7 Amp) fuses blow every time I plugged in the J2 connector to the Power Supply. This could have been the result of having the wrong type rectifier in circuit. Those MR750 diodes should come in today. Tonight, I’m hoping to re-solder those diodes and install the original full wave rectifier circuit board. I’ll give another update tomorrow.

Last night, since the 7-amp circuit breakers arrived, I connected those to the F2 and F3 fuse connector block. With the J2 jumpers in place (bypassing the interlock switch and the bottom switch) and the rectifier circuit still disassembled, I plugged the unit in. No fusses blew.  Since the rectifier circuit was disassembled, I thought I would take a reading off that top secondary winding. So putting my leads across the two orange wires, I got a voltage reading of 19.3 VAC. I was always curious as to what that voltage off the secondary prior to the rectifier circuit would read. Hoping to see 10.5 DC after the upgrade. Hopefully I’ll be able to give a more informative update tomorrow.

[vapuser]

02/28/2020

TGIF, Good morning all, Happy to report that the above Problem 2 and Problem 3 have been resolved. The MR750 diodes have been re-soldered to the original full wave rectifier board. See pic below. I retested all the J5 secondary winding output voltages with a load again and all is still good.

Additionally, I hooked the brick back up in the cabinet and removed the J2 jumpers that were in place to bypass the interlock switch and the bottom switch. I plugged in the J2 connection instead and turned the game on. No fuses blew. Now I feel we’re making progress.  I currently have the bottom switch hooked up, but I have the top interlock switch still removed from the circuit.

Moving forward – Tonight, I’ll reconnect that top interlock switch in place and start re-connecting the additional boards. I’ll start with the PCB board. If no fuses blow, I’ll continue to connect the ARII. At that point I’m hoping to see the red power light on the PCB. With the new Transistor and voltage regulator now replaced, I’m anxious to retest the ARII for those missing 5 volt readings. If all goes well, I report back tomorrow with additional more promising news. Have a good weekend!

[vapuser]

The pic below showing the brick with the rectifier restored back to original configuration.

[Mike A]

Kudos to you for sticking with it.

[bperkins01]

02/28/2020

TGIF, Good morning all, Happy to report that the above Problem 2 and Problem 3 have been resolved. The MR750 diodes have been re-soldered to the original full wave rectifier board. See pic below. I retested all the J5 secondary winding output voltages with a load again and all is still good.

Additionally, I hooked the brick back up in the cabinet and removed the J2 jumpers that were in place to bypass the interlock switch and the bottom switch. I plugged in the J2 connection instead and turned the game on. No fuses blew. Now I feel we’re making progress.  I currently have the bottom switch hooked up, but I have the top interlock switch still removed from the circuit.

Moving forward – Tonight, I’ll reconnect that top interlock switch in place and start re-connecting the additional boards. I’ll start with the PCB board. If no fuses blow, I’ll continue to connect the ARII. At that point I’m hoping to see the red power light on the PCB. With the new Transistor and voltage regulator now replaced, I’m anxious to retest the ARII for those missing 5 volt readings. If all goes well, I report back tomorrow with additional more promising news. Have a good weekend!

I'd consider hooking up the PCB last - you want all the power right before blowing that up....  I went Power Brick --> ARII -->  PCB

[jennifer]

02/28/2020

TGIF, Good morning all, Happy to report that the above Problem 2 and Problem 3 have been resolved. The MR750 diodes have been re-soldered to the original full wave rectifier board. See pic below. I retested all the J5 secondary winding output voltages with a load again and all is still good.

Additionally, I hooked the brick back up in the cabinet and removed the J2 jumpers that were in place to bypass the interlock switch and the bottom switch. I plugged in the J2 connection instead and turned the game on. No fuses blew. Now I feel we’re making progress.  I currently have the bottom switch hooked up, but I have the top interlock switch still removed from the circuit.

Moving forward – Tonight, I’ll reconnect that top interlock switch in place and start re-connecting the additional boards. I’ll start with the PCB board. If no fuses blow, I’ll continue to connect the ARII. At that point I’m hoping to see the red power light on the PCB. With the new Transistor and voltage regulator now replaced, I’m anxious to retest the ARII for those missing 5 volt readings. If all goes well, I report back tomorrow with additional more promising news. Have a good weekend!

I'd consider hooking up the PCB last - you want all the power right before blowing that up....  I went Power Brick --> ARII -->  PCB

I know right?...Must have told him a hundred times, But At this point, it's pretty obvious the problem.

[vapuser]

IT'S ALIVE! IT'S ALIVE! The game is finally showing some signs of life now. I think I still have a ways to go yet. Like I said Friday, I reconnected the interlock switch, and turned the machine on. So far so good, no fuses blown. I reconnected the plugs to the PCB board and turned the machine back on again. Still looking good. I reconnected the ARII, turned the game back on and all the lights came on. The PCB board LED light, the two coin receptor lights, plus the two LED's above the coin receptor. The speaker was even making some noise. For now, I left the monitor unplugged. I noticed that the two LED lights above the coin receptor were blinking, so I inserted two coins. I pushed those LED buttons and it sounded like the game was playing. I was pressing the fire button and rolling the yellow ball. The sound coming out of the speakers was a little fuzzy and staticy, but it sounded like it was working. So now I thought I'd plug in the monitor just to see If it would light up. Nothing. So I disconnected the monitor and checked the voltages on the two plugs. Still no voltage on the six pin plug, and 126 volts on the three pin plug just like before. I left the monitor unplugged and turned the game back on again, but can't get it to sound like it's playing. I hope I didn't cause any damage by plugging in the monitor. Any clue why the 6 pin monitor plug has no voltage? Do you have a schematic of that plug showing pin voltages? I have a feeling that the next step is going to be to remove the monitor from the chassis. As you mentioned previously, that one fried part on the monitor circuit board might be a voltage regulator. Well, one step at a time. What are your thoughts?