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Author Topic: Atari Centipede Cocktail Table is experiencing a few problems  (Read 4441 times)

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vapuser

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Atari Centipede Cocktail Table is experiencing a few problems
« on: September 23, 2021, 06:33:37 pm »
Good evening all, I own an Atari Centipede cocktail table which is giving me a few problems. The first problem that Iíd like to resolve is that the sound out of the speakers is a low pulsating hum. Itís probably relating to a bad cap, but Iím not sure where to look. Does anyone have any suggestions?

This morning, after reading through my Centipede manual,  I decided to removed the Regulator/Audio II PCB board to check all the voltages. I noticed that all the voltages were within range except for two points that showed 36VAC. Each of those voltages were only showing 18.19 VDC and 18.24 VDC. So now Iím thinking that the two 33,000 uf/35v Nichicon caps might be bad. Time to order more parts. Is it possible that these bad caps could be causing the pulsating hum coming through the speakers?
« Last Edit: September 24, 2021, 09:23:35 am by vapuser »

Mike A

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #1 on: September 25, 2021, 06:33:02 am »
I am going to try to get you some help.

Make sure you have the correct manual.

There are differences I believe in the power section between the upright and the cocktail.

vapuser

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #2 on: September 25, 2021, 10:45:42 am »
Thanks Mike. I tried to upload a short video of the sound that was coming out of the speakers, but it was rejected do to size restriction. Even after opening it with VLC Media player and reducing the size it was still slightly too large. Thanks for your assistance.

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #3 on: September 25, 2021, 11:41:15 am »
There are differences I believe in the power section between the upright and the cocktail.
Correct.

Here's some of the related info from vapuser's previous thread.

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.   :dunno




Scott

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #4 on: September 25, 2021, 01:27:16 pm »
interesting.
Is there a difference electrically in the PCB itself between upright and cocktail or are we just looking at a different configuration in the power supply and audio/regulator boards?

vapuser

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #5 on: September 25, 2021, 06:50:40 pm »
09/25/21

Thanks guys for your concerns, but I addressed that problem last year, please see below:
Quote
02/17/2020
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.

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 weíre making progress.  I currently have the bottom switch hooked up, but I have the top interlock switch still removed from the circuit.

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

To bring everyone up to date, No fuses are blowing, the top interlock has been reconnected, the red power light on the PCB board is now lit and all ďappearsĒ to be working properly. Iím now getting an image on the screen and I can now play a game ďblindlyĒ.  By that I mean that I have no ďcursorĒ. When I roll the ball, nothing appears to move. I took apart the entire roller ball assembly and cleaned all the parts and reassembled.

Additionally, When Iím playing, Iím getting a low pulsating hum from the speaker. I thought I might want to tackle that problem first. So I took the Regulator/Audio II PCB out of the cabinet and checked all the voltages. It appears that all the voltages are within range except the voltages at C9 and C10. Those voltages should be 36VAC. Instead, Iím showing a voltage of 18.19 and 18.24VAC. So, I ordered those 3300uf caps in hopes that the rumbling sound out of the speakers will turn into a normal game sound. Please see attached pics.


vapuser

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Re: Atari Centipede Cocktail Table is experiencing a few problems
« Reply #6 on: September 25, 2021, 06:53:03 pm »
Picture of the monitor when the game is turned on.