| Arcade Collecting > Restorations & repair |
| Atari Centipede Cocktail Table is experiencing a few problems |
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| vapuser:
Good evening all, I own an Atari Centipede cocktail table which is giving me a few problems. The first problem that I’d like to resolve is that the sound out of the speakers is a low pulsating hum. It’s probably relating to a bad cap, but I’m 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 I’m 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? |
| Mike A:
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:
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. |
| PL1:
--- Quote from: Mike A on September 25, 2021, 06:33:02 am ---There are differences I believe in the power section between the upright and the cocktail. --- End quote --- Correct. Here's some of the related info from vapuser's previous thread. --- Quote from: PL1 on February 16, 2020, 01:55:42 pm --- --- Quote from: vapuser on February 16, 2020, 10:43:15 am ---Check out reply 32 for a pic of the underside of the brick. That will show the Bridge rectifier and the big blue cap. --- End quote --- 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 --- End quote --- Scott |
| nitrogen_widget:
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? |
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