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Arcade Collecting => Restorations & repair => Topic started by: telonio on October 26, 2021, 03:16:21 pm

Title: Bubble Bobble pcb sound potentiometer issue.
Post by: telonio on October 26, 2021, 03:16:21 pm
Hello,

I have a bootleg Bubble Bobble pcb and it has an issue with the potentiometer of the sound. The sound was very low and intermittent.
I don't know how many khz was this potentiometer so I change it with a 220khz which I had around. With the 220khz there is too much noise only and no sound in game. I guess that the khz are not right for the pcb.

Anyone knows how many khz should be the potentiometer for the sound?

Thanks


This in the picture is the potentiometer that was placed by the manufacturer and was very low and intermittent.

(https://i.postimg.cc/SRVnPcZZ/20211023-112541.jpg)
Title: Re: Bubble Bobble pcb sound potentiometer issue.
Post by: thebyter on October 27, 2021, 03:27:00 am
Potentiometers are (variable) resistors, which are measured in OHMS, not HERTZ, fyi.

I don't have this board to look at or measure, but looking at https://www.arcade-museum.com/manuals-videogames/B/BubbleBobble_Schematics_Cleaned.pdf, this appears to be VR1, which according to the schematic, is a (zero to) 5K ohm pot.  I don't know what the nominal value should be, though; you'll probably have to set it near the middle and sweep up and down until the sound improves -- or find someone with a working unit and get them to measure theirs.

Thanks!
Title: Re: Bubble Bobble pcb sound potentiometer issue.
Post by: telonio on October 27, 2021, 04:49:31 pm
Ah so sorry, you are right thebyter, is OHMS.

I will buy and try a 5K ohm and see if it works ok. However I am sure that there are no such small potentiometers any more here in the market and the 5K will have it's pins pretty wide for the holes in the board.
Title: Re: Bubble Bobble pcb sound potentiometer issue.
Post by: thebyter on October 27, 2021, 05:17:19 pm
there are no such small potentiometers
Well, don't take my word for it.   8)  I'm just going by the schematic I found over at KLOV -- it might be for a different board rev; I might have read the schematic (or the board layout) wrong; the schematic itself might be wrong (it's not unheard of). 

I know there are plenty of little 5K trimmer pots available form Amazon, DigiKey, or Mouser, but I'm not familiar with your country (and 5K is probably going to be no larger than 220K).  Still, it might be a good idea to find someone with a Bubble Bobble board and have them measure theirs.  KLOV is probably a better place to locate such a person, though.

Thanks!
Title: Re: Bubble Bobble pcb sound potentiometer issue.
Post by: PL1 on October 27, 2021, 06:02:46 pm
Instead of guessing the correct value, measure the resistance between tabs 1 and 3.
- Even if there's dirt/corrosion on the surface of the resistive element or wiper arm, you should still get a fairly accurate reading this way.

If you can't get a good reading that way, one of the tab 1 or tab 3 connections to the resistive element may be broken or damaged.
- Start with the knob set to mid-range then crank the knob clockwise while checking resistance between 1 and 2.
- If it reads open/no continuity the whole time, tab 1 is broken/damaged and you need to set it to midrange again and crank it counter-clockwise while checking between 2 and 3.

(https://makeabilitylab.github.io/physcomp/arduino/assets/images/Potentiometer_DiagramWithSchematicSymbol.png)


Scott