Jfrik84 Posted June 26, 2022 Share Posted June 26, 2022 I recently purchased a Mr.Do! Dedicated Cocktail table and found the only mechanical issue is that the sound doesn't work. After some luck picking the locks, I found the speaker wires had been cut very short with no obvious place in sight that they should be connected. My best guess is that this wasn't originally a Mr. Do! since the table has Taito printed on the sides and glass and I suspect when they switched it over, they didn't install a sound board as I don't clearly see one anywhere. This is all speculation since information on this table seems very limited online. I am hoping someone might be able to help me figure out where the speaker wires should be connected. Maybe someone has a diagram or more information than what I'm finding online. Any help to get this unit 100% functional is much appreciated! 1 Quote Link to comment Share on other sites More sharing options...
TheGuru Posted June 28, 2022 Share Posted June 28, 2022 Looks like a bootleg board. According to online Mr Do pinout, speaker+ is pin 10 on the bottom. To wire up the speaker connect the black speaker wire to ground and the other lug to pin 10 on the PCB connector bottom side. Quote Link to comment Share on other sites More sharing options...
Jfrik84 Posted June 28, 2022 Author Share Posted June 28, 2022 1 hour ago, TheGuru said: Looks like a bootleg board. According to online Mr Do pinout, speaker+ is pin 10 on the bottom. To wire up the speaker connect the black speaker wire to ground and the other lug to pin 10 on the PCB connector bottom side. Thank you! After reading that, I found that someone had already soldered a pigtail to the bottom of pin 10. I made the connections and it worked! It's very quiet, but with this information, installing an amplifier should be straightforward now. I appreciate the guidance! Quote Link to comment Share on other sites More sharing options...
TheGuru Posted June 29, 2022 Share Posted June 29, 2022 There's a power amplifier on the PCB. Look for the volume pot and turn it. If that doesn't increase the volume there may be some suspect caps on the PCB that might need changing. The fact that you get any sound means the amp is working and there's 12V getting to it. It's common for caps to be bent over and pull one of the legs out of the cap then some noob sees it and pushes it back in thinking it will be ok. Or they could just be bad or out of specification. Remember that they are probably 40 years old. The pinout shows speaker- is pin 11 on the bottom so you could try joining to pins 10 and 11 on the bottom. But usually speaker- is just a normal ground so it may already be wired to ground. Quote Link to comment Share on other sites More sharing options...
Jfrik84 Posted June 29, 2022 Author Share Posted June 29, 2022 9 hours ago, TheGuru said: There's a power amplifier on the PCB. Look for the volume pot and turn it. If that doesn't increase the volume there may be some suspect caps on the PCB that might need changing. The fact that you get any sound means the amp is working and there's 12V getting to it. It's common for caps to be bent over and pull one of the legs out of the cap then some noob sees it and pushes it back in thinking it will be ok. Or they could just be bad or out of specification. Remember that they are probably 40 years old. The pinout shows speaker- is pin 11 on the bottom so you could try joining to pins 10 and 11 on the bottom. But usually speaker- is just a normal ground so it may already be wired to ground. That sure would be nice if it could be adjusted on the PCB, but I'm just not seeing any kind of adjustment for that anywhere. I tried switching speaker - to pin 11, but that didn't seem to make any change as far as volume goes. It did still have sound after making that change though. You are most likely right that it could be a bad/ old cap. That has always been something a little beyond my skill, but something I've wanted to learn so maybe I can practice with this one a little. Thanks again for the help and suggestions! Quote Link to comment Share on other sites More sharing options...
TheGuru Posted June 29, 2022 Share Posted June 29, 2022 Oh that's an original board. Check the wiring diagram in the manual, page 7.... https://www.arcade-museum.com/manuals-videogames/M/MrDo.pdf You need to add an amp because the original cab used a separate amp board. Wire the game board to the amp then the output of the amp board to the speaker. You can buy a simple amp board on aliexpress or ebay. Search 0.5W Audio Amplifier or 1W Audio Amplifier. Or something similar. Years ago when a local electronics shop was closing I bought out all of the stock of their 0.5W Champ Amp kit especially for this purpose :-) Quote Link to comment Share on other sites More sharing options...
Jfrik84 Posted June 29, 2022 Author Share Posted June 29, 2022 8 minutes ago, TheGuru said: Oh that's an original board. Check the wiring diagram in the manual, page 7.... https://www.arcade-museum.com/manuals-videogames/M/MrDo.pdf You need to add an amp because the original cab used a separate amp board. Wire the game board to the amp then the output of the amp board to the speaker. You can buy a simple amp board on aliexpress or ebay. Search 0.5W Audio Amplifier or 1W Audio Amplifier. Or something similar. Years ago when a local electronics shop was closing I bought out all of the stock of their 0.5W Champ Amp kit especially for this purpose :-) That is actually very excellent news as adding an amplifier is far less intimidating to me than making repairs to a PCB. I will track one down! The guy I bought this unit from bought out an arcade business years ago and I'm supposed to go back this week to look at some more arcades he is going to dig out of storage so I might be able to find one there with a little luck. I'm also building a MAME cocktail cabinet right now and may have a leftover amp from that rebuild when I'm done. It's a Lepy LP 838 if you think that would work. 1 Quote Link to comment Share on other sites More sharing options...
TheGuru Posted June 30, 2022 Share Posted June 30, 2022 (edited) That should work but it's way overkill for an arcade cab. You just need a simple amp using a LM380 or LM386 or one of the other simple amp chips. You can build an amp board on a piece of veroboard and it would be about 1.5" x 3/4". You can get small prototyping boards on ebay for $1. Cut off a piece then build the circuit on it. There's info on the net for my amp kit but like usual it was scanned by a totally clueless noob 20 years ago using a potato and it's only a pic of the board without any useful info so it's useless. I attached a high quality scan of the document that comes with the kit. This is more than enough info to build it yourself in about 15 minutes using a few common parts and some wire. Or buy one on ebay. Edited June 30, 2022 by TheGuru added more info and clarification 1 Quote Link to comment Share on other sites More sharing options...
Jfrik84 Posted June 30, 2022 Author Share Posted June 30, 2022 Thanks for all of the info! I thought that amp might be a little much for such a simple cabinet. Building an amplifier actually looks pretty fun. I seem to find myself buried in projects so I might buy one depending on how soon I'm looking to get this project completed, but I'm definitely going to keep that info in mind. I'd like to learn how to make any repair I need to on these cabinets to keep them running. Thanks again for all of the helpful information. I can say your screen name is accurate! Quote Link to comment Share on other sites More sharing options...
TheGuru Posted June 30, 2022 Share Posted June 30, 2022 There's a lot of info on the net about arcade repairs but there's also a lot of random noob chatter and no solution. I have a lot of very detailed repair logs on my website showing how to diagnose logic faults and lots of other info.... http://members.iinet.net.au/~lantra9jp1_nbn/gurudumps/ If you know what MAME is then you should know 'who' I am and what I've been doing for the last 20 years You're actually lucky I came along as I rarely come here and this probably isn't the best place for arcade repair info. The dedicated arcade people hang out in dedicated arcade forums but this is shifting to cesspits like discord, facebook and twitter unfortunately. It's nice to be able to type whatever I want without the constant censorship of places like youtube with instant deletes for no reason other than some word that some loser 'programmer' added to a keyword list because they think they are bad, while billions of spam messages get through without any issues LOL! Anyway I'm glad your problem is sorted. Quote Link to comment Share on other sites More sharing options...
Jfrik84 Posted June 30, 2022 Author Share Posted June 30, 2022 Also a good resource to remember. Thank you. I tend to work on arcades kind of infrequently and I don't do Facebook. I'm to a point where I have enough arcades now that I really need to learn how to fix them when an issue comes up. Learning should be easy as I do have a mechanical background. I picked up a broken MAME cocktail cab years ago at an auction and it's been sitting ever since and now I'm kicking myself for finally realizing how simple it seems to replace the destroyed PC inside. Just had to do the research! Definitely going to check out your website. Thanks again! Quote Link to comment Share on other sites More sharing options...
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