|
Title: How to measure ram chip voltages? Post by: grantopia on August 11, 2015, 04:54:28 am I've been fighting with my Joust cabinet for 2 weeks as it will not boot. When turned on, the initial rug pattern just repeats, never hitting the "all systems go" screen: http://youtu.be/4jBdBKyFDi4 The LCD indicator was flashing 1,3,1, which looks (per the manual) to be a RAM error in bank 3, with chip 1. I replaced the chip today with a new one, and still seem to have the same issue/error on the LCD. The manual also talks about testing the voltages on the chips. I have a multimeter and it says which pins to test, but I'm so new to this that I'm not sure what pins correspond to what numbers and how to test it. This may seem basic, but I'm assuming the power needs to be on? What do I hold the "black lead" (for lack of a better term) that usually would go to a ground against to check? Sorry for the noob questions, just don't want to make anything worse or fry myself. The cheapest repair quote I got was about $175 so I'm hoping to resolve this and learn at the same time. Any help is appreciated! I will pay in beer __________________ May the force b Title: Re: How to measure ram chip voltages? Post by: iankellogg on August 11, 2015, 07:36:57 am Ignore all the pins except the ones labeled Gnd and VCC
(http://www.evilmadscientist.com/images/articles/avrtargetboards_2.jpg) Pin one is always going to be on the left of the notch on the chip like this photo shows (http://d32zx1or0t1x0y.cloudfront.net/2009/07/atmega8_breadboard_12_lrg.jpg) Title: Re: How to measure ram chip voltages? Post by: grantopia on August 11, 2015, 07:51:33 am Thank you so much! I will try tonight after work and report back!
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 11, 2015, 05:03:46 pm Checked the voltages on the (potential) failing ram chip and got:
Pin 1 @ -5.61 (should be 5) Pin 8 @ 13.20 (should be 12) Pin 9 @ 4.85 (should be 5) Does this seem about right or is adjusting the power supply worth a crack? Spot checks a few other ram chips after reseating them all and got similar results, but I didn't check every one. Kind of at a loss of where to go from here... Title: Re: How to measure ram chip voltages? Post by: iankellogg on August 11, 2015, 05:41:25 pm Yeah those voltages are fine. I would suspect bad ribbon cables or connectors and If those have been replaced it might be time to dive into board repair which I can assist with of you are game.
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 11, 2015, 05:43:57 pm I haven't replaced any...is that fairly simple to do? I'm still pretty new to the repair process. I'm wondering if having someone look at who knows more about what they're doing would be safer. How "deep" would I be going lol?
Title: Re: How to measure ram chip voltages? Post by: BadMonkey on August 16, 2015, 12:23:13 pm Just a thought; a ram error may show up if your processor is bad. An example is my xevious. It was showing a ram error which (after a lot of cussing) I ultimately found to be a bad z80. And xevious has 3 of them. I stole a z80 on a whim from my pac and got it going again. Also, I would recommend checking voltages at your power supply and test points. Good luck.
Title: Re: How to measure ram chip voltages? Post by: iankellogg on August 16, 2015, 12:31:10 pm Bad ribbon cables are often the problem with the William boards.
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 17, 2015, 05:54:51 am Is there a good way to check and or replace these?
Title: Re: How to measure ram chip voltages? Post by: iankellogg on August 17, 2015, 06:11:53 am Checking them is pretty much impossible and not worth the time honestly. Just buy a replacement from any of the arcade vendors. They pretty much all sell them
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 17, 2015, 06:13:44 am Are they difficult to install? I can't picture the board (at work but till check tonight) but I feel like it was "fused " to the board with the roms...
Title: Re: How to measure ram chip voltages? Post by: BadMonkey on August 17, 2015, 10:49:56 pm How is your project coming? Not sure if you have the schematics. If not, I can look them up.
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 19, 2015, 06:25:31 pm Pretty slow, some serious family issues these past few days but I'm back to it. I'm still getting the 1 3 1 error after changing what should have been the bad ram chip, I'm wondering if there could be another or a rom or ribbon cable issue. I'm pretty inexperienced in repair so I'm having a tough time with it...any suggestions are appreciated!
Title: Re: How to measure ram chip voltages? Post by: BadMonkey on August 19, 2015, 06:37:03 pm My experience has always been, voltage, the ram chip, (roms usually give me a sprite issue or garbage), connections such as ribbon cables as Ian has stated, or the processor chip. If you can eliminate all of those I would think you a logic analyzer and a more experienced tech. John has buddies in that realm.
Title: Re: How to measure ram chip voltages? Post by: grantopia on August 19, 2015, 06:48:40 pm Someone on klov recommended rebuilding or switching to a "switcher" power supply...
Title: Re: How to measure ram chip voltages? Post by: BadMonkey on August 19, 2015, 08:09:39 pm Not sure if that will help your ram issue. Switching power supplies are reliable if they are new but if your voltages are ok when you test them(i am assuming you tested them), it is probably something else. Is there acid damage on your power supply?
|