I just came here via Espen Crafts video. I don't own one but I love it when people go through so much trouble to help others without wanting anyhting in return. My compliments!
I have an old MMT-8 that I used for years and just dug it out today. I have misplaced the power supply and though I know it is a 9V and I have a universal adaptor, I can't figure out whether the the original was a center pin positive, or negative. I don't want to fry something by getting the polarity wrong and I couldn't find anything to answer my question in the manual or service manual. It may be in the service manual in some form, but I'm no electronic tech. Any idea as to which it is? I would be willing to buy a replacement adaptor, but I'd really like to know it still functions first.
Man I have an extremely similar problem with my HR-16. On power up, pretty much the same thing,lots of LEDs, no display, nothing responds, etc. Unfortunately, I am no electronics engineer. I saw the similarity of your issue so I tried grounding pin 9 on my CPU as well, but the HR-16 did not boot. I can't find any schematics either One thing I noticed is that sometimes different combos of LEDs light up upon turning the unit on and off repetitively. I even once got the display to show some random characters, but nothing more. I also tried reprogramming and installing a new OS eprom, but no luck there either. Any ideas? Your help would be greatly appreciated!
Sorry I didn't notice anyone had commented here. Replacing the OS eprom is a good start. Do you have a known working unit? I would suggest swapping the main chips cpu/eprom (already done)/ram from a good one as a starting point. Otherwise someone would really need to go through the steps I followed to pinpoint the issue, and if you're getting random characters on the display the ram chips could be bad.
I have a feeling if you disconnect and then reconnect the ribbon cable for the screen, it will work. If it doesn't it's possible the screen is actually broken, but that would take more troubleshooting.
I have one I just bought - the display is there, but very faint. I ordered a nice blue replacement screen for $30 on Ebay. They used the same LCD screen for HR-16, Quardraverb, etc.
Sorry I didn't notice anyone had commented here. If you're into electronics, grounding pin 9 of the cpu will confirm if it's the same issue (and therefor probably needs the same chip replaced). If this is way out of your ability, showing this video to someone who does electronics/soldering will easily be able to fix it for you!
I just came here via Espen Crafts video. I don't own one but I love it when people go through so much trouble to help others without wanting anyhting in return. My compliments!
I totally forgot I commented on Espens video, and didn't notice anyone commented here. Thanks so much!
I've bought 2 like this in the past couple of weeks - sent one back - going to try this fix on the second one! thanks so much!
I have an old MMT-8 that I used for years and just dug it out today.
I have misplaced the power supply and though I know it is a 9V and I have a universal adaptor, I can't figure out whether the the original was a center pin positive, or negative.
I don't want to fry something by getting the polarity wrong and I couldn't find anything to answer my question in the manual or service manual.
It may be in the service manual in some form, but I'm no electronic tech. Any idea as to which it is?
I would be willing to buy a replacement adaptor, but I'd really like to know it still functions first.
It's AC, but can run on DC www.warningwillrobinson.com.au/guides/Alesis%20MMT8%20battery%20power%20mod.pdf
9VAC - not DC. Amazon sells these.
I've turned on comment notifications should anyone else see this and have questions.
Man I have an extremely similar problem with my HR-16. On power up, pretty much the same thing,lots of LEDs, no display, nothing responds, etc. Unfortunately, I am no electronics engineer. I saw the similarity of your issue so I tried grounding pin 9 on my CPU as well, but the HR-16 did not boot. I can't find any schematics either One thing I noticed is that sometimes different combos of LEDs light up upon turning the unit on and off repetitively. I even once got the display to show some random characters, but nothing more. I also tried reprogramming and installing a new OS eprom, but no luck there either. Any ideas? Your help would be greatly appreciated!
Sorry I didn't notice anyone had commented here. Replacing the OS eprom is a good start. Do you have a known working unit? I would suggest swapping the main chips cpu/eprom (already done)/ram from a good one as a starting point. Otherwise someone would really need to go through the steps I followed to pinpoint the issue, and if you're getting random characters on the display the ram chips could be bad.
I have same problem on HR-16b
I have this on a hr 16 and the ground to the leg did correct the reset but how did u trace it to the U- 14 ic chip .
Cool video! I have the same unit mmt-8 all buttons are working but the display screen is blank no letters shown, any pointers on how to fix?
I have a feeling if you disconnect and then reconnect the ribbon cable for the screen, it will work. If it doesn't it's possible the screen is actually broken, but that would take more troubleshooting.
I have one I just bought - the display is there, but very faint. I ordered a nice blue replacement screen for $30 on Ebay. They used the same LCD screen for HR-16, Quardraverb, etc.
Thanks for sharing.
I have the same identical problem just want to know can you help me..
Sorry I didn't notice anyone had commented here. If you're into electronics, grounding pin 9 of the cpu will confirm if it's the same issue (and therefor probably needs the same chip replaced). If this is way out of your ability, showing this video to someone who does electronics/soldering will easily be able to fix it for you!