Akai AX60 Restoration (Part 1 of 3) - Dead Voice and Tuning Fix

How to repair dead voices and fix autotune problems in the Akai AX-60. I also explain how the control volages are applied to the CEM3394 synth voice IC's. **BEFORE ADJUSTING SEE BELOW!** (click SHOW MORE)
*Be aware that if you adjust the negative 6V supply too far negative (like at the end of the video, to 6.3V) the supply may burn out. D7 can get too hot and eventually fail, causing the M5230L that regulates the +/-6V to also fail.
I have now designed a new supply that does not fail when adjusted. Not only that, the new supply seems to "revive" the CEM voice chips, to the point where they now tune perfectly, even with the voltage that Akai specified in the service manual.
All details are in the third video in the series and on my website.
AX-60 Restoration Part 3 - • AKAI AX-60 Restoration...
My website: goltsynth.com
The good thing is, at least we know now that the CEM3394 chips can still be saved or "fixed" even when they don't tune. It would have been nice if Akai ran the CEM's at their recommended power spec because we wouldn't need to do things like this to get them to tune! Anyway, it is what it is.

[@benjaminhroth]

Thanks for this video! It gave me enough info and confidence to repair a broken ax60 I bought for $100 in Seattle. It now has a combination of yellow and red LEDs. It looks cool and sounds amazing. Favorite synth I've ever owned!

[@benjaminhroth]

Also, I retrofitted a 6v DC wall adapter to power the LEDs. I just wired it to the power supply after the switch. I put 3 LEDs in each group. The walls adapter fits perfectly next to the power supply on the right side of the keyboard. Only cost me a dollar at the thrift store!

[@radegast2012]

Excellent! The best synthesizer troubleshooting tutorial on the whole KZbin - keep up good work!!!

[@GOLTSYNTH]

+radegast2012 Thank you! That is a very nice thing to say!

[@miamigroove]

Very nice. I sold mine well over 10 years ago because it had some dead voices. Used to love doing synth repair work.

[@HOMeSKILiT24]

This was a nice guide, the AX80 is built in a similar fashion just 8 voices. My 4th voice has some issues with the saw wave being really quiet and when the OSC 2 is tuned low 16" is gets distorted. The square pwm works fine. I did find a op amp with a suspiciously high voltage. This was nice for some more insight on what to look for.

[@Cubik303]

Very nice explanation of multiplexed control voltages for digital control of analog circuits!

[@Anton-wc7lb]

This is so cool! I’m amazed by the way you’re able to navigate those boards. I’m a huge fan of electronics and circuitry, although this is beyond my level I would love to learn more. How and where did you learn about this?

[@Hauteclaire16]

This is incredible! Thank you so much for making these videos.

[@lahattec]

Bloody genius! I just bought one of these that is said to have dead keys. So maybe a voice chip is bad. Unfortunately for me, I know squat about electronics. I look forward to getting it though, even though I think I paid too much. Thanks!

[@profwaffel]

Make sure the split balance is set in the middle, a lot of users think the voice chips are bad only to discover that they overlooked this slider...

[@BarbieChaite]

I have the dead note problem but with the AX73. I hope your video will help me to fix that.

[@royaljag]

Hey Golt, we recently go our hands on an Ax60. Unfortunately, the voices will not stay in tune at all. Even with the the autotune button and the tune knob on the back, we still couldn't get it to cooperate. Is there anyway we can contact you about possibly sending it over to you and having it fixed? Of course we would be willing to pay for your service.

[@GOLTSYNTH]

At the moment I don't repair synths form overseas because it is hard to get them into Australia. They always want to charge extra tax when it comes in. Also, it's a shame that tuning issues can be fixed quite easily, but then the power supply can die if it is adjusted too much. I am designing my own supply for the AX60 now, once I'm finished I might send some boards out to people.

[@SatTracker]

Thanks for the awesome video series.

[@HueAwkwardstares]

Fantastic video! Thanks much! Would be extremely curious to see a part 3 on how the ax60's arp works when the CEM3394's vcf res is set to 6 and cutoff at 1/2 + the "omni chord" arp setting. I can't really explain what happens when you add a hold pedal and triggers to the ext arp in w/ a s612 connected by voice cable, but it sounds like it's trying to auto correct pitch by how tuning forks or bells where the ST is mainly focusing on dicisions best suited for like blocky square waves. They're both pretty great synths and I'm a bit curious about their unique exp res abilities and their strange pitch/mod wheel routing

[@GOLTSYNTH]

+hue awkward stares When the filter is self-oscillating you can hear the differences in filter tracking between the voices. Even though the filter is suppose to track the keyboard, it doesn't do it at exactly 1V/Oct. Also each voice's filter cutoff has a different offset, so when self-oscillating the filter frequency's are never exactly in tune together between voices. You don't notice when the filter is not so self-oscillating, but when it is each voice can sound different. Especially when you are modulating the filter with the VCO.

[@StarfieldBound]

I learn so much watching your videos. Thank you!

[@krishna34674]

Very Very interesting ! would love to see more.

[@eliyag1]

I don't have the schematic handy, but would changing D7 with a diode that can handle higher currents solve this particular issue or would the higher current fry the M5230L anyway?

[@marcbrasse747]

Thanks for th excellent videos. Not only have I beem given a very elaborate look inside of what is probably one of the most underrated analog poly's but I now also understand how impoertanrt sample and hold is in the operation of a chip driven synth. I sure wish you could take a look at my Yamaha CS80. One of the oscillators has failed (it came back a few times but seems to constantly stay silent now). Maybe I also need to replace a few of those CMOS 4000's , eh?

[@kellerkindrecordings]

That was very well explained, many thanks!

[@Pamberjack_]

Golt! Hello there. I have a quick question. On the strength of your AX60 videos I have aquired one for myself and it's in for repair right now. It's not making any sounds and none of the lights are working. I'm not sure if either of your ones had these symptoms, but can I ask if you have any thoughts as to what should be checked? Thanks!

[@Cody6918]

I was just given an AX80. It does not turn on nothing lights up.. I noticed that the memory switch had been pushed it and I thought that must be it. but no. So what can I check besides all the fuses which are all good. Thanks in advance.

[@dannyhernandez8252]

I was wondering if brand name makes a difference for the chips replaced. I'm finding many versions of both 4066 and 4051 chips. Thanks for the informative vid!

[@vicseven6456]

My AX60 has one problem. The over all pitch/tuning is slightly off. the AUTO TUNE button does not bring it back to 440hz pitch standard. its like there is an overall detune set. any ideas?

[@MrMinusguy]

I think it's interesting to note that my version of power supply does not have a variable resistor. It also only measures -5.6 but still stays more or less in tune.

[@audiohumang]

Hey Golt I just subscribed, thanks so much for your content! Do you know what could be causing the noise when I flip on the chorus in the AX-60? It is somewhat subtle, I wonder if you have experienced this. I see other people in other forums have. One last question, @golt Sometimes after letting my synth sit for a bit the volume will drop. When it happens I push up the volume envelope amount to bring it back. Sometimes this will even happen mid recording. It seems random though.

[@mixolydian2010]

excellent work thanks for sharing your work. ...my new favourite channel.

[@TheMilford]

One of my favorite synths! You need to hear it with the S612 running through it's voice input. Also, after the LED mod, any interest in selling me a few slider caps?

[@waheex]

lovely job and great effort. THe 4051's are spawn of the devil

[@thriveimagedesign]

Hey GOLT! love your videos :) Just wondering if you have ever worked on AX-80's? I have been slowly restoring / repairing one and have run in to an odd issue of the internal batt ( which I replaced with a CR-2032 ) going flat once every few months.

[@jeremyrmcmahan]

Love my Ax60...unfortunately after having no problems with it at all, i turn it on and absolutely no sound is coming out. Is that the voice chips failing? Seems really strange that it would go from being completely fine to not working at all that suddenly.

[@jamesedinger4956]

Hard to imagine all the voice chips failing at once unless there's some catastrophic voltage anomaly

[@jeremyrmcmahan]

@@jamesedinger4956 I took it to in for repair...turned the outboard was busted. Thanks for the reply!

[@alphabeets]

What is that annoying clicking sound when he is talking?

[@SweetChinMuzik1]

Thank you so much for this video!!!

[@mrrothers3024]

hi i have just resurrected a dead ax73 and would like to add the voice leds as its the same voice pcb, what where the resistor values you used in front of led. cheers ps it was a blown -5.8v to cem.The heatsinked transistor on psu board, checked fine with no load but when connected to voice board dragged the voltage down.

[@GOLTSYNTH]

Chris Rothwell I can’t remember the values but it depends on the LEDs you choose. I’d start with 1K or 2K and if they are too bright just keep doubling the value until they look better. I wouldn’t go any lower than 1K as you may start to pull down the CV for the envelope. Just make sure you choose relatively bright LEDs and you’ll be OK.

[@mrrothers3024]

@@GOLTSYNTH cheers chris

[@brickmaj]

Hello, your video was a huge help and a great resource! I'm still having trouble with two dead (or very very quiet) voices: I replaced all of the 4066 and 4051 chips as you did in your video and I have the same issue. The CEM3394s are NOT dead, they work in the other slots. The slots for voice 5 and 6 are very very quiet, you can barely hear them, but they do produce sound. When you take the chips out of those slots there is zero sound. So my question is, what are the next most obvious things to look at? Could it be any of the op amps? In your video you say those typically don't fail. I've got a copy of the service manual and I'm fairly hand with a soldering iron and multimeter, but by no means an expert. Just wondering if you can help point me in the right direction. Thanks!!

[@GOLTSYNTH]

brickmaj it sounds to me as if there is a problem with the lower voice amp or that voice later is not turned up. Voices 5&6 are the Lower Channel Split group. The slider called Level Split Balance must be in the middle of it’s travel for all voices to sound. If the slider is in the correct position then there might be a problem with the auto tune mute for voices 5/6 (TR15), the output amp IC41,IC42 or the offset adjust trim for the lower channel. See the voice schematic diagram (top right corner of the page). I have just put a high resolution copy of the service manual on my website. goltsynth.com

[@brickmaj]

Oh. My. God... I can't believe I overlooked that Channel Split slider. It's missing the cap so I never noticed it was pushed all the way up. I literally changed out all 7 of those chips, a very non-trivial project!! HAHAHA! I stalled on doing the project for so long because of its magnitude. It confused the hell out of me because I was sure all the voices worked when I first tested the thing! Works great now, but I need to fix the tuning voltages as you describe in your video. My auto-tune only works about half the time and takes way too long. Also, some of the voices seem to drift or become noisy(?) after it's been on for a while. Hopefully adjusting voltages fixes that. Thanks again. Your videos on the AX are very very entertaining and informative. Your wealth of knowledge is a fantastic resource to s self-taught amateur synth repairman like myself! Cheers.

[@Unshapenkris]

@@brickmaj Before you fix the tuning issues, remember the finetune knob on the back of the synth, I thought mine was busted because it always tuned 1 semitone down on each key, but just manually tune all of them with the knob on the back.

[@realbacon]

Great video! I have a couple of related but slightly different problems with my AX60 that I've had since 1987. The last couple of years I've noticed that the tuning gets worse the higher up the keyboard I go, so if I tune middle C4 perfectly, C6 will be slightly out of tune, and C7 and C8 even more so. Chords in the upper 2-3 octaves sound really horrible. To make things worse, some voice chips seem to have worse tuning than others over the whole range, making chords sound out of tune also in the mid range of the keyboard. Any ideas how to fix this?

[@profwaffel]

I’ve got the same problem. Did you ever find out how to fix it?

[@profwaffel]

I had the same problem and followed the procedure in the video: turn the potentiometer slightly to the left and hit autotune, repeat the two steps until pitch is in tune again. This did the trick. However the top octave will not tune whatever I do. But at least I got two or three ovtaves back in tune...

[@realbacon]

Thanks for the tip. I'll try that!

[@Ancaja123]

One of the voices on my AX-60 is out of tune. Could this just be this power supply issue?

[@GOLTSYNTH]

It could be the power supply or maybe even a dead 4051 cmos chip. If it's only one voice then it's most likely the supply. Try recapping your supply and check the -6V is correct. Don't adjust it further than -6.1V or the supply might die. It was a bad design. I have made a new power supply for the AX-60 that solves this issue and ensures all voices tune correctly. It's also produces less heat. I plan to do a video about it soon. I will put the board files on my website once it's up so other people can get the PCB's made too. I'll put all the details in the power supply video.

[@buddyvision3914]

Hi, thanks for uploading this AX-60 video. My AX-60's HPF only effects 2 voices. I've noticed in the schematic that the HPF splits into Upper and Lower, with 4 going to the Upper and 2 to the Lower. I'm not in Split Mode, however, with it wired this way, I would guess there's a fault in the Upper HPF path. Do you have any ideas what could cause the HPF to fail in this way? I'm not experiencing any other issues that I know of. I'm going to be working on it soon. Thought I'd see if you have any thoughts. Thanks.

[@lahattec]

GOLT! What IS your website address please?? Thanks!

[@elbartosa]

Hello mates ... I have an Akai keyboard (mpk 2 series) and since 1 month the velocity of some keys is mad (sometimes 127 or 0) i clened it etc but nothing change... On forums peoples told me it's the mainboard ... Can someone help me please .. I'm from Paris and its very expensive :/ thanks :)

[@sssyntax]

Hey there Golt! My beloved AX60 has just lost two voices. If I start at the lowest key, I get as far as 4 voices, then two are super quiet, then 4 more voices, two super quiet and so on.They still play but just very quietly. Might I ask your thoughts on what that might be? Is it a dead chip? Amplifier circuit? Dry solder joint?Cheers man :)

[@sssyntax]

Hey i sorted my missing key problem out with a little help from a gearslutz user. He said...... I had the same issue with mine when I first got it... but I later found out that if you have the synth in NON-split mode and have the balance volume not centered you will have some keys not working as their volumes will be down. weird... but it's possible many people make this mistake. I.e. if you are using the synth in split mode then switch to regular mode but you had the balance adjusted. Hope this helps some folks out. Also, the output board, which also has the BBD chorus circuit as well is easily detached by poping the nylon posts out of the pcb and disconnecting the connectors... you also need to unscrew the two screws on the back panel near the output jacks. Once again, great video :)

[@legato7798]

My AX60 all works well, but the autotune will endlessly lock up the whole synth when it is hot. The seven segment display goes blank and never returns. I can see the autotune sweeping sequence's square wave output at comparator IC40 pin 7, but at the end, there is no relay click as usual and the CPU seems to be in la la land. I must do a power cycle to resume operation. I realized that when I leave the cover open for a while, the autotune does not cause a freeze anymore. So I tried installing a small fan inside near the power supply and let it run for a while with the closed cover. This fixes the problem, but is not an elegant solution. Stragely, the PS seems to be pretty stable even when hot. Here are my readings: COLD: +14.87 -15.43 +5.79 -5.83 +5.20 -5.20 HOT: +14.82 -15.45 +5.80 -5.84 +5.23 -5.23 This is very strange. Could such a small voltage variation cause the AT to freeze the system?! I don't get it... Is it even related - not sure. Negative supply's TR3 gets REALLY hot at 80C when the problem appears. When my fan blows on it, it goes down to about 40C and autotune then works ok. Also, my PS version does not even have the VR1 (2.2K) to adjust the negative down any further. I would be interested in your power supply solution. Can you give us more info? I can buy just the PCB, or a turnkey solution.

[@radegast2012]

Any suggestions how to troubleshoot the CPU - D7811G-144?

[@GOLTSYNTH]

+radegast2012 Not really. Usually it is the 4051's that are the problem. I'd replace all the logic chips on the main board first (74HC...). Sometimes the CPU can lock up because it gets confusing signals from the chips around it. So I'd replace them first. I troubleshoot a CPU in my next video of a Yamaha CS20m.

[@theycallmesnowplow]

Mine has the same issues! Trying to find somebody more capable of doing this than me hahaha

[@EvLoutonian]

Da h'Axxe60!

[@EvLoutonian]

MORE! * bring on da Part II! *

[@danalexpiano]

Pleeeease stop smacking...