MissionBrown

Hi guys, a few days late. The attached sample is at nominal values, 0 trim on the inputs and at unity gain on the faders. I recorded through a Mackie 1604(mid 90's), delta 1010 into reaper. Each voice is played on the recording, along with silence and silence with the feedback pot turned up. I noticed a wee bit of noise on voice 3, but have a lot of stuff hooked up and the house has severe EM problems(playing guitar in here sucks). Thanks for all of your help. Now to see if I can finish some other outstanding projects(including making some music). This thing sounds waaaaay bigger than my Juno 60 :) no_noise.mp3

I only just realised, I can switch between option (A) and (D) with this configuration. Sweet!

Thanks Hawkeye, but it's all been addressed by Futureman adn nILS.

Ok, 8pm was a bit of an over confident statement. But 8:35pm was the ticket. Got held up by dinner, red wine and USA Wipeout(that show cracks me up!). Anyway, put in the rectifier, fired the synth up and I have a freaking perfect piece of hardware! Also I embarrassed myself by doing a happy dance and some terrible white guy hip hop "I fixed the synth" umm... singing. er rap. Either way I've been forbidden from doing an encore. :whistle: Noise free demo to come tomorrow. So, once again. Thanks guys!

Thanks nILS, I always had the impression that they caused weird stuff to happen with dc-dc conversion. But since you kindly folk assure me it prevents meltdown(electronic and mental) I'll have this sucker working by 8pm tonight :)

Thanks Mike, Looks like I'm going back to jaycar to get another rectifier. Everything else is in place, so no biggie. Like I mentioned that I'd not used regulators before, this is also my first project with a rectifier in it. Learning, learning. Cheers A

So.... I'm a little paranoid because I've broken several things in the house today (blew up a humidifier while cleaning it and kicked over a glass in my work area, shards glass and water all over the floor). I don't want to kill my PSU or synth. Anyway, on the mb-6582 rev 2 board, where should I put the positive and negative leads from my PSU for the 9v lines(being fed by 15v)? That is, before the switch where its marked 9VAC. With the board facing me as if it were in the PT case. Do I put the + on the left or the right? I've removed the rectifier and left the caps in place before the regulator. Should I remove those caps? Nearly there....... :thumbsup:

Seem to have a wee power hiccup. Psu don't seem right when plugged in and mb-6582 switched off.... Need to take pic of my mods and get some more advice. One thing though, should I remove the big psu filter caps now that I'm using option D?

Hi nILS, I'll get you a sample as soon as I've re-housed the PSU and modified the MB-6582 to permanently accept the new power arrangement. This is the first time I've worked with Regulators. Actually the first time I worked with Pics too. The feedback pots do pickup noise irradiating from my PC. As for the switchmode PSU, several of the VicMod guys have the t-60c and have reported no problems with noise when powering their Eurorack modulars. Anyway, I hope to get it done today, but I do have a child and that does slow down building time considerably (not that I mind).

More power was the cure. I ran my 15v switchmode PSU into the 9v reg and the hum went away. I used c64's 5v rail in the test and it was just fine. Thanks guys. Now I need to donate some beer money to 4 people :) If anyone is interested I used the Meanwell T-60c +-15v +5dc switchmode PSU. Nice and quiet. PDF Specs I think it cost me $60 Aussie clams.

Just did some more measurements with my "working" c64 psu. The DC after the rectifier is only 10.5v the DC after the regulator is 8.7v 5v measures 5v. So I'm guessing the regulator aint getting enough juice. Furthermore I took Mike's suggestion and removed some SIDs from the board. 8 x 6582 = Lots of Hum 8.7v 6 x 6582 = less hum 8.8v 4 x 6582 = No Hum 8.9v

As requested, the noisy noise. Starts with input tied to ground, ends with feedback all the way up. noisy noise.mp3

Oops sorry. I thought I'd got to that point. Yep, noise is on all outs. I only started messing with a 5v regulator after both of my c64 psu's yielded unsatisfactory results. I have used two different 9v regulators and the noise is still there. The noise does get worse when i connect the fan, that's the #1 reason I suspect the regulator isn't getting enough input. Yesterday I read that regulators need 30% more input than they output to regulate smoothly. Will try the 15v PSU as well as remove some SIDS on the c64 PSU that at least powers the whole lot, even if it is noisy. Fingers crossed!

Good morning Mike I didn't think about my MM being off the mark. I'll have to dig up my spare and check. I did measure 9v from a 7809 on my breadboard fed by a 12vdc supply(no load). Same with the 7805 I tried(got 5.1v) but that sucker got really hot under load. While it did power the 5v rails of the mb-6582 it got really got and started to make that electronic death smell so I shut it down. In any case the Hum was still there, so I think the problem is indeed with the 9vac supply of the c64 psu. I actually have two of them(c64 supplies), one can only power the synth if I have 6 sids maximum on board. Any more than that and the supply from the 5v rail drops to 1v. I did as you suggested and mix n matched the different rails via my breadboard and the hum remains. As it happens I do have a similar switchmode in the house that I bought to use with my MusicFromOuterSpace modular(awaiting rebuild again). It's a +-15 and +5 supply made by Meanwell(I think 60w, it's in an enclosure). 15v should be ok on the 9v regulator shouldn't it? I noticed the 7809 on the MB6582 barely gets warm, but am concerned about how hot the 7805 got on my breadboard without a heatsink. Will need to get another heatsink and do further testing to make myself comfortable. Another thing I thought of after I read your post is that there is concern of the voltage being below the 9v mark after the regulator. This happened with two regulators, is there a possibility of a bad cap or a solder bridge causing this problem? Maybe a faulty chip? Cheers A

Checked my caps. All oriented properly. Should I try a beefier PSU and go for option c? Jaycar 2a AC psu.

Thanks Mike, The levels in my mixer are pretty good. I set the input trimmers to 0 and the faders to unity. The hum is there loud and clear. You can't really hear it when playing the lead, poly and bass engines, but is evident with the drum engine in the gaps between notes. The voltage I get on the psu is 9vac, after the rectifier is just shy of 12vdc on average. The 5v section drops to 4.7-4.9vdc and the 9v regulator outputs about 8.7vdc Would it be a problem to feed 12vdc to the 9v regulator without removing the rectifier? I'm at work for the next 8 hours so I can't check my cap orientation for a while, but I am pretty sure that they're oriented properly. While I have built loads of stuff over the years, nothing has been so arduous as building this machine. That said, if I could spare the cash, I'd happily build another :) Cheers A

Hi Mike, The hum was there when the in was tied to ground (the pots took a while to arrive from OS). It's a lot worse with the feedback dialed up (lots of noises), but more like the 50hz hum on the lines. Though I haven't looked at it with a scope to nail down where the buzz is located. I could live with it if I have to, but I really don't want to. The machine is near perfect! :frantics:

For all intents and purposes, my MB-6582 is complete. I have used PSU option A. The PSU itself works properly, everything measures normal. But... I have this huge hum on the audio lines. It gets worse when I connect the fan and is really loud when I use the feedback pots. I've tried mix/matching the two c64 psu's I have. eg: breadboarded to use the AC and DC supply from each and the noise remains. Even used a separate regulated 5v supply. The only thing different in the PSU filter from the spec is that I'm using a Greencap on c2 instead of a Monolithic. Could this be the problem? Any help would be most welcome. I really want to close this thing up and get playing it.

I measured the output from the psu and regulator. Once everything was plugged in and I'm getting a few percent less voltage than normal. Could this be the source of my Hum? Is the regulator not getting enough juice to run efficiently? Maybe I should re-populate the PSU section for another option? Sooo close to finished I can taste it!

I have a similar problem using option A. on my 6582. It's got quite a loud hum associated with it, which is a bit irritating. It can be masked up by the big fat sounds, but the more delicate tones always have BZZZZZZZ in the background. One time it did disappear, but I have no idea how I did it. Has anyone figured a solution for the C64 psu noise issue? I'm using a green cap on C2 as I didn't have any monolithic caps available in that value. Could that be the problem?

Got it all working. :thumbsup: Is a little buggy, got some strange noises when I move knobs and one of the voices doesn't release. Will trawl the forum for help. They've been beneficial so far. Cheers A 6582 test

Hi Wilba, Looks like you were spot on! I did some testing after reading your suggestion. Luckily I have two c64 psu's on hand. The one I was using stopped lighting up the LCD after 6 chips. The other is fine for all eight. However I have noticed another problem. With one of the chips(it might've been a dodgy connection) all the LEDS lit up but the LCD was blank, this happened twice(different insert/pulls) on the one chip. But when I replaced the PSU and used all chips it didn't happen again. Ok, so I'm on the right track, now I gotta work out the matrix. Thanks Wilba for the design and support! Once I get rocking my midibox and can pack up my solder station (to make the lady of the house happier) I'll donate to your beer fund. P.S. Just did another A/B psu test and the first one isn't up to snuff.

Hi Guys, I'm nearly finished my mb6482(after a year of gathering bits). Seems like I have the problem as noted in post one and now that I have found this thread I'm hanging to get home and test some more. I do have one question. What should the resistance between 5v and ground be? I'm measuring abour 500ohms The reason, before I insert the SIDS I measure 5v and all the voltage test points are fine. The LCD lights up and says ready. Once I insert the SIDS, the 5v line drops to 1v and the LCD lights no more. I'm using option A for the PSU. Your assistance is greatly appreciated.