k5-out-mod.txt _________________________________________________________________________ From: malouin@engin.umich.edu (Curt Malouin) Newsgroups: rec.music.makers.synth Subject: Re: Kawai K5 questions Date: 17 Oct 1994 05:49:24 GMT Organization: University of Michigan Engineering, Ann Arbor NNTP-Posting-Host: azure.engin.umich.edu In article <37k4qi$kdq@bcrkh13.bnr.ca>, Charles Butler wrote: >I have a K5m and had heard there were some mods that can be done to it; >(e.g. boost the output level or reduce the noise present on the output) >If anyone has any info on these mods (or any others) or is a K5 user in >the Raleigh, NC area; please post a response or give me a call at >919-481-7537. I'm going to do this to my K5 and K5m this week. Basically, you want to change the feedback resistors on each of the output op amps. I haven't opened mine up yet, but I understand the analog section is on a board labelled 'MI004'. Look for U6, U7, etc. Resistors R26, R27, R28, and R29 are for the individual outs, and R19 is for the mix. They're 56k. Make 'em 147k. As you can probably figure out this will roughly triple the output levels. The only trick is that the resistors are all 1/8 W, and 1/4W resistors will not fit nicely (they're generally longer and, more importantly, the leads are thicker). I got a bunch of 147k 1/8W resistors from Mouser. I'll follow-up after I've done the mod. Replacing the inverter on my K5m and upgrading both OSes to 2.1 too :-) As a side note, always use the individual outs and Multi mode. Multi mode is quieter than Single. -curt _________________________________________________________________________ From: malouin@engin.umich.edu (Curt Malouin) Newsgroups: rec.music.makers.synth Subject: K5 output level mod Date: 27 Oct 1994 23:10:28 GMT Organization: University of Michigan Engineering, Ann Arbor Lines: 106 Message-ID: <38pc14$fql@srvr1.engin.umich.edu> NNTP-Posting-Host: azure.engin.umich.edu Over the past week I performed the output level mod on my K5 and K5m, replaced the inverter on my K5m, and upgraded the OS on both. Upgrading to OS 1.2 is a cinch. Call Kawai technical support, tell them your serial number, and they ship it to you. It's free as long as you return your old EPROMS. You pop open your K5(m), swap EPROMs, and close it back up. The EPROM is readily accessible in both the K5 and K5m (once you've got it open, that is). If you're LCD backlight is not working, the first thing you should try is heating up the joints and applying a bit more solder (a lot of the inverters suffer from cold solder joints, I guess). If that doesn't work, you need to replace it or live with it (which I've done for a few years - it's not that bad). You may want to look for an alternate source for the inverter, as Kawai now charges $45 a piece! When you open your unit you will be able to see the inverter. It's a white rectangle mounted on the backside of the LCD assembly, mine is labelled "N103-05-5 Nichia 14S7ZT". Remove the board it is mounted on, turn it over and you will see the three solder joints. You'll need quite a bit of heat, but be careful 'cause it's sensitive/expensive. After replacement, my K5m blew the 1A 250V fuse on the LCD assembly a few times. It's fine now, but makes the typical K5 LCD buzz. Anyone know how to get rid of that? Now to the fun stuff. I've avoided setting the flat level low for resonance-type effects because it was just way too noisy. No such problems now :-) The mod basically involves changing the feedback resistors in the output op amps from 56k to 147k. Plenty of volume, even with 0 flat level and a sharp cutoff. You have to watch your volume levels, though, to avoid distortion. Here's what's involved: (1) Get some small 1/8 W 147k resistors. I used Mouser part no. ME 278-147k (1/8 W 147k 1%). There isn't a lot of room on the board, and you would have a tough time getting typical 1/4W resistors in there. Also, the holes are only 7 or 8 mm, and you don't want to have to bore them out so you can get your resistor leads through the board. (2) Open up your K5/K5m. The K5 is simple. Remove the four long screws from the sides of the case and pull up the hinged panel above the keyboard (which is actually every- thing above the keyboard). If you have a K5, lay it face down and remove the appropriate screws. You will need to unscrew the rack ears and the rotating output assembly. (3) Locate the PCB labelled "MI-004". K5: it's on the left side above the keyboard. K5m: it's below MI-003 (it would be on the bottom if you table-mounted the K5m. You need to remove MI-003 and the spacers between MI-003 and MI-004 (the spacers screw into MI-004). You'll see a silver shield between MI-004 and MI-003. Actually, the side facing MI-004 is a conductor and the side facing MI-003 is an insulator, so make sure you put it back the right way or you will short every- thing on MI-003! NOTE: this is how it is on my K5m, yours may differ. There are also some rubber spacers attached to the underside of MI-004 (to prevent the shield from touching it). I had to remove one of them to get at a few of the resistors in question. You'll probably want to peel all of the foam off the pads before you melt it with your iron. I used some Elmer's glue to stick it back on. Anyone know the conductivity of Elmer's glue when it dries? You'll need to disconnect a bunch of ribbon cables, but they're all different sizes, so it's pretty easy to figure out what goes where. Also, keep track of ground lugs and be sure to reattach them. (4) Locate, remove, and replace the resistors: R26,R27,R28,R29 - individual outputs R19 - mix output They're on the left side of the board (looking from the component side). They are all 56k. I had pretty good luck just using desoldering braid, but had to heat and pull a couple of them. If one of the holes closes up, you can melt a little solder onto it (if necessary) and use a desoldering pump/bulb from the component side while you heat the trace side. (5) Put your K5 back together and enjoy! No more need to crank up the preamps to hear your K5... Other tips: individual outs are quieter than the mix out, and multi mode is quieter than single mode. DISCLAIMER: If you are not comfortable handling and soldering sensitive electronic equipment, forget the mod and buy a noise gate. It is not my fault or problem if you cause irreparable damage to your synth. I wouldn't recommend using a $5 Radio Shack soldering iron, either. -curt -- Curt Malouin Senior, Graduating May '95 malouin@engin.umich.edu Dept of Electrical Engineering CAEN Systems Group University of Michigan