Well here's a tale that might amuse you, if not, it might save you a trip to your local repair shop. About 4 months ago my 1571 in my 128D, started acting a little flaky. It seemed to be getting a little persnickity towards what brand of diskettes I bought for use when in CP/M mode. You may or may not use this capability at all, although the problem I am going to describe can still pop up to baffle and confuse the living daylights out of you. What was happening was that when I tried to format a Kaypro IV type diskette (thats an extended format of appx 400K in MFM format) I would start getting an error generated towards the upper tracks on side 1 (top). This would'nt happen all the time, just every once in a while. Change a diskette and she'd be happy. Well as time went on It got to the point that I could'nt even copy from previously formated diskettes into the reu. This only happened on the files which were on side 1, towards the end of the upper tracks. What really puzzled me was that I never had a problem when running anything in Native 128 or 64 mode. Geos ran fine, Copy protected programs loaded without a hitch, Superbase128 never burped or complained, Fast-Hackem kept on hacking. Nothing in GCR format ever failed. Well the day finally came, She bit the DUST. Everything still worked fine as long as I didnt try to use an Extended format MFM disk. Forget about using CP/M with Commodores format, its just tooo slooow, And CP/M is just as disk intensive as geos is if not more so. I went down to the local Discount store and bought a couple of different brands of diskettes, convinced that I was still having a diskette problem, 24 disks format failures later I decided that I had a hardware problem. I didnt know where to start, since Commodore did so much optimization on the 128D, the schematics I had for the 1571 (stand alone unit) wern't much use. Now I really put this piece of equipment through its paces, I keep a 1670 modem and a 1764 REU (expanded to 512K) and a 1370 mouse plugged into this thing at all times. Also added a fan to keep things cool. Figured that maybe I might be pulling down the power supply, so I unhooked everything, popped the hood and tried once again to format a 400k floppy. Nope didnt work, next checked all the connectors for corrosion or looseness, no problem there. Took the Disk drive out of its cradle and popped the drive rom and reseated it in its socket. Reassembled the beast and tried again. Nothing worked. Well I was about to get frantic. Where to turn next? Out came the diagnostics for the 1571. Ran logic check and kept coming up with a u2 failure (drive rom), Well thats normal for this machine, they changed the rom, and don't have a Western Digital chip in the 1571 on the 128D like they do on the stand alone unit. Next on to the read-write tests. GCR format went like a song., but she would burp on any burst mode mfm read. Confirmed trouble, but still no cause. Yea I know that your thinking Alignment problem, but I had dismissed that as I keep the alignment checked at certain intervals, and that I didnt have a problem when in GCR mode. But I still checked it, and there wasn't a problem that is to say on drive 0. Now I had purchased an alignment program that would check both sides of a 1571, but It hadn't got here yet. All I had was one that would check a 1541 single sided and that always checked out fine. I had really concluded that I had an electronic problem either with the drive controller or the Rom chip or possibly the drive Ram. So I ran a program to check the drive ram no problem. Knowing that the decode tables for all the MFM burst reads are in the drive rom I concluded that (hopefully) there was where the problem lied. So I packed it away and slept on it. The next day I went down to the shop to see about how much the chip would cost and how long it would take to get it. Well the Rom wasn't even listed ( lucky for me ) and they weren't about to call Commodore for a 15.00 or 20.00 chip. I was told to double check my rom number and get back with them. Later on that Day when I got home UPS had delivered my Alignment program. Finally get to tackle that old 1571 which has a problem (different drive, different story). First thing I did was run the thing on the 128D. Yep there was a problem on head 1, it was a couple of thousanths of an inch off on track 36 and 70. But I had decided to go on and fix the other 1571 first. Well during my trials and tribulations on it I noticed that during the alignment of the top head that depending on where you set it you got different readings, adding two and two together I concluded that maybe I could fix the 128D in a matter of minutes. Boy I was Brainstorming Now. I've heard stories about the 128D having drive problems and I sure didnt want to have to take mine to the shop or really spend any money on it, so here's the cure. Seems that when Commodore built the 128D it was for economical purposes and that they can save a few cents by selling the 128D instead of a flat 128 and a 1571. Well the people who build the drives for the 128D look like they cut a few corners too. In the following example you can see a the spot I marked where it says this is the point of trouble. Well by not keeping a disk or support in the drive when its not in use seems that the head has a tendancy to lean towards the unsuported side, (see figure 3) the weight of the read/write head coupled with the spring push the head towards it unsupported side causing misalignment. Not really a radial misalignment but one which can cause mysterious things to happen, because the upper read write head isn't parrellel to the disk media, causing bad syncs, poor headers and so forth. Hopefully you can see what I am talking about, this may apply towards any newer 1571 also. The fix is relatively simple, simply use a screwdriver and pry up the read/write head using the clamp brace as a fulcrum. Don't apply too much pressure and keep the screwdriver off the metal spring or flex plate, keep it on the side of the plastic part of the head. When you think that you have it right look at it and see if the head is pretty close to horizontal to the clamp bars see the next example. So as not to confuse anybody and to try to make myself perfectly clear, the point is to pry the head from the side not the front by the read/write head, sorta in a counter-clockwise motion.  @DO NOT GET CARRIED AWAY about 1/4 to 3/8 of an inch will do. Knowing that you do this at your own risk, please be careful. Prying the head too far up may cause different problems that you may or may not be able to fix.  @Do not by any means loosen adjust or mess with the screws that hold the head assy to the stepper mechanism. It might be tempting to think that this adjustment could be made by these screws, but they don't!!!!!!!! These screws should only be loosened by someone who has a scope and a true analog alignment diskette and the skills to go along with it. Usually if this head is out of adjustment (other than by what I've been talking about) the disk drive is junked. Its just plain cheaper to replace it than try to fix it. Believe me it takes a lot of patience to set the upper head by hand. See example next page. Now I hope that all of this is clear. If not please Email me and I will try to answer any questions that you might have. Also I've included for your convenience a program which will format a Kaypro IV disk in 128 mode. What good might this do you, well for two minutes of your time you can check out any 1571 and see if its got a problem or not. Periodically check your drive to see if its developing a slopeing head. Even if you don't use CP/M the problem can get bad enough to start causing problems whenever you use both sides of your disk drive. I've left word of this on the Commodore hotline over in CIN, and as of yet have not received a reply back from them. I've asked them if this was a known problem or if there was some kind of upgrade that might be made available. If not either of these I've asked for a replacement manufacturer that could supply a drive body that would rest in the cradle, and accomodate the C= architecture. Besides a drive is a drive is a drive as long as everything gets hooked up correctly and has close to the same specs. The only reason I asked for a replacement was I know that repeated bending of the flex plate will cause the head to get farther and farther out of alignment, and I don't want to spend three or four hours guessing and getting it positioned close to use one of the commercial alignment programs available. Speaking of which If you buy one of these (either Cardinal or Free Spirit ) let me warn you that neither one of these use a true alignment diskette. They use a standard diskette which has been formatted in some odd balled manner and written with a code that the program can read and determine appx where the head is at. This isnt at all bad, but you can get misleading results and even then your not supposed to use the program to align your drive, you guestimate from the data that the program gives you. Then rerun the program to check you results. A true alignment diskette costs in the neighborhood of $50.00 by itself, and that does'nt include any program that checks it. ( Dysan mfg. ). All in all the programs are probably worth the 25 or 30 bucks if your inclined to do it this way. You can align close to specs, but don't expect miracles. The Format program is included for your convenience. I did not write it, and it is available in the Applications section under Drive utilities 128. Sorry I don't know who wrote it or I would give them the credit they rightly deserve, its a fine program and works flawlessly. Hey let me know what you discover under your C= monster machine. Kevin Schmidt (Q-link aka KevinS28) P.S. A damn good alignment program is available called Multialign 1.6 its on Q-link over in the 64 drive utilities and various other places. ( it does'nt like any drive other than # 8 on a 128D ) supports up to 4 drives and runs under 64 mode, will only check a 1571 on side 0 or in 1541 mode !!