tep392

2 month bump

I'll PM you.

Hi, If your still looking for this I have a working copy with the software CD. I don't know what they might be worth, but I would trade it for a Harmony cart. Perry

I took a look at the 1050 schematic and see that the stepper motor drivers are controlled thru the PIA and don't have any other timing circuits (one shots) like the PC drive. So it seems the 1050 is 100% under software control and no component changes would be needed to take advantage of the fast steppers. Just need to know which parameters to tune in the software. Seek time, track to track, for the Fast Seek TM50's is specified at 6ms vs. 20ms for the standard. Head settling time is 15ms vs. 20ms for the standard.

Now I understand what you’re saying. “Please out the note” confused me. I had a medical procedure yesterday so I’ll blame it on the drugs. A note on the original 180k mpi drive that is busted. There were two parts in the lever mechanism that were broken. A lever that was weak and bent from use. Cracked when I tried to straitened it. And a little tab that holds the disk in had failed from fatigue. Not a great design.

I was searching for a different TM50 related post when I stumbled upon this topic. I just clicked the link @Nezgar provided and it is the same TM50 manual that I was referring to. This page is the schematic for the stepper motor control and two pages prior (page 1 of the motor control schematic) has a table noting the component differences for the various drive versions, including the Fast Seek version.

This post is a bit old, but I wanted to let you know what I found about the Tandon fast seek steppers. I have two Tandon TM50-2FS PC drives. They both are the Fast Seek version and I just installed them in a Percom drive. I also moded the Percom ROM parameter that reduced the seek delay. I've had no problems with it it so far. One drive has a 211005 stepper and the other is a 210323 like your 1050's. So your 1050's might be capable of fast seek. An important detail is the tuning of the one shot's used in the stepper control. The TM50 service manual is available online and the schematic has details of the differences between the fast seek and standard versions. It's basically just two caps and a resistor. I haven't looked at the 1050 schematic, but if it uses a similar driver configuration, then you might be able to identify the equivalent components that would need to be updated.

I noticed it pop up on one of my saved searches the other day. Nice work!

I now have 720K of storage in my Percom! I noticed that the new 5V/12V regulators I installed for the second drive run quite a bit cooler than the original regulators. I had assumed the heat load would just be a function of the voltage dropped and current draw, but it seems the new parts are more efficient as well, so I might go ahead and replace the originals to reduce temps. I could also spend a bit more and change to switching regulators. I did that on my 1050 drives and they run cool now. No more warm floppy disks.

That is strange. The schematic also shows both ports are the same.

I've checked that both SIO ports work identically.

I have a question for the kryoflux experts here. I have an old Monroe OC-8820 business computer that uses a proprietary form of the CPM operating system. I don't have any bootable disks but there are disk images online in TD0 format. The machine uses Micropolis 5.25" drives that have the standard 34pin edge connector used on old PC drives. I was actually able to connect the drive to my Atari using my Percom drive as the interface. Would I be able to use a Kryoflux to write a disk image to the drive? Does the Kryoflux software work with TD0 images or would I need to convert it to something else? Thanks!

The seller myatari on Ebay is Bruce from B&C Computer Visions. He has tons of NOS Atari stuff that he bought from Atari years ago. He has Dos 2.5 on SD disks that will work with your 810 drive. The DOS 2.5 disks that were packaged with the 1050 drives were ED formatted and only boot on the 1050 drives, so be careful what you buy. Avoid Dos 3.0, which doesn't support SD. Atari DX5075 DOS 2.5 SINGLE DENSITY SD Master 5 1/4 disks 2 each for 800,XL, XE | eBay

I was able to put my Percom drive to good use tonight. I have an old Monroe OC-8820 business computer. It uses a proprietary CPM based OS and has two Micropolis 96tpi SSDD 5.25 drives. I don't have any software for it and the video isn't working at the moment. I haven't tested the drives either, so I decided to try connecting them to my Percom controller. In SDX I used the setting for SSDD 80 track, which at 18 sectors/track is 360K, and was able to format a working disk. It was cool to use my Atari to test the CPM machine's floppy drives.

Feedback belongs in the comment section. I have edited the title.

I decided to pick up an inexpensive logic analyzer this week. The Kingst LA2016. It's actually pretty impressive considering the price. My first test of it was to analyze the bitstream and sector layout of my Percom drive. Based on my measurements, it looks like the Percom uses the same bitrate and sector spacing as an Atari drive, so it should be appropriate to run the Percom at 288 rpm. If Percom intended the drive to run at a faster speed, then they should have increased the bitrate to allow the same number of bits per track as an Atari drive. I adjusted my Percom down to 288 rpm and it's running quite well.

I believe the various drives have different ROM's. Phaeron posted a summary of the revisions HERE. If your AT88 has the hardware for the side select signal, then it may also have the same ROM parameters that allow the default number of sides to be set. We should be able to confirm if a disassembly was done for the ROM.

The ROM is for the S1PD and SPD models. Which AT88 do you have?

I'm able to write to both sides of the disk, but there is a quirk. This was all done with SpartaDOS X 4.49. I started out by formatting a disk for DSSD. I wrote files to it until it had about 150k of data. Then I formatted a disk for DSDD and wrote about 290k to it. I shut down the drive and computer for a bit. When I went back to use those disks, I could no longer read or write side two of the disks. CHKDSK would properly identify the disks as double sided. I decided to format a third disk as DSDD. After doing that, I could again access side two of the disks. Very odd. I'm wondering if one of the later ROM revisions fixes this. Mine has V1.11. I've seen that there is a V1.21 and some later version that Jeffrey Worley has. Maybe I should give those a try. Edit: I've decided what I am going to try. I'm going to burn a ROM with "Percom AT88SPD 575C9833.BIN", which I think the the latest known revision and I will modify the default step rate to 00 and the default sides to 01 (sides-1). My Tandon TM50-2FS has the fast seek option with 6ms seek time, so defaulting to to 0 step rate should be ok. Edit 2: I burnt the "Percom AT88SPD 575C9833.BIN" ROM with the changes to default step rate and double sided. It seems to have resolved the issue of being able to read/write the 2nd side. The SDX Format command also defaults to double sided now. Next step is to add the voltage regulators and second power cable so I can put a second 360k drive in it.

I checked the drive that came with the unit and it's running at 296 RPM. I don't know if this is the original Percom setting or not. The drive mech had a single terminating resistor inserted in it, which looked like a bodge to me, so the drive might have been messed with at some point.

The AT88-S1PD is working! I replaced the buffer chips and it started communicating with the 800XL again. The original 180K drive is still not working so I put in a Tandon 360K drive. I'm able to format in SD or DD and single or double sided. I've tried booting single and double density disks without problem. It is a bit flaky though. Every once in a while I get a 139 NAK error. When I have some time I'm going to check all the adjustments. The RPM on the Tandon unit I installed is the standard 300 used for PC drives. Does anyone know what speed Percom adjusted their drives too?

I found the bad chips! There are three 7406 Inverter Buffer IC's that are bad. They are used primarily for the printer port, but there are a few gates used for some of the drive control signals and the TxD signal from the 6850 to the SIO port. I'm guessing that something was attached to the printer port at some point that fried those three chips. I won't have replacement parts until next week, but hopefully that is all it takes to resurrect this drive.

This is the ROM from my drive. AT88S1PD_V1.11.BIN

I've wanted one for a while now. I think I can get a cheap USB unit for under $200 that will do the job.

A logic probe can only tell me if there is activity in a signal, but I'm pretty sure the CPU is reading data from the 6850. I can't tell with the probe if the CPU is trying to send data back to the computer. Maybe it's time I invest in a logic analyzer.