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Strange issue with New Percom Doubler

T

Tibs

Veteran Member
Joined
Dec 10, 2016
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847
Some of you old time Model I users, what the heck is causing me some crazy strange issues with double density disks.

I am using calibrated drives, that are aligned right and the lobes and clamping are correct, and have tried freshly formatted disks using a Model III using the same drive on the Model I.

Single Density works correctly. Double Density is erratic as best. I get data record locked, HIT, Directory read errors, etc. This is more than one drive.

Drives are terminated right (Well I'll double check that its not in backwards). I cleaned the card edge, no difference. This just started.

I'm thinking it might be one of the two controllers going out on the doubler board, but not sure if anyone has any thoughts on if its a support chip dying.

LDOS 5.3.1 and yes, FDUBL (P) is being used.
 
Can you try another DOS? I've generally had good luck in DD using DOSPLUS 3.5.

If SD works correctly with the board installed, that would indicate that the 1771 is good, especially if you can copy a TRSDOS 2.3 disk with the DAMs that only it can read.

Can you test the doubler in another EI?
 
lafos said:
Can you try another DOS? I've generally had good luck in DD using DOSPLUS 3.5.

If SD works correctly with the board installed, that would indicate that the 1771 is good, especially if you can copy a TRSDOS 2.3 disk with the DAMs that only it can read.

Can you test the doubler in another EI?
Click to expand...

Yeah I have another EI. Unless its the same chip in a Model III, I dont have any extra double density chips to drop in the controller to test. (I read and understand the 1793 is an inverted bus versus the 1791). I'll see if I have another 1791 if I get that far.

I'll also test TRSDOS 2.3, and DOSPLUS. Heck I could have a corrupt FDUBL and not even know it.
 
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Yeah it’s the doubler. No dos can operate in double density mode right. I reseated the doubler no change. I don’t have the fdc chip but I can check the support chips with stock
 
I think I might have figured it out. Interference from the hard drive. I thought it was the monitor. Surprised to say the least I don’t know if it’s the cable or the unit doing it. It’s an 8x00 12 megger
 
Yeah, its not that simple I wish it was that simple trust me. I'm about done with this thing permanently - so irritated right now its time to quit for the night.

Without the hard drive, doubler works fine.
With hard drive, doubler doesnt work in double density mode but hard drive works fine.
With hard drive sometimes even without the doubler, floppies may or may not work properly (Really this is more when the EI board is back in the case)
I changed the M1 hard drive adapter, no difference. Hard drive works perfectly fine on the other computers I have, passes all diagnostics too. Same cable, checked it a few times tonight just to be sure.
Changed the EI board, no difference, everything above still happens, I was convinced it was interference earlier.

I haven't changed the Model I CPU unit out (The whole thing, not a part), I'll do that next. If the EI board isn't installed in the case (either board) I'm not having near as many issues, then I put everything back in and it misbehaves. Thats why I kept thinking it was noise form a cable or the video monitor causing something weird to happen. Its not heat related, the bottom isnt even on the EI case and things start getting weird.

This is really the weirdest thing I've ever dealt with, because it makes no sense.

Best I can describe when the floppy drives try and do stuff they get really weird, like they are out of alignment, and this is with or without the doubler, and different 1771s as well.

I guess I could have an issue in the keyboard unit, since everything ties together between these.

Oh, and they are all gold card edges, so not oxidation. These are final design EI boards, not buffered.

FreHD does similar things. I'll try my MISE/MIRE with keyboard unit too.

I'm so in the weeds with it I should have stopped when I was tired, three hours ago.

I could leave the EI board out of the case completely, keep everything connected, and it would work (Double does not like the hard drive though).

These components have all been together for almost a year without any changes, just started acted weirder and weirder and finally today couldn't ready double density disks.
 
Could a solder joint have failed where you're getting noise on the ground plane? Different behavior of EI in and out of the case seems strange.
 
Yeah, I sat up for a few hours brainstorming this. When you get in the weeds you lose all sense of where you are and where you've been in testing.

I'll start from scratch. I have to first make sure my FreHD isnt bad. I have a MISE as well. I'll test them on my bench system to make sure all three of them work. (TRS-80 Drive as well)

Then once I rule out the external drive adapter/drives I'll focus on the EI (and I can switch it with a MISE).

Once I make sure that isnt the issue I'll go back to using a doubler.

I'll sort it all out before I try but I have had to troubleshoot complex enterprise IT systems in the past and you just have to do one thing at a time, and last night I was getting 10 things at a time at the end. I think I might have a bad power supply in the EI. I didnt even check the basics, the voltage.

David, I took someones advice might have been you. DOSPLUS does same thing. TRSDOS 2.3 works as does all three OS. I have used virgin master disks to make sure no corruption and same results. So I am pretty sure its not software related, its something simple that I'm just missing.
 
Tibs said:
Yeah, I sat up for a few hours brainstorming this. When you get in the weeds you lose all sense of where you are and where you've been in testing.

Then once I rule out the external drive adapter/drives I'll focus on the EI (and I can switch it with a MISE).
Click to expand...

Er, did yhou mean a MIRE?

PJH
 
No, I mean the MISE, the MIRE wouldn't really solve my issue since it works flawlessly. Its the real expansion interface and doubler and hard drive that aren't playing nice.
 
With my bench model 1 same issue. With a new EI same issue. So I flipped EI over and issue went away

I think it might be the cpu to EI cable bad
 
Ok, I put the whole thing back together original parts, change the EI cable (From CPU) and it appears to be working now. I think the System Desk might have caused this, because I routed the cable under the wood and it might have pulled the wires from the pins a little, dunno. I'll fiddle with it later. The ground wire for the shield did break on one side, and that could very well be the part that got it all just right (or wrong).

Of course, I cant get a sysgen disk to work, but that has happened before in the past. Dont remember how I fixed it, but I'll get it. Hard drive works but I'm so not typing in all those commands every boot hahahaha

I can sysgen stuff, but the HD whether its drive 0 or not, just reboots to level 2 rom as soon as it loads the configuration.

I had this happen one time before, I might have a bad disk at this point with all the crap I've been doing. I'll make a new master from scratch.
 
Oh, and FreHD is dead, needs a new PIC. I guess I'll program in another one.
 
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