Re: [vcf-midatlantic] newbie
Hello All, I have subscribed to VCF/Mid-Atlantic. I own an IMSAI 80/30 with a Persci 277 drive and a Diablo wide traction printer. These were purchased new in 1978 for the purpose of writing survey and civil engineering software. I successfully used this system for a number of years but retired it for one of the newer DOS based computers. After years of storage, I recently dusted the moth balls from my vintage IMSAI only to discover it will no longer boot. I am severely challenged when it comes to trouble shooting problems I am at a loss as to how to revive my computer. I have all the manuals that came with my purchase making a stack almost a foot high but they might just as well be written in a foreign language. I hope to find someone in the VCF/Mid-Atlantic living close to me that could shed some light on what my problem might be. All the computer repair people think a S-100 bus is something you ride to work in the morning and raised an eyebrow at the mention of an 8" floppy disc. I didn't realize so much time has passed. I live just north of Baltimore in Timonium Maryland only a few miles from I-83. Please get in touch if you would want to lend a hand reviving my IMSAI. I look forward to learning about the VCF/Mid-Atlantic and perhaps meeting some of the members. This is all new to me so i'll try not to embarrass myself by making stupid comments or something similar. For many years I restored early Corvettes but have emptied my shop and now only make a few reproduction parts. Please be in touch, Fred Terry
I hope to find someone in the VCF/Mid-Atlantic living close to me that could shed some light on what my problem might be. All the computer repair people think a S-100 bus is something you ride to work in the morning and raised an eyebrow at the mention of an 8" floppy disc. I didn't realize so much time has passed.
I live just north of Baltimore in Timonium Maryland only a few miles from I-83.
Please get in touch if you would want to lend a hand reviving my IMSAI.
I look forward to learning about the VCF/Mid-Atlantic and perhaps meeting some of the members. This is all new to me so i'll try not to embarrass myself by making stupid comments or something similar.
For many years I restored early Corvettes but have emptied my shop and now only make a few reproduction parts.
Please be in touch,
Fred Terry
Fred Too bad I missed you, I was at the in-laws who live in Timonium-Lutherville for Chirstmas. I have an IMSAI and a few Perci drives. I return to Timonium monthly, if you're still having issues I would be happy to at least help diagnose your problems if not help fix. Persci drives' caps need to be replaced at this point. Every one I have seen. I have my IMSAI 8080 set up on my workbench here at home but I live an hour 1/2 from you. -- Bill
I hope to find someone in the VCF/Mid-Atlantic living close to me that could shed some light on what my problem might be. All the computer repair people think a S-100 bus is something you ride to work in the morning and raised an eyebrow at the mention of an 8" floppy disc. I didn't realize so much time has passed.
I live just north of Baltimore in Timonium Maryland only a few miles from I-83.
Please get in touch if you would want to lend a hand reviving my IMSAI.
I look forward to learning about the VCF/Mid-Atlantic and perhaps meeting some of the members. This is all new to me so i'll try not to embarrass myself by making stupid comments or something similar.
For many years I restored early Corvettes but have emptied my shop and now only make a few reproduction parts.
Please be in touch,
Fred Terry
Fred Too bad I missed you, I was at the in-laws who live in Timonium-Lutherville for Chirstmas. I have an IMSAI and a few Perci drives. I return to Timonium monthly, if you're still having issues I would be happy to at least help diagnose your problems if not help fix.
Persci drives' caps need to be replaced at this point. Every one I have seen.
I have my IMSAI 8080 set up on my workbench here at home but I live an hour 1/2 from you.
-- Bill Hi Bill, Thanks for the reply. I'm not as helpless as I first implied. I restored a few vintage pinballs after wading through their schematics. I have a full set of schematics for the Persci but no diagrams for the power supply. I think this is where my trouble could be. I have no 24v so the latching servos don't function. How do I tell if my capacitors are shot or do I just replace them? Would that restore my 24v? Let me know the next time you might be in the area. I can show you what I have and you will quickly see what is not working. Thanks, Fred T.
Fred Terry wrote:
I have a full set of schematics for the Persci but no diagrams for the power supply. I think this is where my trouble could be.
This is a different Bill, Bill S. I'm about an hour south of you. I have several IMSAIs and other S-100 systems but I do not have a Persci drive.
I have no 24v so the latching servos don't function.
In all likelihood, the power supply is linear. If it is a linear and you truly have _NO_ 24V then you probably have a shot transformer or rectifier. Can you put a scope on the 24V line? You will also want to create a dummy load to properly test with. This could be a few cheap old style flashlight bulbs, wired in series.
How do I tell if my capacitors are shot or do I just replace them?
If you have voltage on the 24V line, just "polluted" with a lot of ripple current, then "shotgunning" all of the electrolytic caps should solve your problem. Bill S.
Persci drives are notorious for needing a lot of work after so many years. There aren't many fully working drives out there that can exchange disks with each other. You will first need to change every single tantalum cap on the 24v rails. This is not an easy task when you get to the ones on the sensor boards. Don't forget to double check the bearings to see if they need replacing or repacking. Then you will need to recalibrate the drive using a scope and finally an alignment disk. If any of the pots don't work consistently across the range you might need to change them. You also may need to change other parts if they are bad during this process. I had had everything from bad opamps to bad TTL chips. This also assumes you double checked your power supply first to make sure it is fine. I don't recall and don't have my 277 docs handy but I think it's 24v, -12,+12, -5 and +5v. I keep a special power-one supply for working on Persci drives since it has all the voltages. Well that's about all I can think of off the top of my head. I can dig up my other docs in a couple of days. Cheers, Corey corey cohen uǝɥoɔ ʎǝɹoɔ
On Dec 26, 2015, at 8:36 AM, Fred Terry via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Hello All,
I have subscribed to VCF/Mid-Atlantic. I own an IMSAI 80/30 with a Persci 277 drive and a Diablo wide traction printer. These were purchased new in 1978 for the purpose of writing survey and civil engineering software. I successfully used this system for a number of years but retired it for one of the newer DOS based computers.
After years of storage, I recently dusted the moth balls from my vintage IMSAI only to discover it will no longer boot. I am severely challenged when it comes to trouble shooting problems I am at a loss as to how to revive my computer. I have all the manuals that came with my purchase making a stack almost a foot high but they might just as well be written in a foreign language.
I hope to find someone in the VCF/Mid-Atlantic living close to me that could shed some light on what my problem might be. All the computer repair people think a S-100 bus is something you ride to work in the morning and raised an eyebrow at the mention of an 8" floppy disc. I didn't realize so much time has passed.
I live just north of Baltimore in Timonium Maryland only a few miles from I-83.
Please get in touch if you would want to lend a hand reviving my IMSAI.
I look forward to learning about the VCF/Mid-Atlantic and perhaps meeting some of the members. This is all new to me so i'll try not to embarrass myself by making stupid comments or something similar.
For many years I restored early Corvettes but have emptied my shop and now only make a few reproduction parts.
Please be in touch,
Fred Terry
BTW - I have 299's not 277's. Similar but different. I replaced the disk sensor in one of mine. Otherwise caps.
299's are way more reliable than the 277 and a much easier design to work on. corey cohen uǝɥoɔ ʎǝɹoɔ
On Dec 26, 2015, at 8:03 PM, william degnan via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
BTW - I have 299's not 277's. Similar but different. I replaced the disk sensor in one of mine. Otherwise caps.
Thanks everyone for the replies. I think about now I am in deep trouble by just being the owner of a 277. Reliability seems to be a problem and I don't own a scope or an alignment disk or would even know how to use them. On another note is my IMSAI 80/30. When turned on the screen fills from the bottom up with alternating vertical lines and triangles. Any thoughts? Thanks Fred T. On Dec 26, 2015, at 8:23 PM, Corey Cohen via vcf-midatlantic wrote:
299's are way more reliable than the 277 and a much easier design to work on.
corey cohen uǝɥoɔ ʎǝɹoɔ
On Dec 26, 2015, at 8:03 PM, william degnan via vcf-midatlantic <vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
BTW - I have 299's not 277's. Similar but different. I replaced the disk sensor in one of mine. Otherwise caps.
On Dec 27, 2015 8:19 AM, "Fred Terry via vcf-midatlantic" < vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Thanks everyone for the replies. I think about now I am in deep trouble
by just being the owner of a 277. Reliability seems to be a problem and
I don't own a scope or an alignment disk or would even know how to use them. On another note is my IMSAI 80/30. When turned on the screen fills from the bottom up with alternating vertical lines and triangles. Any thoughts? Thanks Fred T.
Fred, Please bottom post to keep the flow of the thread easy for digest members to follow.. I.e. put your reply at the bottom of the previous post, and trim out unnecessary text. In order to assist you further we'd need more technical detail. Is this a stock 80/30? Does the system attempt to boot at all? Can you get to a ROM monitor to run diagnostic commands of things like RAM contents, RAM test? Is the s100 backplane getting proper voltage? These kinds of details help greatly because first we need to know if the issue is with the computer, I/O card, ROMs, drives or something else. We need to define the point (s) of failure. You may have to wait until someone with measuring tools can inspect this system if you're not in possession of these things. Bill Degnan twitter: billdeg vintagecomputer.net
On Dec 27, 2015, at 9:45 AM, william degnan via vcf-midatlantic wrote:
On Dec 27, 2015 8:19 AM, "Fred Terry via vcf-midatlantic" < vcf-midatlantic@lists.vintagecomputerfederation.org> wrote:
Thanks everyone for the replies. I think about now I am in deep trouble
by just being the owner of a 277. Reliability seems to be a problem and
I don't own a scope or an alignment disk or would even know how to use them. On another note is my IMSAI 80/30. When turned on the screen fills from the bottom up with alternating vertical lines and triangles. Any thoughts? Thanks Fred T.
Fred, Please bottom post to keep the flow of the thread easy for digest members to follow.. I.e. put your reply at the bottom of the previous post, and trim out unnecessary text.
In order to assist you further we'd need more technical detail. Is this a stock 80/30? Does the system attempt to boot at all? Can you get to a ROM monitor to run diagnostic commands of things like RAM contents, RAM test? Is the s100 backplane getting proper voltage? These kinds of details help greatly because first we need to know if the issue is with the computer, I/O card, ROMs, drives or something else. We need to define the point (s) of failure.
You may have to wait until someone with measuring tools can inspect this system if you're not in possession of these things.
Bill Degnan twitter: billdeg
'Morning Bill, Yes it is stock. It displays meaningless characters on the screen when reset is pressed. I don't know what a ROM monitor is and I don't know where to sample backplane voltage. I think for now I'll place everything on hold until I can learn more about what I have and can then provide something that would be meaningful. I'm just taking list space. Thanks to all who extended a hand. Fred T.
vintagecomputer.net
Fred Terry wrote:
On another note is my IMSAI 80/30. When turned on the screen fills from the bottom up with alternating vertical lines and triangles. Any thoughts?
This is a good sign. It indicates the following: 1) The display circuitry is successfully translating memory contents into a video signal and the video display itself is functional. 2) The CPU is operating, at least to the level that memory contents are being modified in a systematic way. Since you have skipped a number of steps that I would have recommended to verify that the main power supply is "good", I would recommend that you reseat (gently lift and reinsert) each of the cards in the unit and see if that alters the behavior. Before you reseat the cards, turn the unit off, leave it for three or four minutes, then unplug it from the wall and leave it for another three or four minutes. Bill S.
participants (5)
-
Bill Sudbrink -
Corey Cohen -
Evan Koblentz -
Fred Terry -
william degnan