Welcome, Guest. Please login or register.


Author Topic: Broken EP (Read 11552 times)

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #30 on: 2014.February.28. 00:32:09 »
Have you put back the A15 address line to pin 1 instead of the VCC?
« Last Edit: 2014.February.28. 09:34:55 by szipucsu »

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Broken EP
« Reply #31 on: 2014.February.28. 08:13:28 »
You putted back the A15 address line to pin 1 instead the VCC?

Yes :)

Seems really strange.

Memory paging must be working as the old EXOS ROM goes through the memory test fine. The beep test with a15 set to vcc also does the same odd screen scan lines. This is just making the 27512 act like a 27256 with the beep test rom, so I don't understand. It's like having the 27512 eprom in there is causing the problem...

I'll try reprogramming the 27512 with just the beep test rom image I know is working on the 27256. This should tell us if the actual eprom is the problem.
« Last Edit: 2014.February.28. 08:34:47 by Saint »

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #32 on: 2014.February.28. 09:05:06 »
Quote from: Saint
Memory paging must be working as the old EXOS ROM goes through the memory test fine.
But it cannot detect if whole segments are overwritten because of address line problems.
There is the stand alone version of my memory test for cartridge use with original EXOS 2.0/2.1
It is needed to put the lowest page of the cartridge (04h segment), the EXOS call there external testing program. Try to use this with original EXOS ROM.
« Last Edit: 2014.February.28. 09:35:59 by szipucsu »

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #33 on: 2014.February.28. 09:10:33 »
Another idea if the cartridge works.
Put monitor program to cartridge, ASMON or FENAS. Then you can page segments and view contents.
Program EXOS 2.1 to 27C512 low part, and for the high segments some text, for example "this is the segment 02h", and 03h to another.
If the machine started then view in monitor program what you see in segment 02 and 03. if you see the EXOS ROM instead the texts then the A15 stuck as 0.
If the machine does not start, try EXOS to the high part, and texts to the low (now are 00 and 01 segments)
If the machine started with this very strange ROM then the A15 stuck as 1...
« Last Edit: 2014.February.28. 09:38:15 by szipucsu »

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #34 on: 2014.February.28. 09:19:02 »
Some note, not a good news for you :-(
I have some machines with partially defective Dave chips, some of the address lines not working. For example only 1MB address space can be handled insted 4MB, the 1MB space mirrored as 4 times. It this situation the high address lines are defective :-(
But the A15 on system bus also come from the Dave.

In the deffective lines I see instead the right 0/1: floating/1. I thinkig about using transistor or anything convert this to the right 0/1.

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 33.0.1750.117 Chrome 33.0.1750.117
    • View Profile
Re: Broken EP
« Reply #35 on: 2014.February.28. 10:04:41 »
I burnt an EPROM with the beep test at slot 3 on the 27512 and installed with A15=vcc. Worked fine.

Next, I thought I would check A15 with the scope to see what activity there was. I looked at the expansion connector and found the wire which runs A15 to the 2.4 EPROM had come un-soldered. It was glued in place so it looked fine, but the connection had broken away! :oops:

It must have happened while I was handling the PCB de/soldering all the caps. So after all that, it looks like putting the caps in backwards didn't break anything. Phew! It was just me knocking a wire out. :oops:

Hehe, all good news and some fun experience tracking down what was wrong. There are actually 3 more caps to replace next to the modulator / power, then I have a fully electrolytic re-capped  machine.

I hope some more non-working EP's come up on eBay, I think I could get the hang of repairing them with all of Zozo's tips in this thread alone... :)

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Unknown Unknown
  • Browser:
  • Opera 9.80 (Opera Mini 7.5.33361) Opera 9.80 (Opera Mini 7.5.33361)
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #36 on: 2014.February.28. 11:29:40 »
Then now everything working?

Offline jltursan

  • User
  • *
  • Posts: 69
  • Country: es
  • OS:
  • Windows NT 6.3 Windows NT 6.3
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • JLTurSan's MSX page - My little MSX corner
Re: Broken EP
« Reply #37 on: 2014.February.28. 19:04:52 »
If so, excellent work all in all :smt038

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 33.0.1750.117 Chrome 33.0.1750.117
    • View Profile
Re: Broken EP
« Reply #38 on: 2014.February.28. 20:10:21 »
Yes, all working now! I even tidied up the hack someone had done on the cap / resistor layout on the modulator. They seem to have copied the setup in the Issue 1 motherboard, where the Issue 5 tidied it up a bit.

And also thanks to jltursan, as I checked my EXDOS and replaced with 150ns EPROM (I had a 250ns EPROM in there!) and now it boots with the Arabic Issue 5 Enterprise. Funny as the 250ns EPROM booted fine on my old Issue 1 Enterprise!

Thank you all, I now feel happy that my "test" Enterprise is working and I can make a start on the SD card interface prototype. :)

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Unknown Unknown
  • Browser:
  • Opera 9.80 (Opera Mini 7.5.33361) Opera 9.80 (Opera Mini 7.5.33361)
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #39 on: 2014.February.28. 20:36:06 »
Issue 1??? Are yoy sure about this? If i remember right your other machine are EP128. These are usualy ISSUE 6. Few machines are ISSUE 4.

Offline jltursan

  • User
  • *
  • Posts: 69
  • Country: es
  • OS:
  • Windows NT 6.3 Windows NT 6.3
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • JLTurSan's MSX page - My little MSX corner
Re: Broken EP
« Reply #40 on: 2014.February.28. 21:12:26 »
Double yay! (both for having repaired the EP and for the SD project :mrgreen:). 

Maybe the 150ns EPROM has definitely something to do with the Dave speed as Zozo has already pointed out :?:

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Chrome 33.0.1750.117 Chrome 33.0.1750.117
    • View Profile
Re: Broken EP
« Reply #41 on: 2014.February.28. 22:08:07 »
Quote from: Zozosoft
Issue 1??? Are yoy sure about this? If i remember right your other machine are EP128. These are usualy ISSUE 6. Few machines are ISSUE 4.
Sorry, my old EP64 is Issue 4. Not sure where I got 1 from. :oops:

The Arabic EP64 is Issue 5.

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Unknown Unknown
  • Browser:
  • Opera 9.80 (Opera Mini 7.5.33361) Opera 9.80 (Opera Mini 7.5.33361)
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #42 on: 2014.February.28. 22:25:05 »
Can you post photos both Dave chips?
One idea: try to measure the delay from MREQ to Eprom CE on the EXDOS card with both machine. CE generated by using the high address lines from the Dave. If one Dave slower then more delay at the CE.

Offline Saint

  • EP user
  • *
  • Posts: 266
  • Country: gb
  • OS:
  • Mac OS X Mac OS X
  • Browser:
  • Safari 6.0 Safari 6.0
    • View Profile
Re: Broken EP
« Reply #43 on: 2014.March.01. 14:43:13 »
I will get some photos of the two Dave chips later on today if I get a chance!

Here we go... First is Issue 5 pcb and second is issue 4.

« Last Edit: 2014.March.02. 14:58:46 by Saint »

Offline Zozosoft

  • EP addict
  • *
  • Posts: 13517
  • Country: hu
  • OS:
  • Windows 7/Server 2008 R2 Windows 7/Server 2008 R2
  • Browser:
  • Firefox 27.0 Firefox 27.0
    • View Profile
    • http://enterprise.iko.hu/
Re: Broken EP
« Reply #44 on: 2014.March.02. 20:21:13 »
Interesting the different oriented texts! Anyway it is look same, just the date code different. But it is sure these are come from different batch of chips.
The first is which have a problem with the slower EXDOS EPROM?

Jltursan! If I remember right you found same problem about EXDOS EPROM speed? Can you post photos of your Dave chips?

I will look around at my spare machines about can I reproduce this problem?
Anyway I always suggested using least 150ns fast EPROMs. But will be interesting if can be found slower Dave chips, it is can be affect the overclocking ability?