Micro 8088 from Sergey Kiselev support group

[shadow 338 (shadow338)]

hi all,

Sorry if this is not the correct group to ask this but I was wondering if there is any existing group to discuss builds/issues on the awesome Micro 8088 ATX computer from Sergey Kiselev?

Regards.

H.

[Dave White]

This group is just fine for all kinds of retro computers, including the Micro 8088 ATX.

[shadow 338 (shadow338)]

I recently assembled the Micro 8088 and the ISA Super VGA both by Sergey but when I turn on the computer all I hear is a beep every less than a second and there is no video signal. I checked the voltages of all the chips in the 8088 board, rather than that, I have no idea where to start troubleshooting this nice computer.

H.

[Earth Person]

Greetings,

One short beep with no pauses may be the DRAM refresh, programmable interrupt timer or programmable interrupt controller. Also, if you are using the Micro-ATX backplane with LED readout, see which code is being displayed and if the decimal points are flashing.

Vogons has a nice thread where people have built the Xi 8088 and Micro 8088. May find something to help you there, too. I've built both, too.

https://www.vogons.org/viewtopic.php?f=46&t=48477&hilit=micro

W.

[shadow 338 (shadow338)]

I'm using the compact ISA 8-bit backplane and I don't think it has any diag leds. The beep is an intermittent beep (every 1sec). Are you also using the 'ISA Super VGA' from Sergey? I'm trying to establish if this VGA card is supposed to show any video signal even without any cpu board connected.

h.

[Chris Odorjan]

On Wednesday, 28 June 2023 at 13:22:54 UTC-4 henrique...@gmail.com wrote:

The beep is an intermittent beep (every 1sec).

If I'm reading the BIOS source correctly there's 3 possible sounds during the power-on self-test:

1. continuous 400Hz tone = CPU error

2. 400Hz tone followed by an equal length of silence, repeating = low memory error

3. Intel jingle = successful POST

Sounds like #2, check if the two RAM chips are installed correctly (I'm not sure which one is the low 512KB, I don't have my own board in front of me right now).

Can you post a picture of your board?

 

Are you also using the 'ISA Super VGA' from Sergey? I'm trying to establish if this VGA card is supposed to show any video signal even without any cpu board connected.

Do you have a known working 8-bit ISA video card to try with the Micro 8088? Or better still, another ISA system to test Sergey's card with?

--

Chris Odorjan

[shadow 338 (shadow338)]

Chris,

I agree that it sounds like it's #2. So I removed both RAM chips and tested on a Z80 computer that I have and they both work fine. So I re-applied solder on both RAM sockets pins just in case and re-seated the chips. I also tried a combination of installing only one RAM chip but the same beep happens.

Then I removed the GAL chip and used a 74F00 instead and closed both JP3 and JP4 but the beep still happens.

I'm wondering if there is some faulty connection so I'm about to re-solder every single pin just in case.

Unfortunately I don't have any other ISA system or board to test things as I built everything from scratch.

When the 8088 board does work (without video card), it's supposed to beep a proper sequence?

Sending some pics of the boards.

I really appreciate the help. Thank you.

H.

[shadow 338 (shadow338)]

[shadow 338 (shadow338)]

On Wednesday, June 28, 2023 at 11:44:23 PM UTC-4 shadow 338 wrote:

[Chris Odorjan]

On Wednesday, 28 June 2023 at 23:43:10 UTC-4 henrique...@gmail.com wrote:

I agree that it sounds like it's #2. So I removed both RAM chips and tested on a Z80 computer that I have and they both work fine. So I re-applied solder on both RAM sockets pins just in case and re-seated the chips. I also tried a combination of installing only one RAM chip but the same beep happens.

Then I removed the GAL chip and used a 74F00 instead and closed both JP3 and JP4 but the beep still happens.

I'm wondering if there is some faulty connection so I'm about to re-solder every single pin just in case.

When the 8088 board does work (without video card), it's supposed to beep a proper sequence?

I really appreciate the help. Thank you.

Unfortunately we're pretty much at the limit of my troubleshooting skills, your board looks a lot like mine (main differences are that mine's revision 1.1 and has the Faraday chip instead of the Proton one). The only other thing I can think of is to use a multimeter / continuity tester to make sure there's no data or address lines getting linked together by a solder bridge or something (but I'd expect that to affect the ROM, too).

Here's a video where S.M. Baker builds and tests a Micro 8088, the startup tone can be heard (faintly) a little after the 3 minute mark:

https://www.youtube.com/watch?v=m6nKEafyt8c

--

Chris Odorjan

[Sergey Kiselev]

Hi,

As others had mentioned, these beeps mean that the system's low RAM (first 32 KiB) test fails.

Good news are:

- Processor is working

- Chipset is most likely working

- Your BIOS Flash ROM is programmed correctly and working

- Since you've tested the SRAM in another system, that's probably good too

Things to check

- U7, U8, and U9 74F573 latches

- U10 and U11 74F255 transceivers

- Check your ISA backplane for shorts between address lines and data lines

- Try running the Micro 8088 board without any other boards installed in the backplane (and if that works - there is a problem, e.g. short-circuit on one of your ISA cards)

Thanks,

Sergey

[shadow 338 (shadow338)]

Thanks Chris and Sergey!!

I will check all the mentioned bits and report back! looking forward.

h.

[shadow 338 (shadow338)]

good news!

Tested the chips and one of the 74F245 transceivers tested bad so I replaced with a 74HC245 since it was the only I had. The micro 8088 now beeps the POST sequence!!! my mistake not testing every single chip before installing them.

Next I plugged the ISA Super VGA to the backplane and it showed picture with the very initial screen with graphics all garbled but them after a few seconds it showed all graphics correct with the POST setup message. Didn't take any pictures at this point :-( 

This is by far the biggest electronic project I ever undertake in terms of soldering and I had never soldered those big chip so I was pretty happy at this point.

Then I shutdown the computer to plug the keyboard (maybe there was no need), and the micro 8088 still beeps with the correct sequence however the video signal never came back. well short lived VGA card. I musta have swapped slots 20 times and plug and unplug the VGA card and checking and re-checking my monitor eventually I gave up. Well, I'm almost confident the micro 8088 board should be working fine but without video is impossible to do any further testing.

I'm not sure what is up with the card since it worked ounce and then it stopped. No chips are over heating or anything.

If old 8bit ISA vga cards were cheap I would buy one at this point but everything seems to be so crazy expensive on ebay in these days when it comes to retro parts. It became an expensive hobby :(

Maybe tomorrow the VGA card will "decide" to work again who knows.

I have the XT-CF-Lite card ready to go and also a ISA OPL2 Card that I need to complete soldering still.

thanks in advance.

h.

[Earth Person]

Greetings,

When I build most projects, I test every IC (as I can). The Retro Chip Tester, TL688-II or greater usually gets me past all of that. Another great device to have on hand, is an ISA Diagnostic adapter, which basically displasy BIOS Codes and status of the data on the bus. Invaluable at troubleshooting. As for the VGA issue, If you can get some macro shots of the VGA adapter, may help us troubleshoot your issue. Having a jeweler's loop at a minimum will help.

-William

[Earth Person]

Greetings,

Also as I was looking, the pictures provided of what is assembled, look alright. Have you been able to test your video ram?  I do not know where most of your parts sourced from, but at this point in time, I'd test everything you can. If you have no chip tester, invest in one.

-W

[Sergey Kiselev]

You do want to use a 74F245. Acceptable replacements are 74ALS245, 74LS245, 74HCT245. 74HC245 is not a great replacement.

Check and clean ISA card edge connectors on all boards. I'd recommend against using solder plated (HASL) finish for these connectors and adding a few $$$ for at least ENIG finish. Hard gold is better, but more expensive.

Thanks,
Sergey

[Gary Kaufman]

I’d reflow the pins on the trident IC.  I’ve built a few of Sergey’s vga boards and that was always my problem when they didn’t immediately work or were intermittent.  Folks on the S100 forms have also reported that the trident ic’s Are easily damaged by excessive heat but I’ve never had a problem.  As always, thanks to Sergey for many fantastic projects!

[Earth Person]

Greetings,

I did a few rounds with a soldering iron and the device. Tried to keep the heat low. What really helped was using a solder braid. Why I suggest a jeweler's loop, is that it can let you know exactly if there are any solder bridges. There are other ways, of course. Attaching a picture of what I assembled.

-W

[shadow 338 (shadow338)]

Earth,

Agree. No excuses for not testing the ICs. I actually have a TL688-II programmer and that's exactly what I did already and found out that one of the transceivers was bad.
Unfortunately I can't test the VGA card RAM chips as I don't think TL688-II supports them (and I can't afford a Retro Chip Tester...)


Geka/Earth,

I experimented with solder braid on the Trident chip and I didn't like it. I found out that a lot of times it removes large amounts of solder breaking contact, but after soldering, I put the chip under a big magnifier glass and tested every single pin (yes all pins!) for continuity between the top of each pin and the pad on the PCB to confirm that they all have a proper connection. About heat, I usually use low temperatures and I soldered a few vintage chips before so I don't think (and hope) that the temperature that I use and application time did not damaged the chip.
The odd thing is, as I stated previously, the card worked once (or at least it showed the initial POST screen) so I'm struggling to understand why no longer works.


Sergey,

I agree that the replacement should be at least LS or HCT. The HC option was me in desperation as it was the only one I found right away to continue the testing.

Since then I found a HCT and replaced the HC and the micro 8088 still seems to post fine /beep the normal sequence however still no VGA signal :-(

About the PCB surface finish, I hear you and agree but HASL was the only option for me for cost reasons so I hope I don't have major issues now.

Btw, whoever is interested in single pcb's, I have listed them on ebay since I had to order a minimum of 5 and I don't need 4 spares.

[shadow 338 (shadow338)]

!!! Update !!!

I bought an IBM 5150 from a local seller this morning for a very good price. The computer does not turn ON which I believe is due to a faulty PSU but that's another project. Fast forward, I removed the CGA Hercules Graphics Card from the 5150 and plugged it on the micro 8088 back plane and connected to the IBM CGA monitor. it works! I see the POST message (sending pic as well). So this   tells me that there is something wrong with my VGA card and I need to keep troubleshooting that once I have the time.

So memory test rus fine etc, but the keyboard does not work.

The cheap mini PS/2 keyboard that I have connected to the micro 8088 lights up whenever I turn the computer ON (keyboard leds), however the computer does not respond to any key (eg. F1) . I have SW2.3 set to ON which I believe is the correct position. If I set SW2.3 to OFF, the computer beeps the correct sequence but it never send video signal to the monitor so I'm not sure what it's doing.

I removed the PIC and reflash the HEX file as per github instructions (XTATKEY.HEX from file XTAT094.ZIP) just in case but that made no difference. I used this keyboard a couple time on moderns PCs so I know it works but I'm wondering if it's not a "real" PS/2 and that is the issue here.

btw, I do need the bios-0.9.9-xtide.bin BIOS in order to use the XT-CF-Lite right?

cheers.