Update!

I ran out of luck. I did a more closer look inspection because i wanted to take all the components out and clean the case and i was very sad to see this:

You know those "oh no" moments you have in life? This was definitely one of them for me. I tried not to think more about it and just press on with the work:

So cleaned it all the best i could, cleaned the heads on the Tandon floppy drive and some WD40 on the rails. But it was time to check it out. After properly connecting the P8/P9 connectors correctly i tried a power on. PSU works but nothing. No beeps at all. Tried a minimum configuration and again nothing. Swapped RAM banks but still nothing. So i checked the PSU with a multimeter and the voltages are good. It appears that i have a dead mobo one my hands.

Of course there are stuff i can still try, like try to get new 4164 RAM chips just to be sure, but i think the genius that swapped the P8/P9 connectors killed the board for good.

My vacation is almost over so there's nothing i can do for now. I may get a new IBM XT motherboard, preferably the early 64-256KB version which is the one this came with any way, but i'll be happy with the newer one if i can get one cheap.
Other option is to get one of my other 8088 boards, burn a 8KB EEPROM with the IBM BIOS and use it as a temporary replacement. After all, what makes an IBM XT unique is its BIOS.

What does the underside of the motherboard look like? If all the ground (black) lines are connected together, the system would have immediately short-circuited the PSU and may have perhaps burned some tracks, but it's possible this is the only damage. All you may have to do is repair the power supply connector and the PCB tracks below it.

Of course without looking more closely it's possible it has reverse-biased some critical component which has blown, but I would be surprised if this was the case.

carlostex wrote:

And how relevant are those models for an XT? As far as i know those aren't compatible with an IBM PC or compatible.

Unsuspecting people may read that and assume all Model F keyboards have internally mounted spacebars when it's not the case.

The Model F 122 6110344 was used on certain 5150s with a terminal card (it used blue legends to indicate functions of the PC, whereas the non-blue functions were for terminal purposes). It's of course not XT compliant directly, but works on them with the ISA card and a breakout cable.

Early Model Ms that lacked the LED indicators were usually XT complaint and made as replacements for old XT keyboards.

so sad to see the machine won't power ...

carlostex wrote:

Update! […]
Show full quote

Update!

I ran out of luck. I did a more closer look inspection because i wanted to take all the components out and clean the case and i was very sad to see this:
...
Other option is to get one of my other 8088 boards, burn a 8KB EEPROM with the IBM BIOS and use it as a temporary replacement. After all, what makes an IBM XT unique is its BIOS.

Man, sorry to hear that, but on the bright side, you have some nice rare IBM parts to build another one or even some sort of clone (I like your idea of using another 8088 board and burning an EEPROM with IBM BIOS)...at least you have the keyboard and the cool IBM case (and all the I/O cards) to work with. I suspect that down the road, you may even be able to find an IBM 5150 or 5160 replacement M/B if you get lucky. Anyways, I wouldn't give up just yet...having a clone 8088 in a real IBM case is pretty cool IMHO (if you can make it work). The real IBM 5160 XT case is timeless...I wish I had one, with or without a working M/B. 😀

Sometimes i think about it... What would be closer to a real IBM 5160? A real 5160 motherboard with a 3rd party BIOS or a 3rd party motherboard with an IBM BIOS? Although the absolut correct answer is a "real 5160 board with IBM BIOS" if the choice has to be made between the first 2 i'd choose a 3rd party board with IBM BIOS. Everytime you power on the machine it feels proper IBM and no one will have the idea what motherboard is inside. This is good unless one decides to open the case...

But anyway, the plan is always to get a true IBM 5160 board and preferably the early 64-256KB one. BTW, i do have 2 original IBM boards on the machine, which by coincidence were the only 2 i hadn't pictured. The floppy controller and the async card are indeed IBM.

Did you test the addon boards? Just to be sure they didn't burn with the motherboard?

alexanrs wrote:

Did you test the addon boards? Just to be sure they didn't burn with the motherboard?

I couldn't test them all but at least the Floppy and MFM controllers seem to be working fine.

Good. Hopefully the power connector inversion didn't kill anything other than the board =)

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I'm sure it is. But i would need someone in US to get those parts and then ship them to me. And USPS is expensive these days.

eBay GSP is actually useful for us in these circumstances: http://www.ebay.co.uk/itm/161951474265
Shame the pound is getting hammered these days.

bjt wrote:

eBay GSP is actually useful for us in these circumstances: http://www.ebay.co.uk/itm/161951474265
Shame the pound is getting hammered these days.

Thanks bjt!

I've been watching that one for a bit now, looks like it needs a good scrub. Fixing the 5160 is not my priority right now, since i just returned to England.

Now i just want to finish my Turbo XT. I brought with me my Juko Super Turbo XT board. I'm gonna decide between the Juko and the PIM-TB10, gonna test everything i can. I have a feeling that the Juko because it runs at 12MHz will give problems with a Sound Blaster CT1350 i also brought with me for SB, AdLib and CMS capabilities. If that is the case i will be using the 10MHz TB10 instead.

The Juko is according to Checkit a good 10% faster than the TB10, 943 vs 814 Dhrystones. Not that its a big difference but it's certainly cool. I made a deal with Kixs and he will be providing me this beautiful case:

I'll have to clear the 8087 out of the equation if i decide using the Juko, 12Mhz is a bit too much for it. I think i'm gonna also use Sergey's floppy BIOS. Just to make things unique i plan to have 4 functional floppy drives in the system. The reason is that it will make my life easier when i want to use a Gotek. I will be pairing a 1.44MB drive with a 1.2MB on the first controller and a Gotek and a 360k floppy drive on the second. I want the system to be able to tackle all the media.

To use 4 floppy drives i think its better to use DOS 5 and up. It will reserve A: and B: for the first controller, then it will assign letters for Hard Drives (i'll use C: only) and then D: and E: for the last floppy drives. I want to make this work all at the same time, but i think i might have trouble with software not expecting D: and E: floppy drives. If this is the case i'll downgrade to 1 controller and i'll be swapping cables everytime i need. I'll have to use DRIVEPARM to set the proper values to the 360k drive when using it, or use 2M-XBIOS.

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carlostex wrote:

I'll have to clear the 8087 out of the equation if i decide using the Juko, 12Mhz is a bit too much for it.

Well, the 8087-1 is rated at 10 MHz... If you manage to find a good one, perhaps stick a heatsink on there, I think 12 MHz would be doable.
Also, can't the Juko run at different speeds?
I have an XT that can run at 4.77, 7.14 and 9.54 MHz. I would think most XT boards would at least be able to run at 4.77 MHz for compatibility.

It has 24MHz and 14.318Mhz clock crystals. The board works on 2 different dividers. Divide by 2 for the Turbo mode and divide by 3 for the normal mode for respective crystal. So far i'm not too worried about the FPU, but i was considering an heatsink even for the 10MHz board. My 8087-1 runs very hot.

Well, we could make a deal here 😀
I have 3 8088 systems at home, none of which have an 8087. So how about you buy 3 8087-1 FPUs, and then pick the one that runs best on 12 MHz. Then I will buy the 3 other ones from you for my systems 😀
(mine are 9.54, 8 and 4.77 MHz respectively, so any 8087-1 should work in them).

^Thanks Scali, i'll pass on the offer for now. I spent a bit on a good case for my Turbo XT, build that i should be updating soon. I have 2 XT threads around here, an older one based on the Juko board and the newer based on the TB10 board. I haven't decided on which board will make my build here in England but it seems the Juko one will take the cake. I really like the TB10 board too, so i'm currently happy with the boards i own. 8087 is far from being a priority for an XT build.

PeterLI wrote:

I can always help out with shipping from US to EU.

Thanks Peter. I think that if there's something i would like from the US it would be a Tandy SL maybe. There's still the 110V problem though. Sometimes UK Tandys appear on eBay, so who knows. But there's other priorities at the moment.

It's alive!!

I tried powering up the board with a good known working and soon enough one Tantalum blown in a shower of sparks. So i figured out i wouldn't lose anything with an attempted re-cap. So i replaced all tantalums i could. Some were impossible and i don't have all proper tools.

I tried powering up with a minimum configuration and what do you know...1 long and 2 short beeps!. The board is alive. So i got a VGA card and its working. 256K of memory counted fine and oly got 2 errors. A 301 and 601 errors. The 301 obviously went away when i plugged a keyboard in, and the 601 came up because i had no floppy controller connected. So it booted into BASIC.

Next day i tried testing the expansion cards the system came with. Well some of them at least... Floppy controller works, and so does the full height 360k floppy drive. Great. Tried the memory expansion card, and memory count increased by 256K. Also tried the MFM controller that is working well too, but unfortunately the 10MB Rodime HDD is dead. It powers up and spins, but after a few nasty clicks it always spins down until its not spinning anymore. Sounds like the heads are crashing.
I would like to keep this system as authentic as possible, so i'll try to find another MFM drive. I didn't try the Hercules and the ASYNC cards yet but those can wait.

The original PSU must not be working properly. Although when i measured it voltages seemed to be good, it fails to power up the board. It's only 63W anyway, i need to find a replacement one, or ghetto mod an AT or ATX PSU with the rocker switch.

Great work. This XT will live again!