Help Needed with PEB issue

[klrw111-78]

My setup includes a TI-99/4a console black and silver and a beige one (spare), PEB with TI RS232 HDX mod, TI FDC, and a 1K SAMS. The system totally locked up yesterday and upon reboot none of my PEB cards were recognized. Finally got the SAMS card to be seen and functioned properly, but attempts to access the FDC resulted in a Error 0. Pulled all the cards and started looking at the voltage on the PEB bus and read +26V, -26V, 15V, 12V and 5V. From the specs it appears they should be +-16V and +8V on the unregulated rails. Heard of an issue like this before? Transformer issue?

[+arcadeshopper]

do you have anything between the ti and the firehose cable? (the big black one) if not then check the connector (reseat/wiggle with power off) to make sure it's making good connection with the TI, also cleaning both the ti side connector and that one wouldn't hurt. this is the most common failure point..

[Omega-TI]

My setup includes a TI-99/4a console black and silver and a beige one (spare), PEB with TI RS232 HDX mod, TI FDC, and a 1K SAMS. The system totally locked up yesterday and upon reboot none of my PEB cards were recognized. Finally got the SAMS card to be seen and functioned properly, but attempts to access the FDC resulted in a Error 0. Pulled all the cards and started looking at the voltage on the PEB bus and read +26V, -26V, 15V, 12V and 5V. From the specs it appears they should be +-16V and +8V on the unregulated rails. Heard of an issue like this before? Transformer issue?

 

HDX huh? Do you get a blue screen on power up? Does the RS-232 stay lit when the system is turned on? It could be that the battery in the HDX is near death and the DSR is corrupted preventing proper booting of the system.

 

Remove the battery from the card and then re-insert it. Does the TI boot now? If so, go out and buy a new battery then re-load the DSR into the HDX.

[Shift838]

you can also remove all cards but flex cable and SAMS card. If it boots good, then power down (wait 2 minutes; I wait 3 to be safe on mine) and put in the FDC. Power up if all is good power down, wait 2 minutes and put in the HDX. Power up. If it stops there then it has something to do with the HDX, most likely the battery as Omega suggested.

 

if you have a volt meter measure the voltage on that battery and make sure you are getting 3v.

[klrw111-78]

 

HDX huh? Do you get a blue screen on power up? Does the RS-232 stay lit when the system is turned on? It could be that the battery in the HDX is near death and the DSR is corrupted preventing proper booting of the system.

 

Remove the battery from the card and then re-insert it. Does the TI boot now? If so, go out and buy a new battery then re-load the DSR into the HDX.

 

 

 

I pulled that card first. ( I have a wired jumper pin to handle the interrupt issue). After the system died the first time, the beige console would not present the title screen with the PEB plugged into the IO port with all but flex card removed. Switched to the black and silver console and it worked with the peb attached minus all but flex card. After trying the SAMS and TI FDC to no avail, I started looking at voltages.

Edited April 27, 2018 by klrw111-78

[tuf]

Sounds like a cap failed. I'd recap the supply before plugging anything back in.

[Opry99er]

Interface buffers?

[klrw111-78]

Thanks for the input.

 

The FDC and RS232 appear to be dead and I've discovered what caused the initial problem. Fingers on a connector of the extension cable that I was using to connect the PEB to the IO port got bent and shorted out in the process of plugging and unplugging from the port. I've run the AMS test program on the SAMS card and it tests OK. The regulators on the FDC and RS232 cards are outputting 12V and 5V, but the LED doesn't indicate any activity at power on or when addressed. The software test for the cards fail with a "card not present". Is it possible for the FLEX card to work fine for the SAMS, but not the others?

 

Before I risk replacement cards (which I have to procure), I want to make absolutely sure that the values of the unregulated legs of the supply are within norms. I considered the values high (10V over spec with empty cage) for my part, but that may be OK since the voltage will drop some as cards are added to the bus.

[marc.hull]

Those voltages are as normal as you can expect from the PEB. it was built with voltage drop in mind due to max load.

 

I don't think you cooked your fdc or rs232. If anything I would guess you killed your flex cable card or console side port logic.

 

Try a known good console and if the behavior is the same then attack the flex card.

[Shift838]

I would tend to agree with Marc's assumption as well. The flex is most likely cooked. I would procure another flex card if you don't have one and if it turns out not to be the flex card then you have a spare now.

[RickyDean]

And you can repair the flex card with some work, I have in the past.

[klrw111-78]

And you can repair the flex card with some work, I have in the past.

I'm working on that now adding sockets for easy fix next time. Have found two bad 74LS244 ICs on the interface card. Thanks

 

 

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[RickyDean]

Oh My, I just found out last night that one of my p-boxes was an original TI PS with a whisper quite fan, a mod I did about 20 years ago. I had plugged one of my unregulated Geneves into it 4 weeks ago and probably blew some chips. But will have to wait and verify on a verified pbox with a switching PS in it. Oh well..

[+Ksarul]

Ouch! That particular mistake is never a good one. . .

[RickyDean]

Ouch! That particular mistake is never a good one. . .

Yep, have already found half the Geneve memory chips were bad and one 244, maybe video also don't know for sure yet, an sram. And it may have a bad gate array

[RickyDean]

Well a couple of weeks ago I was plugging a card into a PEB on my desk, not realizing that the aluminum bracket on it was bending into the regulator as I plugged it in. It killed voltages coming from the PS to the backplane, I have nothing.

In the process last night I started checking other voltages in some other boxes that I have and found the following on the +5 volt connector pins, I am getting 12 volts to 14.50 volts and on the +12 volt pins, I am getting 21 to 25.50 volts. This is to much per the specs that I found and may be causing some of my issues.

I am therefore going to start converting these to AT or ATX power supplies.

I also on the switched PS box, I do have, found that the 12 volt rail was putting out about 13 volts, not sure whether the chips that receive this power can handle that much, since the regs are bypassed. But will be delving into that too.