ATX Power Supply for PEB - seeking more detailed information on replacing the original PS

[+jedimatt42]

No.  

 

But if I were to do so, I would put a red 5v LED and a 330ohm resistor in series between the psu's 5VSB (standby) power line and a common. 

 

I would not add a hole to the front of the PEB. One could shine it out the fuse hole.

[XLERB]

6 minutes ago, jedimatt42 said:

No.  

 

But if I were to do so, I would put a red 5v LED and a 330ohm resistor in series between the psu's 5VSB (standby) power line and a common. 

 

I would not add a hole to the front of the PEB. One could shine it out the fuse hole.

Nice idea, maybe I will do that!

[GDMike]

Yeah, I wanted an LED in the front of the case but I wasn't about to put a hole in it just for an LED. Then I thought about drilling a tiny hole in the power switch and sticking a micro LED in there. Then I just aborted the whole idea and I said well the PEB cards have lights on em', so I just don't do it at all. But thanks for letting me know in case I change my mind someday with a beat up case or something.

Edited March 27, 2023 by GDMike

[XLERB]

So following JediMatt42's lead, I am installing the ATX PSU and the breakout board in pretty much the same locations. I don't have a 3D printer so I cut up an old CD holder and put it where the plastic TI bracket was, and used a scrap of Plexiglas from a window repair to make a base for the breakout board. Now wiring the 115V socket and switch. That original push button switch is fragile - the lugs break off when I try to un-solder it. But I'll see what I can do. The fan from the new power supply had longer screws than the length or=f the TI bolts so I had to grind down the plastic on the corners of the fan housing but that will work.

 

If the switch isn't usable, maybe one like this one - with a blue LED built in - would fit. But it might be hard because the old switch doesn't actually attach to the front panel, just protrudes through a hole.

[XLERB]

I got it all back together (managed to save the push-button switch with careful soldering and some epoxy glue to hold the joint securely), and it’s putting out the expected voltages. Still have to try my spare cards in it - 32K and disk controller for now. 
 

My only glitch is that the PSON pin didn’t seem to work properly, and I think it’s because the breakout board I bought has a built-in on/off switch that interferes with it. And of course that switch is inaccessible once I put the PEB back together. However, the “standby” pin seems to work when I wire it to the push-button switch. Except it works in reverse - the power is on when the push-button is disengaged, and off when it’s engaged, and only when the internal switch on the board is on. But that’ll do. Odd but seems to work.

 

i kept the rocker switch from the new power supply and put it in the hole on the back of the PEB where the fuse holder used to be, after enlarging the opening to be a rectangle. I like the idea of being able to kill the power completely without unplugging it.

 

Gee, I’ll miss the jet airplane sound when I turn it on now.

Edited April 2, 2023 by XLERB

[+InsaneMultitasker]

1 hour ago, XLERB said:

Gee, I’ll miss the jet airplane sound when I turn it on now

Has this PEB jet engine / white noise been added to any of the emulators, as an optional enhancement?  

 

[+jedimatt42]

The breakout board I used has an on/off switch as well, but I just left it in the off position.

[+mizapf]

5 hours ago, InsaneMultitasker said:

Has this PEB jet engine / white noise been added to any of the emulators, as an optional enhancement?  

This is tempting.

 

However, as long as people ask how to turn off the floppy emulation sound, I'll surely not put any efforts in something like that again.

[+jedimatt42]

47 minutes ago, mizapf said:

This is tempting.

 

However, as long as people ask how to turn off the floppy emulation sound, I'll surely not put any efforts in something like that again.

Hopefully you added the floppy sounds for your own enjoyment and not due to some request. I would assume if you like sounds you should add all the sounds you want... maybe just make them opt-in instead of opt-out.

[+mizapf]

11 hours ago, jedimatt42 said:

Hopefully you added the floppy sounds for your own enjoyment and not due to some request. I would assume if you like sounds you should add all the sounds you want... maybe just make them opt-in instead of opt-out.

Yes, it was for my own joy; the result is, in my ears, really close to the real drive, and it was not a trivial task to achieve that from a few sound samples; hence, I was indeed disappointed getting requests right away how to turn that off¹.

 

As for the PEB sound, this is merely background noise without a meaning, and it does not even change during operation; I never sincerely planned to add something like that. I could, however, consider to create some active artwork with the flashing PEB lights.

 

(¹To those who have not found out: Use the OSD, "Slider controls", settings "Speaker ... flopsndout"; there is one channel per drive, simply adjust the volume between 0.0 and 1.0. That's yet another reason not to hook up four drives if you don't need them. Alternatively, for a permanent change, remove the samples in the samples/floppy folder.)

[XLERB]

15 minutes ago, mizapf said:

Yes, it was for my own joy; the result is, in my ears, really close to the real drive, and it was not a trivial task to achieve that from a few sound samples; hence, I was indeed disappointed getting requests right away how to turn that off¹.

 

(¹To those who have not found out: Use the OSD, "Slider controls", settings "Speaker ... flopsndout"; there is one channel per drive, simply adjust the volume between 0.0 and 1.0. That's yet another reason not to hook up four drives if you don't need them. Alternatively, for a permanent change, remove the samples in the samples/floppy folder.)

I still remember the “clunk” of the original Shugart drive that was my sole disk drive back in the day. I still have it in the basement - I should try it in this repaired PEB just to hear the sound again. (I mention the PEB so I won’t be off topic in my own thread 😇). By the way, it’s kind of funny that the Molex connector for the floppy drive (or whatever) has survived in these new power supplies. Kind of like how USB-A is still everywhere. I had a little trouble stuffing that hydra-headed bouquet of SATA and whatnot connectors into the PEB since I didn’t want to cut them off.

[XLERB]

Yes! Clunking disk drive and all! Thanks to all who helped, especially jedimatt42 and insanemultitasker.

[humeur]

I am surprised that many change their power supply not taking into account the technical specifications of the regulators on the plug-in cards, Yes it works, no doubt to say that it is optimum, I doubt it.

 

A text that clearly explains the principle of these regulators   https://www.sonelec-musique.com/electronique_theorie_reg_tension.html

 

 

"Integrated voltage regulators, whether fixed or adjustable, require (at least in the most popular versions) a voltage difference between the output and the input which is of the order of 3V, to be able to function properly. Thus, a classic 12V regulator (an LM7812 for example) must see on its input a voltage of at least 15V (12V + 3V) for the regulation to work properly. This minimum voltage difference, called dropout voltage"

[XLERB]

3 minutes ago, humeur said:

I am surprised that many change their power supply not taking into account the technical specifications of the regulators on the plug-in cards, Yes it works, no doubt to say that it is optimum, I doubt it.

 

A text that clearly explains the principle of these regulators   https://www.sonelec-musique.com/electronique_theorie_reg_tension.html

 

 

"Integrated voltage regulators, whether fixed or adjustable, require (at least in the most popular versions) a voltage difference between the output and the input which is of the order of 3V, to be able to function properly. Thus, a classic 12V regulator (an LM7812 for example) must see on its input a voltage of at least 15V (12V + 3V) for the regulation to work properly. This minimum voltage difference, called dropout voltage"

Thanks for the caution, I appreciate it. I’m going by the extensive discussion up-thread, and don’t plan to run this as my main box until I can make sure the cards aren’t running hot. I know it’s less than ideal, but I hope it will do. I’m counting on the fact that people have run BBS systems continuously this way without problems. I guess we have to live with the fact that TI made one of its more boneheaded decisions (out of many) to supply everything with 16v and 8v and then have the cards regulate that down. The other broken PEB will be my attempt to properly replace components on the original board, if I can manage to get them unsoldered. I have new capacitors and voltage regulators. That should occupy my next couple months. If that works, it’ll be the one that I feel comfortable using continually.

[+jedimatt42]

For the cards I have eyes on, these are their regulator situations:

• Shift838 IO : 5v
• TI Flex Card : 5v
• Corcomp DSDD Floppy Controller : 5v
• Foundation 128K : 5v
• Mechatronics GRAM Karte : 5v
• PGRAM : 5v
• SAMS 2016 : 5v
• TIPI : 5v, 3.3v
• Rave99 Speech In PEB : -5v, 5v
• TI FDC : 12v, 5v
• TI RS232 : 12v, 5v
• TI 32K Memory : 12v, 5v
• SidMaster99 : 12v or 9v (depending on SID chip)

All of the 12v regulators I observed were LM7812C variants. I think, the deal is that regulation does not work properly on these, but the upstream power supply being regulated and the load in system of the 12v side on each card being relatively low, and the absolutely MASSIVE heat sink attached to most of these cards. 

 

I'd like to measure some of this myself still. 

 

In the long run, I'd also prefer to replace the regulators across the boards with the appropriate DC-DC switching replacements. 

 

 

[RXB]

Using Shift838 PEB Flex Cable replacement and PEB replacement card in a PC case with PC 350watt power supply I have seen the Cards all run cooler.

Placing the cards in a TI PEB and run them for a couple of hours most of them will burn your fingers.

Placing the cards in my new PC case with PEB replacements from Shift838 they are only warm so obviously there is not a issue.

 

The additional 3 super quite 120mm fans also helps I bet.

[humeur]

51 minutes ago, RXB said:

Using Shift838 PEB Flex Cable replacement and PEB replacement card in a PC case with PC 350watt power supply I have seen the Cards all run cooler.

Placing the cards in a TI PEB and run them for a couple of hours most of them will burn your fingers.

Placing the cards in my new PC case with PEB replacements from Shift838 they are only warm so obviously there is not a issue.

 

The additional 3 super quite 120mm fans also helps I bet.

Normal the regulators are outside their normal operation

 

jl

[RXB]

1 hour ago, humeur said:

Normal the regulators are outside their normal operation

 

jl

Yea as the PC power supply is much more modern it does not overpower the cards thus leads to excess heat from cards being overpowered.

Also the 3 120mm fans hardly even faze the 350watt power supply but would over stress a TI PEB power supply.

Heck some hard drives in PEB stress out the PEB power supply.

[XLERB]

I’ll defer to those who know more on this voltage regulator issue, but I do have a working disk drive so this is now a fully functioning spare system, albeit with a single ancient SSSD drive that makes some interesting sounds while in operation.

[+arcadeshopper]

3 hours ago, XLERB said:

I’ll defer to those who know more on this voltage regulator issue, but I do have a working disk drive so this is now a fully functioning spare system, albeit with a single ancient SSSD drive that makes some interesting sounds while in operation.

noise is usually a sign of bad lubrication, have you cleaned the rails and re-lubricated all the moving surfaces? 

 

[XLERB]

40 minutes ago, arcadeshopper said:

noise is usually a sign of bad lubrication, have you cleaned the rails and re-lubricated all the moving surfaces? 

 

Will do that, thanks! .. This is a drive I bought from a guy as a spare back in 1988 or so and it’s been sitting in the basement in a box. The rails and related parts are right there to see. At least it works, unlike my original Shugart from the PEB combo sale from TI in 1984 or whenever that was. I feel like an archeologist. The guy I bought it from had a sticker on it saying “Dsk2” but it works as DSK1. I think he removed the jumper that made it DSK2.

[XLERB]

So… end of the story. Working, with the ancient floppy drive (now quieted down) and even the p-Code card working fine (so that wasn’t the cause of my problems). Quiet, seems to run cool enough. I won’t be running this system 24/7, by any means. (Wish I hadn’t given away the extra flat screen monitor we had kicking around the basement. That old CRT is heavy).

[Wildstar]

If you want to use an ATX power source but at original or close to it voltages.

 

You might need a couple of dc-dc converter if you want to keep original TI PEB voltages. Stepping up the 5v side to 8v and 12v side of ATX to 18v.  I'd you combined a 5v with 12v, you'll be almost at 18v. You have to make sure you still have  clean 5v leg that is stepped up to 8v. Doing it clean is important though. Most cards of that Era worked fine undervoltage and overvoltage more than modern electronics.... they are much more robust to wider voltage swing that would fry today's more sensitive chips.

Edited September 21, 2023 by Wildstar