IBM Model F with Soarer's Converter needs too much power

stefan94452

25 Nov 2021, 09:23

Hi guys,

lately, I've been working on my restoration project of my Model F. Well, restoring the parts turned out to be great, however, I face a problem. As soon as I connect my Soarer's Converter it results in "USB Device taking up too much power, must disconnect immediately". I'm wondering if either the PCB has a short or if I misconfigured my Teensy. I double-checked the wiring at the Teensy, and I'm pretty sure that it is correct. Connecting my Teensy without being attached to the board, my computer detects the Soarer's Converter successfully.

Does anyone have an idea how to check the issue?

PCB board back:
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PCB board front:
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Teensy:
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Teensy:
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fohat
Elder Messenger

25 Nov 2021, 15:23

I have never done direct wiring to an F XT, but the diagram for the 122-key has the colors generally reversed from yours.

Remember that the diagrams show the socket and not the plug.
Attachments
IBM-keyboard-001MF.jpg
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stefan94452

25 Nov 2021, 18:36

Thanks for your answer. I was referring to this thread https://geekhack.org/index.php?topic=17 ... #msg617942.
In addition, I'm going to check the PCB with a multimeter.

User avatar
Muirium
µ

26 Nov 2021, 12:09

Model Fs can draw a lot of power. It's the vintage electronics inside their controllers that do it. For example: my Model F AT just wouldn't work with a Pro Micro running Soarer's Controller. The computer didn't complain, the Pro Micro just couldn't handle it! I swapped that thing out for a Teensy and it worked fine, but as you're seeing some hosts will complain it takes too much power and will deny you a connection. (iPads are especially mean about power draw, I found, back when I was doing that. Likely other tablets and even laptops too.)

So try using another computer, just to see if the XT's controller is working, and your Soarer Teensy too. A *powered* USB hub could do the trick. This could be a host-side limitation rather than anything wrong with the ~40 year old keyboard!

Ultimately, I swapped out my AT's controller for a modern Xwhatsit controller. Solved all the power draw problems, it's as efficient as any USB keyboard now. But the XT's controller is non-detachable so you don't have that option.

stefan94452

28 Nov 2021, 15:50

That saved my day. Thanks for your reply.

Well, apparently on my ThinkPad T14 it doesn't work. I've tested it on an old laptop I had left on my attic, and it worked.
I can confirm that the keyboard needs a lot of power, and my machine couldn't handle it.
At least I know that the board is completely fine.

Any experiences or recommendations with powered USB hubs?

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Muirium
µ

29 Nov 2021, 11:27

Yeah, you're kinda shafted then! If your laptop won't put out the juice, the XT will not run. Annoying they're being so stingy with the power output these days. My 2003 era 12 inch PowerBook used to run an XT and Soarer converter just perfectly on a USB 1.1 port! :lol:

A powered USB hub should do the trick. I've just used the powered hub in my desktop displays over the years, so don't have recommendations for separate kit. Vaguely recall looking into a battery powered one for the iPad many years ago for this exact job. There were some that would charge up over USB when hooked up to a more generous host.

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hellothere

29 Nov 2021, 16:17

https://www.bestreviews.guide/battery-powered-usb-hub (note that not all of these are really battery powered).

I used a powered D-Link USB hub for about 10 years. I still have it sitting next to me, but a couple ports no longer work, so I decided to take a look for you, OP.

Amazon has a bazillion for sale. https://smile.amazon.com/Sabrent-Chargi ... B0797NWDCB and https://www.amazon.com/Splitter-Chargin ... B07G8CMR18 have the most reviews.

I looked at a couple with extra-high voltage (12V) and/or extra-high wattage (24W, 36W, etc.) and it seems that those specs are for the charging ports, only. All the other ports are 5V, 2.4A. Feel free to correct me if I'm wrong.

Coeus

29 Nov 2021, 16:56

This relates to an experience I had with my Model F XT and a converter based on a Teensy. It was connected to a KVM switch which was in turn connected to two PCs. It had been working fine for some time but one day, when I turned on of the PCs off, it started to play up with the other one - random characters appearing or stopping working. It turns out the DC power connection to the KVM had become disconnected so it was relying on the PCs for power. Re-connecting the DC power connection cause the issue to disappear again.

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Muirium
µ

29 Nov 2021, 17:01

You certainly don't need extra high wattage to run a Soarer converter and an XT. And any more than 5v will kill the Teensy!

XT + Soarer works fine on USB 1.1 and 2.0 ports. Those are 0.15 watts maximum, if memory serves, and 5v. That's all you need. Just a pity a modern laptop doesn't even support that!

Higher power stuff is all about charging phones and tablets. Different story.

stefan94452

29 Nov 2021, 18:00

Yes indeed thanks @hellothere, I've tested it on this USB hub (https://www.amazon.de/-/en/RSHTECH-Acti ... B091F7C5K4) that I recently ordered on sale, and et voilà it works like a charm. :D
So for everyone who stumbles upon the same issue, this might fix it.

Thanks for your support here!
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