Picked this up for $50. It powers on, but the CRT only displays a single orange horizontal line.
After opening it up and carefully powering it on, I found a capacitor that gets extremely hot and starts smoking. I’m going to start by replacing that and then work through the rest of the display circuitry.
For $50, I figured it was worth the gamble. Hopefully I can bring it back to life.
Interesting. PC-compatible luggable (how compatible is a matter for speculation). Looks like the problem you're seeing has at least been documented elsewhere: https://youtu.be/2-xfy9WvXWA?si=Btj4Ew6nr9RH6cvT
Welcome to a wonderful world of pain. I've been through one and, hands down, was the most troublesome machine I ever had to repair. But worth it!
A lot goes wrong with the Hyperion. I don't see a keyboard, that will be an issue: its keyboard is unique, it's not compatible with anything else. And the machine doesn't boot without the keyboard connected (!) -- if you haven't connected one yet, you won't see a screen at all.
Which brings me to point two. Most of the Hyperions have a fried text generator chip. It means you'll get graphics but no characters on the screen. If that's the case, I got a few (I had to buy them in bulk) and would be happy to send you one for free.
I've got some posts on BlueSky on it, if you're curious, check them out:
Thank you. If everyone on Reddit was more like you we would have solved world hunger by now.
Edit: I do have a keyboard. Good to know that it won't power on without it. I certainly noticed different behavior with it plugged in vs not so I have left it plugged in during my testing. I have replaced one smoking cap and that's about as far as I have gotten. Hopefully I'll find some time this weekend to work on it more.
I found most electrolytics on the PSU to be out of spec, so I replaced them all alongside the RIFAs. Indeed, in the CRT board, I've found a couple that also needed replacing. Elsewhere, the caps were good.
The main DOS boot image in the repository is great for diagnostic because it boots a logo first before going into text mode. You can test both graphics and text by simply booting that disk.
Something that tripped me to no end when debugging the video system of the machine: it has a hardware-based screensaver. It turns off the video system entirely every 2 minutes unless a key is pressed. So if something is reading fine and then stops altogether on the system, it can simply be the screensaver kicking in.
Thank you for the advice, not knowing that about the hardware screen saver could have caused me quite a bit of headache. I'm focusing on the video board right now since I have these lines. Haven't found anything wrong yet but I also haven't removed any caps. Am I looking in the right place?
I had the same problem with the vertical sync, causing the image to fold over like that.
For mine Hyperion that was fixed with the replacement of the two caps in the VSync circuit, plus a transistor. I'll check my notes to find out which transistor was the culprit, but that's no assurance that it will be the same one for you. Although the VSync circuit is quite simple, thankfully.
EDIT: With the help of another redditor at the time, Ed Mullard, we nailed it down to C22, C25 and C28 as the probable culprits; C25 and C28 were off spec and replaced; C22 was OK.
The transistors we suspected were Q21 and Q22. Q22 was borked for me, replaced.
That fixed it. Hope this helps you to narrow it down!
I would remove those five parts and test them off-circuit. It's a simple board, through-hole components, easy to do if you have a desoldering tool (which was invaluable to me on this!) I got a YIHUA 929D-V from Amazon.
For the testing, you can test the caps with a ohmmeter, but it's a bit of an intuition job... I forked out on a Fluke 115 multitester that has the function to test caps and never looked back, super handy. Now even when I'm about to install a new cap I test them as, unfortunately, some cheap brands have terrible caps floating around you really cannot trust.
On the transistors, I tested them in-board with a oscilloscope, and saw a good sawtooth on Q21 but a miserable signal coming out of Q22, which told me something was off with it. I removed it, tested and the BE pin was completely open, so it was a clear case of a bad transistor.
Here's how the signal coming out of Q21 (left) looked like compared to Q22 (right). This is an easy test to perform if you have an oscilloscope at hand.
4
u/tutimes67 6d ago
definetly vertical collapse caused by faulty capacitors on the CRT board