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+--- Thread: Microbee 128K reapir (/thread-542.html)
Microbee 128K reapir - MikeCornflake - 07-08-2022
G'day,
A little while ago I picked up a 128K premium. Just the main unit, no external drives or power etc.
Right off the bat, none of the keys worked. Following all the advice in a different forum not a million miles from here, I've repaired enough key switches now to establish the Bee can boot to Monitor. Using the monitor, I've established that the time spent repairing key-switches was largely wasted. So many still not working... (Mind you, I haven't tried replacing RN1 yet)
But, you know, chin up and all that. I plan to replace all the key switches with Cherry MX's (thanks Chickenman, Suzy and Brad, your posts elsewhere were useful). I'm not keen though on cannibalizing the existing key-switches (much as I now dislike them, they are part of the provenance of this Bee). I have established that with only a little bit of filing, lego axles cut down can be used as key shafts. So that plan is ongoing. Any advice on securing the shaft to the MX would be appreciated. I used superglue last night, and that seemed to work. Not sure as to longevity of that though, and suspect I'm going to need 2 part epoxy as a minimum.
Next part of the rebuild is the drive unit. I'm getting a gotek up and running. The Gotek requires 5V, and near as I can make out - Pin 4 on the Shugart cable provides 5V (and all the odd pins are ground). Could I just use that?
Many thanks
Mike
RE: Microbee 128K reapir - ChickenMan - 07-08-2022
What exactly are the Lego Axes you are talking about, any on this page https://mybrick.com.au/LegoAxels.html ?
Would these be suitable, where the cross end fits to the Microbee keycap and the hollow end slips over the small Cherry shaft ?
If so I would Super glue them over the Cherry shaft if its a tight fit or 2 pack epoxy if a loose fit.
RE: Microbee 128K reapir - ChickenMan - 07-08-2022
As for the Gotek, not sure about Pin 4, but I just use an old USB cable that I fitted the 4 pin 3.5" floppy Berg connector to and use a small 240v to 5v USB adaptor like this -
This way I can move it to any Microbee or other that needs the Gotek.
RE: Microbee 128K reapir - MikeCornflake - 07-08-2022
@Chickenman:
On the page you linked, I used Black Technic 6L axis (Lego Part 3706). Clamped a flat file in a vise and used the 90 edge to remove enough material for the axle to fit in the keycap. Then cut the axle into required lengths.
I really like your alternate Lego solution! More meat for the glue to work with. Many thanks.
And many thanks for suggesting the USB solution. I wasn't sure if I needed a common ground between the 5V for Gotek and 12V for Bee.
Pin 4 on the Shugart cable was a bust. When connected to the Bee, it only measured 2.5V. I'd got 5V from a Sinclair manual as I've been unable to find the pinouts in Bee documentation.
RE: Microbee 128K reapir - MikeCornflake - 07-08-2022
USB cable for Gotek did the trick! Bee now boots properly - I used a CIAB boot disk for a test. I don't have enough working keys for full tests, but I can verify the following:
I can run Microworld Disk Basic - and get a beep when it starts
I can drop to CP/M, and nearly type DIR (just missing the R) :-)
This is exciting, it's alive :-)
I'm using the Composite Out signal available from the DIN5. I'm not seeing any colour yes, but everything so far black background, white text. I'll dig through the available disks, find something more useful.
But, on the video out, I'm seeing a minor vertical fast-jitter. Everything moves, say a fraction of a pixel up, then bounces back, three or four times a second. Anyone any ideas what this could be?
Update: No colour, I used Chickenman Games Demo Disk. I admit, I was half expecting that, I note the colour bees have an RGB connector on the back, this doesn't have that. What will I need to plumb in to get colour?
RE: Microbee 128K reapir - ChickenMan - 07-08-2022
Good to hear you have some life in the Bee
Try wiggling the key-cap when down, that can help.If its a Premium 128k bee, you should have cursor keys and a 9 pin D shell out the back of RGB/CGA which is colour. The Composite out of the 5 pin DIN is Monochrome only. You will need a CGA monitor or a CGA to VGA or HDMI converter to use a modern monitor.
RE: Microbee 128K reapir - MikeCornflake - 07-08-2022
G'day,
Interesting. Yes, I have cursor keys, and there's a DB9 on the back. Silly me, I assumed it was serial :-) Thanks, I will play. I've no ability that I'm aware of to view CGA, so I'll start looking at adapters.
Cheers
Mike
RE: Microbee 128K reapir - CheshireNoir - 07-08-2022
(07-08-2022, 09:19 PM)MikeCornflake Wrote: G'day,Mike, do you have a 15KHz capable monitor, or an upscaler? (anything with VGA in)
Interesting. Yes, I have cursor keys, and there's a DB9 on the back. Silly me, I assumed it was serial :-) Thanks, I will play. I've no ability that I'm aware of to view CGA, so I'll start looking at adapters.
Cheers
Mike
If so, there's a neat little CGA to VGA adapter made by a guy who goes by the name of Necroware who makes a truly excellent CGA to VGA adapter: https://github.com/necroware/mce-adapter
I've even got a spare PCB somewhere if you have the monitor / adapter.
I can bring it in to work if you like.
John
RE: Microbee 128K reapir - MikeCornflake - 08-08-2022
@CheshireNoir:
I don't know about any of my monitors, and I don't have an upscaler yet. But I note this adapter can be used as an input to the GBS-8200 - I've just ordered one of those and have been looking for something that fixes its known issues. MicrobeeTech CGA to VGA upscaler is out of stock, though I've pinged Ewan, I'd love a Bee branded solution, but in the meantime - yes please, I'd love that PCB.
Many thanks.
Mike
RE: Microbee 128K reapir - CheshireNoir - 08-08-2022
I did the GBSControl mod to my GBS8200.
https://github.com/ramapcsx2/gbs-control
Works well and is really cheap. I even added the optional clock generator. [Also works well with an Amiga as a deinterlacer ;-) ]
John