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Restoring my Microbee - Printable Version

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RE: Restoring my Microbee - dinotron - 20-02-2022

Thanks for the replies guys - All very interesting stuff..

Got some good news - last night, I powered the machine up again - with it connected to a cheapo composite to VGA converter - and suddenly the speaker made a very a loud beep that literally made me jump - and i saw the rom menu on the screen.

It worked perfectly - (the video conversion was a bit flickery and of course only b/w) - I went thru a few of the ROMs - word processor, a graphing utility??, and a couple of others - and of course Basic!

I was surprised, that despite there being no battery connected - that the system remember its state fully from one power cycle to another -- near 1 min and it would boot as i left it... Impressive - i guess that because of that big fat capacitor?

Keyboard worked - but keys were not particularly easy to use - had to press quite firmly and cleanly - and make sure it registered. Took a few attempts to do the PRINT "Dean was here" basic statement, without error.

I have since removed and cleaned the keycaps and brushed and cleaned the base of the keyboard - surprising there was not a lot of dust and dirt for something of this age.

I ran the system test - and let it do it things --- for the most part got passing ticks - not sure what it was telling me about the PAK's - some ticks some crosses - but I was using the ROMS apps, so assume they are all just fine.

But it did report problem with the 'Colour Board' --. Could this be due to not having a monitor connected?

So at this stage have some questions:

1. Any recommendations on how to improve keyboard operation?
2. Retrobrighting - the machine has some yellowing - and the key caps are yellow on top, white at base - what are peoples experience with retrobrighting their Bees? (Did some searching on this and the other forum, but didnt find much recent - wondering what if anything is the most recommended approach these days)
3. Colour board - the system test indicating problem with colour board - does that indicate a problem with it accessing some registers or something with the board? Might it mean trying to figureout the problem? It doesnt look an easy thing physically to diagnose or repair..
4. Next step will be to try and look at the output coming from the board - I have a oscilloscope (although still very much a newbie with it) so was thinking of looking at the output to see whats there - any suggestions of what i should expect


Also got another question - I am wondering if I am on the right forum for discussing this - not sure of the different aims on this forum compared to the https://microbee-mspp.org.au/.

Dean.

RE: Restoring my Microbee - dinotron - 20-02-2022

Hi all,

I have since the last posting, been able to get colour output from my Bee.

I had a look at the project CheshireNoir had posted (https://github.com/ramapcsx2/gbs-control)

Like most converters I found, it does 2 basic things - combine a HSYNC and VSYNC signal to produce a single CSYNC.

And combine the colour and intensity signals into an analogue scaled output, using 2 resistors - a 470 for the colour and a 680 for the intensity.

As the Bee does already produces a single CSYNC signal - I could skip this - and I only needed a way to feed RGB colours to my GBS8200 up-converter.

So, got out the breadboard, found some resisters and wired up a temporary converter to feed the GBS8200 upconverter. (I did add a 1K resister to the CYSNC to reduce the level going to the GBS8200.)

And on powerup I was presented with glorious colours!

Now, I don't really know if this is producing a 'good' matching signals --- no ideas (and barely understand) if the impedance and such things are 'correct'.

Nor do I know if the colour scale is right.

I initially powered on, without wiring the intensity signals - and got some good colours on boot up.  The background was defaulting to black.

So i then added the resisters for the intensity signals - and now I think i am getting more colours - not sure how to fully test this. 

But the picture quality seem fine - but I am not sure if the colours are right.  See attached - never had a Bee with the boot up menu - is it meant to be grey background like is attached?

Anyway - I might when i get a chance, design a little circuit board with the appropriate connectors to make it a little less 'brittle'

   
   

Cheers
Dean

RE: Restoring my Microbee - ChickenMan - 20-02-2022

Well done Dean, thats looking really great. The background should be black but the other colours look good.

To answer your other Q in post above,

1. Wiggle the key cap can help. Best it to replace the keyswitches to new units, see http://www.microbeetechnology.com.au/store/keyboard-replacement-kit-standard-non-premium.html
2. Lots of people use Peroxide/Perborates/etc for retro-brightening but I found you just have to leave it out in full sun for a few days will lighten them up considerably.
3 & 4. I think your sorted the colour board or close to it already Smile

RE: Restoring my Microbee - MbeeTech - 22-02-2022

Hi Dean.
Just a little comment about retrobriting :
If you want to do the key caps, just do the white ones.
Unfortunately, the black ones tend to fade and become light grey and it ruins the look of the keyboard. 
Mind you, I was using a peroxide solution rather than just sun light, so that may have worsened the result.

Also, mostly the keys can be fixed, depending on how far gone they are.
I put together a repair guide which can be found < here >

RE: Restoring my Microbee - dinotron - 22-02-2022

Thanks guys for the advice,

I started the retrobrighting - in the sunlight only.  I put the keys caps out today.  The black ones have come out quite good after just one day.  They are still black, but the writing has whitened up just nice - given the comment of risk of greying the caps --- i will stop with the black caps now.  The white keys still need a bit more time --- not sure of the weather over the next few days - will keep an eye on it.  Also only just put the case and printer top out today - the printer was the most yellow - that might struggle in the sun only...

I tested with the cassette player a couple of days ago - just out in the sun - although it was rather overcast days - after just 2 days 1/2 days in mostly overcast days -- it came out rather nicely - i brought it in today as it seem like enough.

Unfortunately for the cassette player, its has received some serious injuries to the plastic - like its been attacked with a soldering iron.  I think it will have to live with those scares for the rest of its existence.

The keys themselves have loosen up a bit - think just using them a bit has helped -- but I will have a close look at the guide you link thru Ewan - much appreciated.

In regards to getting the colour working -- I need to do some more experimenting to get the intensity signals right - i think i need to buffer the TTL output, before doing the resister grading...  I have sketched out a design that will allow me to experiment - but not with the breadboard --- that was a bit too precarious to work with.  Need to get a proper 15 -sub connection.



.pdf   Schematic_BEE-RGBI-TO-RGB_2022-02-22.pdf (Size: 57.18 KB / Downloads: 312)

   

RE: Restoring my Microbee - CheshireNoir - 22-02-2022

Ooh I bet I know what the "soldering iron" scars are. Someone wrapped the tape drive in the power cable. There is a known reaction in uncommon cases between the plasticiser in the power cable (The additive that keeps the cable flexible) and the hard plastics in some computers.
You end up with "burn marks" around the systems. Most prominent in the corners.

Chesh

RE: Restoring my Microbee - ChickenMan - 22-02-2022

(22-02-2022, 06:57 PM)CheshireNoir Wrote: Ooh I bet I know what the "soldering iron" scars are. Someone wrapped the tape drive in the power cable. There is a known reaction in uncommon cases between the plasticiser in the power cable (The additive that keeps the cable flexible) and the hard plastics in some computers.
You end up with "burn marks" around the systems. Most prominent in the corners.

Chesh
I can fully vouch for that as it is VERY common issue with System 80 when people wrap the power cable around the unit and put it in storage.  You end up with deep black groves on the case Sad  You can scrape out and clean up the black but the groves remain.