My new adventure with my Microbee Premium Series

[The_Huck]

I picked up a Microbee Premium Series 128K from a local e-waste centre, along with it's matching disk drive.

It's the first time I've laid eyes on one of these so I'm about to embark on a discovery journey with this.
Any assistance would be greatly appreciated.

I've watched a couple of youtube videos and I know it's a Z80 processor and some machines came with battery backed static RAM and a machine code monitor built in.

It didn't come with a power supply so that will be the first thing to sort, along with connecting to a display.

   

   

   

There's one DIN socket of the main board which aligns with an unlabelled cutout in the top cover. There's another cut out to the right, labelled Power, which lines up with the speaker terminals shown in the photo.
Someone has soldered a "temporary" power cable to the underside of the main board. 
My first questions are, is the polarity correct and what voltage do I try to power the board with?
   

[MbeeTech]

Hello Huck.

The disk drive has the power supply in it that powers the drives & the computer.
Did you order from our web store just recently? There was an order that went to NZ with a power supply & separate Power/video/cassette lead in it.

If you decide to power the unit up from the wires that have been added, you need 10-12vdc @ 1.5 amps.
You can check the polarity of the wires by using a multimeter and comparing the polarity to what is marked on the main PCB beside the blue electrolytic filter capacitor.
I'd recommend getting the proper DIN lead though, as it provides connection for power but also video out (without which you will have no idea if the computer is working).

It looks to be a late production Premium and has had the required factory mods fitted from what I can see.

In regards to the disk drive, the power supply in it most likely has 3 RIFA capacitors that will need to be replaced as they normally have dried and cracked by now & will explode on power up.
Please check this before applying power to the drive (or have someone check it for you if you are not confident / qualified to service mains powered devices).

This is the normal lead :
https://microbeetechnology.com.au/store/...d-kit.html
We don't have any made up at present, but if you need one & want to order one, I can have it made up straight away.

[The_Huck]

Hi Ewan,

Thank you for your reply and useful information.
It wasn't me that ordered the cable but I did look into it a while ago when I first got the machine.

As you mentioned there are the three 4700pf Rifa caps hiding in the PSU. 
I'm assuming they are related to mains noise suppression? If so, is it okay to run it without them as I don't have any Y class 4700pf caps on hand?

There's a ribbon cable coming out of the front of the drive unit that looks like it plugs into the rear of the main unit. I assume power is delivered via that?
I'll remove the caps and replace them if necessary. 
Once that's sorted I'll power up the disk drive unit without the main unit connected and check voltages.

   
   

It looks like there's no video/cassette lead with mine so I will probably need to get one.

Cheers,
Huck

[The_Huck]

Now that I've had a close look at the drive unit and the power supply, I can see the power socket (2.5mm ID DC) on the rear of the unit.
I'll go ahead and order the power, video and cassette interface lead.
The next question will be - what state is the keyboard in?

[MbeeTech]

G'day Huck.
It would be best to replace the rifa caps before powering up.
I've replied to your PM in regards to the power / video / cassette lead.

The 34 way cable from the drive does indeed connect to the back of the keyboard - it is a standard 34 way floppy cable
that just attaches directly to each floppy drive. It does not provide power over the cable (as you've figured out anyway).
If you end up placing an order for the cable, I'll get a system disk made up for you & include it in the box when posted.

[CheshireNoir]

Hi The_Huck,
I have a similar setup, and mine didn't come with the Video / Power cable either. I made my own (As I didn't need the tape input/output on my Premium, I just skipped those pins). It's just a DIN5 on one end and a composite cable and a barrel jack on the other. The barrel jack goes into the back of the Drive / Power supply. The composite cable isn't strictly needed as the 9 pin DSub on the back of the Premium delivers CGA compatible colour, but if you don't have access to a CGA monitor or a suitable scaler, that might be difficult to use. (I use a 15KHz capable LCD and a Necroware MCE to VGA adapter. It's lovely!)
In the drive unit, my RIFAs were crapped out but I was able to get replacements. I also added a buck converter to provide a more fine tune adjustable output voltage. I also replaced one of the Floppy drives with a Gotek, complete with LCD and rotary encoder in a nice 3D printed mounting frame.

I'm happy to help you with details on my bits and pieces if you wanted to "DIY" it.

Cheers!

John

[The_Huck]

Thanks Ewan.

I've ordered the cable.
I'll go ahead and order some capacitors.

Let's hope the machine's a runner. I figure it's likely the keyboard may need work but we'll see.

Cheers,
Huck

---

Hi John,

Thank you for your offer.
I was considering the DIY method but I just ordered the cable and Ewan kindly offered to put in a disk for me. 

I'll keep the post updated with progress.

Cheers,
Huck

[MbeeTech]

Thanks Ewan.

I've ordered the cable.
I'll go ahead and order some capacitors.

Let's hope the machine's a runner. I figure it's likely the keyboard may need work but we'll see.

Cheers,
Huck

Got your order - thanks.

You will most likely have at least a few keys on the keyboard that are bad.  There is a repair guide available, which, if it's only a few, is worth doing.
However, if it's more than a few, the best way forward is with a keyboard replacement kit (available in the online store) which replaces all the keyswitches
with a much better switch type that is still compatible with the key caps.

[The_Huck]

Thanks Ewan.

I've ordered the cable.
I'll go ahead and order some capacitors.

Let's hope the machine's a runner. I figure it's likely the keyboard may need work but we'll see.

Cheers,
Huck

Got your order - thanks.

You will most likely have at least a few keys on the keyboard that are bad.  There is a repair guide available, which, if it's only a few, is worth doing.
However, if it's more than a few, the best way forward is with a keyboard replacement kit (available in the online store) which replaces all the keyswitches
with a much better switch type that is still compatible with the key caps.

Hi Ewan,

As soon as the cable arrives I'll test the machine. Hopefully there's some life.
Is there a PDF manual available for the machine, such as the one it would've come with?
I'm also interested in programming such as BASIC and machine code/assembly. Is there a monitor/assembler available?

Cheers,
Huck

[MbeeTech]

Hi Huck.
You order has been posted today for the cable. I've included a system disk for you which has BASIC on it, amongst other things.
All of the manuals are available to download from the repository.
Check out this thread for details on access to the repository :

https://microbeetechnology.com.au/forum/thread-15.html

All of the software is available to download as well, but you need a method of getting it onto your machine from there.
There are a number of options - the easiest of which generally is to use a GOTEK drive attached to the system, replacing one of your physical drives.