Microbee twin disk drive unit - Magic Smoke PSU

[MarvinTMRX86]

Hi all, new to the Group and very new to the Microbee but keen to learn
I was given a Microbee and now have the main Model II unit running with the Microbee Monitor welcome screen but have some issues with the twin disk drive unit.
Originally I was getting nothing but then realised the fuse was blown, replaced this and got some life.
When powered on it shows a light on Drive A which I believe is correct ?
After about 5 mins I started hearing some whistling and sizzling and believe that either the Caps are gone (most likely) or the voltage regulators. 
Forgive me, my knowledge is limited to googling and trial and error.
I turned it off immediately and now am seeking advice on how to proceed. 
I really don't like the looks of the old power supply in there. Can I simply replace the PSU with a mini PC power supply that has the Molex connectors?
It looks like there is a controller board underneath which I haven't stripped down to yet.
I'm finding it very tricky finding any information at all on this twin disk unit.
Any advice or guidance greatly appreciated.
Thanks in advance.
-Glenn

[ChickenMan]

Personally I would keep it original and replace the capacitors, Jaycar has suitable ones.

As I said, do NOT power the Microbee via the grey DIN lead as it gets power from the Floppy box via the 50way cable so you need to get its power supply sorted first. The Microbee is trying to boot a floppy from A: drive when its all turned on, hence the light on A: drive.

Its only when BASIC loads that the Microbee will beep or pressing Ctrl G.

[MbeeTech]

Hi Glenn.
Welcome to the forum.

I would suggest that the caps (4700uf / 25v) need replacing, but also the bridge rectifiers could have become problematic.
The bridge rectifiers that it was originally built with were only rated at around 1.5 amps, so close to operating currents at some points.
Todays bridge rectifiers in roughly the same package size will have a much better current rating, so worth the upgrade even if the original
ones are still working. I would certainly replace them if you are unbolting everything to replace the caps.

I can send you a boot disk if you get in touch with your address details (email info@microbeetechnology.com.au).

[MarvinTMRX86]

Thanks Ewan,
I've stripped the PSU down and please forgive my limited knowledge of electrical components.
With regard to replacing the Caps would these be suitable - https://www.jaycar.com.au/4700uf-25vdc-e...r/p/RE6244
As far as replacing the bridge rectifiers do you know where I'd be able to source these and what are the specs I'd need to look for?
I had a look at Bridge Rectifiers at Jaycar and without the technical knowledge I'm unsure of suitable substitutes.
Thanks in advance.

[MbeeTech]

Hi Glenn.
Yes, those caps from Jaycar look to be o.k. They only thing I was concerned about was the component height (which is specified as 25mm on the data sheet) but I think the height of the original
caps is around that anyway. Just thinking about the board to board spacing thats all.
Jaycar have a couple of bridge rectifiers that would suit, but I would choose this one :
https://www.jaycar.com.au/6a-400v-inline...r/p/ZR1360
You may have to form the leads a little to fit where the original bridges are, and be careful to check the polarity when you are installing both the bridges and caps.

[MarvinTMRX86]

Hi there Ewan,
Thanks for your help again, managed to pick up the Caps but my local Jaycar didn't have the rectifiers in stock so may go for a drive over the weekend.
Cheers
Glenn

[CheshireNoir]

I assume these don't have Rifa X2 capacitors in them?
(I know my Disk Systems had Rifa in at least one of the power supplies)

John

[MbeeTech]

I assume these don't have Rifa X2 capacitors in them?
(I know my Disk Systems had Rifa in at least one of the power supplies)

John

Correct.
The power supply in this unit is made up of a transformer and linear regulators, not a switched mode module.

[MarvinTMRX86]

Hi there Ewan,
Hope all is well.
I'm having troubles getting an exact match on the Bridge Rectifiers which I believe are 5A, 100V.

Would these still be OK?
6A, 600V Z0079A
https://www.altronics.com.au/p/z0079a-kb...rectifier/
I don't know enough to know whether the 6A and 600V is still suitable ?

Thanks in advance for your assistance.

[MbeeTech]

Hi there Ewan,
Hope all is well.
I'm having troubles getting an exact match on the Bridge Rectifiers which I believe are 5A, 100V.

Would these still be OK?
6A, 600V Z0079A
https://www.altronics.com.au/p/z0079a-kb...rectifier/
I don't know enough to know whether the 6A and 600V is still suitable ?

Thanks in advance for your assistance.

They should be o.k.  They might just be a little larger physically.