Need major PSU advice on my new beeb...

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Bworp
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Need major PSU advice on my new beeb...

Post by Bworp » Wed Sep 26, 2018 9:43 am

(Edited - changed title and fixed links)

Hey everyone!
A little while ago I posted here that I bought myself a BBC micro, and today it finally arrived. Hooray!
It as very dusty and dirty, but it seems to have cleaned up quite well. (Unfortunately I forgot to take pictures of it when it was complete...)

There are some ... interesting things about it that I would love some advice on.

Firstly, the power plug has clearly been changed to something weird, as you can see here:

https://photos.app.goo.gl/QLDeA6qnSEaJvVbF9

I've no idea what they were plugging the computer into...
Is there anything special I need to know to convert this back to a standard Australian plug?

Next, there was this funny plug rattling around inside the case:

https://photos.app.goo.gl/D1gUU7BkFcZWiMk2A

Is this just a freeloader that doesn't belong, or did it come off somewhere that I should put back on? (it's about 1cm wide)

Next, there's this jumper coming out of the power supply and I can't find its home. Any ideas where it belongs?

https://photos.app.goo.gl/JxqEDcdjTB4HHjf7A

Finally, some of the key switches are very slightly sticky (as in there's a tiny bit of annoying resistance when pressing, and when they come back up). Anyone have any good methods for cleaning them? I thought about giving them a light spray with wd-40, but I'm worried about what it might do to the circuits. Lithium grease occurred to me as well, but I'm not sure.

Thanks, and I will keep you updated!
Last edited by Bworp on Sat Sep 29, 2018 11:04 am, edited 2 times in total.

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1024MAK
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Re: The beeb has arrived! Now I need advice...

Post by 1024MAK » Wed Sep 26, 2018 10:06 am

Hi

First, you have an export version rather than a U.K. version Beeb. By export version, I mean the type that Acorn exported to the U.S.A. and to Germany. So the layout of the board is different and the numbering of the components on the board is different (compared to the U.K. versions).

The power lead you show in your first photo, where does the other end go? Only there are far too many wires for this to be a normal mains connection. If it goes inside the PSU, then you will have to disconnect the wires going to the main PCB (motherboard), take the PSU out of the computer case, and then turn it the other way up. Then take some photos and post up here :wink:

I have not seen the item you describe as a “funny plug” in a normal Beeb before. It could be the cap from a push switch. Either from an expansion or add-on, or an unrelated item.

The red coloured wire that you describe as a jumper, is one of the +5V power feeds to the main PCB. It should connect to a vertical tab type terminal.

Your sticky keys. They are pining for use. Don’t apply any oil or grease. Instead press and release each of the problematic keys around fifty times, or until you are happy with them. If this does not help, you can try the next method. See how you get 9n with this first.

Mark

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Re: The beeb has arrived! Now I need advice...

Post by 1024MAK » Wed Sep 26, 2018 10:13 am

Here is a photo showing one of the +5V connections (and one of the 0V connections) in a USA Beeb.

Image

This photo shows the other +5V and 0V connections.

Image

Mark
Last edited by 1024MAK on Wed Sep 26, 2018 10:17 am, edited 2 times in total.

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Re: The beeb has arrived! Now I need advice...

Post by Lardo Boffin » Wed Sep 26, 2018 11:58 am

I have a working USA Beeb so if you need any further photos for reference then please let me know.
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Acorn 6502 coproc
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc
USA Model B
BBC Master, Datacentre + HDD, pi co-proc, econet

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Re: The beeb has arrived! Now I need advice...

Post by 1024MAK » Wed Sep 26, 2018 1:01 pm

Lardo Boffin wrote:
Wed Sep 26, 2018 11:58 am
I have a working USA Beeb so if you need any further photos for reference then please let me know.
Guess where the photos in my post were pinched sourced from :mrgreen: :lol:

Mark

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Re: The beeb has arrived! Now I need advice...

Post by Lardo Boffin » Wed Sep 26, 2018 4:11 pm

1024MAK wrote:
Wed Sep 26, 2018 1:01 pm
Lardo Boffin wrote:
Wed Sep 26, 2018 11:58 am
I have a working USA Beeb so if you need any further photos for reference then please let me know.
Guess where the photos in my post were pinched sourced from :mrgreen: :lol:

Mark
I have my suspicions!
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Acorn 6502 coproc
BBC model B 32k issue 7, turboMMC, Opus Challenger 3 512k, Pi 3 coproc
USA Model B
BBC Master, Datacentre + HDD, pi co-proc, econet

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Re: The beeb has arrived! Now I need advice...

Post by Bworp » Sat Sep 29, 2018 4:35 am

Great, that picture was just what I needed! Found where the end of that wire belonged no worries! (Which I was for some reason calling a jumper? Blah)
The Australian Beeb is a lot more like the British one than the US one (identical perhaps, aside from the power plug), but clearly similar enough for this purpose.

My main problem at the moment still remains the power plug and the weird custom job they've done on there. Obviously I'm going to have to wire on a standard Australian plug, but there's 7 wires coming out of the cable going into this weird connector. (Is that normal for a beeb? Not the connector, but the number of wires in the cable?)

It's hard to tell from the picture, but a single white wire is going to one pin (Earth I'm assuming?), Red Yellow and Blue all going into another pin, and then Black Green and Brown going to another. These last two I assume would be positive and negative, and there's every chance I'm wrong about the colours as I am colourblind (it's the greens, browns and reds I'm not sure about). The only other reference I can find to this kind of configuration in a cable is for connecting a trailer to a car! (And I don't see any indicators, brake or reversing lights on my beeb!)

So obviously I don't want to rush into this without knowing what I'm doing, especially because I have trouble with the colours (I will do a lot of labelling!). But can anyone explain to me if this is the normal number of cores for the power cable, and if so how to decode it? And if not, anything I should look out for when replacing the cable?


Edit-
Nevermind... I just took out the power supply and... well, somebody's done something VERY questionable with this machine.

https://photos.app.goo.gl/RwAViGA8zEbGTRH87

https://photos.app.goo.gl/9xU8BVoMd1zzTizX9

They've ripped out the whole guts of the power supply and just replaced it with... something of their own invention.
Clearly I'll just have to replace the whole power supply. Does anyone make aftermarket ones? Or can somebody recommend somewhere to get a secondhand one?

Edit Numero Duo-
I found this article from a thread on this forum: https://www.waitingforfriday.com/?p=794
It's for the BBC master, which mine is not, but I'm hoping the steps are the same or similar. My question would be what other power supplies could I use, and are any of them better suited to my system? Also, what steps would be different between the Master and the original Beeb?
Last edited by Bworp on Sat Sep 29, 2018 11:05 am, edited 4 times in total.

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Re: Need major PSU advice on my new beeb...

Post by tricky » Sat Sep 29, 2018 8:04 am

I think that these were generally considered a good replacement if you can't get an original, but higher up the thread, you can find a cheaper alternative solution!
Last edited by tricky on Sat Sep 29, 2018 8:05 am, edited 1 time in total.

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Re: Need major PSU advice on my new beeb...

Post by 1024MAK » Sat Sep 29, 2018 8:39 am

We can’t see your photos. :(

When I paste the (really, really long) link into a new browser window, I find a google sign in page waiting for account details.

For normal size pictures and photos, you can upload them via the attachment tap below the edit box.
If high detail is required, then also include a link to a file stored elsewhere like you have tried to do. I use Flickr myself. It’s always a good idea to log out of any associated account and then check that the link does work as intended.

It is possible to fit another PSU in a Beeb. The Master PSU is not that much bigger than the type used in a BBC B.
Are you intending to use 12V disk drives with yours? By that I mean 5¼” disk drives, or older 3½” disk drives?

5¼” disk drives need both a +5V supply and a +12V supply. Some come in cases that include a internal mains power supply.
Older 3½” disk drives are similar to the above, but the mains powered type are much less common.
More modern 3½” disk drives only need a single +5V supply.

A Gotek floppy disk emulator also only needs a single +5V supply.

The design of SMPSU (Switch Mode Power Supply Unit) fitted in 99.9% of Beebs has a power out connector that can power two external disk drives.

Hence the question, do you want any replacement PSU to power disk drives.

If the asnswer is no, a replacement PSU only needs to provide a main +5V output and an auxiliary-5V output (needed for the audio circuitry, the cassette tape circuitry and the RS423 serial port circuitry).

Mark

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Re: Need major PSU advice on my new beeb...

Post by VectorEyes » Sat Sep 29, 2018 9:08 am

There's a lot of good advice here but in all honesty if it was me I think I'd be watching eBay for spare BBC Micro power supplies or even for machines that are sold as not working out whose PSUs are probably functional!

I'm really curious what the weird replacement PSU in your machine looked like!

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Re: Need major PSU advice on my new beeb...

Post by Bworp » Sat Sep 29, 2018 11:00 am

Blah... google Photos is bloody useless. There doesn't seem to be a way to embed them in forums or anywhere that isn't Facebook!

Anyway, here's the two photos of the PSU and the power "plug"

I'll post some more photos in the near future.

You can also (maybe) access the whole album here:
https://photos.app.goo.gl/UKt7EioDz2BK844EA


Sorry for the non working photos. I feel just a little bit silly now! :oops:
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Re: Need major PSU advice on my new beeb...

Post by Bworp » Sat Sep 29, 2018 11:22 am

Oh, and eventually I would like to get 5 1/4 inch drive (when I can get a hold of an appropriate one). In the short term I have a cassette recorder.

I'm pretty sure I'll go with the Mean Well pt-65a. It seems to be relatively easy to get a hold of, and more than adequate for the job. (Including disk drives, yes?)
My problem is I'm relatively inexperienced with electronics, and I'm worried this might be a little beyond my current skill level. When I got the machine I was expecting to just need to replace a few capacitors, but this will probably require a fair bit of troubleshooting and problem solving...

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Re: Need major PSU advice on my new beeb...

Post by danielj » Sat Sep 29, 2018 11:31 am

The meanwell will do the business for you. You'll have to make the relevant mounts for your PSU case though. There's a 3d printed one for the master as no doubt you've seen, but the only beeb one I'm aware of was measured onto MDF:
viewtopic.php?t=15230

Add to that your PSU case is slightly different to a standard beeb, being a US beeb.

Electronics-wise, follow Simon's instructions carefully, but you'll need to measure the wires to fit your board. This is simply an exercise in "hooking things up" rather than any hardcore soldering/electronics, but it's daunting because it's mains power! Make sure everything's earthed properly using the items advised, that everything's connected to what it's meant to be connected to, and you'll be fine :) You can post pictures here of your progress and people can reassure you as you go through!

d.
Last edited by danielj on Sat Sep 29, 2018 11:33 am, edited 1 time in total.

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Re: Need major PSU advice on my new beeb...

Post by 1024MAK » Sat Sep 29, 2018 2:55 pm

Thanks for sorting out the photos :D

Yeah, your ‘new’ Beeb doesn’t actually have a PSU anymore :(
What you have is some capacitors used for smoothing and wiring to connect to an external power unit.

So as said up thread, the MeanWell looks like the best long term option.

If you happen to have a good regulated 5V PSU capabile of supplying 2.5A or better, 3A or more, then we can guide you so that you can at least test and play with your Beeb.

Although without a -5V rail, the cassette circuitry may not work correctly.

Mark

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Re: Need major PSU advice on my new beeb...

Post by KenLowe » Sat Sep 29, 2018 9:46 pm

The Astec LPT44 is also a good replacement. I think it's pin compatible with the Meanwell.

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Re: Need major PSU advice on my new beeb...

Post by MartinB » Sat Sep 29, 2018 11:08 pm

Over two years ago, I re-lifed the PSU of my main development Beeb workhorse by replacing the original power supply internals with a pair of quality ‘black box’ switched mode regulated supplies as you can see in the pics below. The larger APD unit provides the +5v and +12v rails and the smaller Casio unit provides the -5v. The rating of all three rails is greater than the original including supplying the provisions of the Auxiliary socket.

The thread with the details is here.

589510EE-507B-4156-B4E2-650D5AD31B36.jpeg
70D8D79C-43B0-4BE5-B2D1-F8501D1B78A8.jpeg
2576FF65-AC22-4FD7-B75A-174B38ECD3F5.jpeg
Last edited by MartinB on Sat Sep 29, 2018 11:09 pm, edited 1 time in total.

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Re: Need major PSU advice on my new beeb...

Post by Bworp » Sun Sep 30, 2018 11:15 am

danielj wrote:
Sat Sep 29, 2018 11:31 am
Add to that your PSU case is slightly different to a standard beeb, being a US beeb.
It's the Australian model as far as I know (unless you can tell something from the pictures??)
Not sure how different that is to the UK model.
1024MAK wrote:
Sat Sep 29, 2018 2:55 pm
Yeah, your ‘new’ Beeb doesn’t actually have a PSU anymore
What you have is some capacitors used for smoothing and wiring to connect to an external power unit.
I sorta started to figure that might be the case...

Anyway, I've been doing a lot of reading on the topic, and feeling slightly more confident now hehe...
I think I'll order the PT-65a tomorrow and see how far I get!

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