Miracle Systems Floppy PSU
- bagpuss22
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Miracle Systems Floppy PSU
Hi there,
I have a Miracle Systems Double Floppy with a built in PSU.
Looks like the PSU has gone, so my question is:
Does anyone have spares of this OR can I get it repaired?
Thanks
Russ
I have a Miracle Systems Double Floppy with a built in PSU.
Looks like the PSU has gone, so my question is:
Does anyone have spares of this OR can I get it repaired?
Thanks
Russ
Re: Miracle Systems Floppy PSU
Without knowing the particulars of the unit, I'm quite confident it can be replaced with a modern switching-mode power supply that will also be more reliable, more stable, much cooler and probably weigh 1/10th of the original. You could even keep it outside the unit, if you'd prefer that.
A couple of pictures of the internals would be most enlightening, though.
A couple of pictures of the internals would be most enlightening, though.
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Re: Miracle Systems Floppy PSU
Hi Russbagpuss22 wrote:I have a Miracle Systems Double Floppy with a built in PSU.
Looks like the PSU has gone, so my question is:
Does anyone have spares of this OR can I get it repaired?
The PSU may well be repairable. It depends on the type and what has gone wrong. As Skagon says, we need pictures of the PSU. If possible, use macro mode on the camera. And take photos from different directions including overhead and if it uses a PCB, the underside / track side please.
Mark
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Re: Miracle Systems Floppy PSU
Quite often it is the capacitor which has failed but if you are unlucky, then you melt the copper windings around the transformer.
I have spares here from units where the disk drives have failed - and the PSU on its own (or maybe the case) would come in at under 2Kg, so postage would not be too bad if you need one.
THe one thing I never found was any plastic rivets large enough to put the case back together!
I have spares here from units where the disk drives have failed - and the PSU on its own (or maybe the case) would come in at under 2Kg, so postage would not be too bad if you need one.
THe one thing I never found was any plastic rivets large enough to put the case back together!
Rich Mellor
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- bagpuss22
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Re: Miracle Systems Floppy PSU
Thanks for the replies gents.
I will get the item apart tonight and get some photo's.
I would prefer to repair, if I can, as I am one of those people who
like to keep things as genuine and possible. Call me sentimental!
If that does not work then I will go for a new PSU.
Cheers
Russ
I will get the item apart tonight and get some photo's.
I would prefer to repair, if I can, as I am one of those people who
like to keep things as genuine and possible. Call me sentimental!
If that does not work then I will go for a new PSU.
Cheers
Russ
- bagpuss22
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Re: Miracle Systems Floppy PSU
OK Gents,
I had a look around this tonight, unless I am just a useless software engineer, I would say that 1 of the primary winding has gone and 1 of the secondary as they appear to be open circuit.
240v AC going in, nothing out of the transformer. I am assuming it should be 18v, regulated down to 12v.
I had a look around this tonight, unless I am just a useless software engineer, I would say that 1 of the primary winding has gone and 1 of the secondary as they appear to be open circuit.
240v AC going in, nothing out of the transformer. I am assuming it should be 18v, regulated down to 12v.
Re: Miracle Systems Floppy PSU
Yikes!
Transformer, rectifier bridge, shitty capacitors, 7812, no filtering?
Mate, do yourself a favour and get an SMPS unit to replace that thing... seriously.
P.S. Stupid question: you *have* checked the fuse, right?
Transformer, rectifier bridge, shitty capacitors, 7812, no filtering?
Mate, do yourself a favour and get an SMPS unit to replace that thing... seriously.
P.S. Stupid question: you *have* checked the fuse, right?
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Re: Miracle Systems Floppy PSU
Looks fixable to me (normal get out clause may apply )
With the unit unplugged you are looking to see low resistance readings (from zero ohms to about 10 ohms max) across the fuse, the primary windings and the secondary windings. Check to see if the board has been coated in a protective coating (as this will act as a layer of insulation)As per picture: If you are getting open circuit (sometimes shown as O/L for over load on the meter) or you get very high readings, then the transformer has died. Although transformers (in general) are normally reliable.
Replacement transformers can be obtained, the only problem being the pins may be in different places.
If the transformer is okay, we can move on to the next step.
Mark
With the unit unplugged you are looking to see low resistance readings (from zero ohms to about 10 ohms max) across the fuse, the primary windings and the secondary windings. Check to see if the board has been coated in a protective coating (as this will act as a layer of insulation)As per picture: If you are getting open circuit (sometimes shown as O/L for over load on the meter) or you get very high readings, then the transformer has died. Although transformers (in general) are normally reliable.
Replacement transformers can be obtained, the only problem being the pins may be in different places.
If the transformer is okay, we can move on to the next step.
Mark
Standby alert
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
- 1024MAK
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Re: Miracle Systems Floppy PSU
Looks more like the rectified 9V ac from the transformer is smoothed by the large blue electrolytic capacitor, this the feeds the +12V dc supply to the FDD (but off load will be about 13V). Meanwhile this supply also feeds a 7805 voltage regulator, which in turn feeds a regulated +5V dc supply to the FDD.skagon wrote:Yikes!
Transformer, rectifier bridge, shitty capacitors, 7812, no filtering?
State of the art, it is not, but it does the job.
Mark
PS - Russ, if you are going to measure the voltages with it live /switched on, remember to keep well away from the exposed tracks and connections that are connected (or indirectly connected) to the 230V mains.
Standby alert
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer in Somerset later in the year
QL, Falcon, Atari 520STFM, Atari 1040STE, more PC's than I care to count and an assortment of 8 bit micros (Sinclair and Acorn)(nearly forgot the Psion's)
Re: Miracle Systems Floppy PSU
Mark, I had a second look, I don't think you're right mate.
The only thing I was wrong was the 7812; it's probably a 7805. The output from the transformer goes through the bridge and then directly onto the 7805. The big ass capacitor is between ground and bridge positive, and the two smaller ones are between ground and 7805 in and out.
The drives are obviously +5V only models.
Does the job, sure but... designs like that I wouldn't really trust for anything important.
The only thing I was wrong was the 7812; it's probably a 7805. The output from the transformer goes through the bridge and then directly onto the 7805. The big ass capacitor is between ground and bridge positive, and the two smaller ones are between ground and 7805 in and out.
The drives are obviously +5V only models.
Does the job, sure but... designs like that I wouldn't really trust for anything important.