Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: chrisio on 03 August 2016, 09:44:16
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I know there are some exceedingly clever people on here so here goes.
The power supply for my laser machine went pop in a rather spectacular fashion and it looks as though the fusible link went pop.
I have a new power supply on route however I want to see if it was just a fluke that made it go bang or if its terminal. can I replace that fuse and try again and if so what with. I can't find anything online that resembles what it once was.
The rebel in me says just link it out with a bit of copper wire but seeing how the thing went pop I rather dread the consequences of my actions if I did that. I also realise that its probably a hiding to nowhere but you never know and if it holds then I have a spare power supply for the future.
I have uploaded some pictures for you to have a look at.
Overview
(https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/overview.jpg)
Link to full size image
https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/20160803_093042.jpg (https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/20160803_093042.jpg)
Fuse
(https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/fuse.jpg)
Link to full size image
https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/20160803_093051.jpg (https://www.penrithposters.co.uk/new/wp-content/uploads/2016/08/20160803_093051.jpg)
Thanks in advance.
Chris
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Axial leaded tube fuse: http://www.optifuse.com/fuses-tube.php
Given the spectacular fashion that fuse detonated itself, though, you might want to start looking for dead shorts first - depending on where that fuse is either on the input or output side of the PSU; physical location implies output so perhaps the load has gone dead-short?
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You need to find the cause of the fuse going other wise you are going to end up with another dead psu
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Thanks both of you.
The output side of things does make some sense as I was aligning the lenses and tube and managed to trap one of the tube wires (not the high voltage lead) without noticing. It was running fine like this and only went pop after moving this wire. I will double check the insulation on the wire and go from there.
Chris
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I would agree with the above, but it's also worth checking the diodes in the top left hand corner; a short circuit in any of those will detonate your fuse!
Of course, there are other power components that could be suspect, but you have to start somewhere.....
Ron.
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Looks smps to me, so needs a specialist - cant just go looking for short, by their nature many will show a short even when working.
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Yes, definitely switch-mode, TB, which is why I suggested checking those four input bridge diodes - a most common cause of fuse anihilation!
I also concur with you that apart from that simple check, SMPSs are not an easy fix! However, it will cost nothing and hurt nobody to check any power semiconductors for short circuits because they are under the greatest electrical stress and fail often, especially if they are lightly or under-rated for the job, for reasons of economy.....
Ron
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Whoooosh!
Most of all of that went over my head to be honest. I can poke about with a multi meter and wield a soldering iron with the best of them but when it comes to understanding what the multi meter is telling me I don't really have a clue. With the diodes I take it I can set the meter to continuity and see if I get continuity one way but not the other?
I don't really fancy poking about too much as there is the laser coil at the top of the board and that is in high KV ranges and I bet it would make my hair stand on end if the meter leads ended up in the wrong place!.
I haven't had a chance to look at it today but I would hazard a guess and say that I managed to short the cable out that is in the location of the laser tube because if what aaronjb surmises is correct about that fuse being on the output side of things it would make sense for it to blow when I caught this lead.
I shall have a check tomorrow.
All the best
Chris
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just replace that fuse and then just power up with some rubber marigolds on and see what happens :y
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I certainly am tempted and lets face it, it went once so if the fault is still present it will go pop again.
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Whoooosh!
Most of all of that went over my head to be honest. I can poke about with a multi meter and wield a soldering iron with the best of them but when it comes to understanding what the multi meter is telling me I don't really have a clue. With the diodes I take it I can set the meter to continuity and see if I get continuity one way but not the other?
I don't really fancy poking about too much as there is the laser coil at the top of the board and that is in high KV ranges and I bet it would make my hair stand on end if the meter leads ended up in the wrong place!.
I haven't had a chance to look at it today but I would hazard a guess and say that I managed to short the cable out that is in the location of the laser tube because if what aaronjb surmises is correct about that fuse being on the output side of things it would make sense for it to blow when I caught this lead.
I shall have a check tomorrow.
All the best
Chris
You cant really test diodes or transistors using continuity test whilst there still pcb mounted, best way is to lift one of the legs, but yes as you say with a diode in your hand switch the DVM to diode symbol test and measure both ways, in the old days with an Avo 8 on the bench you would use resistive test bearing in mind the negative lead on the meter would actually be positive in order to read forward current flow. :D
if it was me, and I know I had definitely caused a short which then blew the fuse, I would replace the fuse and switch it back and see whats occurring, but thats me, just dont burn the house or garage down. ;)
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Whoooosh!
Most of all of that went over my head to be honest. I can poke about with a multi meter and wield a soldering iron with the best of them but when it comes to understanding what the multi meter is telling me I don't really have a clue. With the diodes I take it I can set the meter to continuity and see if I get continuity one way but not the other?
I don't really fancy poking about too much as there is the laser coil at the top of the board and that is in high KV ranges and I bet it would make my hair stand on end if the meter leads ended up in the wrong place!.
I haven't had a chance to look at it today but I would hazard a guess and say that I managed to short the cable out that is in the location of the laser tube because if what aaronjb surmises is correct about that fuse being on the output side of things it would make sense for it to blow when I caught this lead.
I shall have a check tomorrow.
All the best
Chris
You cant really test diodes or transistors using continuity test whilst there still pcb mounted, best way is to lift one of the legs, but yes as you say with a diode in your hand switch the DVM to diode symbol test and measure both ways, in the old days with an Avo 8 on the bench you would use resistive test bearing in mind the negative lead on the meter would actually be positive in order to read forward current flow. :D
if it was me, and I know I had definitely caused a short which then blew the fuse, I would replace the fuse and switch it back and see whats occurring, but thats me, just dont burn the house or garage down. ;)
Those were the days! Big MK8 Avo with bakelite case, mirror parallax and current cutout* and apprentices being apprentices! :) More challenged apprentices and winding a transformer, then doing open and circuit tests. Winding the short circuit test rheostat down and an elbow on the Avo *reset button measuring current, created muh satisfying smoke as you timely walked away for our line management turning up to it sort out! :o :o :o Not that I was ever involved in such terrible apprentice acts or worse of course. ::) ::) ::)
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Slightly off-topic, Rods2, but in line with your comment - do you remember how much a revered Avo 8 cost back then, compared to a far more capable DMM of more recent times? Eye-popping price, yes?
Ron.
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The most likely failure will be one of the those rectifier diodes top left, you can test those quite happily whilst still fitted.
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"Marks", I've said that twice already - see above! ;D
Ron.
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Avo 8 8)
Still have one of those in the loft somewhere ;)
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Slightly off-topic, Rods2, but in line with your comment - do you remember how much a revered Avo 8 cost back then, compared to a far more capable DMM of more recent times? Eye-popping price, yes?
Ron.
Used and abused as an MOD apprentice, yes we were aware on £££ costs. The payback was working as a junior and then mid-ranking scientist that was involved in the development, adoption and deployment of world class military systems, some of which are still used on the frontline today. :y The support and introduction to UK industry of leading US standards, resulted in them 'exporting coal to Newcastle' and today, 10% of global arms sales are by UK companies. Something in these days of minimum wage jobs we should all be proud of. :y
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You could buy a new AVO 8 until fairly recently. If memory serves they were about £600! :o
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You could buy a new AVO 8 until fairly recently. If memory serves they were about £600! :o
Are these still the same basic design as the ones I used to try and blow up in the early 80's :-X
What are these things worth second hand ?
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Slightly off-topic, Rods2, but in line with your comment - do you remember how much a revered Avo 8 cost back then, compared to a far more capable DMM of more recent times? Eye-popping price, yes?
Ron.
Used and abused as an MOD apprentice, yes we were aware on £££ costs. The payback was working as a junior and then mid-ranking scientist that was involved in the development, adoption and deployment of world class military systems, some of which are still used on the frontline today. :y The support and introduction to UK industry of leading US standards, resulted in them 'exporting coal to Newcastle' and today, 10% of global arms sales are by UK companies. Something in these days of minimum wage jobs we should all be proud of. :y
These got a name Rod ?
Via PM if you feel its necessary ;)
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You could buy a new AVO 8 until fairly recently. If memory serves they were about £600! :o
Are these still the same basic design as the ones I used to try and blow up in the early 80's :-X
What are these things worth second hand ?
Anything from 40 to 160, dependent on which model 8 and condition.
One of my old Biddy Neighbors picked one up a few years back at a Car Boot Sale a few years back. Get a knock on the door, Hello Chris, you used to work for BT didn't you, me "No", but you all about there stuff though, me "No", oh anyway got one of these, what is it, is worth anything, handed me a big leather case with BT stamped all over it, opened it up and there was a almost brand new Avo8 with all the leads etc inside. She only paid 50p for the damn thing. ::), she sold it on the Bay for over £100, told her she probably would have got more if she lost the case and didn't mention the word BT. ;D
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Are these still the same basic design as the ones I used to try and blow up in the early 80's :-X
What are these things worth second hand ?
The internals have changed a bit over the years in order to make them easier to mass produce. The earlier ones must have been quite labour intensive!
Here's a good resource: http://www.richardsradios.co.uk/avo8.html (http://www.richardsradios.co.uk/avo8.html)
Functionally, they remained pretty similar. As to value second hand, I've picked well used examples up at radio rallies for around the £20 region, cheaper at a car boot sale with less enthusiasts. Rare models probably fetch more from the right person. I guess your £600 price tag would have been subject to heavy depreciation!
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Slightly off-topic, Rods2, but in line with your comment - do you remember how much a revered Avo 8 cost back then, compared to a far more capable DMM of more recent times? Eye-popping price, yes?
Ron.
Used and abused as an MOD apprentice, yes we were aware on £££ costs. The payback was working as a junior and then mid-ranking scientist that was involved in the development, adoption and deployment of world class military systems, some of which are still used on the frontline today. :y The support and introduction to UK industry of leading US standards, resulted in them 'exporting coal to Newcastle' and today, 10% of global arms sales are by UK companies. Something in these days of minimum wage jobs we should all be proud of. :y
These got a name Rod ?
Via PM if you feel its necessary ;)
MIL-STD-1553 databus which was first used in the UK on Merlin helicopters and MIL-STD-1750 standard military computer instruction set. Marconi used both these standards on their winning bid for an F16 HUD. :y