UPDATE: Boiled at 100degC in my old ultrasonic tank softened the varnish enough and I was able to get the E's and I's removed: www.ianjohnston.com/images/stories/IanJ/3457Arepair/transformerEI.jpg
Hi Ian, I think you'll find if you drizzle acetone onto the laminations it will seep inside and they'll come apart. Otherwise the judicious application of a heat gun will do the same. Pre warming in a reflow oven at a low temperature will also help. The welded ones are actually easier to separate as you just cut the welds with an angle grinder.
I tried acetone but it didn't move the varnish at all, not one little bit. Paint stripper is another option provided the bobbin doesn't melt. I didn't try a heat gun though......hmmm! However, the E's and I's are well and truly clamped in there.
I used to salvage ferrite cores out of computer SMPSs and I found that slowly heating the entire thing to around 200°C in an oven softened everything up nicely - same would probably apply to this, although I'd start a bit lower in case the bobbin starts melting! The laminations will be put in from opposite sides and can be whacked out with a ruler as someone else suggested.
Awesome video . What can cause a meter to read 36 volts when connected to a 12 volt battery ? Within a few minutes it gradually drops to 12 volts . Meter has new battery . Thanks
Back feed the biggest secondary winding from another transformer if you get completely stuck. Your lucky though you can measure the coil parameters on your other meter
Shame that transformer was glue together too tight =/ Looking forward to the next part! What voltages does that board need? I wonder if you could just go with a pico PSU and some other regulation to get the voltages required - worst case! It's obviously going to be better with a replacement transformer =D
Maybe you should try powering up the unit with your bench supplies in case the entire thing is fried before trying to solve the transformer issue, never know it might have been a lightening strike that got it.
I've got all the schematics so not really worried about getting the boards working........well, just as long as it's not the A/D Hybrid! The transformer problem is something new, so looking forward to it.
IanScottJohnston - I just had a physical service manual arrive a few days ago, I always try to get a proper manual if I can as the diagrams are usually easier to read
Custom made transformers are at reasonable prices now. Lots of firms here manufacturing any wattages, number of windings, wire gauges and a lot of templates for order. DIY probably would end up more expensive even if you manage to find parts.
Where you have taken an "I" out between 2 "E" pieces you can use a metal rule onto the flat edge of an "E" poking through the centre and knock it out with a hammer, warming may help. If all else fails you can get hold of an e with pliers and pull, or a screwdriver through an outer "E" hole and lever it out. You may damage it beyond re-use but with lacquer when rebuilt it will be fine.
Ive been trying to do the same with my Transformer from my Ada mp1 preamp. I removed all the I. But the E laminations are stuck. I'm going to try boiling it in hot water thanks for the tip
Switch mode psu in an 6.5/7.5 digit DMM is probably not a good idea, besides I want to be true to the originality of the 3457A, including the line selection switches.
IanScottJohnston - I was thinking that as long as it feeds the original regulators they should get rid of a lot of line noise, radiated noise could still be an issue though, can get small din rail ones from mean well for not a lot of money, with reasonable quality.
By your definition My wife had broken seals when I got her. There are companies online that will supply the cores and bobbin but they aren’t kits as such. I cannot remember them of the top of my head etc.
Can you simulate the transformer outputs with bench power supplies to check that the rest of the dmm is working? It'd be a shame to put all the work into repairing the transformer just to discover that something else is fried beyond repair.
I haven't come across an aftermarket replacement, I did look. However, yes, I do want to wind my own for fun. I still have my old coil winder machine. Back in the day we used to do everything from small inductors, to 150VA transformers.
I have lots of transformers that ive salvaged from broken and/or obsolete things over the years including some that i think might fit. Some have multiple secondaries. You have my email address - send me a message with the specs you need and i'll have a look and send you some photos.
UPDATE: Boiled at 100degC in my old ultrasonic tank softened the varnish enough and I was able to get the E's and I's removed:
www.ianjohnston.com/images/stories/IanJ/3457Arepair/transformerEI.jpg
Thinners seemed to worked for me the capillary takes it down to the centre .do in a well vented room .just subscribed
No one can never have enough IAN
Hi Ian, I think you'll find if you drizzle acetone onto the laminations it will seep inside and they'll come apart. Otherwise the judicious application of a heat gun will do the same. Pre warming in a reflow oven at a low temperature will also help. The welded ones are actually easier to separate as you just cut the welds with an angle grinder.
I tried acetone but it didn't move the varnish at all, not one little bit. Paint stripper is another option provided the bobbin doesn't melt. I didn't try a heat gun though......hmmm!
However, the E's and I's are well and truly clamped in there.
I've also got the depotting compound I used on the DC-DC converter a few months ago......hmmm!
I used to salvage ferrite cores out of computer SMPSs and I found that slowly heating the entire thing to around 200°C in an oven softened everything up nicely - same would probably apply to this, although I'd start a bit lower in case the bobbin starts melting! The laminations will be put in from opposite sides and can be whacked out with a ruler as someone else suggested.
Awesome video . What can cause a meter to read 36 volts when connected to a 12 volt battery ? Within a few minutes it gradually drops to 12 volts . Meter has new battery . Thanks
Back feed the biggest secondary winding from another transformer if you get completely stuck. Your lucky though you can measure the coil parameters on your other meter
Yes, I managed to take resistance and secondary voltage readings so have all the info to hand.
Shame that transformer was glue together too tight =/ Looking forward to the next part! What voltages does that board need? I wonder if you could just go with a pico PSU and some other regulation to get the voltages required - worst case! It's obviously going to be better with a replacement transformer =D
Maybe you should try powering up the unit with your bench supplies in case the entire thing is fried before trying to solve the transformer issue, never know it might have been a lightening strike that got it.
I've got all the schematics so not really worried about getting the boards working........well, just as long as it's not the A/D Hybrid! The transformer problem is something new, so looking forward to it.
IanScottJohnston - I just had a physical service manual arrive a few days ago, I always try to get a proper manual if I can as the diagrams are usually easier to read
If it had been struck by lightening (sic) then it would be looking a lot more pale. ;-)
Custom made transformers are at reasonable prices now. Lots of firms here manufacturing any wattages, number of windings, wire gauges and a lot of templates for order.
DIY probably would end up more expensive even if you manage to find parts.
Where you have taken an "I" out between 2 "E" pieces you can use a metal rule onto the flat edge of an "E" poking through the centre and knock it out with a hammer, warming may help.
If all else fails you can get hold of an e with pliers and pull, or a screwdriver through an outer "E" hole and lever it out.
You may damage it beyond re-use but with lacquer when rebuilt it will be fine.
Ive been trying to do the same with my Transformer from my Ada mp1 preamp. I removed all the I. But the E laminations are stuck. I'm going to try boiling it in hot water thanks for the tip
My next video out soon will provide more info how I went about it.
What about using a single 12v/24v switchmode and using that to feed the individual regulator sections?
Switch mode psu in an 6.5/7.5 digit DMM is probably not a good idea, besides I want to be true to the originality of the 3457A, including the line selection switches.
IanScottJohnston - I was thinking that as long as it feeds the original regulators they should get rid of a lot of line noise, radiated noise could still be an issue though, can get small din rail ones from mean well for not a lot of money, with reasonable quality.
By your definition My wife had broken seals when I got her. There are companies online that will supply the cores and bobbin but they aren’t kits as such. I cannot remember them of the top of my head etc.
Go for it !...cheers !
Can you simulate the transformer outputs with bench power supplies to check that the rest of the dmm is working? It'd be a shame to put all the work into repairing the transformer just to discover that something else is fried beyond repair.
I dont see it like that (wierd I know!)......its the new challenge of getting stuck into a transformer repair i am looking forward to.
Can't you find an aftermarket replacement or do you just want to wind one for the fun of it?
I haven't come across an aftermarket replacement, I did look. However, yes, I do want to wind my own for fun. I still have my old coil winder machine. Back in the day we used to do everything from small inductors, to 150VA transformers.
@@IanScottJohnston I see. It will be very educational to see how you wind one. Looking forward to it.
I bet that was the same meter I almost bid on from ebay.
I have lots of transformers that ive salvaged from broken and/or obsolete things over the years including some that i think might fit. Some have multiple secondaries. You have my email address - send me a message with the specs you need and i'll have a look and send you some photos.
Custom toroïdal transformers are quite affordable.
Yes, there's a guy in the UK who did a couple of custom ones for me a few years ago.....definitely a backup plan.
For me a bad transformer would be a nightmare...
My coil winder hasn't been used in many, many years, am looking forward to dusting it off......
IanScottJohnston - I’ve never wound a transformer, I’m not sure I would want to either!
@@TheDefpom you and me both !
@@TheDefpom Been doing it by hand for 60 years. You don't know what you are missing. Very satisfying and complete freedom to effect a repair.
@@jonka1 I think if I ever get some gear that has a bad transformer which I can’t replace then I would give it a go.
I'd build a switchmode power supply.
Trying desperately to be true to the old girl.....including saving the functionality of the line selection switches.
@@IanScottJohnston If I had a coil winder I might make the same decision, I look forward to your work ! cheers.
Boil it in water.