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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 22nd Jul 2019, 7:33 pm   #1
Dekatron
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Default Cracking (literally breaking) the AVO VC1!

It has taken me a long time to release this "Cracking (literally breaking) the AVO VC1", far longer than I intended, but here it is finally and I hope that you will find it a good read.

Before I go into any details, I would like to thank all those who have helped me in getting this far, and especially two people:- Richard Allan at Richard’s Radios for assisting me with measurements on his AVO VC1 and David Stockton, GM4ZNX, for help in pointing out where to start to looking for data on the Siemens Ferrite core.

I have included all of the design files used with Designspark 7.2 so you can look at the circuit boards and change them as you please (really not necessary as they work just fine) and also the Gerber plot-files used for manufacturing the boards. If you do as I did when I ordered the circuit boards I made the positive side red and the negative side black (on converter and battery clip) and the other two in whatever color you feel, that makes it easier to identify the positive and negative side/electrode. The PCBs are designed so that they only fit on the correct side due to the fact that the slots are moved by a small amount so they differ.

This version should be small enough to fit in all AVO 8 meters, my earlier design had problems to fit inside the battery compartment of some early AVO 8 meters so I had to shrink its length and width.

All information to wind your own transformer is included in the document.

Please let me know if there is anything you think I should change or add to the document.

You have to rename the two zip-files with the .z01.zip and .z02.zip to .z01 and .z02 respectively to get the three part zip-file to extract properly into a pdf-file.
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Old 22nd Jul 2019, 10:54 pm   #2
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Default Re: Cracking (literally breaking) the AVO VC1!

You have to download all three .zip files:

"Cracking (literally breaking) the AVO VC1!.ZIP"
"Cracking (literally breaking) the AVO VC1!.z01.zip "
"Cracking (literally breaking) the AVO VC1!.z02.zip"

and then rename the last two to (removing the .zip extension):

"Cracking (literally breaking) the AVO VC1!.z01"
"Cracking (literally breaking) the AVO VC1!.z02"

then double-click the zip-file:
"Cracking (literally breaking) the AVO VC1!.ZIP"

so it unzips the PDF-file "Cracking (literally breaking) the AVO VC1!.pdf".
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Old 30th Jul 2019, 11:11 am   #3
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Default Re: Cracking (literally breaking) the AVO VC1!

Martin, that is an excellent and most carefully described piece of work. The diagrams are wonderfully clear.
Now the circuit and coil details are available, anyone can have a go at making one.
Thank you for taking all that time to write up the whole project properly!
Superb work.
-Jeremy
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Old 30th Jul 2019, 12:46 pm   #4
The Philpott
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Default Re: Cracking (literally breaking) the AVO VC1!

Outstanding. No more leaky, expensive 15v batteries!
'Sweden, 10 points'.

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Old 30th Jul 2019, 5:20 pm   #5
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Default Re: Cracking (literally breaking) the AVO VC1!

Thank you Jeremy and Dave!

I hope this will save some AVO 8's from leaky batteries as well as showing that there is no magic inside the VC1, just a very nicely designed small voltage converter.

I do have a bunch of prototypes left over, I use two myself in my two AVO 8 Mk7, and these are of the first type that only fit in the AVO 8 Mk 5, 6 and 7 as their size is to big for earlier models. There are six (6) black ones of Type-1 prototype and five (5) white ones of Type-2 prototype.

Of the smaller Type-3 Prototype version (Final version!) I only have six complete sets of PCBs without components, this version is small enough to fit in most models earlier than Mk 5, but since AVO might have made changes to the battery compartments I can't guarantee that they fit in all cases/versions as I don't own all different versions/models.

If you are interested in any of these then please make an offer. Shipping them one by one from Sweden is expensive (probably some GBP £15 or more in shipping for one, not much more for more of them as they are light) so if anyone is willing to do a group buy and then distribute them to those interested who lives in the same country that is very welcome!

There is of course no warranty for these prototypes and you use them at your own risk if you decide to use/buy them - and as I write in the document (includes the ones you buy from me):

"One thing that I can’t guarantee in my design is the isolation voltage that AVO specifies in their datasheets. I have tested all my prototypes with a BM400 series Megger on both 500V and 1000V and the insulation resistance is well above the 100MΩ that AVO specifies. But if you build your own this can’t be guaranteed of course (except if you have the transformer wound professionally). The PCB is designed to follow the requirements of isolation but that is no guarantee either. I can’t take any responsibility for this design if you decide to build one by yourself, I can only ask of you to not use it professionally as it has not been tested by the authorities."

I've load-tested them all and also tested them in my AVO Mk 7 and Mk 5 (now sold) and they all work as they should, if you buy one and it doesn't work, or dies, you are welcome to return it to me (at your own cost) and I'll reimburse you - I'd really like to find out why it died and what you did when it died!

It is possible to un-solder the components from any of the Type-1 and Type-2 prototypes and move them to the Type-3 smaller prototype if you are careful, it will require good un-solder techniques especially for the transformer as it has so many pins, and also the two metal clips keeping the cores together,that are soldered.
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