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Old 19th Sep 2020, 3:08 am   #41
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

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Originally Posted by G6ONEDave View Post
The 6 volt relay has been a challenge and I ended up with a 5 volt coil type, so will either use some extra resistance or possibly a diode in series with the coil.
The 5V one should be fine as is.

Relay coil voltage specs are 'nominal', as in they have a % variation, usually stated in the data sheet, for their operating range (I'm not talking 'pull-in/drop-out' specs).

The attached pic is the spec for the relay I use in my Noise Canceller kit - coil voltage for a nominal 6v coil is 4.8 - 14 V (and 4 - 11.7 for the 5V one).
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Old 19th Sep 2020, 11:33 am   #42
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Thanks Terry, I was thinking of an extra 10 ohm resistor in series with the existing 47 ohm feed, so giving a total of 57 ohms in series with the relay coil across the approx 12v dc supply. Just did not like to permanantly over run the coil by 20% with a possible effect on it's lifetime before failure.
I have noticed that the parts list for this project is a little sparce on full component specification, an example is the zener diodes, there is no wattage rating quoted other than ZD1 is shown on the circuit diagram as being 1W, no mention of ZD2 wattage. However the ZD1 in the article photo does not look like a 1W. Likewise with ferrite pot core transformer and relay 2 makers type. Luckily I have some 5volt dil reed type relays, so relay 1 was doable from my own store of parts. I did have to check the data sheet of my stock relay to check pinout compatability. I am not meaning to sound picky and probably this was not a problem if using a supplied kit of parts back in the day. It's just a little bit awkward when not using a supplied kit all these years later.
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Old 19th Sep 2020, 10:20 pm   #43
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Bizarre - I posted a reply earlier today which has apparently vanished or never posted.

I wonder why they specified a 5V and a 6V relay in the circuit, if the actual voltage required is so variable?

Dave, I don't believe there was ever a kit. It's a Silicon Chip article republished in EPE, so most of the references are to Jaycar for parts purchasing. To my knowledge, all the bits EPE and Silicon Chip sell are firmware and boards for their published projects.

What's the consensus on that waveform? Does it look like everything checks out? Certainly the results are better than the previous IRF540N...
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Old 20th Sep 2020, 11:45 am   #44
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Uncle Bulgaria, in your scope waveform, does the mark space ratio change when the voltage selection is altered or does the waveform only change in amplitude with a change of voltage selection? I ask, as the EPE mag text suggests that the waveform amplitude is altered to get the different volt selections but I would have expected a change in frequency might take place.
I am now working on the enclosure for this project. I am using a re-purposed Denon minidisc casing, which is a sort of elongated rack case. It will be used sideways on, as it were. I will post some pics when I get it something like. The mains tx is actually an old RS filiament type with 2 windings of 6.3volt at 1.8amp, so wired in series giving 12.6volt at 1.8amp. Perhaps a waste for such a tx but it was the most suitable to hand. The enclosure top will have the control panel and a latchable door for the reforming chamber. Currently considering some insulation material for inside the chamber, so as to avoid any shorting of the capacitor contacts.
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Old 20th Sep 2020, 12:46 pm   #45
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

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Originally Posted by G6ONEDave View Post
Uncle Bulgaria, in your scope waveform, does the mark space ratio change when the voltage selection is altered or does the waveform only change in amplitude with a change of voltage selection? I ask, as the EPE mag text suggests that the waveform amplitude is altered to get the different volt selections but I would have expected a change in frequency might take place.
It's my understanding that the voltage selection switch merely changes the ratio of the voltage divider on the secondary side of the transformer. As I've at present got a 200R resistor between the drain of the IRF540N and where the primary input of the transformer would be, there's no connection to where the HT would come off. I haven't tried changing the voltage selector while scoping the waveform, but I would hypothesise it wouldn't change anything as there's no link.

The case sounds very fine. I'm making a first attempt at a dovetail box for mine, inspired by those old wooden-cased instruments!
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Old 20th Sep 2020, 1:02 pm   #46
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Hi!

I've just unpacked the pot core transformer that came from Poland for my copy of the project, it has "AL 4515" in paint figures on it so hopefully it should be suitable!!!!

It was advertised as "transmission transformer" so there are existing windings to remove from it first!

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Old 20th Sep 2020, 1:52 pm   #47
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Maybe we should hold a competition on where the furthest place is that a specific component was sourced for this project.

Following the circuit description, it mentions that the switched resistor chain on the tx secondary gives feedback to the MC34063, on pin 5 if I'm reading the circuit correctly. This is why I asked my question re the mark space ratio and waveform amplitude. I can't check this myself at present, as my tx has not arrived yet. I will have a look at this once it does.
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Old 20th Sep 2020, 3:11 pm   #48
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Here are some pics of the case progress showing inside pcb position area (2605), underneath internals (2611), case bottom cover (2613) and loose top panels (2607). A few more to follow in next post.
Dave
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Old 20th Sep 2020, 3:15 pm   #49
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

And here are the next 3 pics being; rear case (2608), sacrificial paper overlay on cut control panel (2614) and the metal control panel with holes (2617). The bracketed numbers refer to the photos.
Dave
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Old 20th Sep 2020, 5:03 pm   #50
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Just a note about the panel layout in the EPE mag. Having done the 133% enlargement as mentioned in the text, there is a problem with my resultant printout. The width seems to be OK, within 0.5mm on the pcb mounting hole centres, however the mounting hole centres top to bottom of panel are 5mm too much! Might be an artifact produced by my A3 printer, but be careful if expecting it all to marry up, check your measurements carefully before drilling. Thankfully I haven't drilled any pcb mounting holes into my metal control panel. I discovered this whilst trying to drill pcb mounting holes on my enclosures internal chassis plate. Looks like I will have to scan EPE mag page to computer and try to correct this issue with software of some sort.
Hope my warning is not too late for you guys.
Dave
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Old 21st Sep 2020, 12:38 am   #51
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

You can check the mark/space ratio change by feeding an adjustable voltage into pin 5.

The circuit shows a voltage of 1.25v on that pin, so varying above and below that should give you a change in the drive output waveform.
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Old 21st Sep 2020, 4:11 pm   #52
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Well I went ahead and connected the transformer again. Apart from a nerve-racking buzzing the voltages at the test points checked out! As the FX2241 has to be raised off the board by a few thicknesses of rubber strip so as not to interfere with the components, once I clamp it down this should ease.

Thanks for the tip about the case layout. For me that won't be a problem as I've been planning to make up my own control plate rather than the pre-made one.
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Old 21st Sep 2020, 5:36 pm   #53
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

I thought it best to mention the control panel overlay just in case you or anyone else for that matter might have the same issue and wonder ***, after they have drilled all the holes.
For my build job the pcb is a bit further away from the control panel, which helps to accomodate the heatsinks, also my selector switch is not the pcb mount type. If I can get the overlay into the appropiate software, I will remove the adjust preset sections and the pcb mount holes. Also I will extend the buff background to cover a larger area and possibly remove the black outer line.
The chamber for the capacitor to go in is, as you may have noticed on the opposite end to the published article. This was to save too much extra work with the metal bashing!. I will however need to remove a large section of the internal chassis fit a blank panel in it's place, so as to get the 4 mounting points for the pcb.
All the switches and LED will be fixed to the metal control panel and the display will be fitted to the pcb on extended brackets.
The ferrite pot core that I ordered from Bulgaria is listed as type: N48 B65671-L 400A 48 P26x16 AL400 +-3%. What a mouth full of a type reference, I just hope that it will be OK!
Re the buzzing tx, I wonder if the bobbin is rattling a bit or possibly loose windings are to blame or if it's simply the whole tx vibrating. I will report on what mine does once it's all arrived and is assembled.
Oh! nearly forgot, thanks Terry re your thoughts on the drive waveforms and feedback pin. I thought something must change other than just the voltage amplitude. I hope to investigate that soon.
Dave
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Old 21st Sep 2020, 6:27 pm   #54
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

OK, That is a 26 by 16mm round pot core made by Siemens. N48 material is good, and will run best at frequencies somewhat above human hearing so it shouldn't buzz.

Al = 400 is good, too. It means a 1 turn winding gives 400nH multiply 400nH by the number of turns squared to get the inductance of a winding. This core is already gapped and nicely accurate. You don't need to add any shim to get useful inductance values. So a 10 turn winding will give you 100 x 400 nH which is 40uH

Let's see if that's useful. MC34063 with inF timing capacitor... datasheet! Ah, he used the datasheet example value... so typically 33kHz or a period of 30us.

Let's arbitrarily say the max on time is going to be about 75% of the period.... that's 22us.

THe supply is about 11v so the current in the transformer primary will ramp at
11v/40uH amperes per second. that's 275,000 amps per second. Good job it doesn't turn on for long! 22 microseconds max. So that gives a peak current of 6 amps. This is beginning to sound a bit too powerful. THe energy stores is a half times L times I squared. So that's 720 microjoules. and it happens every cycle, 33,000 cycles per second so we get 23.7 watts of output.

Yes, I think this is a bit too powerful and we need more inductance. We could do this with either a higher Al value core (less gap) or by going for more turns.

Doubling the turns will give us four times the inductance, and so a quarter of the current

So we get 160uH and that will reach (11/160uH) * 22us = 1.51 amps peak

so the energy per cycle is 182 microjoules times 33 kHz that gives us 6 watts.

That sounds better. So with your core make the primary 20t and the secondary 160t. Drop your wire gauges to get the numbers of turns to fit.

Be sure you're using a fast rectifier. UF4007 is OK 1N4007 won't turn on or off fast enough and it'll spoil everything.

The datasheet says the current sense resistor should be 0.3/Ipeak

Now I got I peak to 1.57A with a guess at power scaling.... 0.3/1.57 so that 0.27 ohm resistor ought to be 0.19 Ohms. So it's going to scale the max power back a little more for us, which is fine.

This ought to work properly

David
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Old 22nd Sep 2020, 2:38 am   #55
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Hang on, David - I thought the original Jaycar part was an FX2240 clone, which has an Al of 3437-8227.

I've done your calculation with my current FX2241, where I calculated the inductance (as per the 'pot core pairs' thread and your excellent tutorial) as 84µH for the ten turns. The output is therefore about half of what you've calculated above. That still comes out at 11W. Considering the FX2241 with an Al of 5815 is bang in the middle of the FX2240 value, isn't this within bounds? Should I be altering down the current sense resistor as well? Would it be worth measuring the voltage drop across the 0.27 ohm resistor?
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Old 22nd Sep 2020, 3:07 am   #56
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Testing 10V and 25V capacitors on the bench, the display takes some time to rise to the rated voltage. A ferrite issue? After a few minutes running there is no warmth to the ferrite or the IRF540N.
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Old 22nd Sep 2020, 6:20 am   #57
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Ah, but the Jaycar part with its high Al value is used with an added non-magnetic shim to add a gap to it. This brings the Al value crashing down quite dramatically.

The Siemens part Dave above has comes already gapped. The centre post is ground down a little compared to the outer, so when assembled the magnetic circuit is up the centre post and back down around the wall. There is no gap in the wall, so it acts as a self-screening arrangement.

Think of the ferrite as a good magnetic conductor, and think of the flow of flux as a circuit. Air is a not so good magnetic conductor. So if the magnetic circuit is all ferrite you get a lot of overall conduction around the magnetic 'circuit' make a gap, and the far lower magnetic conductivity of the air in the gap brings the overall conductivity down a lot. This brings down the inductance.

So you could think that the bit in these parts which does the real work is the gap! Sounds silly, but it's a good viewpoint. The ferrite provides a magnetic conductor from one side of the gap to the other, and helps collect the magnetic flux from the windings. But the gap dominates the inductance per turn , the Al value.

The guy who designed the capacitor reformer cheated. He specified a core with no gap. These things have their uses, mostly as lower frequency transformers, ordinary transformers. But for this step-up power supply it's being used as an energy storage inductor and it really needs a gapped core to prevent saturation at the current it's going to be driven to. The gap, created by the shim does this. The inductance comes down a lot, but this application doesn't need much inductance, but it does need the right amount of inductance, with some tolerance.

So from the calculations I did for Dave's Siemens core (And Siemen made cores in N48 material in all sorts of sizes and shapes, and they also did each with a variety of gaps giving a range of Al values... by the way, they marked gapless ones 'oL') suggests that the shimmed gap should bring the overall Al value down to roughly 1600nH/turn squared. to wind up with the right inductance to make the supply work. So the thickness of that plastic used to create your gap is fairly important.

Dave's got a core which is already precision-gapped, so we know his Al value and we can adjust the number of turns to land the primary winding inductance where we need it to be.

If you've built yours without a shim, and the Al is 5815, then the 10 turn winding will give you 581500 nH which is 581.5 micro henries. The supply will work with this, after a fashion, but its power capability will be reduced rather a lot. I reckon 160uH would be about right. So the non-magnetic shim for yours is important.

So it all comes down to historical availability of cores. I worked in a lab where we had a range of Siemens cores in labstock. For this sort of job I'd have walked along a corridor lined with thousands of Raaco drawers and looked for an RM8 sized core in N28 or N48 material (quite similar) and found the Al400 or Al800 gapped version, then I'd calculate the turns I'd need to suit. Those luxuries of availability are long gone! So the guy designing the reformer understood that the gapless cores were more commonly available than any one of the gapped Al values, so he set about creating his own gap to convert that core into his choice of Al value. It would have helped so much if he'd explained this and said what his created Al was or what the finished inductance was.

So you see there is a big difference between just blindly following instructions to build something, and having to get down and dirty with the design maths. Provided you can get the original specified parts, you can build it blindly, but with the maths, you can take liberties.

David
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Old 22nd Sep 2020, 10:17 am   #58
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

Wow David, thank you so much for the indepth information on the ferrite tx and what to alter the windings to. Now if only there had been a manufacturers type listed in the parts list, things would have been so much easier. The rectifier diode on the secondary of the tx is specified as a UF4007 and that is what I have fitted, so should be OK there. I may have to order a 0.18 ohm 5watt res, I've not checked my stores yet.
I keep refering to 'my store', it refers to my stock of components when I was trading and as the resale value was peanuts, I kept it all. All very useful when doing various build jobs and the occasional repair, restoration. Sadly I didn't have a suitable pot core tx for this build.
I always fit the specified components when they are available, with suitable replacements if not. Occasionally I might fit a higher wattage resistor than the specified type, this is because not everyone will overate the component to run cooler. I don't like having components running hot! I don't know where UB found the original tx type, so I am either going blind or perhaps UB found out from an alternative source than the EPE mag.
All I am using is the Aug/Sept issues of EPE and any info in this thread.
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Old 22nd Sep 2020, 12:36 pm   #59
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

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I don't know where UB found the original tx type, so I am either going blind or perhaps UB found out from an alternative source than the EPE mag.
All I am using is the Aug/Sept issues of EPE and any info in this thread.
Dave
This project has been rumbling on for a while, Dave! I started this thread for help on my actual construction after struggling with the lack of information about the ferrite, to make it easier for subsequent searchers to find anything useful. You might want to read my original thread ('Ferrite Pot Core Pairs?')about this device's ferrite where David and others knowledge of them led me to test the inductance, after getting a selection of cores from MrBungle and Diabolical Artificer.

David, I have got a shim in there because of your previous information about minding the gap, and how it was the important part! I have a hazy memory that I tested the inductance with two mica shims (they came with the FX2241) and reduced it to one on analysing the results. I'll have to check again using the signal generator method discussed before knowing for sure. In my notebook I have the value of 84µH for this core with this shim.
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Old 22nd Sep 2020, 12:55 pm   #60
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Default Re: EPE Electrolytic Capacitor Tester/Reformer Construction

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0.18 ohm 5watt res, I've not checked my stores yet.
The 0.27 shown in the circuit diagram will be OK, no need to change it. You should be able to get plenty of volts 0.18 simply came out of my wet-finger guess of total available power. The power supply will simply change the on-time to charge up the inductor field enough that the output voltage is right. This resistor just sets how hard it is prepared to try if it ever has to go flat-out.

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