Since my dual 2N3055 driven flyback power supply was accidentally thrown away, I was pondering building another until coming across subject mentioned assemblies. They're on eBay and elsewhere. Looks like various drivers with flybacks. Example:
formatting link
Questions would be:
1) Do these have built in diodes? I DO want to be able to drive a HV multiplier.
2) Performance/ versatility/ durability comments? Any specific recommendations of one over the other, etc? Most seem to fall within the $15-$20 US range. The 3055's with flyback and tripler could output 30-40 KVDC with mA's available. Could one of the prebuilt Chinese units do the same?
Might be cheaper to buy than to build another from scratch so your thoughts/ experiences appreciated.
Haha, 2n3055, you're talking 45 years ago!! For the last 35 years, we use MOSFETs.
It's a shame they never provide schematics or similar information. You do get a nice set of parts, and can reverse engineer to get the schematic, and then start making changes.
Interesting that there weren't more responses. I would have thought some folks would have tried them out for the "tinkering" value alone. And the cost would have covered just the cost of a single flyback, at least of the kind I used to use. There are also the Chinese Marx generators that appear to be driven by these circuits. They call them "levels" when referring to number of stages with what appears to be 20 stage the highest level (20 level) offered. They specify "10-15 cm" spark lengths with their "6 level" generator which makes sense with a 20 KV flyback driver circuit. There are videos around of the Marx generators though, but hard to confirm spark lengths claimed.
Well, I had some trouble with the 3055's. Too much arcing at tripler output would burn them out quickly and they way I had everything set up, they were a pain to change out. I finally switched out to a more robust transistor and had no more problems, but I couldn't tell you which transistor that was now. It has been some time.
I'm a big user of eBay and AliExpress, and purchase lots of high-current and high-voltage stuff, to supplement my pile of unusual parts, but I'd not come across the items you found.
MOSFETs are more robust than BJTs, in that they can handle excess drain voltages, and simply go into a safe avalanche, the same as a zener diode (however the breakdown comes with ns response times, so the wiring must be low inductance). MOSFET gates are vulnerable, but if they're driven with a serious gate-driver IC, with low-inductance wiring, they're quite robust. The issue is high RF-frequency during arcing.
You have to be careful of the ebay China parts. Seems that many of the high power and some other parts are not up to what they are suppose to be.
I have bought some things from China via ebay. Most have been good.
I did buy some RF transistors and they would hardly make any power after about 7 MHz and replaced them with some RF Parts company and those had the full power at 30 MHz where I wanted to use them. Friend bought some rated for about 5 or 10 watts and all 6 of them were bad from the start. The first 2 he put in fried his circuit. He measured the other 4 before instlling them and they were all shorted.
I have seen some pictures of the internals of the 2n3055 transistors from China and some had a very small silicon area compaired to the 'good' ones. They would test good but probably only good for about 1/2 to 1 amp.
** 2N305s have been around since the mid 1960s and undergone number of chip redesigns in that time.
The JADEC specification does not determine the chip itself - only its ove rall performance. Long as the watts, volts amps, gain and Ft etc are OK you can label it as a 2N3055.
After discovering fake Motorola power BJTs in 1982, I began cutting the top s of dead and suspect TO3 examples to see what was inside.
Verrry interesting ....
In the case of 3055s, older examples use a large chip with solid metal bond ing attachments. Later ones, particular from Motorola use a much smaller ch ip with aluminium wires. Nothing wrong with either.
Some of the fakes I came across were 2N3055s relabelled as the vasty better MJ15003 types. Others turned out to be high voltage switching devices with tiny chips and even power Darlingtons - visible by the presence of a small er transistor on the same chip.
One particularly egregious fake from India had two chips inside, wired in p arallel in a desperate attempt to meet the Motorola spec. But that idea doe s not work.
Another fact that I uncovered is that Motorola like to change the chips ins ide their power BJT devices without warning. Devices sold since the 1990s as the classic 2N3773 or MJ802 types are in fact MJ15003s relabelled.
Fine for new designs, which is all Motorola ever consider, but can cause al l sorts of strange behaviours in older ones. Repairers beware.
Plus the price is double or triple that of the more recent part.
Anecdote:
A famous audio engineer from the UK called Doug Self got trapped by this.
He published a design in Wireless World magazine for a "Blameless Amplifier " using MJ802 and MJ4502s from a stock of old ones he had. It had vanishing ly low THD.
When folk built his design using the parts and PCB as specified they could not achieve nearly the same result.
Lots of weeping and gnashing of teeth went on in the letters pages.
Nobody ( but me it seems) figured out the cause was Motorola being deceptiv e.
It's a shame China parts can be so varying in quality, but I too am not immune although in a different capacity: faucet vacuum aspirators. I had a really nice glass one, US made, that would pull up to at least 28" Hg with standard faucet pressure, then one day my carelessness broke it. It was a Kimax? and they were no longer available, so I decided to try a stainless steel aspirator from China. It could hardly pull 15" Hg, a far cry from the advertised 28-30" Hg! I contacted the seller and got an immediate refund with no argument, so I'll bet, at least in this instance, that there were a lot of insufficient aspirators. That wasn't the only one I tried as I tried out several other metal ones, but none would pull vacuum like the glass one did. That's when I finally decided on a single stage pump but, after 2 years, that Chinese made pump has leaked.
Yes, they do have built in diodes so you won't be able to drive a multiplier.
If you can still find a flyback without built in diodes, go with the better mosfet circuit recently discussed. The hard part would be finding the flyback.
Yo, Bogan, Mr. Terrell may not be my most favorite person, but on his very worst day of his entire life, he is happier, a better human being and far more worthwhile than you on the very best day of your life.
I expect that a diet of Sausage Rolls and Foster's Beer has that effect - oh, right. I expect that you cannot afford the sausage, only the rolls. Sorry about that.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.