>
>
> 1) Do these have built in diodes? I DO want to be able to drive a HV
> multiplier.
Yes, they do have built in diodes so you won't be able to drive a
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.
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.
> Thank you,
> Jon
Reply by Jim Horton●November 3, 20192019-11-03
On 11/3/19 2:46 PM, Ralph Mowery wrote:
> In article <qpn7mi0btm@drn.newsguy.com>, winfieldhill@yahoo.com says...
>> 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.
>>
>>
>>
>
> 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.
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.
Reply by Clifford Heath●November 3, 20192019-11-03
On 4/11/19 5:53 am, Winfield Hill wrote:
> Jim Horton wrote...
>>
>> Interesting that there weren't more responses.
>
> 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.
On Sunday, 3 November 2019 18:53:19 UTC, Winfield Hill wrote:
> Jim Horton wrote...
> >
> > Interesting that there weren't more responses.
>
> 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.
>
> > Well, I had some trouble with the 3055's. Too much arcing
> > at tripler output would burn them out quickly ...
>
> MOSFETs are more robust than BJTs, in that they can handle
> excess drain voltages, and simply go into a safe avalanche,hur chat
> 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.
>
Another nice vintage high voltage transistor is the BU105.
I used to salvage them from the junk piles at the back of
television repair shops in the days when such places existed.
They generated useful output at around 1MHz.
John
Reply by Ralph Mowery●November 3, 20192019-11-03
In article <qpn7mi0btm@drn.newsguy.com>, winfieldhill@yahoo.com says...
> 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.
>
>
>
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.
Reply by Winfield Hill●November 3, 20192019-11-03
Jim Horton wrote...
>
> Interesting that there weren't more responses.
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.
> Well, I had some trouble with the 3055's. Too much arcing
> at tripler output would burn them out quickly ...
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.
--
Thanks,
- Win
Reply by Ralph Mowery●November 3, 20192019-11-03
In article <MPG.3828e830c88373c7989bfc@news.east.earthlink.net>,
rmowery28146@earthlink.net says...
>
> Many are using the 2n3771, 32,33 series or there about numbers to
> replace the 3055's for more power and reliability.
>
>
>
make those last numbers 72 and 73.
Reply by Ralph Mowery●November 3, 20192019-11-03
In article <qpn15r$j13$1@dont-email.me>, jhorton@nospam.net says...
>
> 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.
>
>
>
Many are using the 2n3771, 32,33 series or there about numbers to
replace the 3055's for more power and reliability.
Reply by Jim Horton●November 3, 20192019-11-03
On 11/2/19 8:27 PM, Winfield Hill wrote:
> Jon I wrote...
>>
>> Since my dual 2N3055 driven flyback power supply was
>> accidentally thrown away, I was pondering building
>> another until coming across subject mentioned assemblies.
>
> Haha, 2n3055, you're talking 45 years ago!!
> For the last 35 years, we use MOSFETs.
>
>> They're on eBay and elsewhere. Looks like various drivers with
>> flybacks. Example: https://tinyurl.com/y4lzxt85 Questions ...
>
>> Might be cheaper to buy than to build another from scratch
>> so your thoughts/ experiences appreciated.
>
> 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.
Reply by Winfield Hill●November 2, 20192019-11-02
Jon I wrote...
>
> Since my dual 2N3055 driven flyback power supply was
> accidentally thrown away, I was pondering building
> another until coming across subject mentioned assemblies.
Haha, 2n3055, you're talking 45 years ago!!
For the last 35 years, we use MOSFETs.
> They're on eBay and elsewhere. Looks like various drivers with
> flybacks. Example: https://tinyurl.com/y4lzxt85 Questions ...
> Might be cheaper to buy than to build another from scratch
> so your thoughts/ experiences appreciated.
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.
--
Thanks,
- Win