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Messages - johnf
1
« on: November 05, 2023, 11:35:06 PM »
Most incandescent bulbs use a little argon to help stop evaporating the tungsten filament
Has anybody tried this with multi-halide arc lamps??
4
« on: May 09, 2022, 05:39:51 AM »
hopefully you made your pulleys so that they are tapered from the middle ie the middle is greater diameter than your outside edges. doing this gives automatc belt centering much like railway wheels stay on the centre of the track. commercial VDG's run at about 70km/Hr belt speed. Otherwiswe nice build
5
« on: May 04, 2022, 11:22:09 PM »
When i'm repairing Glassman HV PSU's I test all the multiplier stack capacitors individually at their rated DC voltage looking for leakage I have a Danbridge JP30A to do this with https://www.danbridge.com/product_detail.php?indexs=46without this I have never found a problem at low voltage measurements ie they measure within tolerance but at elevated voltage the leakage is way out of spec
6
« on: March 26, 2022, 10:44:15 PM »
Yes that amp looks like about 1.2kW of RF out maximum I few years ago I built this for my HAM hobby in this case the BLF188XR is soldered to the heatsink to get very good thermal performance as this little FET consumes 50 volts at 55 amps and will give about 1.3 kilowatts out although I have set the ALC now to 1000 watts as this is my second fet. I forgot to put the antenna on one night and tried to put 1.3kilowatts into an open circuit and I punctured a few of the paralleled fet inside the package
7
« on: March 26, 2022, 10:30:32 PM »
Twospoons Before you attempt this there is a crown in China who will regas this tube for you we have one of these at work and we bought a new tube from syrad approx $8000US$ The chinese want about a 1000 dolllars to recondition it
8
« on: March 21, 2022, 08:23:04 PM »
Coupling close to 1 or K as it is often referred to. The perfect transformer has a coupling ratio of 1 ie all the input energy is translated to the output. In practice we can get very close ie coupling ratio of 0.96 is as good as I have measured mine own designs. To measure this one measures the inductance of the primary with the secondary open circuit and again with the secondary short circuit So coupling factor k = 1-(shorted inductance divided by the open circuit inductance) Lets say the primary measures 10 micro-Henrys open circuit and 100 nano-Henrys short circuit = 1-(0.1/10) = .99 The measured value of the shorted inductance is called the leakage inductance As coupling factor goes down the leakage inductance goes up which with flybacks manifests itself as high reflectance from the secondary to the primary and this energy gets absorbed by the snubbers on the switching device with out the snubbers your switching device will see much higher voltages than your DC bus
9
« on: March 13, 2022, 11:16:45 PM »
Use Shell Diala S5 do not mix other oils in unless replacing it all
10
« on: February 18, 2022, 10:43:49 PM »
Not quite yes the turns ratio comes into it but also the leakage inductance and a few other things like winding capacitance so you will tend to get a higher voltage than the turns ratio suggests
11
« on: February 18, 2022, 04:15:51 AM »
Steve Internet modem supplies are the bane of all amateur radio operators Cheap Nasty and noisy and thats when they are new they go downhill from there. Most hams try to find a 50/60Hz transformer version to replace them trouble is of course your neighbors with the SWPS version
12
« on: February 07, 2022, 03:28:13 AM »
No picture No actual core spec or pic with ruler No number of primary turns No measured inductance No measured leakage inductance Around 20kHz +-? Probably your Turbo Encabulator
13
« on: January 22, 2022, 05:27:37 AM »
If you have two identical cores make two and put them back to back then run some power at various frequencies through them, losses are exacerbated by a factor of two so it should be easy to see
14
« on: November 26, 2021, 09:17:07 AM »
Steve we used to do this to generate very big compression waves in sea water for geotectonic sonar used 500uF charged to to 15kV and two electrodes about half a meter apart about 100 meters down in the sea. water got ionised between electrodes resulting bang then gave us a look at the underlying strata on the sea floor (oil exploration). Repetition rate about 10 hz triggered spark gap fired the charge down the coax cables to the electrodes. Used to test it in the university carpark in a trough of sea water --better than any buyable fire cracker - needed very good ear protection to get near
15
« on: October 15, 2021, 07:46:28 AM »
Parallel 10-1000 meg-ohms per kv depending on circuit topology as for series this depends on power of the supply but I tend for a minimum of 1000% of the max current ie a supply of 100kV 100mA you would use a 100k ohms supply impedance = 12 meg ohm. More if you want to protect your supply or less if you are adventurous
16
« on: October 01, 2021, 08:50:32 AM »
Yes I was wondering why the grid RF bypass cap had to have such a high voltage rating
17
« on: September 29, 2021, 07:39:27 AM »
I tried to "Modify" my post but the board refused to act!!!
I meant to say that tuned circuit "Q" is made better by increasing capacitance with reducing inductance ie "Q" is proportional to "C" in a tuned circuit
18
« on: September 29, 2021, 07:35:03 AM »
Your last answer has all the clues you had to reduce primary turns and increase the capacitance to get good sparks
ie "Q" was not enough "Q" = high circulating currents and if these cannot be got the voltage rises
you need pulse rated capacitors that have enough voltage stand off and current capacity
19
« on: September 29, 2021, 06:24:54 AM »
All they need to do is buy cheap lesser spec'ed overrun parts from a legit maker and remove the markings and put new laser marked part number on from an expensive part. Measuring Gate capacitance is easy for Fets not so reassuring for IGBTs of course. Once upon a time I worked for a very large electronics company and one line of products we made were 2 way radios (RT's) for trucking firms Taxis and law enforcement for worldwide sale. We had several of our designs copied in an Asian country and sold at much cheaper prices worldwide. We then started making fake parts ourselves this involved a cmos 4013 all the markings taken off legs then bent around the other way and circuitry put around it to make it look like a well known Switch mode controller IC. WEe marked these ourselves with a commercial inkjet printer that used uv cure. You guessed it our design was copied and they were having terrible trouble making it go. It would not work with the unitrode part, they asked us for spares and we sold them a few hundred parts for many many terns of dollars each. Our vendor mark on our fake parts looked like the Signetics logo who never made items like tis
20
« on: September 17, 2021, 10:06:53 AM »
You might want to consider it a room warmer (not heater) with that filament power I've got a glass water cooled anode triode that has a kilowatt heater that I might do something similar to comes out of a 7.5kilowatt induction heater
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