Testing SM's Valve Heater Phase

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Author Topic: Testing SM's Valve Heater Phase (Read 40528 times)

Peterae	Re: Testing SM's Valve Heater Phase « Reply #25 on: 2012-08-03, 17:54:27 »
Group: Administrator Hero Member Posts: 3960	Thanks Allphase & gyula only just seen your posts, that explains the over current condition with SM's setup.

Peterae	Re: Testing SM's Valve Heater Phase « Reply #26 on: 2012-08-03, 20:25:22 »
Group: Administrator Hero Member Posts: 3960	This video shows 1 Anode connected and one open circuit, i am scoping across the heater, i do not have any silicon diodes in the anode and the hash can be seen again over 450V [youtube]http://www.youtube.com/watch?v=WVltnHBa04M&feature=youtu.be[/youtube] This video shows 1 anode connected to the HT transformer and the other Anode open, i scope each anode to see what we have on the open 1, a waveform can be seen which is proportional to the connected anode voltage, there is no sign adjusting the heater phase adjusts an open anode waveform, this ac waveform is there also with the heater turned off, if i load it with a 100K resistor it diminishes to about 100mV if the other anode has about 250VAC on it, the most amazing thing i found is that if i disconnect all mains from each device and lay just a scope probe near the valve i get nothing while scoping the open anode i get 100mV mains on it, an open anode seems really good at picking up mains in the room with nothing connected to the mains at all. [youtube]http://www.youtube.com/watch?v=VO_hd6MAClc[/youtube] In this video i try monitoring the hash and turning off the heater, the hash is still their when the heater is first turned off but does stop as the heater cools and emission ceases enough for the HT rail to drop below 450V, i am wondering if the hash is occurring at set times relating to the 50Hz(not sure i explained that that well) [youtube]http://www.youtube.com/watch?v=G5QlhkCAwds&feature=youtu.be[/youtube]

Peterae	Re: Testing SM's Valve Heater Phase « Reply #27 on: 2012-08-03, 22:12:42 »
Group: Administrator Hero Member Posts: 3960	Both anodes connected together and connected to +of FWB, 0V of FWB connected to 0V of Cap, + of cap connected to heater. I had to disconnect the 0V tap of the transformer, it did not like this being connected. [youtube]http://www.youtube.com/watch?v=tMq8Gg2hcXQ[/youtube] Here we have the FWB with 0V of the FWB to one anode and +of FWB to other anode, i am scoping across the heater. [youtube]http://www.youtube.com/watch?v=mt1Gaf2PkYs[/youtube] Same as last test but scoping Anodes,Here we have the FWB with 0V of the FWB to one anode and +of FWB to other anode, i am scoping across the Anodes. [youtube]http://www.youtube.com/watch?v=C6K0bDXLMUU[/youtube]

Peterae	Re: Testing SM's Valve Heater Phase « Reply #28 on: 2012-08-04, 10:46:19 »
Group: Administrator Hero Member Posts: 3960	I did some tests this morning with the hope of trying to use the FFT to analyse this noise, things did not go to plan Firstly using the Valve as a full wave rectifier with the transformer set for 500V DC, i then put in my full wave rectifier and rewired the 0V when i switched on i have a 1000V DC double than what i had with the valve alone, I should have reset the variac down after the previous setup, the result was that the 1000V knocked out Ch2 of my DSO, it seems to have lost the AC ability as if the internal cap has gone short, i am guessing right now it probably has being Surface mounted. The other thing was i tried *1 probe setting to look at the Hash, this gave me a scale of 10mV instead of the previous 100mV, the waveform is very different, the ripple is much more rounded instead of being triangular, and from what i could see the noise was gone, i still need to do some more checks this was all done in a rush this morning. Don't you just love it when you can trust your equipment to give you accurate waveforms GRRRRR

ion	Re: Testing SM's Valve Heater Phase « Reply #29 on: 2012-08-04, 14:35:02 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Peterae: Double check by switching probes. You may have burned out the divider resistor in your probe if you were using 10X probes. Probes (10X) usually have a small trimmer cap across the divider resistor to compensate the shielded wire capacitance. If this opened, you would lose some AC HF response. If you have a schematic of the front end amplifier and attenuator of the DSO, maybe I can lend a hand. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: Testing SM's Valve Heater Phase « Reply #30 on: 2012-08-04, 15:26:10 »
Group: Administrator Hero Member Posts: 3960	Thanks for the offer ION, i am trying to track a diagram down, no luck so far. It uses relays inside, i can here them clonk when i switch between AC & DC, it's stuck on DC because it behaves exactly the same when set to AC mode, instead of getting rid of the DC component the waveform sits on top of the DC. I will try another probe but felt it's more likely to be inside the scope, we will see, not much time today to look at it.

Peterae	Re: Testing SM's Valve Heater Phase « Reply #31 on: 2012-08-05, 16:09:42 »
Group: Administrator Hero Member Posts: 3960	http://www.freewebs.com/valvewizard/bridge.html Some interesting stuff on why to use a full wave silicon rectifier before the valve. Quote What's more, the reservoir capacitor can be place between the silicon bridge and and valve, and it can be larger than if the valve alone were used. This means that the silicon diodes handle the ripple current, further reducing stress on the valve. Quote If the filament supply has a centre tap then the HT may be taken from there, which will help to reduce HT noise induced by the filament. It's looking like i need to connect the primary of my phase driven heater transformer to the primary of my HT transformer, then i can adjust the phase of the HT supply, it would appear the noise we maybe looking for is more likely to come from the heater transformer. « Last Edit: 2012-08-07, 20:36:19 by Peterae »

Peterae	Re: Testing SM's Valve Heater Phase « Reply #32 on: 2012-08-07, 09:59:46 »
Group: Administrator Hero Member Posts: 3960	Well i checked for shorted caps on my Hantek and did not find any on Chan2, it uses 3 relays for input v/div selection but impossible to trace out, i presume it is a multi layer PCB. There is no circuit available and the chip numbers are milled off. So next step i emailed hantek explaining the problem, just had an email which suggested C96, which indeed having removed it was open circuit. Having swapped the associated cap from Chan 1 which measures 56nF i have moved this over to Chan 2 and Chan 2 now works, just need to dig out a replacement for Chan 1 and i will be up and running again

BEP	Re: Testing SM's Valve Heater Phase « Reply #33 on: 2012-08-07, 10:44:58 »
Group: Guest	?? They have never answered my emails for support. I'm surprised

Peterae	Re: Testing SM's Valve Heater Phase « Reply #34 on: 2012-08-07, 12:54:30 »
Group: Administrator Hero Member Posts: 3960	I would imagine it's a simple fault they have probably logged, i did request a circuit diagram so i could fault find, from what i understand they would never give out a diagram so this may have tipped them into providing a cure, they replied within a day. Strange fault, i was looking for a S/C cap which would seem logical as it was passing the dc component, i must check maybe it has a leakage resistance or something. I can forward her email address if you require a direct line

Peterae	Re: Testing SM's Valve Heater Phase « Reply #35 on: 2012-08-07, 21:34:38 »
Group: Administrator Hero Member Posts: 3960	I am back in business now with the scope. I followed the advice in my previous post about placing the bridge before the anodes and also placing the cap before the anodes, so the + of the cap is connected to both anodes and the + of the bridge. The 0V of the bridge is connected to my 0V of the cap, this is interesting. Here's a scope shot across my heater, 1 probe each end with the scope probe earths connected to the cap 0V. Notice how each end of the heater is now out of phase by 180 Degrees and each heater end is showing as half the pk-pk. I would be interested for anyone that's clever to have a shot at explaining why this is to me because it does not make any sense to me I also thought i would try mathing these on the scope to try and work this out, if i add them i end up with a small heater sine, if i sub Chan 1 from Chan 2 i end up with my true heater drive waveform. EDIT i will add that each Chan on the scope is sitting on 500V DC when that scope shot was taken. There is a 100K load across the cap before the anodes, but i do not have a load from the cap 0V and heater HT. I can adjust the heater amplitude from zero to 6V as usual. The heater phase adjustment makes very little difference. ------------------------ Testing SM's Valve Heater Phase ch1ch2offphase.jpg (122.11 kB, 607x610 - viewed 818 times.) « Last Edit: 2012-08-07, 22:40:24 by Peterae »

ion	Re: Testing SM's Valve Heater Phase « Reply #36 on: 2012-08-07, 23:10:35 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	If you have the time, scratch up a simple schematic of your present setup with location of probes and grounds so we have a clear picture of the current flows. Back of a napkin is OK. This would be helpful and appreciated. Thanks in advance. « Last Edit: 2012-08-08, 01:36:53 by ION » --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: Testing SM's Valve Heater Phase « Reply #37 on: 2012-08-08, 07:56:57 »
Group: Administrator Hero Member Posts: 3960	I have attached the diagram from that article see below this is my setup, the cap is connected across the bridge 0V and bridge +V, i also have a 100K across this cap, so to scope i connect to the bridge 0V both probe earths and then each of the scope probes are across each side of the heater. I am not using RLim I will draw a full diagram with the cap a bit later. All i have done is move my load resistor and smoothing cap from the cathode to the anode, while still using the bridge 0V as my 0V reference ------------------------ Testing SM's Valve Heater Phase bridge4.jpg (16.84 kB, 456x120 - viewed 762 times.)

Peterae	Re: Testing SM's Valve Heater Phase « Reply #38 on: 2012-08-08, 09:36:33 »
Group: Administrator Hero Member Posts: 3960	unfortunately i don't have a camera here, i will bring it home later to do a video of this. To recap If i turn the heaters off the sine's disappear, if i adjust their amplitude then the scoped sines adjust relatively. I have snapped 2 more shots with the math function subtracting Chan1 fro Chan 2. The variac feeding the HT does not matter what voltage it's set to, i have turned it right down to give me about 7V DC on the heater(cathode Potential) for which the sines sit on so i can grab a dc scope shot. So 2 scope shots one is set to AC and the other set to DC, the red chan is the math subtract function wave. EDIT oh yer just to make sure i still do not have some strange fault on my scope i placed both channels on one side of the heater to check they were both showing the same phase, they were ------------------------ Testing SM's Valve Heater Phase ch1ch2sub.jpg (146.86 kB, 607x610 - viewed 761 times.) Testing SM's Valve Heater Phase ch1ch2sub2.jpg (149.34 kB, 607x610 - viewed 725 times.) « Last Edit: 2012-08-08, 10:30:51 by Peterae »

Peterae	Re: Testing SM's Valve Heater Phase « Reply #39 on: 2012-08-08, 11:17:04 »
Group: Administrator Hero Member Posts: 3960	Here's the diagram. The next thing that needs to be done is try using the anodes as my scope earth and then scope each heater pin. I could also try adding a load i am sure this will attenuate the sine waveform but i wonder how much, as each device is isolated this is sort of 1 wire stuff, but the question still stands how can each side of the heater filament be showing these waveforms. Thanks Peter ------------------------ Testing SM's Valve Heater Phase img013.jpg (88.23 kB, 2018x816 - viewed 762 times.) « Last Edit: 2012-08-08, 11:43:40 by Peterae »

ion	Re: Testing SM's Valve Heater Phase « Reply #40 on: 2012-08-08, 12:01:10 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	Looks to me like capacitive coupling through the output transformer back to the scope grounds. I believe you will get the same effect if you unplug the 5U4 and / or and replace the filament heater with a resistor. A lot of this depends on how your output transformer is wound. The inter-winding capacitance coupling can act like a center tap on the filament winding, thus giving you the phase difference with respect to ground, especially so if your scope is earthed. --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: Testing SM's Valve Heater Phase « Reply #41 on: 2012-08-08, 13:45:04 »
Group: Administrator Hero Member Posts: 3960	Hi ION I will try some of what you say, the scope is connected to a battery powered notebook so there is no physical connection to anything. Taking the valve out will be interesting. i could also disconnect the anodes to see what happens.

Peterae	Re: Testing SM's Valve Heater Phase « Reply #42 on: 2012-10-12, 16:49:54 »
Group: Administrator Hero Member Posts: 3960	What do you chaps make of this http://www.smeter.net/daily-facts/7/fact22.php Barkhausen Oscillation There is an unusual and little-known way to make triode vacuum tubes oscillate at frequencies far above where they normally can be used. The method involves operating the control grid at a moderately high positive voltage with respect to the cathode and the plate at a zero or negative voltage with respect to the cathode. Under these conditions the grid attracts electrons from the cloud of electrons emitted by the hot cathode. Those electrons are accelerated to high velocity by the relatively high positive charge on the grid. Some electrons hit grid wires, but most miss the grid and fly on through toward the plate. However, the plate is negative with respect to the grid, causing most of the electrons to reverse direction and head back toward the grid at high velocity. Some returning electrons hit the grid, but most fly on through toward the cathode. However, the cathode is negative, so most of them reverse again and continue oscillating about the grid. This oscillation mode is known by the few who know about it as Barkhausen Oscillation (different than Barkhausen oscillation criteria). ©2005 Martek International All rights reserved.

ion	Re: Testing SM's Valve Heater Phase « Reply #43 on: 2012-10-12, 17:40:50 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	These oscillators rely on transit time of the electron cloud. More here: http://en.wikipedia.org/wiki/Barkhausen-Kurz_tube --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: Testing SM's Valve Heater Phase « Reply #44 on: 2012-10-12, 17:45:26 »
Group: Administrator Hero Member Posts: 3960	ION looks like it is a well known effect. That article explains it much better THANKS

Peterae	Re: Testing SM's Valve Heater Phase « Reply #45 on: 2012-11-01, 22:43:29 »
Group: Administrator Hero Member Posts: 3960	In a thermionic valve are photons emitted along with electrons from the heater, the reason i ask is if a crt has a cross suspended inside and the electron gun fires at the cross then a shadow appears on the phosphor, now if a magnetic field is applied you get 2 shadows, one moves relative to the strength and direction of the magnetic field, this could be called the magnetic shadow effect, the other shadow is resultant from photon emission, photons do not get deflected by a magnetic field and do not exhibit the magnetic shadow effect.

poynt99	Re: Testing SM's Valve Heater Phase « Reply #46 on: 2012-11-02, 00:34:59 »
Group: Administrator Hero Member Posts: 3217 It's not as complicated as it may seem...	It probably depends on how hot the heater gets. Not all light is visible to the human eye, so no doubt there will be some photons emitted as well. However, these photons would be emitted in an omnidirectional pattern away from the source. --------------------------- "Some scientists claim that hydrogen, because it is so plentiful, is the basic building block of the universe. I dispute that. I say there is more stupidity than hydrogen, and that is the basic building block of the universe." Frank Zappa

Peterae	Re: Testing SM's Valve Heater Phase « Reply #47 on: 2012-11-02, 08:33:42 »
Group: Administrator Hero Member Posts: 3960	Thanks Darren, one of these days i will get a valve and dismantle it, i presume it depends if the valve is directly or indirectly heated, i know a CRT has a direct path for photon emission. ION's & radiant energy must also exhibit this shadow effect i think, where ION's can be deflected. Question then would be can radiant energy be deflected by a magnetic or electric field, i think the answer should be no. If a radiant pulse exhibits similar phenomena as photons then the interaction between atoms and the energy transferred is not dependant on the intensity of the radiant burst but by the frequency components of the radiant burst or selective bandwidth, this is why some transients generated by spark gaps have greater disruptive effects than others. The end result is that i don't really know what i am talking about « Last Edit: 2012-11-02, 09:30:28 by Peterae »

ion	Re: Testing SM's Valve Heater Phase « Reply #48 on: 2012-11-02, 21:13:34 »
Group: Elite Hero Member Posts: 3537 It's turtles all the way down	From Peterae: Quote ION's can be deflected. I can but it is not that easy --------------------------- "Secrecy, secret societies and secret groups have always been repugnant to a free and open society"......John F Kennedy

Peterae	Re: Testing SM's Valve Heater Phase « Reply #49 on: 2012-11-02, 22:09:37 »
Group: Administrator Hero Member Posts: 3960	Hi ION Great to see you online and that you have not been deflected by storm sally. Wow that thing looked nasty on the TV, times like this we all need back up energy systems to cope with these huge weather swings. Peter

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