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Author Topic: starting work on the amp  (Read 185890 times)
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« Reply #125 on: August 27, 2016, 09:37:10 PM »

I thought W7TFO held the worlds collection of those!  Good to see others can appreciate beautiful meters!
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« Reply #126 on: August 28, 2016, 09:55:12 PM »

Hi,
I used a TECO-Westinghouse FM50-101-C VFD on mine, works great.
http://www.factorymation.com/Products/FM50_115V/FM50-101-C.html
73
Frank
KJ4OLL



I will look into that brand of unit. the price is about the same. The nice ebay seller going to e-mail me the manual on his (no name) goods.

I really like that blower you have there, have heard they are fairly quiet. How is it working out in the amplifier? Do you measure the pressure to get the CFM yet?


But the 1HP Dayton-powered beast is here and may as well use it. The biggest noise from the blower is what sounds like ball bearings. They don't sound as though bad but maybe about dry. Time also to investigate that and I hope there may be a grease zerk on the motor ends.

The air noise is high but I hope the blower can run at a fractional speed for just the one tube. I think it used to cool a couple of 20KW tubes.

The 'electronic brain' panel now has six Octal relay sockets, more than needed I hope. I also took a 20-25 place screw terminal strip and mounted it for the junction point. All the 120 and 240 'control' stuff except the plate transformer and what's in front of it should be able to be connected there and it ought to make troubleshooting simpler.

The wire terminal strips are like the picture and https://www.amazon.com/Separable-Connector-Positions-Terminal-Barrier/dp/B00DUX005Y  but way older and of USA manufacture. They are asymmetrical meaning one side has a 'foot' with a screw slot and the other end accepts the next section. They just fit together.

One 'end piece' is needed for each complete assembly. There is no limit I guess to the number that can be stacked together but from just this one experience I recommend a screw be installed about every 8 sections for rigidity. These took #6 hardware and cut washers were used so the screws won't loosen.

I had a choice of spring loaded (WAGO) type where the wires are just inserted, the common very popular non-modular barrier strip style where crimp/solder lugs are held by screws, or modular screw type that clamps down right onto the wire ends. The box is full of many kinds and some are DIN mount.

I chose the non-DIN modular screw type because no crimp/solder lugs are required and several wires can be inserted and the screw tightened onto them, and they can be unhooked as needed easily for work. The ones I have are good for 10A 600V. I didn't want to mess with DIN rail.

The planned position for the panel is recessed in the lower half of the rear of the rack - and well away from all the HV stuff. Servicing should be safer. Something learned from the Tucker transmitter - when the back doors are open and interlock bypassed, everything from 115V to 3500V is right there. Something to avoid I guess - don't build safety problems into a piece of equipment.


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« Reply #127 on: August 28, 2016, 10:18:11 PM »

It cooled a pair of 4CX10,000's and a quad of 8122's.

About 600CFM.

73DG
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« Reply #128 on: August 28, 2016, 10:21:11 PM »

And I have a couple of those centramax blowers that are single phase..
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« Reply #129 on: August 29, 2016, 07:14:38 AM »

Hi,
WOW you have really made some good progress on that amp!

The blower is a three phase Rotron Centrimax, found NIB on eBay for $100.
I wanted a single phase, but they were all many times the $$$.
Still cost less to buy the three phase and a $99 VFD!

As you probably know, the VFD can run the blower @ whatever frequency you need to obtain shaft RPM /pressure desired.

Used a manometer to verify that pressure meets the EIMAC 3CX3000A7 requirements.

https://www.youtube.com/watch?v=MNo1uH9-q38

The blower is quiet, but the volume of air required by the EIMAC is loud.
I have to roll the amp out behind the shack, operate it remotely.

Blower pressurizes plenum I fabricated, w/ choke and cathode drive inside.
Used a pressure switch to kill the HV and filament heater if air pressure is lost, so as to protect things.

73
Frank
KJ4OLL


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« Reply #130 on: September 04, 2016, 02:00:33 AM »

My blower is from two 4CX10,000's and a quad of 8122's?

 Smiley

I got some real work done this morning. The controls panel is partly done, that is the soldering part. the rest is wiring with screw terminals and wire lugs. Previously a black terminal strip was shown, but it is was for testing and not going to be used in its current place. The wires going to it will go to this panel. Just a change.

A hole had to be made to bring the wires from the right three Octal relay sockets to the front of the panel to connect to the new terminal strip. A grommet should be used but some care was taken to allow the bundle of wires to pass through the center of the hole and not touch the sides. The wire is #14 solid so it's self supporting. Some clamps may be added later but it seems unnecessary.



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« Reply #131 on: September 04, 2016, 02:07:25 AM »

Some other things that may or may not be used have turned up. Some were just discussed, like the huge 'panel lamps' and the small industrial rotary snap action switches. The panel lamps take a 2" hole and use Edison base lamps. There are no markings on the lamps and all are open.

These switches may do for a 'test' mode or whatever, if necessary.

A nice 24VDC coil relay should  be OK for keying control, and another time delay was found. It can be disassembled and hacked for other time ranges if needed.

This and the next couple are just parts found for possible use, no decision has been made.


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« Reply #132 on: September 04, 2016, 02:15:15 AM »

These RF or high voltage switches should be usable. Does anyone know what they are from and what voltage they will take? Are they up to 4800VDC? How about use in the RF tank for switching a coil or cap in/out? They are pretty anyway.

Next, a GE rectifier stack. This monster is pretty old and I wonder if anyone knows what it may be from?

Lastly this UTC 54874 item. says in and out, maybe audio.


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« Reply #133 on: September 04, 2016, 02:22:46 AM »

This imposing switch (as well as the GE rectifiers, audio thing, and HV shorting switch) was dug out of the garage. There is a large pile of stuff there for many years. I have always wanted to use this switch. For scale the escutcheon is about 5" square.

The high voltagse shorting/discharge switch is something that ought be standard on all high power gear. Anyone know what it is from?

Its purpose is to short out up to three HV  terminals to ground when a door or cover is opened.  Hopefully, before that happens the usual mains interlock will remove input from the power supply!

OK well I should do some wiring in the amp tomorrow (wow, later today..) maybe mount up the inrush resistors.


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« Reply #134 on: September 04, 2016, 03:10:24 AM »

Those rotary switches with the red phenolic and porcelain insulators were typical in WW2 US Navy transmitters by Westinghouse and RCA.

They will easily handle your RF or HV loads.

I have one of those Dwyer liquid manometers as previously shown, will forward.

73DG
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« Reply #135 on: September 04, 2016, 07:47:54 AM »

The rectifier stack looks similar to those used in cathodic protection of pipelines, typically 20 to 60 volts at several amps. May also have been used in RR signaling, etc.
-very choo choosih looking  Grin
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« Reply #136 on: September 04, 2016, 01:02:47 PM »

I'm encouraged by the info on the switches. Maybe I can add a 'tune' position using the center tap of the power transformer as a selection for half plate voltage.

With the liquid manometer, how does one prevent the liquid from evaporating or becoming contaminated?
There may be a usable Magnehelic dry type manometer unit here. I got a bunch of them from in 2"-5" ranges ST when they decommissioned the fab. There are a couple of them mounted on my furnace. It amuses the HVAC guy, but it tells me when to change the filter.

They are a bit large maybe 5" diameter face. With care it might mount behind the MV tubes so it can be seen in that chamber but won't make the front of the amplifier look strange due to the incorrectly styled bezel. Alternately it could be mounted opposite a 5" CRT modulation scope. But that accessory has not even been considered yet, so much to do first.

I made my own manometer for testing blowers a few years ago. it's been very useful. It's a U shaped clear flexible tubing 1/4' diameter ID on a meter stick. The tubing need removed and cleaned out, hence the above question about the Dwyer unit.

Very interesting on the rectifier stack. Glad it was not 'tested' for what it looked like to me - a HV stack. The diodes themselves seem elaborate with the cup and a glass bead on each. Maybe I can ask on a railroad board assuming there are those.

Last afternoon I realized this thing has a lot of wires in it and I was having issues looking at the schematic, then looking at what is in front of me and making the mental images match.. I made this picture to help me get the right wires in the right places. No fancy CAD here. Good thing, I forgot to do the coil wiring for the control interlock relay. With a week between sessions, things get forgotten.


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« Reply #137 on: September 04, 2016, 06:58:01 PM »

today went well. Added the missing leads. also figured out the places for jumpers to go, as each relay has its own terminal positions on that block. It is maybe more trouble to build it that way, bigger block and all, but it allows easier troubleshooting or easier changing to a different kind of relay. time to redo the schematic section again (ugh)  to reflect the larger terminal block, that is very time consuming. It's best to do it this way, as there is one place for all the control wires to meet up and each wire has its place. It's also mounted at a height in the rack so a person can sit on a chair and work on it. Thinking about some old man having to work on it some day.. mounting complicated panels near the floor or at the top is for the birds! Just make it easy to work on.

I did not get the regular sequence of events to happen, as another jumper needs added and there is a wiring mistake preventing the filament timer from starting. Look at it this way, there were no smoking wires or blown breakers or anything like that. I am sure the 70A breakers will pop, but don't want to ruin anything finding out.

The sequence should be:
control circuits powered (the interlock prevents working until that is OK)
blower on
air switch closed (I am faking it)
filament power applied
30 second delay
plate power applied through soft start resistor
1 second
soft start resistor bypassed -full power.


If power is lost or any breaker except the control breaker turned off, all stops and the 30 second delay is enforced. The control breaker powers the blower directly so it can be left on as desired. The filament breaker can also be on with no plate voltage, as long as the air switch gives its testimony.

Keying is by cycling the main plate relay, which makes the soft start happen again. - so every time it is key-down, there is a 1 second delay. Sorry CW folks! Maybe later an electronic TR switch (with chain mail undershorts!) can be made and break-in methods can be tried, but that can wait until the amp is working correctly.

The blower motor was revisited, this one is actually a 1.5HP unit. 1000CFM@4" SP. I believe we are well into the overkill range here. There may not be enough airflow through the tube and the blower motor may overload. I don't understand that part of blowers yet but if the air is stopped off, the motor will take too much current. Worst case at 4KW dissipation and 10,000 FT the tube needs 185CFM @ 2.55", and at sea level 127CFM @ 1.4"

Jacob's Tesla project is moving along. He has rewired the old lambda supply to be as like the schematic previously discussed as possible. Dang he's raided my power resistor stash too. Thanks to all that cared enough to help on this non radio project. He has been learning a lot, especially how to think when modding something from one schematic to another very different one. If we were in a video game he would have gotten the next level experience in hands on electronics today. He said something like 'It suddenly became clear once I was working on it'. I'm proud of him for this, so may young people can't be bothered to learn anything worthwhile or spend time thinking and doing. I suppose I'm old fashioned but the choices I see for youngsters today are to:
1.) fill the brain with carpet remnants and Jello Jigglers(tm).
2.) fill the brain with powerful analysis and reasoning skills.
Hey kids! Pick one!

And thanks to all that are advising me as this amp project goes along. I know it is taking a long time but it's sincerely appreciated.  Smiley


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« Reply #138 on: September 06, 2016, 05:56:44 PM »

The manometer I used has a fill plug that is replaced after, sealing the unit.
The liquiid supplied is of the specific viscosity for the mechanism.
Don’t know about the evaporation rate, but the meter has an adjustable zero point, so it can be “calibrated” for losses over time.
Also, twice the volume of liquid needed is supplied with the unit, so if in future years I can’t zero any more due to diminished volume, all I have to do is remember where I put that bottle of red stuff.

But it really does not seem to be an issue, as once the pressure is set, unless the blower has a fault or a major air leak develops, the manometer use is a one time thing.
I could remove the manometer and still be assured the volume/flow numbers for the 3CX3000A7 are good, and remain where I set them.

The fail-safe is an electrical switch that is operated by blower pressure.
So if anything occurs to reduce the air pressure, the pressure switch shuts down the filament and HV instantly.

Very powerful blower you have there!
If there is anything else needing airflow, and you have determined the blower has excess capacity, consider ducting some of the flow elsewhere.
I used some of the excess air to cool the rectifier.
73
Frank
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« Reply #139 on: September 06, 2016, 10:59:06 PM »

Perhaps someone will drop off a theater organ.  Shocked 

A pressure switch is a great idea - an alternative to the traditional airflow switch using a vane. Are there any disadvantages to either method?

Perhaps if the air blows the tube from the socket, the pressure switch will prevail in the safety contest.

Dennis, I think your Dwyer would be very useful here if the correct magnehelic is not found - it also does not require me to punch a huge hole. I nearly broke my arm on the CRT hole for the Tucker.


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« Reply #140 on: September 07, 2016, 09:09:38 AM »

I tried and tried to get a vane switch to work.
Attempt #1 (fail)
https://www.youtube.com/watch?v=AxLVPkwmFzM

Attempt #2 (fail)
Worked fine until I put the plenum cover on, then the vane started oscillating in a way that interrupted the microswitch circuit.
Tried baffles, etc. No luck eliminating the vane oscillation.
https://www.youtube.com/watch?v=YuudZ3Pcnvk

Then one of my many Elmers, who retired from the commercial HVAC business, gave me a very colorful rant about how much he hated vane switches, and how many service calls are due to the vane switch problems, etc.

Thus the change to a “DWYER 1910-00 LOW DIFFERENTIAL PRESSURE SWITCH 0.07 to 0.15 W.C.”
 No problems so far!

73
Frank
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« Reply #141 on: September 08, 2016, 02:49:37 AM »

I see, the air switch required more flow than was present. I noticed that the flow as you said was enough for 2KW dissipation. A level of cooling for 4KW is wanted in this one so that the option is available for CCS operation at full power. After seeing the air switch videos, I understand now about the amp being very noisy and being moved away from the operating position when it is to be used.

The blower on-hand - it is noisy enough on the premise of airflow. Unknown whether a more reasonable size blower will be enough pressure-wise considering the couple of twists and bends in the tubing that will have to be made. 4" tubing should be able to be used for the high pressure side, but it may not be required to be that large.

I think most of the air noise in the 1000CFM blower is coming from the blower intake. the db meter has not been used to try and check, as of yet. I wonder of the 3CX3000 anode helps quiet the noise from below the tube as the air passes through it.

There's a unique opportunity to experiment with  silencing techniques regarding the air flow. if I understand right, those tend to 'consume' pressure like a resistor drops the voltage as current flows through it. Inside HVAC ducts there is some felt like material, whether it is for noise or condensation or what, I don't know. Noise also seems to come from velocity and impingement and rough surface transitions.

The point is that industrially, much louder things are silenced pretty well. Large industrial blowers can have silencers attached - sometimes they are bigger than the blower, but these reduce the otherwise horrendous noise. Modern trailer mounted portable generators in the 100KW size are very quiet compared to older ones. Looking inside, there is what seems to be a simple labyrinth of some sort through which all of the air flows, Air goes in, and comes out carrying the exhaust with it.

If an air stream of z area and y CFM makes z dB of noise, and the velocity is lowered by expanding the area to >>z, and the air forced to move through a couple of sound absorbing baffles, would that no quiet it a lot? An air horn on a blower intake works too, but with what principle I don't know.

If the racket can be cut by even 10dB it is well worth trying. It's a new discipline to try and learn something about, especially when so many comments relate to blower noise and even mounting blowers outside to reduce noise.

some fun info comparing popular "QRO" tubes:
3CX3000
4KW dissipation = 127CFM @ 1.4" water (at 10K FT altitude, 185CFM @ 2.55")
(not stated but this probably assumes the extra margin for filament 375W and grid 225W dissipation)

4CX5000A in SK-300A socket
4KW diss. = 145CFM @  1.1" water
6KW diss.  = 230CFM @ 2" water (SK-300 socket 200CFM @ 2.5" water)
(The above assume a margin of 1200W extra for filament 770W and screen 200-300W)

In the drawing below, it does not take into account completely the differences between the two tubes because the 4CX5000 has a slanted inlet at the bottom of the anode and the 3CX3000 has a straight vertical inlet. The main difference seems one of pressure when mounted in the sockets, which are very different, and everything else, but look at the area and volume of the cooling air flow in the straight, enclosed, tubular section of the anode. How interesting. Here is maybe a more interesting way to look at the similarities of cooling those two tubes:



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« Reply #142 on: September 13, 2016, 09:46:27 PM »

If we may digress back to the Tesla project, which consumed much time last Sunday, I re-drew the class A voltage amp schematic with measured voltages so it should be very clear.

There is a serious problem which we do not seem to be able to get past. The frequency response is poor. it is pretty flat from about 400Hz to 4Khz, then gradually drops off, and at 15KHz, there is almost nothing. The 6L6s and all the rest of things not needed for the stage to work have been removed and the measurement is being made at the point shown, with no load, no grids, etc. to mess it up. This is to isolate the circuit in which the trouble appears.

The voltage gain at 1KHz is about 9. Measured 90V p-p out with 10V p-p in. The tube is not really made for voltage gain, just for handling HV switching. The tube definitely will work at 70KHz, as that is the approximate frequency of the half wave present in the resonant deflection circuit in a TV set.
I tried a 50K plate load, got about the same thing with less gain due to a lower plate voltage.

The voltage from the generator stays constant.
There is no signal higher than a few mV measured at the cathode, nor at the screen, which are the two degenerative points.

Putting a 10mH inductor in series with the plate load resistor helps, but only when the inductor is the only load present is there any signal of consequence and that is about 60V p-p. It can be tuned with a 1000pF air variable cap.

But none of that RF-style plate tuning circuit stuff should be needed at <100KHz, right? And, if the thing had any ultrasonic-frequency gain at all, it would give much more than 60V p-p when resonated! It should not be needed, this is not a 160M amp.

I do not understand this at all. It goes against expectations, very odd issue. I would expect the gain to fall off but at a much much higher frequency. I thought about peaking circuits, but surely not at this low frequency.

Tube is
grid to plate: 0.6pF
Cin G1 to all: 15pF
Cout p to all:7pF

The drive source is a tube H/P oscllator, rated for 50 ohms and unloaded, so I do not think the Miller effect is to blame and the 10V p-p appears at the grid at 77KHz.

There is something perhaps very obvious going on but I must be too dumb to see it. Could anyone advise me on this?


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« Reply #143 on: September 13, 2016, 10:50:13 PM »

The progress on the RF amp, BTW:
Got all the control relays wiring sorted out and working. There had been a couple of wiring errors. There is still one exception but it does not affect the basics and should be pretty simple to figure out.

The blower relay is working to prevent filament power from being applied unless the air switch is closed.

The time delay for the filaments, including MV rectifier heating, is working so that the plate power can't be turned on until the Mercury is heated for the correct seconds (1 to 150 can be set).

The soft start is working and whenever the plate is enabled, the soft start is enforced. It's 5 seconds but it can be modified to 1 second.

It was found that if the interlock relay was pulled, the blower and filaments stayed on. It means that the neutral is being found somewhere for both of the time delay relay coils. Seeing these take very little current, it would not take much. The schematic has to be reviewed to find the cause.

But anyway the good news is that the controls work, and the filaments and HV section can start being wired up. It's great news!
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« Reply #144 on: September 14, 2016, 10:13:11 AM »

hi Patrick .... gain dropoff with inc F .... might try a screen bypass cap, electro paralled by poly ...see if that helps....

what happened to bipolar supply?
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« Reply #145 on: September 18, 2016, 07:30:12 PM »

hi Patrick .... gain dropoff with inc F .... might try a screen bypass cap, electro paralled by poly ...see if that helps....

what happened to bipolar supply?

The supplies are still there, the schematic was redrawn with just one to make it as simple as possible to find the trouble. Have not had time to try the caps yet.

In the meantime Jacob tried a solid state driver. Lost one 2n3055 already. However the thing is as shown, 12V DC supply, and 6V p-p in, 100V out wih 3200 Ohm load, >500V p-p with no load and the tuning cap across the secondary. That is a microwave oven inverter transformer there, the drive is darlington circuit, single ended.
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« Reply #146 on: September 18, 2016, 07:32:22 PM »

On the amp, got some work on the rectifiers done.


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« Reply #147 on: September 18, 2016, 07:52:02 PM »

Eimac HR-8 plate connectors were handy. Black #12 solid core wire goes from there to the tops of the hash chokes. The crimp on ring terminals make this simple. The stiffness of the wire reduces movement. It's only 600V insulation in this link but there is nothing close for arcing. An insulating rigid support such as a Lexan rod or bar may be run across the rack just above the hash chokes plate leads and secure them there. The chokes tend to wobble in a resonant manner when the rack is moved. They are not as substantially mounted as I would have thought being from an RCA BTA-5.

The SS rectifiers will be wired in series with the plates of the tube rectifiers. It will make a 31KV per leg bridge. To the right of the SS rectifiers modules is maybe some space for a bleeder and HV meter multiplier, etc.

I was not going to mount the SS rectifiers up that high because I wanted that space for a 50 ohm to balanced transmission line matcher, but they would not fit anywhere else without <2" clearance and I did not want them near the 'electronic brain' panel because that may have to be accessed with the TX on from time to time. Also with the tube rectifier height, the space above them for the matcher was smaller than wished.

Whatever transmitter these SS rectifier banks are from, it is good because the length of each module is such that when they are center mounted vertically between two 1U panels, the mounting holes on the 1U panels line up with those in the rack.

There is enough room on the other side for the RF amplifier chassis and the matcher. It's not the best thing but it will have to do.


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« Reply #148 on: September 20, 2016, 07:32:51 PM »

Are those 575A's Patrick? Talk about unobtaineum! I had a hard time finding a matching pair for the 20V3. 

Mike
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Patrick J. / KD5OEI
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« Reply #149 on: September 24, 2016, 01:09:46 PM »

Mike, They are 673s which are the same except use the Super Jumbo socket instead of the Jumbo socket. There are maybe some 575A here and if they turn up I will let you know. At this point I'm a 673 shop.

Understand about matching with the 20V3. That's a very cool transmitter.

So, looks like tomorrow will see some more work done. Hopefully it will be the filament wiring to the 673s and then if time permits the wiring to the HV transformer, choke, and filter cap. A bleeder still has to be made up with insulators etc. and a temporary HV voltmeter set up. Can't wait to light up the 673s.

It is slow going but it takes care to avoid creating dangerous situations while also keeping cost down. Here is an example of the work of someone else showing why a schematic should not be just copied into hardware without understanding of what's going on physically. The handiwork is very nice and little expense seems spared, but I'm concerned about the bleeder resistor bank for the high voltage power supply. I think it is supposed to be between 7KV and 10 KV on that with a 100uF filter across it.


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