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1-10 of 21 messages
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VIKING INVADER 2000 POWER SUPPLY HELP
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by AC0FA on November 6, 2009
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Hi,
I just need a hand in diagnose fix viking invader 2000. Has been working to spec recently. 800w out on cw Meter readings ok. seens to have developed an intermittent fault around the 5R4GY circut.
The one of the 6146 finals in the 200 went out with blue light and flashes a few days ago. The other final tested at 20%. Both were replaced with tubes like new. The 5R4GY also tested bad and was replaced.
I was following the procedure in the manual for checking the adjustment of the screen voltage transformer tap at the bottom of page 8 in the manual.
Removed the fuses from the HV transformer, In order to check the screen voltage at the 11pin socket found on the top of the original 200 power supply that is now bolted to the back of the 2000 supply.
I turned the pa plate control on and the transmitter power on the 5R4GY tube warmed up as usual. Then I saw a blue glow in the tube the elements in the tube turned orange then the fuse blew. When I replaced the fuse and tried again the same thing happened.
This hapened before I was able to get a voltage reading.
Where do I start?
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by KA5N on November 6, 2009
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A blue glow in a tube usually means it is gassy
(Sometimes you will see a slight blue light in the glass of an amplifier tube which is harmless) but a glow inside the tube is bad news.
Also do not power up any final tubes with no plate voltage to check the screen voltage or you may blow the screen up.
Allen
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by AC5UP on November 6, 2009
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As a general rule if the plate shows color (dull red through orange) the tube is drawing way more current than normal. Yeah, there are commercial tubes where color is normal, but in the case of a 5R4 that would indicate a partial short downstream from the rectifier.
If it were mine the next stop would be whatever checks I could do on the filter caps, bleeder resistor and anything else in the plate supply. I have a hunch there are electrolytics with balancing resistors in series across the HV, and one of them is shorted... A dead short would likely pop the fuse immediately so look at things in series with other things that would give a partial short.
It's also possible the new finals are so badly in need of neutralization they're oscillating, (?), but that would be a long shot.
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by AC0FA on November 6, 2009
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So it would appear I have replaced the bad 5R4 tube with another bad gassy 5R4 tube. I can replace and all will be well.
I suppose I should not attempt another voltage test.
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by AC0FA on November 6, 2009
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So one of the two 225 amp 50kv bleeder resistors cannot be removed without solid stating the 5R4?
It would appear the previous owner tried to pick up some more punch and another 100w on audio peaks.
By removing the top one. I supopose I should put it back in.
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by WA1RNE on November 6, 2009
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"I was following the procedure in the manual for checking the adjustment of the screen voltage transformer tap at the bottom of page 8 in the manual.
Removed the fuses from the HV transformer, In order to check the screen voltage at the 11pin socket found on the top of the original 200 power supply that is now bolted to the back of the 2000 supply.
I turned the pa plate control on and the transmitter power on the 5R4GY tube warmed up as usual. Then I saw a blue glow in the tube the elements in the tube turned orange then the fuse blew. When I replaced the fuse and tried again the same thing happened.
This hapened before I was able to get a voltage reading."
>>> The procedure on page 8 is used for setting the primary transformer tap for screen supply based on the expected input line voltage.
> The 5R4GY rectifier - V101 - is associated with the exciter's 6146 PLATE supply (800 volts dc)
*** It does NOT provide SCREEN voltage for the exciter or the PA.
> The 5U4 rectifer - V102 - provides plate voltage (300 vdc) for the 12BY7 Driver.
>>> So if the 5R4GY is gassy and/or overloading, you have a 6146 exciter plate supply issue. If the drive setting is too high you may be causing the 6146's to draw to much plate current.
** PLEASE ** - I don't know your background and don't mean to be condescending, but this transmitter is a complicated beast. You need to gain a better understanding of the transmitter before you get hurt or killed - or the transmitter suffers some catastrophic failure. (I'd rather the latter, obviously.)
You also alluded to the previous owner making some modifications:
"So one of the two 225 amp 50kv bleeder resistors cannot be removed without solid stating the 5R4? It would appear the previous owner tried to pick up some more punch and another 100w on audio peaks.
By removing the top one. I supopose I should put it back in."
More the reason for exercising caution and another good reason for seeking technical assistance from a fellow ham, engineer that can help you through this - not over the Internet.
...WA1RNE
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by W8JI on November 6, 2009
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A high vacuum rectifier like a 5R4 or any of the 5*4 family will glow BLUE while warming up into a short or a heavy overload.
It does not mean the tube is gassy just because you see the glow. It can be gas, but since it is followed by orange plates it is pretty obvious the tube is running into a short.
Time to unplug everything and check some HV resistances and look for a short.
Tom
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by WB2WIK on November 6, 2009
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I don't have the schematic to look at (although I also have not yet looked on BAMA) but there's something scary about this statement:
225 amp 50kv bleeder resistors
225 amp 50kv bleeder resistors???
Do you mean 225W 50K Ohm?
I'm not even sure what you mean, but if you believe there's such a thing as a 225 amp 50 kV resistor, you probably should not be fooling around with this power supply!
Do you have a local Boat Anchor expert?
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by AC0FA on November 6, 2009
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The bleeder resistor was a different thread. Sorry
Of course I will put it back in.
But as long as Steve has joined in,
Let me post the question. Why the heck would any one remove it?
R307 and R308 in the HV supply for the PL-l75a's
50k ohms 225w wouldn't you need them both?
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RE: VIKING INVADER 2000 POWER SUPPLY HELP
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by WB2WIK on November 7, 2009
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I don't know why anyone modifies anything. However 50K 225W is a hell of a big bleeder.
If the power supply was choke-input (maybe it is, I don't have the schematic), those require a lot of bleeder current to regulate properly. But if someone modified it to remove the choke, then you wouldn't need nearly as much bleeder current, just enough to discharge the filter capacitor(s) in a reasonable amount of time, like getting it down to a non-lethal level in 30 seconds or so.
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