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Author Topic: Heathkit Warrior HV problem  (Read 11324 times)
KF4SNJ
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« on: October 04, 2010, 11:21:22 AM »

Hello All,

I recently replaced the HV transformer in my old Warrior with a new one from Harbach (Peter Dahl). The original one went up in smoke. It pegged the meter on the front of the amplifier so I thought maybe it was the solid state rectifiers. I replaced them as well with the Taylor upgrade for 866's from RF parts. It still pegs the HV meter and I'm out of ideas. Anyone have any idea of what may cause this problem?

Thanks,

Ron
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K2DC
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« Reply #1 on: October 04, 2010, 01:41:46 PM »

If you're comfortable with it I would (VERY carefully) check the plate voltage with a meter directly on the plates with the covers off.  That step is not for the inexperienced or the faint of heart - there can be LETHAL voltages involved.  If the plate voltage looks good then, powered down and sure that the caps have bled off, check the resistors in the meter circuit.  It sounds like it could be a meter circuit problem.  But if you've never done it before, get help before you even think about it.

GL & 73,

Don, K2DC



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KF4SNJ
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« Reply #2 on: October 04, 2010, 08:55:15 PM »

Thank you for your reply, Don. I have questioned the accuracy of the HV meter on the front of the amplifier as well. I don't have a meter that will test HV but I know someone who does. I was thinking of just replacing the meter resistor anyway, without checking the HV. All it takes is a .45 cent resistor so not much lost there if I'm wrong!


73's
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G3RZP
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« Reply #3 on: October 05, 2010, 10:39:13 AM »

Just make sure the resistor is rated for the voltage it will get across it.
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KC8VWM
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« Reply #4 on: October 05, 2010, 11:54:48 AM »

Something tells me you have an open resistor elsewhere in the amplifier which is causing the meter to peg.
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PA3GOS
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« Reply #5 on: October 08, 2010, 03:55:56 PM »

I don't have that specific schematic at hand but like KC8VWM says, it is likely that there is also a resistor to ground.
This makes a voltage divider to which the meter is connected in the HV meter-setting.
Check that resistor and/or replace it. It's very likely, conciddering your problem, that that resistor is an open circuit or has come loose.

Good luck and we'll hope to hear the outcome,

Tjalling PA3GOS.
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K4DPK
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« Reply #6 on: October 08, 2010, 09:01:32 PM »

Are you certain the meter is reading voltage when it pegs, and not in the current position?

Phil C. Sr.
k4dpk
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PA3GOS
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« Reply #7 on: October 09, 2010, 01:59:08 AM »

Phil's question made me think...

Ron, do you have any idea why the original transformer went up in smoke?
If a dead short caused it, it may well be that the shunt resistor (for measuring current) is open now, thereby protecting the transformer but a danger to the meter.
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W8JI
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« Reply #8 on: October 10, 2010, 02:04:28 PM »

Hello All,

I recently replaced the HV transformer in my old Warrior with a new one from Harbach (Peter Dahl). The original one went up in smoke. It pegged the meter on the front of the amplifier so I thought maybe it was the solid state rectifiers. I replaced them as well with the Taylor upgrade for 866's from RF parts. It still pegs the HV meter and I'm out of ideas. Anyone have any idea of what may cause this problem?

Thanks,

Ron

The Warrior has a choke input power supply. A choke input supply runs at .9 times secondary RMS voltage when properly loaded by a bleeder resistor.

You should have an 1800 volt transformer each side of center tap. If the bleeder resistor opens, the HV will go from around 1600 volts to 2500 volts. The thing is though the metering system works from that bleeder, so if it opens the HV meter reads zero!!! The bleeder never goes down in value. So any resistors causing the HV meter to be off would be the three 4.7 ohm resistors in parallel that go from the bleeder to ground.

Measure the ground end of the bleeder and it should be about 1.5 ohms. If it is higher than 1.5 ohms, the 4.7 ohm resistors are the problem.

The LAST thing on earth you ever want to do is measure that voltage with a handheld or bench meter of any type unless you have a special HV multiplier probe that is safe and you totally know what you are doing. You would be far better off to test the big 60k 100 watt resistor like I suggested!!!

Maybe you have another problem like Phil suggested, and it isn't the HV too high.

73 Tom
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KF4SNJ
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« Reply #9 on: October 23, 2010, 09:12:08 AM »

Thank you to everyone who responded! Armed with some GOOD ideas in hand I hope to lift once (hernia) and repair the old Warrior. Grin Grin
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W4VR
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« Reply #10 on: October 23, 2010, 09:22:08 AM »

Ron, I had the same problem many years ago with a Warrior amplifier.  I replaced the transformer, the rectifiers, the filter capacitors, and the bleeder resistor.  It worked fine after that.
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WB4IUY
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« Reply #11 on: October 24, 2010, 11:16:24 AM »

Please reports back with the problem, once found. Good info and suggestions here.

Dave WB4IUY
www.WB4IUY.net
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Dave WB4IUY
www.WB4IUY.net
G3RZP
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« Reply #12 on: October 25, 2010, 03:39:34 AM »

Tom said

>The LAST thing on earth you ever want to do is measure that voltage with a handheld or bench meter of any type unless you have a special HV multiplier probe that is safe and you totally know what you are doing.<

I have a hand held HV probe, rated to 40kV DC for a DVM, and with lots of insulating discs between the business end and the handle. I do not use it as hand held probe - it gets attached before power is applied. The DVM is placed on an insulated sheet and not touched - even though it ought to be safe on the bench and the probe used as hand held!
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G3RZP
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« Reply #13 on: October 25, 2010, 01:00:15 PM »

Tom said

>The LAST thing on earth you ever want to do is measure that voltage with a handheld or bench meter of any type unless you have a special HV multiplier probe that is safe and you totally know what you are doing.<

I should have added that if you do NOT follow his advice, it is very likely that it WILL be the last thing you on earth!
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KF4SNJ
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« Reply #14 on: March 31, 2011, 02:27:08 PM »

Well, five months later the Warrior is repaired Grin. The problem was the shunt resistor and the bleeder resistor. Works fine now.
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