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 Post subject: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Sun 16, 2019 3:03 pm 
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Joined: Nov Thu 08, 2007 10:44 pm
Posts: 103
I received my tester back after being modified by Roger Kennedy with a new meter and solid state replacements for the 5Y3 and 83 tubes. This requires using a Variac at 93-94 volts. I obtained one; it has a dial that reads in imprecise increments, i.e., 91 then 104; 93-94 volts lies just a scootch beyond the 91 mark; the volt meter on the unit is more imprecise than the dial.

My problem is: if I adjust the Variac at 93 volts when I first turn on the tester the meter needle jumps beyond the line test point. So it is not possible to run 93 or 94 volts into the unit and have the needle at line test.

If I lower the voltage on the Variac to bring the needle to line test my readings are lower than if I used 93 volts and ignored the meter being to the right of line test. For example, I tested a known good 6BQ7A tube. Lowering the incoming voltage to bring the needle to line test the tube read 5000 M/hos; testing at 93 volts it read 6000 M/hos, which you would expect for this tube.

So how do I accurately use this tester? Is there something that I can measure the current coming from the Variac?

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Sun 16, 2019 3:42 pm 
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Joined: Jan Thu 24, 2019 1:22 pm
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Location: Centennial, Colorado 80122
Its likely Roger intended for the variac to be set at 92-93 VAC, then adjust the 6000 to line adjust on the meter.

He is trying to minimize the increased voltage drop across the line adjust rheostat that occurs when you remove the transformer filament load of the two rectifier tubes by going to solid state.

I have always questioned converting Hickok's to solid state unless they have internal metering like the 539B/C models for this very reason. Even on my 539B/C conversions with metering I load the filament winding's of the transformer at 50% of the tube load.


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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Mon 17, 2019 3:38 am 
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Joined: Nov Thu 08, 2007 10:44 pm
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I get what you’re saying. But I set the Variac then turn on the Hickok. The instant the tester turns on the meter needle goes crazy going way past line set. No way in hell to bring the needle back to line test using the tester without lowering the input vintage on the Variac.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Mon 17, 2019 6:07 am 
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Joined: Aug Wed 31, 2011 11:23 pm
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Location: Tucson, AZ
This was a common problem with most Hickok SS replacements that do not use a zener to drop the voltage to the appropriate range that would be at the tube tester line set. By reducing the operating voltage to anything less than the line set (100V) it brings down all the other working voltages including the filament and bias. Not a good working solution in my book, in particular because you have no adjustment/reading of bias voltage. Getting the correct working voltages at the line set/designed working voltage of the unit is key to good results. I also found that the impact of loading the transformer for the absence of the tube filaments did not have a significant impact in the accuracy (tube readings and operating voltages) of the different tube testers I looked at when I came up with this design. That being said, there may need to be some adjustments of the zener voltage for some Hickok models.

I find it all a bit ironic as All Tube Testers white paper on this subject talks about the importance of maintaining the proper operating voltages according to the line set.


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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Mon 17, 2019 11:07 am 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
rivieraranch wrote:
I get what you’re saying. But I set the Variac then turn on the Hickok. The instant the tester turns on the meter needle goes crazy going way past line set. No way in hell to bring the needle back to line test using the tester without lowering the input vintage on the Variac.


I would start by verifying that the output of your external variac is what you think it is. Don't trust the built in meter, use a calibrated volt meter and set the external variac for nominally 100 volts for starters. See if that allows your zero set on the Hickok to be within range, or close. Then you can experiment with the external settings.

As a test set your external variac for say 90 volts, turn on the tube tester, let it stabilize, and then bring your external variac up to 100 volts or whatever makes the Hickok read properly on the zero set meter. That's the one you really care about.

Wild needle swinging is not normal, but may be a function of the external variac. Tough to tell from here. Might want to put a DVM across the variac output and see what happens when you turn on the Hickok.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Mon 17, 2019 12:07 pm 
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Joined: Jun Fri 19, 2009 6:34 pm
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Location: Long Island
What am I not getting here? I don't mean to disparage somebody else's equipment, but the Hickok 6000/A is a very simple, basic mutual conductance tube tester that was designed for field service work. There are plenty of circuits for solid state 83 replacements which include Zener diodes and resistors online that are reported to work well in them without any other modifications. This is not a Hickok 539C and no matter what anybody does to it, it never will be. If it came to me, I'd put it back to original configuration--minus the variac.

A lot of people think mutual conductance and transconductance are the same thing, but there is a subtle difference when it comes to tube testers. In a mutual conductance tester, only the first grid is "tested" with the other grids connected to the plate, so all tubes are effectively tested as triodes. But in tubes with more than one grid, each electrode influences the transconductance, so if one wants to measure that, all the grids need to be connected to appropriate (e.g. adjustable) voltages. A mutual conductance tester is simpler, lower cost, and smaller, but the compromise is that you only see the effect of the first grid on the plate current, so there is a small loss of precision and the numbers have to be "fudged" to a certain extent.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 2:28 pm 
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Joined: Nov Thu 08, 2007 10:44 pm
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Obtained multimeter and, well damn! What do you know? The actual voltage is 94 when the Variac's dial reads 78! So the Hickok is easily brought to line test.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 2:54 pm 
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rivieraranch wrote:
Obtained multimeter and, well damn! What do you know? The actual voltage is 94 when the Variac's dial reads 78! So the Hickok is easily brought to line test.

What's the maximum number on the dial of the Variac? 120? Perhaps it's wired for 0-140 volt output but has the wrong dial scale. What's the maximum measured output of your Variac?

(78/120) * 140 = 91

Sometimes the dial scale has 0-120 on one side and 0-140 on the other, to accommodate either way of wiring the Variac.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 3:44 pm 
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Joined: Nov Thu 08, 2007 10:44 pm
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A Chinese made unit with a scale of 0-130

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 5:02 pm 
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rivieraranch wrote:
A Chinese made unit with a scale of 0-130

Yikes! So the max output should be about (130/78) * 94 = 156.7 volts! Best to use a DMM to measure the output voltage on that thing. Be careful not to turn it up too high.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 5:44 pm 
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Joined: Nov Thu 08, 2007 10:44 pm
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Roger.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 6:01 pm 
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Joined: Jan Thu 24, 2019 1:22 pm
Posts: 139
Location: Centennial, Colorado 80122
That confirms that Simpson still makes great analog meter movements, since that is what Roger Kennedy uses. Best to install a couple of pin jacks on the variac housing to monitor the AC output with a digital multimeter any time the 6000 is used.


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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 6:34 pm 
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Joined: Nov Thu 08, 2007 10:44 pm
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I just loosen the plug going into the variac and carefully meter the prongs.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 7:51 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
Quote:
I just loosen the plug going into the variac and carefully meter the prongs.

..........we're gonna miss ya ....... ::plays taps on the harmonica::::

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 8:41 pm 
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Joined: Aug Wed 31, 2011 11:23 pm
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Location: Tucson, AZ
You really do not care what your measure coming out of the variac, you just set the rheostat on the tube tester deck to 100 (full on) and then use the variac to bring the line voltage up until the tube tester meter is to the set line. This assume that the meter line is accurate, if you were told that the line voltage needed to be a certain voltage, then get an inexpensive digital meter that is self powered off the AC to set that voltage. The scales on variacs are a rough approximation and the scale output changes based on if the you have a high low voltage switch for different taps/voltages out.

If you had tube rectifiers and turned up the voltage to 150+ volts you probably would have cooked them, and maybe something else.


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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 10:53 pm 
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Why are you using a variac with the 6000?
No need for that, wasn't designed to require one. 1000's were made and worked correctly without a Variac. Why over complicate it so much?
Does it have the correct line set rheostat in it.

edit: Yes I see where Roger Kennedy messed with it. Sounds like he screwed it up

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 10:57 pm 
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Is this like replacing the starter in your car with the furnace blower motor and having to plug it to AC to start it. LOL

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Tue 18, 2019 11:06 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
The idea behind using an external variac is just to reduce some heat in the case, since today's line voltages are higher than when the 6000 was designed, the internal variac has to work harder (drops more voltage). Does it "need" to be done this way? Probably not, but it does keep the thing a bit cooler with minimal fuss........Once one understands how it works and uses it properly.

Since my bench at the shop is almost 100% vintage equipment (or switching supplies in the newer stuff) I just put one of those Chineseium Red Variacs on the entire bench and dropped it about 9 volts if memory serves. (yes, my line voltage there is high even by today's standards, again from memory, somewhere around 124V). I picked up a CVT for almost nothing at one Estes auction, so one day I'll play with that perhaps, but the variac seems to be doing the job plenty well.

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Wed 19, 2019 4:06 pm 
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going to solid state on the 83 and 5Y3 reduces the heat dramatically right?

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 Post subject: Re: Using Solid State Modified Hickok 6000 with Variac
PostPosted: Jun Wed 19, 2019 4:54 pm 
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Joined: Nov Wed 30, 2016 7:35 pm
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Location: Sunbury, Ohio 43074
reduces heat, yes. dramatically? I'd not use a word that serious. Also introduces any number of possible other issues if one is not aware, and can recalibrate the tester.

I have chosen to keep the tubes in mine. Works fine that way, lasts forever. Why mess with it?

ymmv.........

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