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Old 19th December 2008, 03:44 PM   #1
skidave is offline skidave  United States
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Default Anyone Have a Hickok 800A

Need some help with a Hickok 800A. Anyone out there with the same model willing to help?

I am having trouble understanding some the test functions via the 1950's manual and I don't know if certain funtions work at all.

Mutual conductance test seems to 'read' values and it varies from tube to tube; so I am assuming it is measuring.

Thanks,

Dave
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Old 19th December 2008, 10:49 PM   #2
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I have a 600a that I use regularly (just used it a couple of hrs ago), so I may be able to help. They should be quite similar.

Here are a couple of links to useful Hickok manuals, tube data, etc.

http://bama.sbc.edu/hickok.htm

http://dynakam.com/arf_members_web/hickok_data.html

I use several different tube charts to cover all of the common audio tube settings, such as the foreign tube data and obsolete tube data. The only tube that's not in my tube data (that I need) is the 6550. I test them on the KT-88 settings for matching.
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Old 20th December 2008, 06:29 AM   #3
Colt45 is offline Colt45  Serbia
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set up the line voltage with the rheostat on the far left, and check it frequently when testing (P7, iirc), as it will change with fil load of bigger tubes.

mutual conductance / gm is what ya want.. "P4". if you dial in the numbers from the rollchart, the bias is important, but the "english" settings just scale the meter to good/bad instead of actual numbers... you can turn to one of the red dots if you prefer a real 0-3000umho or whatever scale.

remember to turn the knob on the far right? through all positions first, for short check. (or something like that.. it's been a while since i've used mine... better than a year probably, so hopefully i remember
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Old 20th December 2008, 02:47 PM   #4
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Quote:
Originally posted by Colt45
set up the line voltage with the rheostat on the far left, and check it frequently when testing (P7, iirc), as it will change with fil load of bigger tubes.

mutual conductance / gm is what ya want.. "P4". if you dial in the numbers from the rollchart, the bias is important, but the "english" settings just scale the meter to good/bad instead of actual numbers... you can turn to one of the red dots if you prefer a real 0-3000umho or whatever scale.

remember to turn the knob on the far right? through all positions first, for short check. (or something like that.. it's been a while since i've used mine... better than a year probably, so hopefully i remember

That pretty much sums it up....You can also check gas by setting the english dial to 73, press P5 and adjust the bias dial so that the meter reads 100 on the 3000 scale, then while holding P5 press P6 and check meter movement. If the needle moves less than 1 division, than the tube is good.

To check rectifiers (diodes), you press P3 after setting your dials; you are just checking emission, since there is no gm value for a rectifier.

Before inserting tubes, check that the filament voltage dial is set correctly to avoid overvoltaging your heaters.

The above applies to the 600a, but it should be the same for the 800a.

One more thing, as you move the far right switch from 1 to 5 to check for shorts (before going to tube test), if the shorts light illuminates on any of the 1-5 settings, do not continue to the "test" position, as you could damage the tester. That would indicate that the tube is shorted, and needs to be pitched.

The 600a has a switch in the lower right corner that in the "down" position is for testing large (octal, etc) tubes and in the up position for testing miniature tubes. It's the switch that says short/test.
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Old 22nd December 2008, 01:45 PM   #5
skidave is offline skidave  United States
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Thanks everyone. I had some time to test some old and new tubes I don't use any more. I used the calibration instructions I found on the web and everything seems to be with a relatively close tolerance (for the age and amount of use) for the tester. The various tubes I checked match the number for mutual conductance on the meter and rectifiers seem to check ok as well.

Here is a question that I don't understand...when I purchase tubes, the boxes have 'numbers' on them for matching purposes. The numbers for a pair of 12AU7s I have are 86 / 84 for one tube and 78 / 82 for the other. Where do the number references come from? Is this a calculated value? Or is this the number from another type of tester and they are used for reference on that particular tube tester only. Obviously, I know now my tester will work for matching...I'm just seeking more knowledge.

Thanks,

Dave
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Old 22nd December 2008, 02:24 PM   #6
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Quote:
Originally posted by skidave


Here is a question that I don't understand...when I purchase tubes, the boxes have 'numbers' on them for matching purposes. The numbers for a pair of 12AU7s I have are 86 / 84 for one tube and 78 / 82 for the other. Where do the number references come from? Is this a calculated value? Or is this the number from another type of tester and they are used for reference on that particular tube tester only. Obviously, I know now my tester will work for matching...I'm just seeking more knowledge.

Thanks,

Dave

I believe those numbers are from other testers, such as the military versions of the Hickoks; their meters do not read out micromhos directly, but on a quality scale of 0-120 (for the TV-7 tester and other Hickok TV series)
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Old 22nd December 2008, 02:30 PM   #7
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ALWAYS do the shorts test first!

The bias Pots in these cannot be replaced. they are a special control with a taper that no other MFG has ever made as far as my research has shown. A shorted tube can burn up a Bias pot quick. I cant remember of the 800 has a Bias bulb/fuse like most Hickoks, But that should only be a #49 bulb, other bulbs have a different current rating.
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