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 Post subject: Can I use a SECO HC8 to measure audio tube cathode current?
PostPosted: Nov Thu 12, 2015 10:39 pm 
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Joined: Jul Sun 09, 2006 3:11 am
Posts: 6672
Location: Aurora, CO 80013
I'd like to plug it into the socket on my Hickok 752 or 605 to match audio tubes. I'd also like to test audio OP tubes in-circuit. If so, which test socket?


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 Post subject: Re: Can I use a SECO HC8 to measure audio tube cathode curre
PostPosted: Nov Fri 13, 2015 12:14 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 11060
Location: Latham NY 12110
You use the socket under the list of tubes. You pull it out and plug into the tester and tube goes into it. The only problem is the meter is for 300 ma which is nowhere near what the tube tester is going to provide. Maybe replace the meter with a 100 ma unit.


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 Post subject: Re: Can I use a SECO HC8 to measure audio tube cathode curre
PostPosted: Nov Fri 13, 2015 1:59 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 30698
Location: Pocasset, Cape Cod, MA
A couple of possibilities: a plug-in adapter with removable jumpers, or the octal adapter (I don't know who made it) with normally-closed spring contacts. You insert the current probe, made from double-sided printed-circuit board, which connects the meter.
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 Post subject: Re: Can I use a SECO HC8 to measure audio tube cathode curre
PostPosted: Nov Fri 13, 2015 7:16 pm 
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Joined: May Wed 06, 2009 7:01 pm
Posts: 854
Yes, you can measure audio tube cathode current with one of these, but as noted by Lou, the 300 mA scale is too large for what you want to do. Also, the meter in these is obviously not a precision piece. The cathode break for pin 8 is used for most audio tubes.

I use a pair of Seco HC-6 to do exactly what you want to do with yours. The HC-6 has a low quality meter also ranged to 300 mA. However, the HC-6 also has a pair of pin jacks for direct measurement of voltage across the meter and its shunt which allows more precise measurement for apple to apple comparisons.
Here's a previous ARF note on the HC-6
http://www.antiqueradios.com/forums/viewtopic.php?p=914649

You can add those pin jacks to the HC-8 (I did not see any in the picture) or a simple cathode break adapter with a 1 or 2 ohm resistor and a digital voltmeter will do what you want.

The BQ6, DQ6 tube series use pin 8 for cathode so that is the socket to use.

-- Rich


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