My apologies - - Re: Thanks but...

Posted by ruffscruff (A) on September 2, 2005 at 10:00:15

In Reply to: Thanks but... posted by anumber1 on September 1, 2005 at 15:36:29:

Hi - I have to apologize for giving out info that I didn't know first hand or somehow verified myself - I don't usually do that. Especially since there might be someone reading it and taking it as being correct which they should be able to do from what we post here.

In any case, I'm not sure where I read that the settings were the same for 600 and 6000 but glad you posted to correct that they're not.

At the time I had even seen it in more than one place, but had no way to verify any of it so "assumed" myself that it was correct.

Something else I remember reading (and probably won't help you any) is that the charts probably weren't updated as often as they should have been. In particular, some of the tester companies were just going out of production around the time the 6DJ8 family of tubes was coming to the market. They had a lot of trouble in coming up with the settings making it difficult to this day to test that family and get accurate and/or consistent readings on the Hickoks. Again - I can't verify this.

Someone suggested to me to adjust the bias setting for a known 6DJ8 until I got the correct nominal gm reading. Since I know very little about tester circuitry or testing for that matter - I found that changing the bias only a little made a huge difference in the nominal gm number.

And the last thing I can't verify is that when they made the chart settings it was done in a "backward" fashion. That is - they knew the tube design specs and made then "made up" the settings that would give the desired gm reading. I'm not sure I believe they did this, but I guess certain parts make sense because each tester manufacture had to come up with a way to get a nominal 1250 gm reading for a 12AX7 for example. So they did what they had to do to get there.

Lastly - I play a lot at ebay and just did a search for 7591 and came up with a hit for an Eico tester (link below). You might not need another tester and I really don't know anything about this one except they specifically mention that it has settings for the 7591 and 6550 so it might be a later model than the Hickoks. I don't know the seller and not really pushing the product, but I do remember spending over $2,000 for tubes when trying to retube a couple of preamps I was interested in and more then half of them were not up to spec. So for another $200 "buy-it-now investment" it might be worth looking into. Then you can test on two different testers to verify constancy??

Yet another reason I'm so happy I love the SP-3C sound so much. You know it has eight 12AX7 and since they're all the same that works for me! Those 6DJ8/6922 were drivng me nuts!

Thanks for your posting and I'll try to stick with my past tradition and not post anything I don't know first hand!

"Scruffy Fran says the truth is out there" ARC SP-3C, ARC D400MKII, Tympani 1D, Creek CD50MK2

http://cgi.ebay.com/Eico-628-Tube-Tester-for-guitar-amp-hifi-radio_W0QQitemZ7543278540QQcategoryZ25422QQssPageNameZWDVWQQrdZ1QQcmdZViewItem (Open in New Window)

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Kimber Kable

Follow Ups Full Thread

Topic - Tube tester settings - anumber1 07:35:22 09/01/05 (4)

Re: Tube tester settings - Hodges 23:10:40 09/01/05 (0)

Site with tester settings - - Re: Tube tester settings - ruffscruff 15:00:30 09/01/05 (2)

Thanks but... - anumber1 15:36:29 09/01/05 (1)

My apologies - - Re: Thanks but... - ruffscruff 10:00:15 09/02/05 (0)

Follow Ups

My apologies - - Re: Thanks but... - ruffscruff 10:00:15 09/02/05 (0)

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