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 Post subject: Eico 625 tube tester quetion
PostPosted: Dec Sun 20, 2009 6:10 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 86
Hello,
I just bought a eico model 625 tube tester and the guy i bought it from said that the model 625 testers don't need to be calibrated. He said to change the 6H6 tube, resistors and cap up to specs and it will work like new. For the price I paid for it, I took the chance not knowing a whole lot about tube testers in general. And for the amount of times I'll probably use it, I think it was worth the chance. But still i want to have it right so does anyone know about the eico 625 and if what guy told me was was right.
thank you


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 Post subject:
PostPosted: Dec Sun 20, 2009 6:44 pm 
Member

Joined: Feb Fri 13, 2009 5:09 am
Posts: 350
Location: Santa Clara, CA
Are there any pots inside? If so, you can be sure there is some adjustment that can be made. Download the manual and see. I don't know about the 625, but on the 666 there was a calibration procedure. Since these Eicos were mostly kits, the calibration was usually pretty simple and did not require specialized instruments or precision standards. The procedure was usually at the end of the assembly instructions. Get your manual (and supplement) here:

http://bama.edebris.com/manuals/eico/

Also, see if there are updated chart settings, there were many updates and corrections for the 666 ("Satan's Choice"!).

--Bob


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 Post subject:
PostPosted: Dec Sun 20, 2009 7:06 pm 
Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 34328
Location: Sandpoint, IDAHO 83864
This topic would attract more responses if it were in the Test Equipment form, so I will move it there, but I will leave a shadow so it will get double exposure for a while.
Curt

_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!


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 Post subject:
PostPosted: Dec Sun 20, 2009 8:38 pm 
New Member

Joined: Aug Fri 14, 2009 5:05 am
Posts: 10
Location: Dallas
Carmine,
The Eico 625 shares its design with a few other testers to include the Knight 600 series, which I have. In my research for the Knight I found this page, http://tubesound.com/2008/05/31/knight-600-tube-tester/ which outlines the calibration for the Knight testers. It may be applicable to your Eico.

I have an operations manual for the 625 that I got from the BAMA site but it doesn't mention anything about calibration. There's oodles of stuff out there for the 625 which you should be able to find with a little perseverance.

FYI: A tube data book for the Eico 625, dated 1978, is posted on the Archives page of this site.

Good luck.


Paul


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 Post subject:
PostPosted: Dec Sun 20, 2009 8:42 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 86
Thank you guys I am going to take your recommendations.


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 Post subject:
PostPosted: Dec Tue 22, 2009 12:07 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1512
Location: Oswego, NY, USA
Carmine,
In addition to the above information, there was also a calibration sequence published in the original Triplett 3413 parts list & diagram, giving the sequence of resistors to check and change out to obtain the general merit/value readings you want (based on your average, known good tubes). This would get done after you checked every resistor and other components for tolerances and condition. The TTT3413 and your tester are basically the same, except for the 6H6 instead of the copper oxide (meter-grade) rectifier. I could attach the Triplett diagram with the explanation in an email, but your ARF profile doesn't list your email. Most people say that these emission testers don't need calibration other than checking parts tolerances, but you can calibrate each range with this procedure...if you wanted to do that. I don't know why Eico, Heath, and Knight didn't bother to re-publish the original Triplett calibration sequence; maybe they didn't want to include a bunch of extra cal resistors or three extra trimpots in their kits.

Fred


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 Post subject:
PostPosted: Dec Tue 22, 2009 12:30 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 86
Thanks Fred i would appreciate the info my email is TVCARM@AOL.COM The booklet that came with the tester so i am in the process of changing resistors, cap and tube. So any additional for calibration info would be appreciated. Thank you very much.
Carmine


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 Post subject:
PostPosted: Dec Tue 22, 2009 4:19 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 1512
Location: Oswego, NY, USA
Carmine,

I will try emailing to you the original Triplett 3413 pages that show the "selection" (AKA calibrating) resistors for the Line Regulation and the three range resistors. When you go to compare the Eico 625 circuit diagram to the Triplett 3413 diagram, you will notice that the Eico's R6 is the equivalent calibration resistor which can be altered to adjust the Line Regulation (which makes the applied filament-heater voltages correct when the meter's reading is at "LINE" mid-scale). R2 is the calibration resistor to fine adjust Range 1; R5 can be changed to adjust Range 2; R4 can be changed to adjust Range 3; then Range 4 should be acceptable as long as R1 (the 7 to 10W-rated 2.5K Ohm resistor) is good. It is possible that if all your tester's resistors are within tolerance, the meter's response is good (1ma/~50mv), and the 6H6 is good/stable, you may not need to change any of these "calibration" resistors....and I think alot of it depends on how picky you are & which tubes you decide to use for calibrating the ranges. Triplett (according to the engineering sheets) used "bogeys" (special labelled RMA or mfgr-supplied tubes with listed test values), which are now pretty much extinct.

Fred


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