Re: Grid Bias Adjustment on 475A
That and perhaps what he asserts is nonsense? The grid is most assuredly biased relative to the cathode on this, and probably any, CRT. -Chuck Harris Michael W. Lynch via groups.io wrote:
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Chuck Harris <cfharris@...>
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#175789
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2230 deja vu
Hello Many moons ago I saw a topic on here regarding the 2230 and a storage display problem and as far as I could tell it never reached a conclusion. Unfortunately it is the problem I have now...or
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Kevin
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#175788
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Peter Keller's Book Mailing Status
This morning I mailed 76 of Peter Keller's books. These went to 72 people in the USA who ordered Peter's book. At the request of our currently shorthanded post office staff I have been asked to wait
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Dennis Tillman W7pF
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#175787
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Re: Grid Bias Adjustment on 475A
David, This may be the source of confusion for those of us not as well versed in these issues. Regardless of your fine technical explanation, TEKTRONIX still calls R1375 "GRID BIAS" on the schematics.
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Michael W. Lynch
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#175786
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I also would be interested in a set of boards if they aren't too pricey. A source of the mechanical parts is plug-ins for the 5000 series scopes e.g. 5103, 5440, which use exactly the same form factor
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Mac Perkins
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#175785
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Re: Grid Bias Adjustment on 475A
" unable to get a visible spot on screen at the +15 V intensity level as indicated in the service manual. I had to crank the intensity up nearly to maximum, and then the trim pot (R1375) for grid bias
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David Campbell <k_8_b_y_p@...>
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#175784
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Re: Grid Bias Adjustment on 475A
Jeff, Can you measure the voltage drop across the diode? That is partially how I discovered the "bad" VR1374 on my 475. You should measure 82V across the diode. Here is my conversation with Chuck
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Michael W. Lynch
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#175783
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Re: SC-502 transistor
Why bother trying to find unobtainum parts when Tektronix specifies "official" modern/current production substitutes (see crossref document)?
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Ke-Fong Lin
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#175782
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Re: SC-502 transistor
Can't help you with data on those GE transistors but WB Parts seems to have has a pile of them in stock: https://www.wbparts.com/rfq/5961-01-048-5632.html They were used by the military and exist
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Thomas Garson
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#175781
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Re: SC-502 transistor
Hi Giovani, Look for the Tektronix part number in the service manual, it should be something like 151-0426-00. Then use the semiconductor cross reference (big PDF file):
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Ke-Fong Lin
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#175780
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font/typeface for Tektronix binder spines - was Re: [TekScopes] Push button font
Turns out I have considered something suitable for binder spines before: View/Reply Online (#146250): /g/TekScopes/message/146250 I also took a shot of my own shelf with some sample
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toby@...
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#175779
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Re: SC-502 transistor
From Tek specs, it's a D44H11 NPN, currently available from STMicroelectronics, OnSemi, etc. at price of approx. 90 eurocents each Icmax = 10 A Bvceo = 80V hFE 60 @ Ic = 2 A Vcesat = 1 V ft min = 50
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unclebanjoman
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#175778
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11801C T2325 error diagnostic repair
Can anyone shed light on what is involved in repairing a unit showing that error? Thanks, Reg
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Reginald Beardsley
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#175777
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Ah yes, the switch is physically constructed as two gangs of 12 contacts, with two oppositely opposed wipers per gang. You can insert some pins to physically limit rotation so the two wipers never
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Jared Cabot
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#175776
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Re: A question from the unwashed relative to: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Thank you Harvey! That is pretty much what I had surmised but I was not sure. So, I have three function generators and a few DMM etc... My RTB also has a generator and frequency counter and more.
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Lawrance A. Schneider
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#175775
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
I also would be interested in a set Stan
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Stan Corbett
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#175774
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SC-502 transistor
HNY to everybody! In my SC-502 scope transistor Q855 died. It is a GE X44HR242 in TO220 case, but I was unable to get its specifications in order to find a suitable substitute. Thanks for your help
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Giovanni IZ5PQT
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#175773
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
ADT name to the list as well, please.
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Stephen
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#175772
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Hi all, I'll add my name to the list as well. You have to grab these things as they go by! Cheers Phil / W1PJE
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W1PJE
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#175771
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Re: I built a TM500 mainframe tester, and updated the design. Someone might find this useful?
Jared, Your manual lists S3 as 4P6T. Entering that part number in Digikey shows it as 2P6T. Is there a typo somewhere?
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Steve Goldstein
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#175770
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