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Got a Tek 454A the other day and did a quick test. It turns out that the only way to see a trace on the screen is to hold down the “Beam Finder” switch. As soon as it was released, the trace was

Hi Barry, My comments are inline below. Ozan Noted. At -15.1V this test doesn't say much about Q8051 (output is not completely cut off even if Q8051 was fully on) but see the note below for

Mark, I have checked all the resistors. Thanks for your comments! I have a lot to consider at this point. Barry

Barry, Q7042 crosses to a 2N2219A. This is a 3W transistor. A bit of power is needed to drive the series pass. Your list of parts are small signal, not enough power in this case. That could be your

Ozan, I verified the terminals are NOT swapped! When I short across C-E of Q8051 the output voltage goes to -15.1. Q7042: E=-34.2 B=-34.2 C=-32.5 Is it possible that the replacement transistors

Hi Barry, By removing transistors and seeing +0.6V we confirmed power transistor is not responsible for the fault (at least not the -33V output issue). Voltage across R9041 is 0.672V, this turns on

Ozan, Many thanks for your help in this matter. Glad to learn as much as I can! I replaced all the transistors (except the pass transistor) and I still have -32.5 at the output. The voltages you

Jack, I do not know if the FETs are factory or not. The screwdriver adjustment for d-c balance is in the screen circuits which is likely not connected to anything in these adapters. That will cause

Thanks!

Thanks!

12BA6s are easy to find and their rating are close. Try them if 12AU6s are hard to find. Because there are four of the 12AU6s, it may be possible to use easy to get 6AU6s by rewiring the filament

Can anyone identify these parts I find in my 575 curve tracer. Is this a mod that tek made? The dc balance doesn’t adjust properly, and the dc adjust pots appear to have been replaced with

The following photos have been uploaded to the Pictures of substitute parts for the 12au6s in my 575 curve tracer ( /g/TekScopes/album?id=299641 ) photo album of the

Anita Abranovic <anita.abranovic@...> added the photo album Pictures of substitute parts for the 12au6s in my 575 curve tracer ( /g/TekScopes/album?id=299640 ) : Can

Anita Abranovic <anita.abranovic@...> added the photo album Pics of substitute parts for the 12au6s in my 575 curve tracer ( /g/TekScopes/album?id=299639 )

Barry Testing transistors out-of-circuit on a Tester is NOT a fail-safe diagnosis. I also have an Peak Atlas DCA, and many's the time that it showed a transistor OK, but under load in the circuit it

Mark, Replace the FET, maybe both. Also Q50 is rated at 12V. That could have gone bad due to the increase in voltage. Something like a KSP10BU that is 25V would replace Q50. Mark

Look at the FET specs, 30v PS overvolt may have damaged the FET. Definitely abnormal if it's hot. Check the FET current Jon

From memory, an '8.' on the 7-segment display often indicates the scope can't read the contents of NVRAM. Jared

Hello from central TX! I have a DC503 counter where it's difficult to get the input A level adjusted correctly. Connecting a scope at any point between the input JFET pair and the TTL logic, you can