Tektronix tektronix 7603 repair free download

File name tektronix_7603_repair.pdf

10th June FREE NOTES 2010 ON ELECTRONICS b y d o k t o r p y t a [ a t ] g m a i l . c o m Tektronix 7603 mainframe repair In today's episode I'm going to describe briefly the repair process of the TEK 7603. Fig.1 Tektronix 7603 in good physical shape but "dead" 10th June FREE NOTES 2010 ON ELECTRONICS b y d o k t o r p y t a [ a t ] g m a i l . c o m Symptoms: Completely NO reactions after powering the unit: no fan hum, no scale illumination, blanked CRT, "POWER ON" lamp on the front panel was off. Repair: After opening the housing it became obvious that I've bought option 01- the cheapest version without CRT readout and without the fan. So two problems off :). At the beginning I downloaded the service manual from the best website for test equipment enthusiasts - " http://bama.edebris.com/manuals/ ". It was found that the +5V and +15V voltages were missing, they even went 0,6V negative. I started tracking, which voltages in the power supply section are +15V dependent. I have disconnected supply cables from every board in the scope EXCLUDING the main board. Why? Because the main board provides all "SENSE" feedback connections and without these feedbacks most of the PSU circuits can't work properly. Please refer Fig.2 for details. Fig.2 +5V PSU schematic diagram 10th June FREE NOTES 2010 ON ELECTRONICS b y d o k t o r p y t a [ a t ] g m a i l . c o m As You can see, the +5V can't work until the +15V supply is provided. To ensure my thesis I connected external bench power supply set for 15V and 1A of current limit. The CRT turned on and the scope was brought back to life. It was a time to find the cause of +15V PSU failure. After few minutes of measuring few potentials the diagnosis was : Q931 fault (Fig.3). I found it's parameters on the web and the closest equivalent I had was BSX61 (fT doesn't matter in this circuit, voltage and current ratings are important). Fig.3 +15V PSU schematic diagram I checked everything once again and it worked stable and properly. All voltages coming out from the PSU unit had less than 2% tolerances, so I could go further with checking. I connected all boards' supply connectors back on their places. 10th June FREE NOTES 2010 ON ELECTRONICS b y d o k t o r p y t a [ a t ] g m a i l . c o m Than I used two TEK plug-ins I was sure to work fine: vertical amplifier 7A26 and time base 7T80. I also applied 1kHz 1V test signal to the vertical