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Old test gear

6/4/1999 2:50 PM
Old test gear
I've just gained possesion of some old tektronix test gear. It's one rackmountable unit containing a type 160A power supply, a type 162 waveform generator, a type 161 pulse generator and a type 360 indicator.  
I'm loving the old stuff!  
My only problem is that the oscope section only works for 5-15 minutes and then the trace dissapears. If I turn it off and let it cool, the trace will return.  
Is there anyone out there with any info on this unit or any resources I could access in an attempt to repair it? I'd hate to junk it. The tubes are just too cool.  
6/5/1999 8:07 AM

Don't have specifics but there are few circuits within the scope you might check.  
1) If you have a meter capable of measuring about 1.5kv, you could check the 'scope's anode voltage - if you can't measure voltages this high you could make a voltage divider, 10x, to use with your meter. You can monitor the voltage at the power supply - often 'scopes used a hv supply with the anode grounded and a cathode that is at high negative voltage to ground. If this is a tube scope, replace the rectifiers as a start.  
2) If you 'scope has a blanking circuit, check for a bad resistor, capacitor, or connection that opens after heating.  
3) Check the connections/components in the "intensity" control circuit. Send me the specific CRT number and I'll let you know which socket pin to monitor.  
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6/6/1999 4:45 AM
Paul Perry

I had a big blue 'boatanchor' tek with this symptom, it was due to leakage in the EHT transformer loading the voltage down, people get around it by removing the EHT rectifier valve and replacing with a solid state EHT rectifier, so the filament current is no longer required.
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