Tektronix 465m - bad LV power supply?

gabeschine wrote in news: snipped-for-privacy@i13g2000prf.googlegroups.com:

well,first check to see if any internal fuses are open,the 32 unreg has a fuse. it could be bad electrolytics;they dry out with age or their ESR rises and the raw,unregulated supplies are not high enough for the regulators to work.

TEK PS supplies all reference to one supply,and use pullups so if one supply dies,they all go out.

HV multipliers are prone to fail,too;that's the black box with a heavy red lead that goes to the front of the CRT.

Google for BAMA and download a service manual for the scope so you will have schematics to work from.

innews: snipped-for-privacy@i13g2000prf.googlegroups.com:

Thanks - got the schematics. Tested all the fuses I could find (4 of them) and they all check out.

Your ref to the PS - does this mean that if the PS dies, I would see anything from the Scale Illum. feature? That's the only part of the scope that still works when power is on.

Now I need to go and learn what everything you said means :). Thanks again

gabeschine wrote in news: snipped-for-privacy@l22g2000prc.googlegroups.com:

I hope you got the circuit descriptions,its VERY handy in learning about how your scope's circuits work.A great aid in troubleshooting. TEK used to write very good circuit descriptions for their instruments.Not anymore.

One more thing,TEK regulated power supplies often use "foldback" current limiting;where when one supply gets overloaded,it *shuts down* that supply instead of simply limiting it's current output. Since that supply may be used in some of the other regulated supplies,they ALL drop in voltage.

innews: snipped-for-privacy@l22g2000prc.googlegroups.com:

...

The manual can be downloaded from this site:

Circuit Descriptions should be in this file, AFAIR.

hth, Andreas