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Old 27th Oct 2018, 10:00 pm   #21
factory
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Default Re: HP 180A Oscilloscope - reviving and resurrection

This scan of the manual for the Navy (AN/USM-281A) version of the 180A looks much better than the one from Agilent.

Volume one;

http://www.virhistory.com/navy/manua...9-125-0110.pdf

Volume two;

http://www.virhistory.com/navy/manua...9-125-0120.pdf

Hope this helps.

David
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Old 28th Oct 2018, 8:25 am   #22
Diabolical Artificer
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Default Re: HP 180A Oscilloscope - reviving and resurrection

So the primary's sound ok, what about the secondary, do both winding's have continuity? A quick "buzz" test is sufficient most times, IE diode test, if not do a DC resistance test as on the primary.

Do you know if the oscillator is working? If you haven't a scope you could check to see if you have AC with your meter. Check if the AC is present on the secondary with the leads unconnected. Make sure your meter has enough of a voltage range though. to reduce the voltage on the meter check each secondary independently.

Whilst the secondary is unconnected check the following circuitry's resistance. Also check you have good ground connection's.

Andy.
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Old 28th Oct 2018, 8:35 am   #23
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Default Re: HP 180A Oscilloscope - reviving and resurrection

But use an analogue meter to measure the oscillator output. A DVM seems to have so much leakage capacitance across the range switch that the whole few hundred volts goes straight into the ADC. I blew up my first DVM, expensive in those days, by doing this.
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Old 29th Oct 2018, 8:21 pm   #24
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Default Re: HP 180A Oscilloscope - reviving and resurrection

Thank you very much! I´ll have look. Expecting a delivery of some components yesterday so fingers crossed.
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Old 30th Oct 2018, 8:45 pm   #25
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Default Re: HP 180A Oscilloscope - reviving and resurrection

I did some final measurements and observations today. I replaced the oscillator transistor and to my amazement I was able to get a faint hissing sound from the HV transformer. There is some voltage present on the secondary part. It is out of scope for my meter but it is there. On the other hand, there is no significant voltage present behind the voltage multiplier at the HV suction cup. Just some 923V or so. The device is now packed and I have it in my storage since I need to go on with my life But still... I wonder....
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Old 31st Oct 2018, 7:20 am   #26
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Default Re: HP 180A Oscilloscope - reviving and resurrection

It needs proper investigation, swapping parts will only get you so far, and could make things worse. So, EHT tfmr probably ok but something further down the chain is pulling EHT down, hence my advice to check resistance and ground/s.

"The device is now packed and I have it in my storage since I need to go on with my life" I kind of understand where your coming from, but I'm like a terrier, once I get into a problem I like to solve it, only my my knowledge level lets me down. Hopefully one day you'll have another look once your a bit more savvy.

Andy.
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