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Old 21st Sep 2021, 9:24 pm   #1
mongoose1951
Diode
 
Join Date: Sep 2021
Location: Stuttgart, Germany.
Posts: 1
Default HP8640B Problem

Just moved to Europe from USA. Changed the power setting for my HP8640B to 240V. Initially tested fine generating an 10 MHz signal.
After few minutes there was a loud pop and smoke from lower left front.

10 MHz signal was still on the output and display was normal.

I shutdown and inspected, no visible issues noted.

Have not done a complete check yet.

Any ideas? Did it not like European voltage? Did it get damaged in shipment? Did an old capacitor fail? odd that after such a spectacular incident (here was a lot of smoke), it still worked.

I like my 8640B, suggestions will be appreciated.

Ron
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Old 21st Sep 2021, 9:38 pm   #2
Keith956
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Location: Oxfordshire
Posts: 719
Default Re: HP8640B Problem

I don't know if the 8640B has a Rifa cap like many other HP instruments, if so that would be the first thing to suspect. Look around the AC mains input socket/switch area for a yellow-gold coloured capacitor between live and neutral.

They are often OK for years on 110V but when you change the voltage settings to 240V for european operation, they go bang (been there, done it
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Old 21st Sep 2021, 9:46 pm   #3
factory
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Join Date: Jul 2009
Location: Cheshire, UK.
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Default Re: HP8640B Problem

My mid 1980's 8640B has a dead metalized paper RIFA capacitor near the mains input on the back, could the smoke coming from the front because of the cooling fan?
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David
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