HP 651B Help, Manual, issues

Zero Cool · 21st May 2008, 01:01 AM

My Faithfull HP 651B oscillator seems to be having some problems of late with DC offset at the output. The signal still looks good, but with offset.

I first noticed this when testing a bunch of opamps that came from a mixer that got hit by lightning. I built up a breadboard and would notice that as i tested more and more i was noticing lots of DC offset from the opamp. I determined it was the oscillator that was the problem. short the output for a second and no more offset!!

SO, something has gone wrong in my 651B, maybe the caps are dying or a resistor has opened up or something. I need to find a manual. But thought i would ask if anyone has ever worked on one of these. if there are any tips or info.

Zc

Zero Cool · 21st May 2008, 01:43 PM

I managed to Buy a Service Manual CD from www.ArtekMedia.com

GREAT! guy! I emailed him stating i needed the manual right away and asked if i made an ebay purchase could he email me the PDF of the manual from the disc and send me the CD later on. Well he emailed me back and sent me the manual in PDF! straight out! Awesome!

I Sent him paypal for the CD plus a little extra for being so generous!

So looking at the service manual i see there is a big 1200uf capacitor at the output of the amplifier. The parts list just says 34D special and no other part information. 1200uf but no WV. I will have to open the unit up and take a look. I bet that cap is going bad.

Zc

21st May 2008, 01:01 AM	#1
Zero Cool Audio Junkie diyAudio Member Join Date: Sep 2004 Location: MN	HP 651B Help, Manual, issues My Faithfull HP 651B oscillator seems to be having some problems of late with DC offset at the output. The signal still looks good, but with offset. I first noticed this when testing a bunch of opamps that came from a mixer that got hit by lightning. I built up a breadboard and would notice that as i tested more and more i was noticing lots of DC offset from the opamp. I determined it was the oscillator that was the problem. short the output for a second and no more offset!! SO, something has gone wrong in my 651B, maybe the caps are dying or a resistor has opened up or something. I need to find a manual. But thought i would ask if anyone has ever worked on one of these. if there are any tips or info. Zc

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21st May 2008, 01:43 PM	#2
Zero Cool Audio Junkie diyAudio Member Join Date: Sep 2004 Location: MN	I managed to Buy a Service Manual CD from www.ArtekMedia.com GREAT! guy! I emailed him stating i needed the manual right away and asked if i made an ebay purchase could he email me the PDF of the manual from the disc and send me the CD later on. Well he emailed me back and sent me the manual in PDF! straight out! Awesome! I Sent him paypal for the CD plus a little extra for being so generous! So looking at the service manual i see there is a big 1200uf capacitor at the output of the amplifier. The parts list just says 34D special and no other part information. 1200uf but no WV. I will have to open the unit up and take a look. I bet that cap is going bad. Zc

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