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Products => Test Equipment => Topic started by: eccoblackfin on May 04, 2015, 08:56:29 pm

Title: New Simpson 422 and HP Oscilloscope
Post by: eccoblackfin on May 04, 2015, 08:56:29 pm
Hello all!  This is my first post to the forum, and I've got a few questions on my equipment.  First off, I have a Simpson 422 function/sweep generator, and it works beautifully.  Almost.  The square waves are near-perfect, as are the triangle waves, and the sine waves are..well, they're also triangle waves.  Where do I start with this?  My gut feeling is a leaky/bad filter cap somewhere, but I have only little experience in these things(I bought it to help do the labs for class).  I've had utterly no luck finding a repair manual, or even a schematic, anywhere(anyone here have one handy?).  I can provide a picture tomorrow, if necessary.

And my HP 54200A oscilloscope.  This thing is also near perfect..although the fan is quite noisy.  The other issue is that it won't turn on unless grounded..and if ungrounded, it leaves you with a pretty nasty shock.  Any ideas on where to look for this ground fault?
Thank you much for your help, everyone.
Title: Re: New Simpson 422 and HP Oscilloscope
Post by: barry14 on May 04, 2015, 09:28:23 pm
The Simpson 260 site, simpson260.com, has a schematic of the Model 420 Function Generator which may be helpful.
Title: Re: New Simpson 422 and HP Oscilloscope
Post by: dom0 on May 04, 2015, 09:30:22 pm
and the sine waves are..well, they're also triangle waves.  Where do I start with this?  My gut feeling is a leaky/bad filter cap somewhere, but I have only little experience in these things(I bought it to help do the labs for class).

There will be a network of some resistors and diodes (a sine shaper), it's probably broken one way or another.

Or maybe just the switch for waveform selection is stuck, dirty, ...

And my HP 54200A oscilloscope.  This thing is also near perfect..although the fan is quite noisy.  The other issue is that it won't turn on unless grounded..and if ungrounded, it leaves you with a pretty nasty shock.  Any ideas on where to look for this ground fault?

See the manual of the device ; it must be operated with grounded sockets only. Don't float your scope.
Title: Re: New Simpson 422 and HP Oscilloscope
Post by: eccoblackfin on May 06, 2015, 04:08:53 pm
Thank you for the suggestions.  I was hoping someone had the schematic for that particular generator, because I don't think that the sweep function and such is just an add-on to the standard 420.  I'll study it more in-depth later this week.  And I'll poke around and see if I can find this 'sine shaper'.  It'd be nice if it was just a bad diode that could be swapped out with ease.

As for the scope..it wasn't really my intent to float it(this was the first time I powered it on, just to see if it worked..didn't have a probe in it or anything), but I don't think it should be using the ground as a current path.
Title: Re: New Simpson 422 and HP Oscilloscope
Post by: eccoblackfin on November 17, 2016, 12:21:53 pm
So, despite raising the long past dead post on this one, I thought the update would be useful.  I contacted Simpson instrument, and asked them nicely if they could simply scan and email a PDF of the original service manual for the 422 function generator (for free).  They happily obliged!
I'll be sending it to the Simpson 260 site likely today or tomorrow, but in the meantime, if anyone would like a copy(or could tell me how to attach a 7mb file to a post here) I'd be happy to share it with you.