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54615B Trigger Control Failure

Question asked by Lab-rat on Mar 27, 2012
Latest reply on Dec 21, 2013 by wonghoi

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For the past few days I’ve been trying to locate a replacement keyboard P\N 54600-66052 for the HP54615B oscilloscope. Evidently Agilent dropped the support for this item in 2006 and no longer has replacement parts.

I have narrowed the scope’s failure down to a single mechanical rotary encoder that is used for setting the trigger level via the front panel. The part has 9707 and 1-2-36 stamped on its rear cover. It is a 3-pin, 2 quadrature channel, 9 pulse per rotation, no detent, continuously rotating encoder. Is it possible to find the original manufacturer’s part number for this part or a functional replacement? It's a shame to mothball this scope over such a minor issue.

Thanks for any help you can give.

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danish Aug 9, 2012 5:13 PM

I am having a similar issue with both of my 54616C oscilloscope. The knobs for time and voltage (both channels) on both oscilloscopes generate unstable values when turning the knobs. Two clicks in the same direction may produce one step up followed by one step down. This is really annoying in an otherwise nice piece of equipment. Clearly the rotary encoders are producing unstable values. They are either worn or dirty.

Is it possible to get schematics of the scope?

Is it possible to get manufacturer and part no. information on these rotary encoders?

Thanks
Michael

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algoss

@ danish on Aug 13, 2012 4:36 AM

There's probably somewhere within Agilent to get this info, but I just Googled "54616 manuals" and got the following link: 5461X User and Service Guide

This might be the best you can do.

Al

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wonghoi @ danish on Dec 21, 2013 9:43 PM

I have this scope as well. The encoder gets dirty and greasy over years. If it's moving erratically, just dial it 200+ full rotations at each direction (do not alternate) until your hand get tired. If it doesn't work, PM me as I do have some parts scopes that I can salvage the keyboard from. Good luck!

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Lab-rat Aug 27, 2012 11:24 AM

I found an somewhat mechanically and electrically compatible encoder except that it was 12 pulses per revolution instead of 9. Unfortunately this didn't fix the problem it appears that IC that receives this signal is staying high on one of the two channels. It doesn't appear to be caused by the keyboard circuitry but rather by an IC on the system board. Without a decent schematic I have little hope of solving this issue.

The encoder part number is PEC11-4020F-N0012 and can be found at Mouser. Note that the common terminal on the old encoder is on the lower left of the device while the replacement's common is in the middle so jumper wires need to be soldered for this to work.

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danish Aug 9, 2012 5:13 PM
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I am having a similar issue with both of my 54616C oscilloscope. The knobs for time and voltage (both channels) on both oscilloscopes generate unstable values when turning the knobs. Two clicks in the same direction may produce one step up followed by one step down. This is really annoying in an otherwise nice piece of equipment. Clearly the rotary encoders are producing unstable values. They are either worn or dirty.

Is it possible to get schematics of the scope?

Is it possible to get manufacturer and part no. information on these rotary encoders?

Thanks
Michael
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- algoss @ danish on Aug 13, 2012 4:36 AM
  Mark Correct
  Correct Answer
  There's probably somewhere within Agilent to get this info, but I just Googled "54616 manuals" and got the following link: 5461X User and Service Guide
  
  This might be the best you can do.
  
  Al
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- wonghoi @ danish on Dec 21, 2013 9:43 PM
  Mark Correct
  Correct Answer
  I have this scope as well. The encoder gets dirty and greasy over years. If it's moving erratically, just dial it 200+ full rotations at each direction (do not alternate) until your hand get tired. If it doesn't work, PM me as I do have some parts scopes that I can salvage the keyboard from. Good luck!
  Like • Show 0 Likes0
  Actions
Lab-rat Aug 27, 2012 11:24 AM
Mark Correct
Correct Answer
I found an somewhat mechanically and electrically compatible encoder except that it was 12 pulses per revolution instead of 9. Unfortunately this didn't fix the problem it appears that IC that receives this signal is staying high on one of the two channels. It doesn't appear to be caused by the keyboard circuitry but rather by an IC on the system board. Without a decent schematic I have little hope of solving this issue.

The encoder part number is PEC11-4020F-N0012 and can be found at Mouser. Note that the common terminal on the old encoder is on the lower left of the device while the replacement's common is in the middle so jumper wires need to be soldered for this to work.
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54615B Trigger Control Failure

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