Author Topic: HP 5246L Counter Troubleshooting/Repair  (Read 474 times)

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Offline valley001

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HP 5246L Counter Troubleshooting/Repair
« on: January 25, 2019, 08:49:15 pm »
Hello all,

Next up is an HP 5246L counter.  I have been playing around with it and and noticed that, when connected to my HP 650A (behemoth) signal generator, I get very accurate readings on the 1ms, .1ms, 10us, 1us, and .1us settings but 10ms, .1s. 1s it is counting high, double or more the indicated frequency from my scope. 

I do have a service manual on the way.  The operating manual has you adjust the time base by externally triggering a scope to 100Khz (if I recall), but I do not have the ability to externally trigger my scope currently.    If the readings are accurate on the shorter time base settings this would mean the internal time is good right? 

When I use the check mode it is also inaccurate until I get into the Mhz range, but its not too far out reading 9989Khz or so out of 10,000Khz. 
« Last Edit: January 25, 2019, 09:04:48 pm by valley001 »
 

Offline coromonadalix

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Re: HP 5246L Counter Troubleshooting/Repair
« Reply #1 on: January 25, 2019, 09:14:33 pm »
Maybe some kind of input divider stage / prescaler problems

 If you have the service manual  try to follow the signal path   you should end with the signal going into a gate, the gate will receive the 1sec 0.1 sec .... timings to let it thru the counter section.
 

Offline jfphp

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Re: HP 5246L Counter Troubleshooting/Repair
« Reply #2 on: January 26, 2019, 11:06:31 am »
It is probably the decimal counter, the last big board on the right of the displays boards (view from top) near the plug in slot : common failure on the 5246, 5L/M and 48L/M. A replacement board with ICs was very early the answer from HP.
 

Offline valley001

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Re: HP 5246L Counter Troubleshooting/Repair
« Reply #3 on: January 26, 2019, 04:27:55 pm »
It is probably the decimal counter, the last big board on the right of the displays boards (view from top) near the plug in slot : common failure on the 5246, 5L/M and 48L/M. A replacement board with ICs was very early the answer from HP.

Thanks for that information.  I had a look at the one in my unit and it is all discreet components.  Ill start there when the manual arrives. 
 


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