Author Topic: help - troubleshooting an old scope  (Read 229 times)

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Offline nitzane

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  • Country: il
help - troubleshooting an old scope
« on: November 14, 2017, 11:09:22 PM »
Hi guys, newbie here.

I recently bought a used hp 54645A off ebay.

It boots ok with no error messages, shows both traces and properly shows the square test signal.

Theres one issue with it - the display seems to freeze when i toggle traces on and off, and when i try to toggle vectors.

After a hard reset the splash screen shows "PANIC - DSP COMMUNICATIONS TIMED OUT".

Also - sometimes the display would boot up jumbled. I reckon the jumbled display is related to the freezes.

no joy with the hp/agilent documentation.

Iv'e included some photos, hopfulley they would make up for my non native/professional english.

Has anyone seen this before?

Thanks,
Nitzan
« Last Edit: November 16, 2017, 04:42:03 AM by nitzane »
 

Online capt bullshot

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Re: help - troubleshooting an old scope
« Reply #1 on: November 14, 2017, 11:30:04 PM »
Don't know the innards of this particular scope, so can't help you in detail.
Your problem looks like a intermediately bad internal connection, maybe warm up of the scope influences it. So check for any kind of board-to-board connections, re-seat them. If none applicable or cleaning the connectors and re-seating doesn't help, check for supply voltages to be correct, and search for bad solder joints. If documentation is helpful in defining and locating circuit blocks, I'd search for  the failure somewhere on the data busses from the Main CPU to the DSP part (as I said, I cannot help you in details, you'll have to find this out for yourself or wait for others to join this thread).
Don't know if this scope suffers from that, but check for leaking SMT electrolytic caps - if there are any, remove, thoroughly clean the board and put new ones in.
Safety devices hinder evolution
 

Offline nitzane

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  • Posts: 3
  • Country: il
Re: help - troubleshooting an old scope
« Reply #2 on: November 15, 2017, 07:15:40 AM »
Thanks captain, ill reconnect all the cables!

what does the fact that the freeze happens only when toggling vectors and traces tells us?


Nitzan
 

Offline nitzane

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  • Posts: 3
  • Country: il
Re: help - troubleshooting an old scope
« Reply #3 on: November 20, 2017, 05:17:10 AM »
ok, a little update.

i have opened up the scope, disconnected all cables and reconnected them. nothing changed...

i have noticed i can toggle traces on and off, it freezes when i try to do this rapidly (about 3 seconds). the freeze always occurs when turning vectors on and off.

i have managed to put my hands on the scope's schematics here https://archive.org/details/HP54645NCLIPImgs


i noticed theres a sheet named DSP BUS(sheet2), but everything is still very complicated to me :-[  any usual suspects?

 


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