EEVblog Electronics Community Forum
Products => Test Equipment => Topic started by: 1980s_john on March 08, 2017, 10:28:17 pm
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Hi,
I recently bought a faulty HP 54520A scope, the screen came on with a button-down power up so it has the same flat lithium battery problem as any of these similar 1990s HP scopes. I disassembled the scope using the excellent guide here:
http://codeterrific.com/electronics/hp-54520a-oscilloscope-fix/ (http://codeterrific.com/electronics/hp-54520a-oscilloscope-fix/)
A few points to note, I found a 16mm open spanner ideal for removing the front and rear BNC sockets. My unit had a slightly different number of screws than noted above (eg had to remove the four top lid screws that would be used to attach the accessories bag), and also note need to remove coax connector to front panel calibrator output. My unit was not quite as grubby as shown but it was fairly full of dust bunnies; I need to sweep it out and the take the PSU apart and video board out the dust them too. All the caps look good but I will check these for high ESR just in case.
Having removed the main board I see the battery has a date code of 95-07, so 21 years old. I was surprised to see that the lithium battery had leaked some white powder, I haven't yet removed the battery but hope this will come off the PCB with IPA. It doesn't seem to have rotted any traces thankfully.
Lastly the battery type - it is roughly 47mm long 3V lithium, size is CR17450. It is fitted with PCB tabs, two pins on + end and one pin on - end. I see these are readily available from Panasonic (BR-A) and others. Do not buy AA size as these are too long.
Next job is to order a battery and fit it.
My warning is to anyone who has one of these scopes and hasn't replaced the battery to check the state of it now.
Regards,
John
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Thanks for the heads up. I'm in the market for one of these at the moment so a good one to watch out for. I'd probably replace that battery straight up based on this.
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Just to confirm the fix worked fine. The website referred to is 404 but thankfully is on the internet archive:
https://web.archive.org/web/20161021210626/http://codeterrific.com/electronics/hp-54520a-oscilloscope-fix/ (https://web.archive.org/web/20161021210626/http://codeterrific.com/electronics/hp-54520a-oscilloscope-fix/)
Regards,
John