old HP1740A o'scope problem
"Bill Martin" wrote in message
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On 09/30/2015 05:19 AM, JC wrote:
On 9/30/2015 12:24 AM, Bill Martin wrote:
Hi,
Anyone have a list of "usual suspects" with this HP1740A scope when
there is no display at all? Front panel lights seem working, but that is
all I find so far. Have not opened the case yet, nothing seems to "smell
bad" so far. I won't be stressed if it can't be fixed, I bought it for
the nice rolling stand it was sitting on...I have another similar,
slightly newer antique scope that is still working that can use that
stand.
TIA,
Bill M
All the interboard connections on these are suspect for dry/bad joints
especially on the power board where you can get a nice burn up from the
arcing. Also the vertical output chip fails so you will get a trace but
no deflection. If you can go over all the joints carefully you might
have an easy repair.
Ok, I opened it up, there do not seem to be any burn marks on anything.
Wiggled the connectors too. Should I be able to see a glow from the ctr
filament without removing the metal shielding? So far I see no light, nor
detect any warming near the neck end of the tube...one additional data
point: the red "reset" led on the front panel is on all the time, and
there is no illumination of the faceplate.
Do you have a copy of the service manual? Have you checked the power supply
test points? Be careful, there are some points that can bite you.
The screen illumination is done by a flood gun.
Do you have another scope?
Regards,
Tom
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