On 10/01/2015 01:35 PM, Tom Miller wrote:

"Bill Martin" wrote in message
...
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


I do have another scope...it is even working. No service manual for this
one, I have the 1743A service manual, which should be "close" at least.
Yeah, I know about being bitten, got 300Vdc from a Klystron plate cap
once. Long ago, but you don't forget. So far all I have done is
superficial, really obvious kind of stuff. Not likely to put a lot of
effort into this, since fixing it could easily cost more than it is
worth...just curious what is ailing. I'm suspicious of the crt itself at
this point. If I can get it working, will likely give it away, to
another "old guy" buddy that could use it.

Bill