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.
Nice to know. Thanks for the info.
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
Pretty good copy here:
It really is not a bad scope. Good to over 100 MHz, two channel w/ delayed sweep.
It could be something minor like a bad capacitor in the power supply. Go check the supplies first.
Also, you will need to figure out how to fab some new feet as the originals are most likely gone.
Good luck and 73
Thanks for that, and yes, the feet on both my scopes are falling apart.
Bill
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