HP 8165A goes a little crazy

I

Ian King

Guest
I bought an 8165A function generator on eBay and, while the function
generating stuff appears to work fine, the display is a bit wacky. It works
fine for a few minutes, but then both single LEDs and the seven-segment
displays start to do goofy things (like staying lit when they are clearly
deselected, and showing 0000 MHz). I have some thoughts on why this is
happening - of course, it sounds like some sort of thermal intermittent -
but the 8165's control board is not easy to get to *unless* you have the
magic extender board.

That's why I'm here. Does anyone know where these extender boards might be
found?

While I'm here: has anyone else experienced this sort of problem? Any
suggestions? I'm not averse to replacing a "usual suspect" IC and hoping
for the best. Thanks in advance for any advice you can offer -- Ian
 
On 14 Nov 2003 09:27:14 GMT "Ian King" <iking@killthewabbit.org> wrote in
Message id: <bp275i$cja$0@216.39.146.95>:

I bought an 8165A function generator on eBay and, while the function
generating stuff appears to work fine, the display is a bit wacky. It works
fine for a few minutes, but then both single LEDs and the seven-segment
displays start to do goofy things (like staying lit when they are clearly
deselected, and showing 0000 MHz). I have some thoughts on why this is
happening - of course, it sounds like some sort of thermal intermittent -
but the 8165's control board is not easy to get to *unless* you have the
magic extender board.

That's why I'm here. Does anyone know where these extender boards might be
found?

While I'm here: has anyone else experienced this sort of problem? Any
suggestions? I'm not averse to replacing a "usual suspect" IC and hoping
for the best. Thanks in advance for any advice you can offer -- Ian
Click to expand...
You have a schematic or service manual? If not, try here:
http://teknetelectronics.com/ Click on the free manual link, and sign up
for free. They might have one.
 
owners manual and programming guide on
ftp://ftp.agilent.com/pub/callpub/EOS/1998/8165 if you don't already have
them...
erie



"Ian King" <iking@killthewabbit.org> wrote in message
news:bp275i$cja$0@216.39.146.95...
I bought an 8165A function generator on eBay and, while the function
generating stuff appears to work fine, the display is a bit wacky. It
works
fine for a few minutes, but then both single LEDs and the seven-segment
displays start to do goofy things (like staying lit when they are clearly
deselected, and showing 0000 MHz). I have some thoughts on why this is
happening - of course, it sounds like some sort of thermal intermittent -
but the 8165's control board is not easy to get to *unless* you have the
magic extender board.

That's why I'm here. Does anyone know where these extender boards might
be
found?

While I'm here: has anyone else experienced this sort of problem? Any
suggestions? I'm not averse to replacing a "usual suspect" IC and hoping
for the best. Thanks in advance for any advice you can offer -- Ian
Click to expand...
 
Thanks for the pointer. I have the service manual, which I obtained on CD
from this very helpful guy named Dave Miller, and I've printed up the
schematics of the board in question. I think it comes down to the way the
8165A maintains state for the displays (both the 7-segment and the
individual LEDs in the buttons): it has two RAM chips that hold state
information and are scanned to refresh the displays. I suspect that there
is some gremlin that is causing the RAMs to be written to at inappropriate
times and/or with incorrect data. The unit responds to its pushbuttons and
keyboard just fine, and does exactly what I tell it to (including the sweep
functionality, which is very cool), but just "forgets" what the displays
should say. It's also interesting that if I do something that refreshes the
7-segment - for instance, modifying the frequency - the correct information
does reappear, but then goes away again once I hit another button.

Still looking for the extender board.... -- Ian

"Erie Patsellis" <signworks@consolidated.net> wrote in message
news:3fb6ab6a_3@127.0.0.1...
owners manual and programming guide on
ftp://ftp.agilent.com/pub/callpub/EOS/1998/8165 if you don't already have
them...
erie



"Ian King" <iking@killthewabbit.org> wrote in message
news:bp275i$cja$0@216.39.146.95...
I bought an 8165A function generator on eBay and, while the function
generating stuff appears to work fine, the display is a bit wacky. It
works
fine for a few minutes, but then both single LEDs and the seven-segment
displays start to do goofy things (like staying lit when they are
clearly
deselected, and showing 0000 MHz). I have some thoughts on why this is
happening - of course, it sounds like some sort of thermal
intermittent -
but the 8165's control board is not easy to get to *unless* you have the
magic extender board.

That's why I'm here. Does anyone know where these extender boards might
be
found?

While I'm here: has anyone else experienced this sort of problem? Any
suggestions? I'm not averse to replacing a "usual suspect" IC and
hoping
for the best. Thanks in advance for any advice you can offer -- Ian
Click to expand...
 
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