I did find one thing that was causing some erratic behavior on the screen, and that was a switch on the back panel of the scope that had failed so that it was open all the time except for when you were putting pressure on the lever.
The switch is labeled Brightness; maximum/normal, and as far as I can tell it just joins or opens a connection between pins 6 and 8 on U4
Sadly this did not fix all the random behavior, the trace still flashes randomly sometimes.
what is Q10 doing?
I find it hard to believe that there is a mistake in the HP manual
U8 and U7 are the only ICs on this board that do not have a HP part number on them, and although they have the same P/N, one is a plastic package and one is a ceramic, leading me to believe that they have been replaced?
It is also huge...I'd say it's stretching the definition of "portable oscilloscope".
I am slowly working through this thing bit by bit, and hopefully I will eventually find the source of the problemIt is also huge...I'd say it's stretching the definition of "portable oscilloscope".
I attached a picture of how much space this thing takes up on my bench, it's massive and heavy!
EDIT: I don't know why my pictures are always upside down on forums I post to.
I had written it off as a characteristic of the storage tube.
I really should do some more research into storage scopes since I have no prior experience working with a scope like this.
My unit strugles to meet it for sure, in fact mine barely goes beyond 250MHz...
The more I work on this scope and dig through every corner of it for problems, I am noticing more small differences between my scope and the manual, including modifications that seem like they were done at the factory so to speak. I have no way of knowing if the hardcopy of the manual I have is original to the scope, but it has this page; (see picture), which seems to suggest that this manual and scope was shipped out to the customer before the manual was complete. This would explain the lack of the chapter on service in my manual, since the service section was probably not done yet.
It seems to me that it is a real possibility that my particular scope was produced and sold very early on in the 1727A production, and thus is a little bit more prototype than most. further lending to this theory is the fact that the serial number is as follows; 1947A 00075, does that mean that my scope is the 75th unit?
If Oculus is still watching this thread, I would be interested to know what the serial number of his scope is
The more I work on this scope and dig through every corner of it for problems, I am noticing more small differences between my scope and the manual, including modifications that seem like they were done at the factory so to speak. I have no way of knowing if the hardcopy of the manual I have is original to the scope, but it has this page; (see picture), which seems to suggest that this manual and scope was shipped out to the customer before the manual was complete. This would explain the lack of the chapter on service in my manual, since the service section was probably not done yet.
It seems to me that it is a real possibility that my particular scope was produced and sold very early on in the 1727A production, and thus is a little bit more prototype than most. further lending to this theory is the fact that the serial number is as follows; 1947A 00075, does that mean that my scope is the 75th unit?
If Oculus is still watching this thread, I would be interested to know what the serial number of his scope is
OK, this is real interesting. Mine is 2452A1208. the first two digits generally indicate years since 1960 for instruments newer than 1960 or so. The date, however, indicates the engineering revision date. So yours is a 1979 revision and mine is another revision that was done in 1984. Here's where it gets fun. I consulted my -hp- catalog collection and the 1727A does _not_ appear in the 1979 or 1980 catalog. I don't have a 1981 catalog, but it's definitely in the 1982 catalog. You, sir, may have a prototype on your hands. This might explain the weird bodges and stuff.
The more I work on this scope and dig through every corner of it for problems, I am noticing more small differences between my scope and the manual, including modifications that seem like they were done at the factory so to speak. I have no way of knowing if the hardcopy of the manual I have is original to the scope, but it has this page; (see picture), which seems to suggest that this manual and scope was shipped out to the customer before the manual was complete. This would explain the lack of the chapter on service in my manual, since the service section was probably not done yet.
It seems to me that it is a real possibility that my particular scope was produced and sold very early on in the 1727A production, and thus is a little bit more prototype than most. further lending to this theory is the fact that the serial number is as follows; 1947A 00075, does that mean that my scope is the 75th unit?
If Oculus is still watching this thread, I would be interested to know what the serial number of his scope is
OK, this is real interesting. Mine is 2452A1208. the first two digits generally indicate years since 1960 for instruments newer than 1960 or so. The date, however, indicates the engineering revision date. So yours is a 1979 revision and mine is another revision that was done in 1984. Here's where it gets fun. I consulted my -hp- catalog collection and the 1727A does _not_ appear in the 1979 or 1980 catalog. I don't have a 1981 catalog, but it's definitely in the 1982 catalog. You, sir, may have a prototype on your hands. This might explain the weird bodges and stuff.
This is indeed strange, as the 1727A was introduced in the April 1982 issue of HP Journal:
https://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1982-04.pdf
Though HP journal not neccesarily articled the newest instruments, but there was no point to advertise a years old tool either...
BTW in that article they went into highlight the strengths of the new tube (and less the drawbacks obviously).