Hi all,
here again some progress on my 2465B revival.
I will share my info on the steps I took so far:
- Recap Power Supply & tests of the old Caps afterwards... ;-)
- Repair/replacement of the Delayed Time Base lever inside the front-panel
- Removal of the Dallas and placement of a socket so it can be replaced when I get my programmer
- Cooling of my Tek U800 and how
- Pictures of the previous replacement of the four caps on the A5 board
Although I am a big fan of "If it ain't broken, don't try to fix it..." I do think this 2465B could be the scope I will use till I die, so I decided to do the recap.
Mainly because when Tek build this thing, they made sure all new components were up to spec, so now, after more than 25 years, I thought it could be useful to renew the old parts that are known to age.
So yesterday I did a full recap of the Power Supply, that job took me a few hours, but all-in-all, not too bad.
I just replaced everything, but I sure was curious about how necessary it actually was, so today I did a quick capacity and ESR test with one of these small all-in-one testers.
As it turned out, more than half of the capacitors were in fact OK!?
Even so, I am happy knowing all parts are now new and "future-proof".
The caps that were bad were:
3,3uF, 350V
10uF, 160V
10uF, 100V
47uF, 25V
4,7uF, 35V
Tantalum 4,7uF
and funny enough, one of the 15 Ohm resistors went up to 4968 Ohm!! without any markings or change of color.
When I got my 2465B, the VAR knob inside the Time Base was missing, and as it turned out, the pull to delayed time base was not working either.
When I looked in to this the little lever that operates the slide switch inside was broken, so that had to be replaced. (I am not a great fan of glue...)
Qservice in Greece had this part, so that was an easy fix.
Next, the Dallas chip.
Almost all the parts have a 90-ties datestamp on them, so this means the Dallas is -still working- in almost 16 year of extra time!
I choose to go for the original, so today I removed my Dallas and put a socket on the board.
Reading and copying must wait till I receive my programmer, but at least the soldering bit is done today.
I used a simple push-and-release manual tin-sucker that worked OK on all pins but pin 14. (because of the ground-plane inside the board)
I removed the tin from the holes, and then, using a small pointed pair of pliers, I wiggled the pins one by one from left to right, to make sure they were loose inside the holes before pulling on the chip.
To remove the Dallas I applied the soldering iron to pin 14 while carefully pulling the Dallas out.
After that I placed a socket on the board, I choose the double action flat surface type of socket, because they seem to work a bit better with pins of unequal thickness. (tin residue on the used Dallas)
After that, the moment of truth was, will it still have calibration info in it??? Yes!! (I am a happy bunny right now!)
And now the final part: cooling of the U800.
The consensus seem to be, that the TekTronix made chips are "better" in terms of failing on the long term.
Mine is not getting hot, but it may have to do whem touching the chip is is just doing almost nothing?
Maybe when the scope is running on a very high frequency with a high repetition rate, it may get hot due to more capacitive load??
Anyway, I decided to help this little chip a bit.
What I did was, I removed the nut where the metal tab from under the chip is, and made a brass (for thermal conductivity) bushing the same height as the remaining part of the chip.
So basically, I try to guide the heat through this bushing to the top, and there transfer it to a cooling element.
I also put some thermal conductive grease on top of the chip, although this may be of little effect.
The cooling I found at Mouser's, it is a double to-220 part.
I will start adding pictures to show what I did.
Un saudo,
Satbeginner (Leo)