RIFA, Nichicon, Sprague and Cornell Dublier is my guess.
Replaced capacitors
You have hidden all the brand names. On purpose?
How many were faulty?
Care to list them for us?
What do need them for? I have the complete parts list, with replacements that I have previously posted. There have been some updates as I have worked on each board. Do you need the updated list? I will be posting that later, but was going to wait until I have complete finished.
I have knob problems with my 2465B CT scope. On the front panel, the two bottom halves of the VOLTS / DIV knobs have set screws that are stripped. Probably because somebody screwed them in far too tight. How do I get these off, and where can I get either a knob replacement or a set screw replacement (assuming I get them off without damaging the knobs)?
Additionally, two of the smaller knobs with a blank front (e.g. like the TRACE SEP knob) and two of the smaller knobs with a line on the front (e.g. like the POSITION knobs) have their internal "cap" broken. These are my fault because they were on so tight I had to pry them off with a screwdriver. Unlike the ones under the CRT, which came off with just finger pressure, all of the knobs on the main panel were stuck really badly. Where can I get a knob replacement for these?
These knobs are common to pretty much all of the 22xx and 24xx series, so I would think that they are out there somewhere.
Thanks.
I have a 2465A, which has the digital board similar to the earlier 2465B serials, that is, with through hole components, and with the separate SRAM and battery, rather than a DS1225 module. My calibration data is intact but the battery is original, so I can assume that it will not be intact for too much longer.
The separate SRAM/battery is a mixed blessing: on one hand I can more easily desolder and replace just the 4 pin battery a 28 pin NVSRAM. On the other hand, I have no way to read out and save (or restore) the calibration data itself. After browsing the service manual, I got the idea to put the processor into the diagnostic NOP loop. It will cycle through all addresses on the address bus, with the intention of allowing the testing of address bus and decoding (chip selects). I thought that the data could be captured by using either a logic analyzer or by piggy-backing an NVRAM and supplying write pulses for each address so that it captures the data that the SRAM presents to the bus when it is addressed. One issue is that I don't have a logic analyzer. Does anyone have an opinion about either of these methods? Should I just replace the battery and cross my fingers that I'll never need to restore the data?
Tektronix had a change in their manufacturing process. At one point they closed their hybrid production plant, or it was sold to a subsidiary of Maxim.
When Maxim started to produce the U800 for Tek, the troubles were introduced. The bad chips are having the maxtek marking, and not the Tek marking on them.
There is a reliability report floating around on the internet with statistics on this chip, made by Maxim.
Basically what happens is the the die comes loose from the heat sink. if this happens, you will notice a gradual shift of the characters on the screen to the left on power on.
If this situation continues, eventually, the chip burns out....
In my scopes all U800 got an heat sink, despite the fact that they all were Tek branded. Be aware that the IC heat sink is a -5.2 volts
Added link to Maxim report https://www.maximintegrated.com/en/qa/reliability/general/RR-B2A.pdf
FireDragon:
Typically the recommendation is to avoid recapping the mainboard. Can't recall the specific reasons why, think it had to do with issues of the multilayer PCB. in any event good job, did you notice any improvements in performance in recapping the main board.
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.
Additionally, on the A3 Inverter board there are three more RIFA capacitors and it can be seen that all three are cracked. They may still be working, but probably not for long. The A3 Inverter recap does not include those because I need to order replacements. It can also be seen looking at the bottom on the replaced capacitors that one looks like it was starting to leak, a second appears to have damage to the bottom (pre-leak?) and I am not at all sure if some of the rest are slightly bulging or not. They certainly aren't completely flat, but that may be a construction difference.
A3 Recapped Inverter Board
Here is the damage, apparent bad components and recapping of the A3 Inverter board for my 2465B CT scope.
Additionally, on the A3 Inverter board there are three more RIFA capacitors and it can be seen that all three are cracked. They may still be working, but probably not for long. The A3 Inverter recap does not include those because I need to order replacements. It can also be seen looking at the bottom on the replaced capacitors that one looks like it was starting to leak, a second appears to have damage to the bottom (pre-leak?) and I am not at all sure if some of the rest are slightly bulging or not. They certainly aren't completely flat, but that may be a construction difference.
A3 Recapped Inverter Board
I've been following this thread for days now, including all the links to other information. This is a great thread full of good information and populated with great posts. Thanks to all of you who have contributed here.
FireDragon, it appears as though you may have fallen prey to a documentation error. Specifically, on the A3 inverter board, the documentation has the info for C1132 & C1115 reversed. It may just be the picture you've provided, but it's worth checking it out.
See this post from HowardLong https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/475/ for complete information.
Again, I've been very impressed by the content and quality of this thread.
FireDragon, it appears as though you may have fallen prey to a documentation error. Specifically, on the A3 inverter board, the documentation has the info for C1132 & C1115 reversed. It may just be the picture you've provided, but it's worth checking it out.
Damn .. what happened to those toasted resistors ?
Are their resistances still within the printed values especially for those are not toasted ?
Btw, thanks for the contribution to this thread.
RT1010 and RT1016 are negative temperature coefficient thermistors. They have a high resistance when cold to limit surge current when the unit is first turned on, then their resistance drops as they heat up to allow adequate current flow to the power supply. Perhaps one or both have failed shorted, or drop resistance too fast etc. If they allow too high an initial surge current, you certainly could blow the fuse.
Do they meet their cold specification?