You have to bridge in the voltage while changing out the lithium battery or you will lose the calibration data. I forgot where I saw the procedure. If I find it I'll post the link. My older 2465 DMS has NVRAM so no battery issues.
Looking forward to your teardown. So far I haven't had any power supply issues but I know that day will come where I'll have to recap to inverter and power supply boards. So far all the voltages are in spec.
One "gotcha" regarding the DMM option. The power up self checks do check some basic DMM functions but will NOT flag the DMM calibration. The DMM option manual states to perform a calibration if you suspect it to be out of spec. That's exactly what I found out as I posted in this thread. If you find the same with yours I can give you some pointers on how to get a reasonable calibration cheaply
Thanks. This is a BCT which does not have the DMM, but does have the frequency counter. When choosing this unit, I had several priorities...
1. 2465B / 2457B - but preferably 2465B because the CRT is more easily replaced and is larger. I don't really need the CRT features of the 2467B. I wanted a 2465B because while it is far more than I need at the moment, but I can only afford to do this once so I want the most bang that I can get.
2. I wanted a unit without SMDs. Easier to maintain and appears to have a lot fewer service "updates" apparently due to Tektronix still trying to fine tune the SMD version. Also, no Dallas chip to deal with. Once the procedure is known, changing a battery is not a big deal.
3. I wanted a unit with the frequency counter because I need one. Option 09 gives 7 digits without an external time base and 8 digits with. Since my next purchase will be a GPSDO that is more than sufficient in terms of accuracy. Anything more than that - or even to match it - would be very expensive. So that narrows the field down to the BCT, BDM or BDV. Also, I have very limited space on my work bench and the integrated frequency counter helps there as well.
4. I already have a DMM of about the same accuracy as that provided by option 01. That accuracy is not much to write home about and increases the size of the scope. So while a BDM or BDV is ok, optimal is the BCT.
With this unit I hit all of my points exactly. It is an early model (s/n B010xxx), but there are no service updates listed for any s/n below B050000. There are some board variations, but those appear to more layout than anything else. So, while I paid more for it than I might have for a plain 2465B in the same shape, I think the cost difference was worthwhile. Certainly cheaper than buying a separate frequency counter. When it failed, the $50 rebate from the vendor paid for most of the parts which reduced the cost further (since I would have recapped it anyway - just not as soon).
I may need pointers on the tear down. I haven't taken out any board yet that requires desoldering. I have had the options out several times. There are two areas where it is a pain. First is the ribbon cable that tends to get pinched. It is hard to get that in right. The second is the two cables at the very end which go onto the same pins. It is not clear which cables go where. I figured that out because one of the pins goes to the resistor / capacitor that I will be changing for option 1E, but the manual is useless there.
The case and back were not the cleanest and had permanent marker, floor scum and sticker goo all over them. I have cleaned all of that of so the case looks nice now. I haven't had the front of the scope off yet, so it is still a bit grungy.
I may also need help identifying some parts. My part list was as accurate as I could make it, but I am sure that there will minor corrections (radial vs. axial / aluminum electrolytic vs. tantalum electrolytic / polar vs. bi-polar, etc.) which are not spelled out in the service manual. Also, I don't have the 24x5B / 2567B options service manual. I have been unable to find it online and am not willing to pay for what should be a free manual unless it is absolutely necessary. My understanding is that Tektronix made all of that information publically available.
Right now I am waiting on Mouser. The parts shipped on the 24th so they will probably sometime early next week.