Very well done. I like your solution for the power supply, restoring equipment to original condition is desirable but sometimes just not practical. With such a sensitive instrument it would be nice to shield the supply - perhaps an aluminum hobby box without the cover could be found with the appropriate size. I would like to see part 3, the alignment. Regards, David
I think first some doubled up aluminium foil could be used to empirically prove whether the supply really *needs* to be shielded or not, or whether no difference can be detected between one being present or not. I'd argue the biggest reason for the previous supply needing one is gone - we are no longer trying to keep 200V around any more, anywhere but the wiring from mains input to transformer.
@@ivolol A very good suggestion. I doubt that the power supply enclosure was related to safety issues with the 200 v supply as this voltage is routed to all of the switches and the indicators - so lots of contact points outside the power supply. I was suggesting a source for a cover if needed. Regards, David
Let’s be honest, everyone watching these videos will pretty much insist on chapter 3. Now that you’ve sowed the seed of course 🙂 Using LED’s was the smart move here, the future-proofing alone will show us that. Personally I still prefer the TF-2700, it’s just more… beautiful I think.
Was about to ask why you didn't replace the neons with LEDs, until you did. I'm always interested in seeing calibrations. Seeing instruments line up to perfect 0s (or at least perfectly expected digits) is like ASMR to me. It's interesting / confounding to me that we can "easily" get resistors to 0.005% tolerance (thanks, Vishay) but can basically never get anything but 1% capacitors, and practically no-one is willing to give a better than 0.5% rating for their instrument testing them until you spend big $$.
This is a very kind offer but I first want to try something else. The manual says for the accuracy check a 100nF cap with 0.01% tolerance is needed. For the trimming (cal) they actually want a 10nF 0.01% cap. I have now got four 10nF 0.9% caps. I measured those with my LCR meter (0.5% accuracy) and another LCR meter at 0.25% accuracy and for all four, the two LCR meters agree with each other to about 30pF difference. That gives me some confidence that my LCR meters are still reasonably accurate. My plan is therefore to check the 4 caps with the B642 to see if it agrees with the 2 LCR meters. If it does, I would not touch the B642 cal. If it doesn't, I may set the B642 to read the same as the two LCR meters. Only problem is time. My day job workload has increased drastically and family also wants attention...
![Build A Power Supply - With Junk Box Parts! [The BC-348 Series.]](/img/1.gif)
Very well done. I like your solution for the power supply, restoring equipment to original condition is desirable but sometimes just not practical. With such a sensitive instrument it would be nice to shield the supply - perhaps an aluminum hobby box without the cover could be found with the appropriate size. I would like to see part 3, the alignment. Regards, David
I think first some doubled up aluminium foil could be used to empirically prove whether the supply really *needs* to be shielded or not, or whether no difference can be detected between one being present or not.
I'd argue the biggest reason for the previous supply needing one is gone - we are no longer trying to keep 200V around any more, anywhere but the wiring from mains input to transformer.
@@ivolol A very good suggestion. I doubt that the power supply enclosure was related to safety issues with the 200 v supply as this voltage is routed to all of the switches and the indicators - so lots of contact points outside the power supply. I was suggesting a source for a cover if needed. Regards, David
Let’s be honest, everyone watching these videos will pretty much insist on chapter 3. Now that you’ve sowed the seed of course 🙂
Using LED’s was the smart move here, the future-proofing alone will show us that.
Personally I still prefer the TF-2700, it’s just more… beautiful I think.
Was about to ask why you didn't replace the neons with LEDs, until you did. I'm always interested in seeing calibrations. Seeing instruments line up to perfect 0s (or at least perfectly expected digits) is like ASMR to me.
It's interesting / confounding to me that we can "easily" get resistors to 0.005% tolerance (thanks, Vishay) but can basically never get anything but 1% capacitors, and practically no-one is willing to give a better than 0.5% rating for their instrument testing them until you spend big $$.
I am very grateful for this video, as it will help me to calibrate my B642. Please do Pt.3 🙏🙏🙏
I am still looking for good ref caps to do the calibration
@TheHWcave i will have a look in my stash. I think I have a few 200nu 0.05% caps
@TheHWcave i found a few 0.5% if you think it will be ok, I am glad to post it to you. It's silver mica cap.
This is a very kind offer but I first want to try something else. The manual says for the accuracy check a 100nF cap with 0.01% tolerance is needed. For the trimming (cal) they actually want a 10nF 0.01% cap. I have now got four 10nF 0.9% caps. I measured those with my LCR meter (0.5% accuracy) and another LCR meter at 0.25% accuracy and for all four, the two LCR meters agree with each other to about 30pF difference. That gives me some confidence that my LCR meters are still reasonably accurate. My plan is therefore to check the 4 caps with the B642 to see if it agrees with the 2 LCR meters. If it does, I would not touch the B642 cal. If it doesn't, I may set the B642 to read the same as the two LCR meters. Only problem is time. My day job workload has increased drastically and family also wants attention...
Part 3? Of course we want to see it.
I will, but I am still on the hunt for caps that can serve as reference for cal