PCB assembly discussion

Instructions and discussion for constructors of our nixie button kit
jmmcg
Posts: 55
Joined: Sat Apr 11, 2020 2:45 pm

Re: PCB assembly discussion

Post by jmmcg »

I noticed that the brightness of individual nixies seems to vary considerably (turns out this is not the case...). Of the two buttons I have working, their nixies are the brightest. Another two I have tested are much dimmer and I simply cannot get the relay to fire. After being brave & swapping the nixie from the "brightest" button with a base of a "dim" one and testing all the other nixies against the "bright" base, I can confirm that they all appear equally as bright on the "bright" base. Also the "bright" nixie appears dim on the "dim" bases. Clearly these is absolutely no issue with the nixies and they are all equivalently bright. Moreover re-assembly of the "bright" button was fine: I did not need to re-tweak my pot for R4, it worked straight away, clearly once set up correctly the buttons are robust and very stable. I have tried swapping T1, the diode and the PIC chip from either the working button or spares, successively, none had any effect on the "dim" nixie.
I conclude that I must have made some error in the assembly of the "dim" bases, specifically, methinks I need to examine my coils...!
jmmcg
Posts: 55
Joined: Sat Apr 11, 2020 2:45 pm

Re: PCB assembly discussion

Post by jmmcg »

jmmcg wrote:XXXsnipXXX I have tried swapping T1, the diode and the PIC chip from either the working button or spares, successively, none had any effect on the "dim" nixie.
Into the base of T1 I see a nice 5V square-wave at 111kHz for both "dim" and "bright" (i.e. that part of the PIC chip is fine). Also the voltage for both is 5V at pin 2 on the PIC chip.
  • In the "bright" button I observe:
  • [list]
  • in the output of T1 a rather jagged wave, about 31V peak-to-peak.
  • On the R1 side of D1 I measure about 25V DC.
  • On the C1 side of R1 I measure about 27V DC.
  • On the T2 side of D4 I measure about 32V DC.
[*]In the "dim" button I observe:[/*]
  • a similar waveform but about 20V peak-to-peak. Yet the T1 was swapped. Other "dim" buttons show a similar about 21V peak to peak from T1.
  • On the R1 side of D1 I measure about 17V DC (yet I replaced D1, others are similar).
  • On the C1 side of R1 I measure about 18V DC.
  • On the T2 side of D4 I measure about 22V DC.
[/list]
So I conclude that the maximum voltage to T1 is somehow lacking in the "dim" buttons. Yet how it is lacking I am baffled. Tony, could you please advise?
Last edited by jmmcg on Tue Aug 18, 2020 6:23 pm, edited 2 times in total.
jmmcg
Posts: 55
Joined: Sat Apr 11, 2020 2:45 pm

Re: PCB assembly discussion

Post by jmmcg »

jmmcg wrote:XXXsnipXXX
So I conclude that the maximum voltage to T1 is somehow lacking in the "dim" buttons. Yet how it is lacking I am baffled. Tony, could you please advise?
A thought: I have read a tiny bit about transformer windings and the effect of the secondary being wound in the opposite direction to the primary. Now in the two working buttons I believe I wound the secondaries of L1 in a clockwise direction, whereas for the others I believe I inadvertently wound the secondaries in an anti-clockwise direction. (Damn that ambidexterity!) Might having the secondary now having an out-of-phase voltage & current effect the maximum voltage? Should I re-wind those secondaries of L1 in a clockwise direction?
I have just tried this and it had no effect. Drats.
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