Help!

jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

On page 2 of "3 - Clock PCB assembly" [1], it says:
Fit the mustard/beige resin dipped 22p (marked 220) capacitors x2 in locations marked for C7 and C8:

**Batch2 kits will be marked 33 (not 333, note only 2 digits)
I think I have a black batch 3 kit. The capacitors provided were marked "220". I presume this is correct?

[1] viewtopic.php?f=24&t=107&start=10
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

In "3 - Clock PCB assembly" I have got to page 3 the first power-on test. It states:
You should have a reading of a few mA which rapidly drops to less than 1mA as C5 charges.
Initially I see about ~0.9mA dropping in about 5 seconds to ~0.6mA. I presume there is something wrong with my work? (Note that My AVO meter is a bit rubbish, maybe it peaked higher at the start.)

I could not spot any bridges.... Any tips?

Note that the PIC controller chip data sheet is here: http://ww1.microchip.com/downloads/en/D ... 41391D.pdf to check the power to it.

[1] viewtopic.php?f=24&t=107&start=20
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

jmmcg wrote:In "3 - Clock PCB assembly" I have got to page 3 the first power-on test. It states:
You should have a reading of a few mA which rapidly drops to less than 1mA as C5 charges.
Initially I see about ~0.9mA dropping in about 5 seconds to ~0.6mA. I presume there is something wrong with my work? (Note that My AVO meter is a bit cheap (so slow to react), maybe it peaked higher at the start.)

I could not spot any bridges.... Any tips?

Note that the PIC controller chip data sheet is here: http://ww1.microchip.com/downloads/en/D ... 41391D.pdf to check the power to it.

[1] viewtopic.php?f=24&t=107&start=20
Apparently was working already: I temporarily wedged in the resettable fuse and got the beeps as noted in the test. Huzzah! (Looks like my worry about my cheap AVO meter might be right...)
Tony
Site Admin
Posts: 951
Joined: Tue Jul 24, 2012 8:05 pm

Re: Help!

Post by Tony »

The current specified was more of a maximum value to alert anyone seeing 10s of mA to switch off quick. Some meters won't catch the initial inrush either.
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

I mentioned I was having an issue with one of the clocks: two of the 5 nixies fail to light. V2 and V3 fail to light. V1, V4 & V5 light. The clock PCB seems to be ok now: it appears to respond to controls, etc. All the blue & amber LEDs light. The waveforms for the nixies V1, V4 & V5 on their anodes are the same, a rather complex square-wave-ish shape, whereas for V2 and V3 the anode waveform is significantly different, a much more spikey repeating waveform, with no square edges. (NB all of the nixies work.) I measured the waveforms on the nixie PCB, transistors T2,4,6,8 and 10. (In my instance A92 B 331s were supplied.) I am not sure of the pin out, but presume the base is the middle pin. For all of the transistors the waveform on the base pin looks like the same rough square wave. At the pin (collector?) that supplies the anode, the waveforms are the same for the nixies, V1 (ok), V4 (ok) & V5 (ok) yet the "collector" waveforms for V2 (fails) and V3 (fails) are the same as each other, yet different to the working nixies V1, etc. So this seems to me that the two transistors, T4 & T6 are not functioning the same as T2, T8 & T10, as all of the base & "emitter" wave-forms look identical (the "collectors" differ). I have checked all of them for dry-joints (reflowed the solder for all of the joints on the board, twice). I am no export, but might presume, that T4 & T6 are not functioning as required (curiously in a similar manner - most odd). What is your advice? Should they be replaced? (Sadly I have no spares.)
Tony
Site Admin
Posts: 951
Joined: Tue Jul 24, 2012 8:05 pm

Re: Help!

Post by Tony »

Check the anode voltage is reaching the nixie itself, try removing a working tube and comparing the waveform.
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

Tony wrote:Check the anode voltage is reaching the nixie itself, try removing a working tube and comparing the waveform.
I rechecked that the anode waveforms look the same as the "collector" waveforms, so the waveforms are getting to the nixies, without issue. For V1, V3 & V5 the peak-to peak voltage is about 460V. When I removed V1 (working) the peak-to-peak voltage dropped to about 260V and the square-wave was cleaner. For V2 (not working) the peak-to-peak voltage is about 200V very variable, the waveform is much more jagged, so much less energy is being delivered to the nixie, I suspect. When I removed V2 the peak-to-peak voltage dropped to about 160V and although the wave form became a "cleaner" square-wave, it was still much more noisy than the for V1, when removed.
Tony
Site Admin
Posts: 951
Joined: Tue Jul 24, 2012 8:05 pm

Re: Help!

Post by Tony »

The first thing to eleininate is the LED - the blue LED is in series with the MPSA42 base and can sometimes cause problems. Just bridge it for now to see if there's any change. The high voltages and resistances can make taking readings a bit confusing so replacing suspect transistors is the easiest way to eliminate them.
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

Tony wrote:The first thing to eleininate is the LED - the blue LED is in series with the MPSA42 base and can sometimes cause problems. Just bridge it for now to see if there's any change. The high voltages and resistances can make taking readings a bit confusing so replacing suspect transistors is the easiest way to eliminate them.
I tried shorting out the two blue leds under the tubes in question. This had no effect.
jmmcg
Posts: 52
Joined: Sat Apr 11, 2020 2:45 pm

Re: Help!

Post by jmmcg »

[SOLVED]
jmmcg wrote:XXXsnipXXX
I tried shorting out the two blue leds under the tubes in question. This had no effect.
A replacement nixie display PCB kit was supplied and that fixed this problem.
Post Reply