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Old 1st Mar 2019, 10:24 am   #1
Arium458
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Default Digeec nixie clock

I have a Digeec nixie clock which is faulty. The tubes light up but do not change. I cannot reset the time using the buttons, and seconds do not begin to count. From this basic description, does this sound repairable?
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Old 1st Mar 2019, 10:59 am   #2
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Default Re: EEC nixie clock NFU

Is it like the one in this thread https://www.vintage-radio.net/forum/...ad.php?t=72158 ? Things which once worked can almost always be repaired provided that they don't need unobtainable parts. I'm not sure whether that's the case for this 1971 circuit though.

Cheers,

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Old 1st Mar 2019, 11:09 am   #3
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Default Re: EEC nixie clock NFU

Yes, just like that but without the tenths of seconds.
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Old 1st Mar 2019, 4:46 pm   #4
G4YVM David
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Default Re: Digeec nixie clock

They look fab. I cant help yiu, but I hope you sort it. I love Nixie tubes. Wish I had one
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Old 1st Mar 2019, 5:00 pm   #5
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Default Re: Digeec nixie clock

If the digits are lighting up, that means the power supply and at least some of the ICs must be working fine. It's just that either the "units of seconds" counter stage is not counting, or all the counter stages are being held permanently in "reset".

Does the clock always read "midnight" at power up?

Can you get a picture of the circuit board, showing the numbers on the ICs?
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Old 1st Mar 2019, 5:33 pm   #6
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Default Re: Digeec nixie clock

The clock always reads 01 40 00 (or 1 40 00 in 24 hour mode)

I have attached some photos, but you'll have to let me know which parts you need to see in detail.
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Old 1st Mar 2019, 6:00 pm   #7
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Default Re: Digeec nixie clock

Another thread here: https://www.vintage-radio.net/forum/...ad.php?t=75458
A brochure, but no real help I'm afraid.
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Old 1st Mar 2019, 6:34 pm   #8
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Default Re: Digeec nixie clock

Interesting to see mention of other Digeec clocks here. I really hope to get mine working again, although I am barely competent with a soldering iron.
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Old 1st Mar 2019, 6:44 pm   #9
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Default Re: Digeec nixie clock

You could try a post here: https://www.vintage-radio.net/forum/...play.php?f=145 if you don't feel able to tackle it yourself. Chances are that the fault will be repairable as it appears to use standard components.
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Old 1st Mar 2019, 7:07 pm   #10
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Default Re: Digeec nixie clock

Is there any way to get to the 'lower' PCB in one of the photos that seems to be full of DIL-packaged ICs?

I'd start by checking the +5V supply rail. You have some TTL chips on the PCB you can see, look up the data sheets and identify the power connections. Check with a voltmeter and 'scope that you have +5V without significant ripple between the Vcc pin and the ground pin.
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Old 1st Mar 2019, 7:57 pm   #11
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Default Re: Digeec nixie clock

The heatsinking for that TIP29 is a touch "interesting"!

It looks like things have been running hot round it, too.
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Old 1st Mar 2019, 8:34 pm   #12
Arium458
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Default Re: Digeec nixie clock

I also got the impression there were indications of overheat there once I opened it up. I think I really need someone brave enough to take this on as a project.

Quote:
Originally Posted by AC/HL View Post
You could try a post here: https://www.vintage-radio.net/forum/...play.php?f=145 if you don't feel able to tackle it yourself. Chances are that the fault will be repairable as it appears to use standard components.
Thank you. I will try that.
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Old 16th Mar 2019, 8:05 pm   #13
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Default Re: Digeec nixie clock

The fault was repairable and the dodgy components were the two blue electrolytics which were down to the odd pF or ten.


Here's how it looks now....
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Old 16th Mar 2019, 11:47 pm   #14
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Default Re: Digeec nixie clock

Result! With no DC smoothing to speak of, the poor clock must have been resetting itself every 10 milliseconds!

This story, by the way, is a great advertisement for having an oscilloscope on your bench -- even a basic one is better than nothing. First poke of the probe tells you the power supply is full of ripple, swap the caps out, job's a good 'un, time for a brew!
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Old 17th Mar 2019, 2:30 am   #15
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Default Re: Digeec nixie clock

'Fraid I wasn't that organised. I suspected power supply issues but I didn't want to 'scope anything since the circuit is non-isolated- there's a normal transformer for the 5V side AC, but the DC 0V rail is tied to mains neutral to enable the Nixie HT to come straight from half wave rectified mains. A bit odd but cheaper I suppose.


I just pulled the capacitors and checked their ESRs. A quick prod round the rest of the PSU bits showed no obvious faulty bits and two new caps fitted later, it worked. It's on soak now.
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Old 13th Jun 2019, 12:30 am   #16
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Default Re: Digeec nixie clock

Unfortunately it's only lasted about 3 months


Back with me for investigation- so far I've found that the mains TX has died. It was taking out 500mA fuses on its input and when tried on the bench out of the unit straight on the Safebloc it emitted the magic smoke.


Unfortunately it's an odd size and has a 10V off load secondary so it may be difficult to find a drop in replacement.


The clock itself looks promising, fed with 5V dc and mains for the nixie supply, it lights up at 014000 but without a 10V ac supply to trigger the counters it doesn't do anything else. I've got some old 220V : 6.3V mini transformers which give about 9V off load- I'll try adding that to the mix tomorrow to see if the clock really is OK. They won't do as a fix, though, I know from looking at their waveforms that they're running into saturation at 240V input (they came from a French vide-grenier many years ago).
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Old 13th Jun 2019, 11:26 am   #17
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Default Re: Digeec nixie clock

Yay!

The clock still ticks. Adding 9Vac to the brew got it going.

Now I need to source a transformer. It needs a single secondary, around 10V off load and rated to drive a bridge rectifier, capacitor filter with about 400mA dc load.

Core is 43*35*15mm, fixing centres on top of clamp are 33mm- it's mounted "upside down".

Mains input is on mounting hole side of TX.

See attached pic.....
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Old 13th Jun 2019, 2:51 pm   #18
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Default Re: Digeec nixie clock

It might not be easy to find an identical transformer with fixing centres on top. This slightly larger and has 2x5V ac at 6VA:
https://uk.rs-online.com/web/p/chass...rmers/0504694/

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Old 13th Jun 2019, 7:02 pm   #19
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Default Re: Digeec nixie clock

That's a good spot! Looking at the spec, it may be possible to transfer the stack clamps over. I've got a quote for a rewind as well so I've passed the decision back to the owner over cheaper probable fit/fix or dearer guaranteed fit/fix.
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