Flickering & Dim Segments Moderators: adafruit_support_bill, adafruit

[rsc]

My clock assembly seemed to go smoothly and when initially turned on all systems looked good ... other than the 2nd digit of the 'seconds' display and the AM/PM marker - the two far left & right digits - are dim compared to all the others. As time passed ( ~10 minutes), some of the digits started to flicker - randomly - first it was the 1st digit of the 'minutes' display and then, after turning the clock off and on, the flickering move to the 'hour' digit. Then, after turning it off/on again the problem moved to the 'seconds' digits. Pretty weird, eh? If I turn it off for awhile and come back and turn it on all the digits are stable for awhile before flickering begins. If I let it continue to flicker the flickering gets progressively worse and the digit will eventually completely shut off/disappear. Turn it off for awhile and come back and turn it on and all is OK, for awhile.

Even with the flickering continuing, the clock maintains time and all menu functions are selectable. No segments within the display are missing, before the flickering begins.

I have redone all the solder joints on the tube and headers with no change in performance/results.

Any thoughts?

[adafruit_support_bill]

If you post some photos showing all your soldering and connections we'll see if we can spot any potential issues.

[rsc]

Thank you for your quick response. I've attached some photos. You've probably never see such poor soldering - I am new at this and old! ;-).

[adafruit_support_bill]

Ah! An Ice Tube. We don't see many of those these days. We unfortunately had to discontinue the Ice Tube a while ago due to the scarcity of the VFD tubes.

Can you read the markings on Q3? Earlier versions of the kit shipped with a ZVP3306A as part of the voltage boost circuit for the display. We later switched to a ZVP2110A for more stable operation.

[rsc]

Again, thanks for the quick response! Yes, it is the older ZVP 3306. Do you think this is the problem? If so, where might I get a replacement?

[adafruit_support_bill]

We do not stock these anymore since the kits have been discontinued. But you should be able to find one at Mouser or DigiKey.

https://www.mouser.com/ProductDetail/Di ... %2Fw%3D%3D

[rsc]

Thank you, hopefully that does the trick!

[rsc]

I got one of the ZVP2110A and just replaced the old ZVP3306A. That did the trick - no more flickering! The last digit of the seconds display is still dim compared to all the others, but otherwise the clock works perfectly. Any thoughts on correcting the dim digit/segments? Notice in the photo, how all the other digits have a glowing halos compared to the last digit of the seconds.

[adafruit_support_bill]

It is normal for these clocks to show a brightness gradient with digits to the right getting dimmer. There are several threads on the topic if you search the forums. Forum member jarchie has done a lot of work with these clocks and has some hacks to improve the performance.

viewtopic.php?p=223266#p223266

[jarchie]

A dim final digit is usually due to insufficient current across the tube filament, and replacing Q3 with the ZVP2110A--as you have done--usually solves the problem. To further increase current, try temporally shorting both sides of R3 with a spare wire to see if this brightens up the final digit. If that helps, replacing R3 permanently with a jumper should be fine.

On the software side, you could install one of the alternative firmwares that allows adjusting the brightness of the final digit. My xmas-icetube firmware has per-digit brightness controls that could help (forum, GitHub).

[rsc]

Thank you jarchie, great advice, shorting R3 fixed the dim digit problem. The two center digits are the brightest, but the difference between all the digits is only slightly noticeable. I'd like to upgrade to your xmas-icetube firmware and will have to figure out how to download and install it.

[jarchie]

Thank you jarchie, great advice, shorting R3 fixed the dim digit problem.

Excellent! I'm glad bypassing R3 works well for your tube.

The IV-18 tubes are designed for 5v AC across the filament, but the Adafruit design uses DC instead. At 5v DC there is a noticeable brightness gradient across the entire tube. But the tube is robust and still works well with filament voltages as low as 2.5v or so, and this virtually eliminates the brightness gradient issue. So the Adafruit design deliberately under-powers the filament by dropping the 5v DC clock voltage with Q3 and R3. But for the occasional tube (like yours), the default choice for Q3 and R3 drops the power too much, resulting in the dim digit issue.

Since the sole purpose of R3 is to drop the voltage and deliberately under-power the tube filament, replacing R3 with a jumper is fine as a permanent solution and does not over-power the filament. In fact the filament is still under-powered as there also a significant voltage drop across Q3. I would guess your filament is only getting about 3v or so right now. But this is fine--ideal even--since it prevents the brightness gradient issue.

The two center digits are the brightest, but the difference between all the digits is only slightly noticeable.

This sounds like natural tube-to-tube variation, so I think that you've found the optimal voltage/current for your tube.

If the small amount of brightness variation bothers you, the per-digit brightness controls in my firmware might be worth a try. In the Ice Tube Clock, each digit is displayed one at a time, but so rapidly that it appears that the entire display is lit. The xmas brightness control works by allowing you to increase or decrease the relative time spent displaying each individual digit. The net effect is to make individual digits appear brighter or dimmer.

I'd like to upgrade to your xmas-icetube firmware and will have to figure out how to download and install it.

I have been known to send preprogrammed chips to people, but it's more fun to learn to program your own chips. As an added benefit to going the DIY route, you can adjust compile-time options yourself. This can be useful to support some of the hardware hacks and mods described on this forum.

If you choose to program a chip yourself, I wrote tutorials a while back for both Windows and MacOS X. And I'm happy to help through this forum.

Anyway, good luck and happy hacking!

[atocom]

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