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Ice Clock Tube does not light up
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Ice Clock Tube does not light up

by BarneyRubble on Thu May 29, 2014 10:58 pm

HI

I went through the instructions step by step, measured the voltages along the way as per the instructions. When I finally plugged in the tube - no glow... so I stepped back and measure the boost voltage - 13.9 volts... so I removed the Maxim MAX6921 chip from it's socket and the voltage went back up to 61.5 volts. Attached is a back and front view of the board - all the components are in the right places..... I am measuring the boost voltage on the cathode of D3 as per the instructions. The voltage on the Source and Drain of Q3 are 4.707V and the Gate voltage is 0v - this is without the Maxim chip plugged in.

Without the Maxim chip plugged in the pin 1 of the IC2 socket measures 61.60 V - same as the boost voltage on cathode of D3. Once I plug the Maxim chip in this drops to 13.9V.

All measurements taken with the VFD unplugged.
Attachments
photo 2.JPG
Back Side of Board
photo 2.JPG (150.5 KiB) Viewed 622 times
photo 1.JPG
Front Side of board
photo 1.JPG (145.52 KiB) Viewed 622 times
Last edited by BarneyRubble on Thu Jun 05, 2014 9:19 pm, edited 1 time in total.
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Re: Ice Clock Tube does not light up - boost voltage low

by adafruit_support_bill on Fri May 30, 2014 6:26 am

Those voltages all sound normal. The boost voltage does drop to the 14v range with the Maxim chip installed.

Post a photo showing the solder-side of the tube board, as well as a closer shot of the solder-side of the VFD end of the main board. A little larger than what is currently posted would be good - so we can see more detail.

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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Sat May 31, 2014 4:13 pm

BarneyRubble wrote:The voltage on the Source and Drain of Q3 are 4.707V and the Gate voltage is 0v - this is without the Maxim chip plugged in.

In normal operation, there should be a ~1.2 volt drop across Q3 (across the source and drain). What are the Q3 voltages with the side board installed?

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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Sun Jun 01, 2014 8:02 pm

Hi jarchie - the Q3 voltages with the sideboard installed are 4.632 and 3.108 a source/drain voltage drop of 1.573 volts. Attached are the photos as requrested above. The only thing I can see is there is a bit of flux but that should not matter?
Attachments
P6011542.jpg
P6011542.jpg (119.05 KiB) Viewed 578 times
P6011539.jpg
P6011539.jpg (95.68 KiB) Viewed 578 times
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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Mon Jun 02, 2014 12:07 am

BarneyRubble wrote:Hi jarchie - the Q3 voltages with the sideboard installed are 4.632 and 3.108 a source/drain voltage drop of 1.573 volts. Attached are the photos as requrested above. The only thing I can see is there is a bit of flux but that should not matter?

I doubt the excess flux matters--it doesn't look burnt. A voltage drop of 1.6v seems reasonable, and your soldering looks good by my eye.

This is a long shot but... I've had trouble with unwanted rosin conduction using Adafruit lead-free solder. I thought this was an unusual problem until my father had the same issue with a roll of Adafruit lead-free solder that he bough a year later. So even if the rosin doesn't look burnt, I do recommend cleaning it away with alcohol and a toothbrush if you're using Adafruit lead-free solder. But if you're not using the Adafruit lead-free solder, I doubt that cleaning the rosin will help. But it doesn't hurt to try.

The next thing I would try would be to run the clock with the side PCB inserted in a completely dark room, and give your eyes a chance to adjust to the dark. Do the two IV-18 filaments glow?

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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Mon Jun 02, 2014 12:28 am

HI jarchie - I am using multicore 5 core 362 flux solder tin/lead 60/40 mix. it is the stuff we use at work for surface mount rework so should be good stuff. Now.....the people in the office think I am mad. I cannot find a dark room so what I did was put the clock inside my camera bag and pushed my head in there too - what I saw.... 2nd digit on the clock, bottom segment, pulsing on/off at 1 second duty cycle. Occasionally one other segment lights up.
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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Mon Jun 02, 2014 2:10 am

its the tube I think. I have another kit and as a last resort I soldered up the tube out of that one. Most of the segments in that one light but by all means not perfect - no where near perfect in fact. I think I have 2 unlucky tubes.....
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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Mon Jun 02, 2014 5:56 am

BarneyRubble wrote:no where near perfect in fact. I think I have 2 unlucky tubes.....

I'll wager that both tubes are good. Shoot me a personal email with your postal address and we can test my theory.
<www.jarchie.com/email>

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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Mon Jun 02, 2014 6:46 am

Mail sent. I live in Australia....
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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Tue Jun 03, 2014 9:00 pm

BarneyRubble wrote:Mail sent. I live in Australia....

Got it, thanks! In the meantime, there are a couple more tests that I think are worth trying.

Measure the voltages from Q3 to the filament (test points 1-5 in the image below). To check for a bad tube filament, you could also disconnect the side board and check the filament resistance (test points 5 and 6 in the image below).

test-points.png
test-points.png (53.66 KiB) Viewed 535 times

It is also remotely possible that the problem is with Q3. The test for that is straightforward and described in this post.

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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Tue Jun 03, 2014 9:20 pm

Voltages

    TP1 - 3.195
    TP2 - 2.110
    TP3 - 2.105
    TP4 - 2.108
    TP5 -2.104

Resistance across TP 5-6 - 13.9 ohms

Bypassing Q3 made no difference.
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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Wed Jun 04, 2014 7:52 pm

All of those measurements seem normal. Did you try bypassing Q3 with the tube where a few of the segments light? If not, that might be worth a go.

The other components involved in the display circuit are the driver chip (MAX6921) and the microcontroller (ATmega168v); it might be worth replacing those parts with the corresponding parts in your other kit to see if the problem lies there.

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Re: Ice Clock Tube does not light up - boost voltage low

by jarchie on Wed Jun 04, 2014 8:09 pm

BarneyRubble wrote:its the tube I think. I have another kit and as a last resort I soldered up the tube out of that one. Most of the segments in that one light but by all means not perfect - no where near perfect in fact. I think I have 2 unlucky tubes.....

One thing is bugging me... When only some segments light, the problem is almost always Q3, so it was a surprise to me that bypassing Q3 didn't work. And I've seen a bad Q3 cause a blank tube as well as one where only some of the segments light.

I'm betting you did the Q3 bypass test correctly, but just to confirm, the picture below shows the two pins of Q3 should be shorted:

Q3-bridge.jpg
Q3 bypass points
Q3-bridge.jpg (60 KiB) Viewed 514 times

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Re: Ice Clock Tube does not light up - boost voltage low

by BarneyRubble on Wed Jun 04, 2014 8:29 pm

Yes Sir that is what I am doing.
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Re: Ice Clock Tube does not light up - boost voltage low

by adafruit_support_bill on Wed Jun 04, 2014 9:01 pm

One thing is bugging me... When only some segments light, the problem is almost always Q3, so it was a surprise to me that bypassing Q3 didn't work.

That was a surprise to me as well. But 2 'unlucky tube' would be even more unusual. I'm curious to see how jarchie's theory pans out. Please keep us up-to date. We'll make sure you get your clocks running one way or another.

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