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Author Topic: Unexplained Navitron TDC3 failure (solar thermal system).  (Read 4724 times)
garyh3
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« Reply #15 on: May 18, 2020, 09:41:49 AM »

Did you remove the LCD or how did you replace the cap's under the LCD display ?
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Robl
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« Reply #16 on: May 18, 2020, 07:46:46 PM »

I didn't remove the display, I didn't want to damage it.  I used a butch pair of wire cutters, and chopped the caps into bits from above.  Then more delicate ones to trim the remainder nicely.  Then I soldered new caps onto the through-hole pads from above, just using a big blob of solder, no attempt to push anything into the hole, didn't want anything falling out the other side.  When I'd finished the new caps had maybe 8mm long leads, while the original were flush mounted on the pcb.
It's still ok today, don't want to jinx it mind.
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Robl
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« Reply #17 on: May 29, 2020, 08:05:44 AM »

My TDC3 failed again yesterday, in exactly the same way. 
Screen blank, pump off, transformer inside warm.  I took it apart, waited 5 mins, re-inserted it, and it's working again.

2 weeks ago I replaced the electrolytics with like for like, and all has been good until now.

I've inspected all of the solder joints, and they all look good.  No amount of banging on the unit makes it turn off when it is working, nor on when it is not working.

Does anybody have a circuit diagram, or any more ideas?
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Robl
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« Reply #18 on: June 29, 2020, 11:41:47 AM »

And again, failed yesterday (no display, pump doesn't run).  This time I was slightly more prepared, as I had presoldered wires coming out of the unit, monitoring the regulated 3v3 and the unregulated 15v lines.  I found:

When running normally, I get 3.25V dc +90mV acrms on the 3v3
And 14.56V dc + 90mV acrms on the 15v line

When it's failed, I get 3.28V dc + 1mV acrms on the 3v3
And 16.29V + 13mV acrms on the 15V line.

My conclusion from the above is just that it takes less power when failed.

When it was in the failed state, I unplugged it, shorted out the 3v3 and 15v lines, counted to 10, unshorted, put it back.  The +15/3v3 came back, but it did not fix it.

My conclusion from this is that it's not a software crash for any reason (caps, psu...).

I tried uplugging again, "heavily tapping" the processor and what looks like the crystal, plugged back, still didn't work.

Waited 30mins, plugged back, it's working again.

I appreciate I'm going to have to replace the unit, but its a faff, and I have enough to do.  It seems to be thermal, as the only thing that fixes it is time spent off.

In the meantime I bought a Navitron sale Grin 12v solar thermal controller  - mainly as it avoids the annoying connection technique the TDC3 has.   
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Robl
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« Reply #19 on: August 11, 2020, 08:51:28 PM »

I think Iíve fixed it:-).  The unit has two crystals, 32khz for a real time clock, and 8Mhz for normal running.  The 8MHz one didn't always start when I powered the unit from dc, needing a touch on one of the pins to get it going.  I bought another (31p farnel), and it starts up every time now.  Iím guessing the old part esr (equivalent series resistance) increased as it aged, until there is insufficient gain to guarantee oscillations.
Fingers crossed, if it lasts 2 weeks itís good.  If not.... gah.  Theres no glycol left in our system at the moment, Iíve just been refilling with water for the last few months.
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Alan D
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« Reply #20 on: August 11, 2020, 09:07:08 PM »

Hello Rob

Ref "  Theres no glycol left in our system at the moment, Iíve just been refilling with water for the last few months. "

I installed two systems. Mine and next door. In the first few weeks of Navitron selling the panels. Never had Glycol
in the systems. Might be a problem further North.  snow
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Robl
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« Reply #21 on: August 30, 2020, 10:18:22 AM »

I hadnít fixed it:-(.
It failed again yesterday, no idea why, 3v3 good, no lights, no action, Off/on fails to fix, grrr.
Today I removed it, replaced it with the one I got from the Navitron sale (thank you Navitron!).  New one is not as sophisticated as the tdc3, but I didnít really use most of the features, just Ďrecoolí if it gets too hot(new one has it). So itís fine.
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Alan D
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« Reply #22 on: August 30, 2020, 08:31:45 PM »

Ref " Does anybody have a circuit diagram, or any more ideas? "

Does it boot up if you touch any crystal pin or only one of the pins. ?
I have found adding a 20 puff silver mica capacitor across the two pins might do the job.
Yes the frequency will change a Knatts Coook
Not that you need it now.
If you want to post it I will have a play.

Regards

Alan
« Last Edit: August 30, 2020, 08:33:18 PM by Alan D » Logged
Robl
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« Reply #23 on: August 30, 2020, 10:35:59 PM »

I think the crystal was marginal, so it didnít always start up on power up.  That was fixed with a new crystal.  Iíd already replaced all 3 electrolytics with like for like.  The crystal didnít explain why the unit stopped every now and then, nor why itís not starting up at all now.  None of the failures were Psu related btw, 3v3 was always there even when unit failed - I soldered some wires onto 3v3/0v, and ran them out of the unit to check. 
You canít open the unit up without disconnecting the mains, safety first, very annoying.  Prior to crystal changing, failure was associated with no 8MHz oscillation (I have an oscilloscope, and ran the unit from 15v dc prior to its voltage regulator).  Not that I gave it much chance today  - off/on 10 times, disconnected in frustration! 

Youíre welcome to it, I think it would just be a source of frustration though, and donít recommend it except for spares!  Pm me your address if you want it......soon, bin day is Tuesday here :-)
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