D8 fried on 720!

[Nano07]

Welcome to TTF.

Supermod Mikealder should see this thread and give advise. check back.

Thanks DHN!

 

[canderson]

I didn't know the term SMT...

"Surface Mount Technology" vs. the older "Through Hole Technology". The parts all sit on the surface with no leads sticking through the board.

Also I did a search on Zener 5.6v Diode and found these... would they be ok?

Apart from the fact that they're huge compared to the original, yes. You really want to find a shop somewhere that sells surface mount equivalent parts to what you showed us. The new SMT parts are tiny compared to their older 'through hole' siblings. If you could figure out how to solder one of those big boys to the board, yes, they would work. Not knowing what site to look at in your part of the world for parts, I can't recommend a specific component to you. Just be sure that if you buy the one you showed us, that you are CERTAIN that the end with the black band goes where the white band was on the original SMT part. These can't be installed willy-nilly .. they have a very specific polarity and have to be installed the right way round to work.

 

[canderson]

You'll want a soldering iron with a VERY fine tip. If the tip that comes with it is a bit blunt, feel free to file it down to a fine point and use solder to cover it again. Someone who has some basic soldering skills should be helping you with this project! See other thread for more details regarding the diode itself.

 

[Nano07]

"Surface Mount Technology" vs. the older "Through Hole Technology". The parts all sit on the surface with no leads sticking through the board.

Apart from the fact that they're huge compared to the original, yes. You really want to find a shop somewhere that sells surface mount equivalent parts to what you showed us. The new SMT parts are tiny compared to their older 'through hole' siblings. If you could figure out how to solder one of those big boys to the board, yes, they would work. Not knowing what site to look at in your part of the world for parts, I can't recommend a specific component to you. Just be sure that if you buy the one you showed us, that you are CERTAIN that the end with the black band goes where the white band was on the original SMT part. These can't be installed willy-nilly .. they have a very specific polarity and have to be installed the right way round to work.

Thanks so much for your comments on both threads canderson. Things are getting a bit clearer now!

I thought they looked big, but was not sure if they were supposed to look like that.

Now that you explained the SMT, it all makes sense

I'm going to try to find the equivalent small component then. About the polarity... I'm not sure where the band should be pointing because (as you can see in the photo) it's a bit toasted and I can't really tell.

I'll see if I can find an image on the net to see better...

This is the only place close to where I live that has components... I'll see if I can find an SMT version there...

Jaycar Electronics - Search results ZENER 5.6v

 

[Andy_P]

Here's a comparison of some various surface mount components alongside a "normal" wire-ended resistor on the right.



The diode you need will be about the size of number 5 or 6... scary stuff if you're not used to it!

 

[Nano07]

Thanks for the info Andy.

I think I found it. Would it be this one?

Altronics - Your One Stop Audio Visual & Electronics Supplier


I also found this place that sell components and they seem to have more variety. Can someone help me choose the proper one?

http://australia.rs-online.com/web/...=searchProducts&searchTerm=Zener+5.6v&x=0&y=0

THANKS

 

[canderson]

Thanks for the info Andy.

I think I found it. Would it be this one?

Altronics - Your One Stop Audio Visual & Electronics Supplier

Nope - that one looks round (odd). You need something that will lay flat on the board.

I also found this place that sell components and they seem to have more variety. Can someone help me choose the proper one?

RS Australia | World Leading Distributor of Electronics, Electromechanical and Industrial Components Your search for Zener 5.6v

That's more like it, but here's the thing - you need to get in there with a set of dial calipers or a really file scale and see how big the part actually is. For example, the part from your 2nd supplier comes in what is known as a DO-219AB package (that's known as the JEDEC number) whose dimensions are pretty well set in stone -- in this case, about 1.8 x 2.8mm for the black plastic part. If you'll measure the D8 on your board, we can no doubt come up with something for you.

 

[canderson]

I responded to your component selection over in the other thread. See you there!

 

[dhn]

This thread may look weird but I just merged the other thread with this one. No point having similar discussions in two places.

 

[Nano07]

Nope - that one looks round (odd). You need something that will lay flat on the board.

That's more like it, but here's the thing - you need to get in there with a set of dial calipers or a really file scale and see how big the part actually is. For example, the part from your 2nd supplier comes in what is known as a DO-219AB package (that's known as the JEDEC number) whose dimensions are pretty well set in stone -- in this case, about 1.8 x 2.8mm for the black plastic part. If you'll measure the D8 on your board, we can no doubt come up with something for you.

@Canderson. THANKS! I'll see if I can find a fine scale to measure it...

@dhn Sorry for the mess, and thanks for merging the threads. I just deleted all the duplicate msgs left in this thread..

 

[mr_milo]

Harpo (and anyone else that can help),
The same component also fried on my Go920. I have the skills to replace it, but don't know what the part is. What part did you try? I'm looking at Zener diodes at Digi-Key, but the 5.6V versions are very diverse. Thanks for any help you can provide.

 

[Nano07]

Hey mr_milo,

Unfortunately I won't be of much help as I still have mine disassembled and haven't done anything yet.

I live in a small town and can't find anyone local to help me, so I never did it.

I ended up installing Tomtom in my iPhone, and after a while Navigon with 3D reality view. I must say that I was quite impressed by the quality of the graphics, and voice guidance compared to the bland look & sound of tomtom in 3D (I've been a tomtom fan for many years, but now I think they dropped the ball and some companies are catching up)... a few months ago, if you asked me, I would have said that nothing could take me away from tomtom, but now... i'm not so sure... I think they have to lift up their game a little bit ;-)

Next time I'm planning a visit to the city, I'll try to find someone that can help me fix the unit (I don't like having broken gadgets lying around); so if you find the component, please let me know

Thanks man, and sorry I couldn't help you more.

 

[Jsaila]

I possibly have a similar prob. on my 720. The car power connector started playing up at the tomtom usb end, Before I got round to replacing it (I must fix that sometime syndrome) the 720 died, green light only in car or docking station.Fearing the worst I threw it in the cupboard for a year to look at sometime.Now is that time and I discover the car chargers are notorious for killing devices with their sensing nonsense. I have stripped the 720 down and checked battery volts which are zero even after 24 hrs plus on the PC (green light on). Checked all over board and no sign at all of any smoke mode. I presume d8 is intended to protect the cct. but it 'looks' perfect. If I plug just the board into the dock I get green light but nothing on the red and black pins of the battery plug. Is this a valid test, is it worth investing in another battery? Could a dead battery prevent the device powering up from the dock. Without any cct diags I'm stuffed so if any one can suggest any other action or compnents to check, if not I have a fancy doorstop which has had little use. Appreciate any advice.
.

 

[canderson]

After a year at that age, the battery is likely toast. They don't like full discharge conditions.

Pull the battery and check the power at the pins on the board during power up. No voltage there would indicate a shot charging circuit.

 

[Jsaila]

Thanks for the quick reply canderson. Pity its not what I wanted to hear but it confirms my worst fears. I have again tried measuring the volts on the socket to the battery with battery both connected and disconnected but it was zero in each case (note: I have the board disconnected from the front panel and plugged into the dock)
As I say results were as per my earlier post.so I put meter across zener which on a straight diode test appears functional, as I dont know what components comprise the charging circuit I've hit a brick wall. One thought is to try and see if it works feeding external 4.5 volts which I can rig up from 3 cells. Nothing to lose I suppose but it is frustrating, Tomtom didnt think this one out very well if a 10 quid charger can zap a 200 quid bit of kit. Do the newer modles have this "feature" I am thinking of putting any cash into a smartphone and an app. Any thoughts appreciated, even bad ones.

 

[canderson]

OK. Let's assume for a moment that the problem is in fact D8. As SMT parts go, it's a whopper (well, compared to a lot of them). What I've not taken time to do was can opener an operating unit and measure the breakdown voltage, if there is one. We've all been assuming, it seems, that this is a zener. Should be easy enough to determine that.

If I take the time to open one up and sort it, are you or any of your posse locally able to pull an SMT part of the board and replace it? I'd give you a Digikey number, but I know that's typically not where you source parts on your side of the Atlantic.

Oh, and the battery can be replaced easily enough as well, and at that age, probably needed it anyway. Instructions are here on the site.

 

[Jsaila]

thanks for that kind offer, before I try removing components with my shaky old hands and poor eyesight I thought I'd wire in another power source to the battery socket j7 and see if the unit starts up. Was just going to put two cells in series to give me 3v, do you think that might do the trick?

 

[canderson]

The nominal voltage on the pack inside is 3.7V. I don't know for a fact, but suspect that the logic is going to require 3.3V minimum. A pair of 1.2V or 1.5V cells probably isn't going to cut it. You'll need a pair of lithium cells (e.g., Energizer lithium AA cells) at peak capacity around 1.7V, and even then, if there's any onboard regulation, that might not be a happening thing, either. It might be worth a try, but I really don't think you can succeed with NiMH or alkaline or similar lower voltage cells.

 

[Andy_P]

three cells and a zener?

 

[canderson]

Not much of a regulator, but I guess OK for the short term. He'll have to current limit the zener somehow or toast it and such the batteries dry real quick, but knowing what the resistor should be is a crap shoot without more info about current draw of the circuit itself. Would be great if he had a little bench supply he could dial up to 3.7V!