My WFly wft-08 has died - HELP

[He Who Shall Not Be Named]

Good stuff, Tom. My transmitter went down about two weeks ago -- I was working up a new charging lead and assumed I got the polarity wrong and clobbered a diode or something. I'll check my units fuse. Thanks for the thread, you're teaching me stuff.

And a shout-out to WFly for the tech support. Much appreciated.

David

[trout]

Here is the response I got:
Hello Tom,

Here comes the spec of the fuse, you can change it if you can buy it.




Have a nice day

So I searched last night, and I can get 50 of these cheaply from China, but it was about 4 week estimated time of delivery. So I ordered from Digi-Key and ordered:

F3289-ND

FUSE SLOW 250VAC 1A AXIAL

I think it is the right one.

[trout]

Now that a solution is at hand..... I want to figure what caused this, so it does not happen again (if I can prevent it). Are my batteries too strong for this? The batteries I am using are NiMH 1.2V with 2850mAh. They are in series, 8 of them, that on paper should only be 9.6v, but there must be an overage because they tested between 10.4 and 10.8v fully charged. Do the mAh also add together in series? If that is the case then this pack offers more than an Amp in power which is what the fuse is rated for since 1Amp = 1000 miliamps and my pack added up equals 2.28A. This is just me thinking this out and opening the door for discussion. Thoughts?

[KevinMc]

Ugh! I've got some catching up to do!

Heat! Yes it is a killer for computers and now that you mention it, when I ran the sub in the inflatable pool, the removable box in the back of the transmitter with the frequency on it seemed mighty warm to me (that may be normal), but I did not remember that until you mentioned it.

Did you have the antenna up or down when doing this? When the antenna is down it causes an impedance mismatch which fouls up the energy transfer from the final amplifier stage to the antenna. The two results are that the transmitted signal is not as strong (good for range checking) and that the final output amplifier stage runs hotter (not so good for anything). I make a point of not running my tranmitters for any longer than necessary with the antenna collapsed.

Now that a solution is at hand..... I want to figure what caused this, so it does not happen again (if I can prevent it). Are my batteries too strong for this? The batteries I am using are NiMH 1.2V with 2850mAh. They are in series, 8 of them, that on paper should only be 9.6v, but there must be an overage because they tested between 10.4 and 10.8v fully charged. Do the mAh also add together in series? If that is the case then this pack offers more than an Amp in power which is what the fuse is rated for since 1Amp = 1000 miliamps and my pack added up equals 2.28A. This is just me thinking this out and opening the door for discussion. Thoughts?

The fuse rating (1A) and the battery capcacity (2.85Ah) are two independant things. The first is sized for the rate at which your transmitter should be drawing current, where the second represents how much capacity your batteries have. You could think of the fuse rating like the maximum safe speed a car is allowed to travel at, your battery capacity then becomes the size of the gas tank. A bigger gas tank (battery) would allow you to drive for a longer period of time without affecting how fast you may drive. Make sense?

I also double checked your part number and I noticed that the fuse you've selected is a "slow blow" type - these are generally only used on circuits which electric drive motors or solenoids as these things have a significant "inrush" in the current when first turned on. For electronics like this a normal or fast-acting is typically more appropriate. (I also see that Digikey doesn't have any in stock with that form factor though.) Best to as the WFLY folks if one's that's all right.

To answer your capacity question, the capacity stays the same when you put batteries in series, you only add the voltage. When you place batteries in parallel the capacity adds and the voltage stays the same.

[trout]

Kevin, you make perfect sense! Thank you for clarifying! I am disappointed I got the wrong type of fuse....sigh...... Maybe I do have to order one from China. Do you have a source for one either in Canada or south of your border?
Thank you for all your knowledge and willingness to share.
Peace,
Tom

[KevinMc]

Your first source for parts is also mine. I did have a look around and found that the fast-blow equivalent of the part you've bought would be 0874001.MXEP and it's currently in stock at Mouser.com. (I haven't looked at what their shipping rates are, but they're probably on par with Digikey.)

As for choosing "the wrong type", remember it may not matter but just be aware that what you've got is not quite the same as what was in there before. The guys from WFLY may be fine with substitution of a slow-blow, or they may not, but only they can tell you.

No worries on all the explanations - the only way our hobby will continue to move forward is by people sharing what they know. I've been fortunate to have many people share things with me so when ever I can I like to pass what I've learned along as well.

[MFR1964]

Tom,

There is a makeshift solution, take a big glassfuse with the same specs, solder some wires on the ends and replace it for your faulty fuse, in my profession i use this method when i don't have the right size fuse.
Even new fuses can blow, i think it's because the fuse can't meet the needed specs or is a poor example of production.

Greetings Manfred.

[trout]

@Kevin Thank you - I went ahead and ordered it from mouser.com, I found it last night, but wanted to see if you recommended someone else.

@Manfred - That is a good solution.

[WFLY Technician]

Hello Tom,

How is the thing going now?

Joanna

[trout]

Joanna,
I have some fuses on the way. Do you care if the fuse is slow blow or fast blow fuse?
和平,
Tom

[Scott T]

There are small fuse that are similar in the plug of christmas light string.
They are probably slow blow or two high a amp rating.

Scott T

[trout]

Scott,
You really are a great thinker! You come up with some really good things. I would love to encourage you to build, what can we do to help you? PM me and let us talk.
Peace,
Tom

[WFLY Technician]

wfly always use the fast blow fuse to protect electric parts.

Joanna

[trout]

Thank you, I now have both types coming in any day now. I will update this forum of the results.
Peace,
Tom

[trout]

The fuse came in and I installed the new 1a 250v fast fuse. It was exciting to install and the anticipation was high. Put the battery pack in, and.......

NOTHING!

It still does not work. What a let down.

I really need to see what WFly will do now. How can I get this resolved soon????