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OT: Tennis ball machine PCB testing

The part numbers are printed on them. Whether the FET has actually failed, I'm not sure. Something looks a little iffy about the joints.
 
I'm taking the opportunity to learn about these transistors. I had taken the part number and searched it to find immediately a video of someone fixing a similar machine by the same company. He seemed to be having the same issue and was able to swap an identical part. Surely the company don't set their machines up to fail in such a manner. Is there a way to protect these transistors from becoming overloaded by a little strain on the tiny motor?
I'd believe I'm being paranoid but it sure sounded and inferred they had a side hustle going when I explained the issue ...it was all very matter of fact and I've never heard of anyone so quickly say to take out a PCB and send it in. Either way I need to get it repaired and will take extra precaution the next time.
thanks
 
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Here is a look at the entire PCB along with the only protection I could find on the system and that trip switch was located next to the battery charging port and seems irrelevant 1000004131.jpg
 
The red jobbies look like crimped butt connectors. And boy, in that photo (though not very clear) all the solder joints on those 4 devices look a bit suspect. In that lower section, looks like a couple FETs and a couple of Schottky/barrier diodes, if I'm not mistaken. JST knows this stuff better than I do, I'm just a hobbyist.

The one IRF 2204 (now top right) looks like it's showing signs of either rework (leftover flux mess and terrible looking solder joints) or heat damage to the board. The black part you've got to the left is just a plain old momentary switch by the look of it. Not sure what its function would be. A fuse would generally be found somewhere on the plus side of the battery power circuit between it and the circuit board. Sometimes on the circuit board, but I don't see anything on this one. What other components are on the back of the board? I see several sets of pins besides the connector terminals.
 
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The red jobbies look like crimped butt connectors. And boy, in that photo (though not very clear) all the solder joints on those 4 devices look a bit suspect. In that lower section, looks like a couple FETs and a couple of Schottky/barrier diodes, if I'm not mistaken. JST knows this stuff better than I do, I'm just a hobbyist.

The one IRF 2204 (now top right) looks like it's showing signs of either rework (leftover flux mess and terrible looking solder joints) or heat damage to the board. The black part you've got to the left is just a plain old momentary switch by the look of it. Not sure what its function would be. A fuse would generally be found somewhere on the plus side of the battery power circuit between it and the circuit board. Sometimes on the circuit board, but I don't see anything on this one. What other components are on the back of the board? I see several sets of pins besides the connector terminals.
Thanks.. I believe it is heat damage on that left upper hexfet ISR2204S. and the black switch is a reset.
Are there any reliable places I can send the board in and have it diagnosed/repaired
This seems to be above my level of experience and even though I enjoy learning this stuff though the risk/reward don't seem favorable on this project for me.
Thanks for the reply!
 
Yep, didn't look it up before, looks like a thermal overload/breaker. I don't know of any repair places offhand, usually do that myself. Maybe JST will. You don't want to send it back to the OEM? If the price isn't exorbitant and you don't want to do it yourself that may be your best bet. I'd ask if that $150 is the repaired price. I don't think you'll get it a whole lot cheaper anywhere else.
 
I would do it myself if thought the odds were in favor of that being the only issue. That hexfet (upper left) def looks cooked so I may give it a shot. Don't think I have much to lose at trying it.
SP wants $150 to diagnose and I'm not sure if that is diagnose and repair but I shot them another email this morning.

Appreciate the replies .. thank you!
 
here's the part 2 continuation video
showing problem persisting and having to replace a transistor below the mosfet. This put me into deeper water than only swapping one mosfet. I may do some more homework and take another run at it
 
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Go for it. It's already broken. Can't get much worse. And BTW, the Q6 he replaced is one of those troublesome little BJTs I mentioned earlier. They are generally what switches the control power into the FETs in a circuit like this.
 
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Yes....

If a Mosfet or IGBT fails, the gate normally is shorted to the drain and source internally, since the chip inside actually melts through.

That shorts the gate drive to the higher drain voltage, and often kills the driver device. It is just about a standard procedure to replace the gate driver parts when replacing a Mosfet or IGBT, and is sometimes needed even with a bipolar transistor.

If the failure is the power device getting vaporized, then the damage may go farther, and can make repairs impractical. I have seen holes burned in the PCB, traces vaporized, etc. You do not seem to have any such problem, from the pics posted.
 
Yes....

If a Mosfet or IGBT fails, the gate normally is shorted to the drain and source internally, since the chip inside actually melts through.

That shorts the gate drive to the higher drain voltage, and often kills the driver device. It is just about a standard procedure to replace the gate driver parts when replacing a Mosfet or IGBT, and is sometimes needed even with a bipolar transistor.

If the failure is the power device getting vaporized, then the damage may go farther, and can make repairs impractical. I have seen holes burned in the PCB, traces vaporized, etc. You do not seem to have any such problem, from the pics posted.
Thank you for the inference.. great info!
 
From looking at your latest picture, I was going to say that board was probably wave soldered on the side shown, then all the through-hole devices on the other side were hand-soldered. BUT, everything around your suspect devices looks terrible. Maybe it's because of the pictures, but looks like solder whiskers all over the place in your first picture; R117 or U24 for example. The green color indicates a soldermask, which protects a wee bit against shorts due to bad soldering, but not reliably. If it were me, I would inspect every solder joint in that area and correct the whiskers with a scribe or exacto knife. If that is the way it came from the factory, that is pretty bad soldering. Most people who hand-solder for a living (if there are any left) take pride in their work.
 
And, if it was replaced, possibly in the rework station, or much later if the thing was not bought new, the IGBT may not have been soldered down well to the minimal heatsinking provided by the copper pad under the tab. While it is not super effective heatsinking, the overload may have finished it off due to poor soldering. Might have done that anyhow, but you have to give it a chance at least.

If you replace it, get it soldered down decently. It can be done without cooking the device, but you have to get in and out quickly. Don't use lead free, as it melts 100F or so higher than tin-lead No idea if the original maker used a lower melting solder, which is sometimes done.
 
From looking at your latest picture, I was going to say that board was probably wave soldered on the side shown, then all the through-hole devices on the other side were hand-soldered. BUT, everything around your suspect devices looks terrible. Maybe it's because of the pictures, but looks like solder whiskers all over the place in your first picture; R117 or U24 for example. The green color indicates a soldermask, which protects a wee bit against shorts due to bad soldering, but not reliably. If it were me, I would inspect every solder joint in that area and correct the whiskers with a scribe or exacto knife. If that is the way it came from the factory, that is pretty bad soldering. Most people who hand-solder for a living (if there are any left) take pride in their work.
Noted... It did come from the factory this way and for reference it was purchased new from Silent Partner and is one of their more advanced premium machines Quest Scoop model. I decided to send the PCB back to SP and they sent me a repair bill of $140. From looking over the itemized bill It appears they added newer components and upgraded the PCB a bit. I will take pics and upload before reassembly as a thank you for those who took the time to comment and offer helpful feedback. My suspicion is they make tons of money repairing these pcb's one can't help but wonder if the model is by design... sort of planned obsolescence.
Customer service however is best I've seen as far as convenience and turnaround. Very quick to answer your questions via email and Steve @ SP has quite a rep for great customer service. I personally don't feel like a machine of this value should have fried components for overloading a hopper and they did indicate they add heatsinks to deter this from happening so easily in the future. The machine has been well taken care of and has only been used maybe ten times over last few years. Pics of the new improved PCB coming soon!! Stay tuned lol
 
Here is the PCB returned from SP
along with an itemized list of parts replaced. Maybe some inference can be gained regardless
 

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Thanks to all who kindly took the time to help this newb.. I, despite trep getting the better of me, gained something in the value of information and look forward to my continued journey into this incredibly fascinating field ...in hopes of learning as much as I can and maybe even becoming a jedi like most of you.
But even more importantly, maybe even priceless, was this community's flocculation and flux. What a great community!!
With that I leave my own gift: .."Fluxus" and book called "Grapefruit" as revealed by John Lennon regarding his song "Imagine" in his last interview.
Cheers
 








 
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