Any ideas what could have gone bad in this Ryobi Tek4 charger?

[Sparky_NY]

The charger is also covered by the same warranty.

A story... As mentioned, I live in Anderson SC, the home of TTI which owns Ryobi, Ridgid and more. A few years back I bought a Ryobi combo 18V impact driver, drill , 2 Nicd batteries and carry bag at their factory sale for $35 !! Well, that night I charged them up and one of the batteries started melting ! Next day I called them, told the guy what happened and he sent me two Lithium large batteries and the charger for free along with a prepaid return label for the original ones. He never asked for a receipt or any proof of purchase. He told me they no longer carry any NiCd stuff so he was sending me Lithium batteries and charger. I was floored by this ! I only paid $35 for the combo pack and the batteries/charger he sent would cost over $200 retail at the time ! Ryobi does not have the lifetime guarantee especially on batteries, much less bought at the factory sale !

[J Tiers]

Low grade"? Matter of opinion. Appears to be a mid grade board, appropriate to the product. The "crap on the bottom" may be just flux residue that has been there for a while in different environments. Many commercial boards are not washed.

The primary-side controller I cannot read the text on, but it resembles a Power Integrations chip, with their old logo. PI has a very good line of products, and a lot of application data for this sort of application.

There does not appear to be feedback, so the PI chip (if it is one) is running with primary side regulation, which is fine with the secondary regulator. An effective design that works fine.

It appears to have a battery controller on the secondary side, I cannot read that text on that one either, past a couple letters.

Several of the solder connections on the secondary side look nasty. I have fixed a number of power supplies by just resoldering bad joints.

Also, a diode can be bad/shorted, without being burnt-looking, and usually the primary side controller will shut off and not operate into a short. Usually that is the first diode in line, the one carrying the transformer output. That appears to be D201.

Some probing with a meter can check the diodes. Be aware that there may be odd reverse readings due to the way the components are usually connected.

[A.K. Boomer]

[QUOTE=J Tiers;n1921663]Low grade"? Matter of opinion. Appears to be a mid grade board, /QUOTE]

ehh yeah matter of opinion - and im calling it low...

even just due to the fact that what i call mid grade has things soldered on straight and not all jacked up...

of course there is "crap grade" seen plenty of those - and also "never shoulda even be built crap grade" so that gives some wiggle room to the low grade comment...

[gellfex]

I would start with the bridge rectifier labeled DB1. It looks like it has gotten hot. You should have around 170-180v at the output. Looks like they are using a very, very simple switcher. U101 controls the high side switching and runs open loop. Either of those two could cause the issue. You could also probe on the output of the transformer and se of there is anything there. You could have bad diodes on the output there.

The whole underside looks to be a mess. Did it get wet?

That's just an artifact of the pic, nothing appears unusual about DB1, or any component. I guess it's just toast, I don't have the knowledge to save this. I can hack it to the Imax, and I have a charger coming off Ebay with a 3rd battery and a driver. For you electronics guys, this little driver is the sh*t!

I appreciate the help guys, maybe someday we'll try this exercise with a truly unique item I have that needs help, a 70s vintage 4 channel PA amp of Italian mfr with sweet mechanical reverb that probably has a blown power transistor. I could never get myself to pitch it!

[J Tiers]

ehh yeah matter of opinion - and im calling it low...

even just due to the fact that what i call mid grade has things soldered on straight and not all jacked up...

That's not uncommon for consumer grade products done in SMT. Straightness does not add function, and there is nothing wrong with the board as far as location and straightness. Everything is on its PC pad, as it should be.

You DO see straight lines in MIL, and other high end stuff, but that is for "inspectability", and not for actual function. When things are lined up it is easy to see a problem when doing 100% inspection. Most of those will have the parts held in position by a dot of adhesive before soldering. Not typical consumer construction.

Call it whatever you want, your problem.

It's not "low end", you see that in really cheap warped brown paper/phenolic PCB stuff.

[A.K. Boomer]

JT my edit and your post were both at 12:46 :-)

[gellfex]

So the new charger came, a different model, and interestingly it has only 2 contacts of the 4 on the battery. The tool only has 2 contacts. Did they give up on a battery thermistor?

[mattthemuppet]

probably moved the thermistor or whatever those extra contacts were for onto the protection board in the battery itself.

[MattiJ]

Dried out electrolytic capacitors are always good bet on power supplies.
This particular one looks? to have Capxon branded electrolytics that are also widely known as Crap-con..