Shazzam Tsunami Hydroflosser Repair

[Adler]

I picked up a hydroflosser on the cheap (broken, of course, my favorite). It has no power. I opened it up and found that its a pretty simple circuit.

Two Ni-MH batteries, a motor, and a charging/managing circuit.

Also, interestingly, this "Name brand" product seems to be a custom branded chinese piece of poop which casts doubt on the box's claims that it was invented by "celebrity dentist, Dr. Raymond Frye". 

I think the problem is D4, a diode I assume. This is where my expertise runs out though, what should I get to replace it? what size is this? do you agree that this is likely the cause? (I tested resistance in both directions and both were infinite)

[c4757p]

invented by "celebrity dentist, Dr. Raymond Frye". 

"celebrity dentist". Hmmm... maybe I should reconsider my choice of professions.


That's one odd-looking diode. Are you sure that's not an LED? I can't see it too well in the photo. If it's an LED it may as well test infinite - threshold voltage is too high for the meter.

[David_AVD]

Does you DMM have a diode test function?  That would be a more reliable test than resistance.

[Adler]

invented by "celebrity dentist, Dr. Raymond Frye". 

"celebrity dentist". Hmmm... maybe I should reconsider my choice of professions.


That's one odd-looking diode. Are you sure that's not an LED? I can't see it too well in the photo. If it's an LED it may as well test infinite - threshold voltage is too high for the meter.

D1, D2, and D3 are LED's, pretty sure D4 is different.

Does you DMM have a diode test function?  That would be a more reliable test than resistance.

Thats a very good point. I should proabably have thought of that. In diode mode it settles at 0.945v in one direction and tests infinite in the other. That doesn't bode well for my diode theory, does it...

[c4757p]

No, seems like a perfect diode, though 950mV is a bit high.

[David_AVD]

Time to get back to basics; have you tested the battery and the motor ?

[Adler]

Interestingly, when I bridge that diode (probably ill advised), the charging light starts blinking. Maybe 950mV really is too high?

Time to get back to basics; have you tested the battery and the motor ?

I would expect some life from the LED's with a dead battery or motor. Maybe I expect too much. The batteries are quite dead right now but I bet this device works with no batteries at all, straight from the wall.

[David_AVD]

Depending on the circuit, drained batteries can pull the the main voltage rail down to the point where nothing works, even if it's on charge.

[Adler]

Depending on the circuit, drained batteries can pull the the main voltage rail down to the point where nothing works, even if it's on charge.

I tried disconnecting the batteries to rule them out. Nothing worked at all, including the blinking charge LED when I bridge D4. I don't think that rules out the batteries, so that is still an option. Not too easy to get 2.4v NiMH cells in this size, though.

[David_AVD]

Why can't you just wire in a temporary feed from a power supply?  Just don't try to charge it of course.

[Adler]

Why can't you just wire in a temporary feed from a power supply?  Just don't try to charge it of course.

The main reason is that I have not yet obtained a universal power supply. I could always use a wall wart but I have a theory that may be simpler.

Looking at these batteries, they look mysteriously like normal AA cells. There is printing on only one cell and it says 2.4v I am thinking that goes for both cells. I'm going to wire in a battery pack in parallel with some good NiMH cells.

[Adler]

Battery pack in... it turns right on.

It is still possible that the charging system is dead. But I think we have found the issue.

Thanks for all your help and I apologize to the humble diode.

[amyk]

Welcome to the world of OEM... looks like Risun sell the RST5002 themselves, and here's another rebrand of the same thing which is probably much closer to their OEM price.

(I'm still not entirely sure what this thing does though. Pressure washer for teeth?)

[Adler]

Yup, pressure washer for teeth.

Im not sure it is fixed yet. I charged the original batteries in an external charger and they seemed to hold a charge. So, I resoldered them in (I hate doing that, its always nerve-wracking soldering to batteries) and everything works. My cause for concern is that I plugged it in the charge about 4 hours ago and the light is still blinking, I guess I'll check it again tomorrow morning.

[amyk]

You can check the voltage on the batteries, it should be 1.4-1.6V per cell if they're being charged. If it's anything like an electric toothbrush the charger will be of the trickle type, so they will take a long time to charge.

[Adler]

Well, unfortunately, this story isn't over. I left the unit charging for a day and it is now quite dead.

I intend to attempt to draw up the circuit daveCAD style to better understand it when I have time, I think its just double sided. Any suggestions of where to start? I'm still thinking that diode looks funny...

[David_AVD]

Maybe it just needs new batteries?

[amyk]

Any suggestions of where to start?

I'd start with the battery terminals.

[Adler]

Maybe it just needs new batteries?

The batteries charge in an external charger and hold a charge. I would think that indicates that they work, no?