Ultrasonic not Heating board failure? Need help fixing!

[bugnut]

I have a seldom used Rovsun 15l ultrasonic. Well the heater has quit working unit is only 16 months old. Light comes on, ultrsonic still work, but no heat. So like everyone on TGJ I thought it should be repairable. So I have opened it up. When I look at the electronics there are what appears to be three matching boards. I have just given them the general inspection and see immediately that the middle board differs from the other 2. It appears to me a component has failed as the white sticky stuff is only on the middle board. Hence the questions? Can someone tell me what the white stuff is? What item has failed? And if this is even my issue. Looking for a little electrical help to track down the issue! TIA

 

[Benw455]

The white stuff keeps the smoke in.

 

[pcmeiners]

A little description of the white blob might help. Is it rubbery, dry, wet, hard , soft. Is it comming out of the capacitor near the transformer/choke ? It should be fairly easy to figure out which component failed if the other boards are OK (and powering up) by taking voltage readings from a known good board

 

[vwpieces]

Check if you have voltage at the heater wires.
I had a Horrible Freight ultrasonic that blew the heater in 3 days. I just took it back for exchange.
And do not run it Empty. Not good for the heater (cough, cough ) or the sonic thingy.

 

[PCustoms]

Looks like sloppy thermal paste or RTV to me, not a failed component.

Per above knowing it's consistency will help

 

[BillK]

I doubt that those boards have anything to do with the heat. They are the drivers for the ultrasonic transducers. Where is the ehating element ? Have you looked at it to see if there are any burnt spots on it ? On mine it is a simple heating element on the bottom of the unit. It is controlled by an on/off switch and a thermostat. Totally seperate circuit from the Ultrasonics. Do you have any type of wiring diagram ?

 

[LS6 Tommy]

It's a bad capcitor.

Tommy

 

[pcmeiners]

Stop guessing guys until the OP posts some information.

 

[bugnut]

Removed the board yesterday. I have no print for the unit. The white material was sticky, it also did not wipe off easily. I would give it a texture similiar to caulk. I thought originally it could be a capacitor, as I have seen capacitor bulges on other items. The yellow part closest to the white material is a capacitor so I have ordered a couple. Currently awaiting parts....Thanks all!

 

[PCustoms]

The white material was sticky, it also did not wipe off easily. I would give it a texture similiar to caulk.

Thermal paste. Look where the heater is mounted and you will find more.

To troubleshoot, can you swap boards?

I don't think the cap is your problem....

 

[BillK]

I think you are way off track. The three boards are not for the heater. Find the heating element. Put an ohmeter across it and see if it is open. Check to make sure it is getting voltage from the switch and thermostat.

Post some pictures of the heating alemment and the two knobs on the front.

 

[gregs]

I think you are way off track. The three boards are not for the heater. Find the heating element. Put an ohmeter across it and see if it is open. Check to make sure it is getting voltage from the switch and thermostat.

Post some pictures of the heating alemment and the two knobs on the front.

I agree. Thermal paste from a sloppy job. Guessing would be the "switch" for the heating element which is probably a relay on a board. Or a broken connection in the element. You need to test some things before firing the cannon.

 

[bugnut]

All so after reading further comments and more youtube here is what I have.
Image one is heater setup, when poking around some more the comment about paste may be correct.
So meter shows reading all wires disconnected and checking resistance. pic 2
Voltage checks show zero voltage when wired and powered at the top black and red terminal, heater turned to 122f and heater light displayed. pic 1
Checking voltage at top black and right red terminal at center of heater there is 110 pic 1
Checking voltage at top black and left red terminal center of heater there is zero shown pic 1
Checking voltage at top black and at the place the screwdriver is pointing and all along the heater surface shows 110 pic 3
Unit is Rovsun 15 liter pic 5

So help me diagnose some more, thanks and I really appreciate the input!!

 

[BillK]

Where is the meter connected when you re reading the resistance ? It should be across the two terminals at the left where the black and red wire are hooked to but with the wires unplugged ?

 

[PCustoms]

Check the thermal switch on the heater too, if that's junk nothing will work as it's a safety.

It's the round piece in the middle of the heater.

 

[BillK]

Take the two wires of the round black part in the middle and read across them for continuity. That part is most likely a safety overheat shutoff.

 

[bugnut]

Where is the meter connected when you re reading the resistance ? It should be across the two terminals at the left where the black and red wire are hooked to but with the wires unplugged ?

Check the thermal switch on the heater too, if that's junk nothing will work as it's a safety.

It's the round piece in the middle of the heater.

Take the two wires of the round black part in the middle and read across them for continuity. That part is most likely a safety overheat shutoff.

Again thanks for the help!

Bill, the resistance reading was taken as you suggest-the terminal at the top red/black, wires disconnected, above the yellow tag and below the wire tie.

PC/Bill, I awoke at 3:30 this morning and realized I had failed to get a resistance reading on the thermal switch, duh oh. So I have that now!

Well, you may have put me on to something. As a very quick test I plan to jumper the thermal switch and fire up briely to see if the water heats!

 

[BillK]

Well, you may have put me on to something. As a very quick test I plan to jumper the thermal switch and fire up briely to see if the water heats!

That was going to be my next suggestion

 

[PCustoms]

^^^^yep

There should be very little, if any, resistance across that switch, as it should be normally closed (NC). When the heater reaches a temp (either max, or a safety temp) It should have infinite resistance and be open, shutting the heater off. When it cools down, it will close again and allow the heater to run.

I am involved in a product that uses 2, 1 is to cycle the heater during use and the other is set as a safety. They're cheap parts, my money is on yours has failed

 

[bugnut]

Bill and PC I did the jumper experiment and found that the heater would work and water warmed up. Imagine That!
So I will be ordering the thermal switch! Please note the temp is actually 14.0c

 

[BillK]

Glad you figured it out

 

[PCustoms]

Please note the temp is actually 14.0c

What switch did you buy?

14C is slightly below room temp.....

 

[BillK]

What switch did you buy?

14C is slightly below room temp.....

I think thats just his test temperature to show that the heat is working.

 

[bugnut]

Bill is correct, water temp was ~8c at the start and water warmed up also I could see the heater actual warming the water now that I know the location and shape of the heater. I order this from Amzn, looks identical to the one removed. 2 pack for under 10$ Winner
Winner. I cannot thank enough for the help!

 

[RPH]

180 c* seems high. That 356*f, that would allow the water / fluid to boil out. 80*c (176*f) would be a safer temperature.

 

[PCustoms]

180 c* seems high. That 356*f, that would allow the water / fluid to boil out. 80*c (176*f) would be a safer temperature.

It's not water temp, it's surface temp on the backside of the heater.

 

[bugnut]

Replacement was same as factory. Thermocouple and selector switch MAY limit heat to 176f. I usually run it at about 122f.


Thermal switch received and installed. Quick check of resistance and it shows to be working. Buttoned up, sitting upside down on the counter waiting for the rtv to set. Return to action tomorrow!

Again thanks all!

 

[bugnut]

Well after waiting for things to dry we turned her over, filled with some Evaporust and shes back in action! A couple days, much advise and 10$ in parts!! Happy Happy!
Again thanks all!!