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I have an mspa b-121 Castello hot tub spa. The bubbles/jets work, in fact everything seems to work, except when the heater button on the control panel is pushed, I get an f7 error. I'm pretty handy if I have some guidance. Short of just starting to replace expensive parts and hope for the best, anything I can test to try and narrow down the issue or potentially fix it? I have a multimeter if electronics require checking. Everything I've read around this error or issues in general, is basically no support other than referral to a sales rep in your country that just wants to sell you parts without any kind of troubleshooting or narrowing it down to be sure. Seen far too many people with issues where they are basically just playing the swap the parts game. I've soldered circuit boards from scratch previously, but always with guidance as to what goes where.

Posted by Nick Bergstrom on


5 Related Answers



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SOURCE: Canon XL2 - eject button issue

It is probably a faulty switch, in any case, either is the switch or a wiring problem, the camera must be taken apart to fix this.
The job must be done at a repair shop.

Posted on Oct 12, 2008


Charles East

  • 331 Answers

SOURCE: Hot Spring Spa pump won't run just click on circuit board....

Check for voltage at the pump, before assuming the relays are out... then check for voltage before and after the relay contacts

Posted on Apr 14, 2010


Charles East

  • 331 Answers

SOURCE: We have a Great Lakes spa with a Balboa control

Contact Balboa's Customer support department directly at 800-645-3201, follow the prompts to customer tech support (or press 0 and ask for customer support). You will need to be at the spa, control panel open and ready to read off the chip number, and you will need to be proficient with a test meter (AC voltage). The SN error is related to a bad sensor(s), but can also indicate a failed board. An incorrect sensor set will also create this problem, so confirm you used the exact or compatible replacement. If the SN code issue is no longer a problem, but the spa is still not heating, look and see if the heater led is on. If it is, you likely have some burned relays on the board, which can be replaced cheaper than replacing the board. If you need more help, email me at [email protected]

Posted on Aug 30, 2010


  • 64 Answers

SOURCE: galaxy dx-66v its hard to explain but the sound

I have found bad cabling and bad grounds on this and the other board in the freq counter can.

Posted on Sep 12, 2010

Al Kizina

  • 170 Answers

SOURCE: Heat not working - I have taken apart whole dryer and tested everything - last is control board?

You need the dryer checked with a volt meter point to point to see where you are loosing the voltage. This must be done with the power on and is dangerous for someone who has no background in this type of troubleshooting. If the unit has a circuit diagram that you can read, you need to check for voltage on the circuit board. This unit operates on 240 volts and can cause serious injury if the powered terminals are touched. If there is voltage on the circuit board that going to the heating element, the board is probably good.
I think you have done about as much as you can, and maybe it is time to call a service company.

Posted on Dec 24, 2015

Testimonial: "That's exactly what I was thinking! Thank you so much for confirming that. It sure was fun taking it apart and I learned so much. Who knew there was an ohms calculator! Lol. Thank you again."

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