Mini Max CT250 Spa Control/Power Board

[dcapper]

Does anyone have a schematic for a Mini Max CT250 Spa Control/Power Board? I found three blown diodes and no markings on them.

[CapLeaker]

Re: Mini Max CT250 Spa Control/Power Board

maybe upload some high resolution pictures so we can see where they go and figure it out.

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

First pic of a diode. My camera isn't very good.

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

Here's the board. All the caps are the same from what I can tell. They are all apart of the relays circuit.

[R_J]

Re: Mini Max CT250 Spa Control/Power Board

That is a MELF diode, where is it in the circuit and what is wrong with it? is it shorted?
It might be a GL41M 1A 1000V Fast Recovery, or a schottkey or it could also be a zener diode, does it only have one color band and is it green?

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

That is a MELF diode, where is it in the circuit and what is wrong with it? is it shorted?
It might be a GL41M 1A 1000V Fast Recovery, or it could also be a zener diode, does it only have one color band and can you make out what the color is?

It's like a greyish band. There is three of them shorted but the others are reading out of circuit .5 one way and ol the other way.

[R_J]

Re: Mini Max CT250 Spa Control/Power Board

Do you have a picture of the circut where they are located, They might be 8.2v zener diodes or they may just be ordanary diodes

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

The pic above. Look at the two middle relays. One diode above the top relay. One in the middle of the two relays. And one near the top heat sink. Then there's a few by the right three relays. The blown ones are by the middle relays. I tried to take a better pic of the diode that I attached.

[R_J]

Re: Mini Max CT250 Spa Control/Power Board

If the diode is across the relay coil it will just be an ordinary 1amp diode, if the diode is across a control line to ground it could be a zener diode for protection on that line.

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

If the diode is across the relay coil it will just be an ordinary 1amp diode, if the diode is across a control line to ground it could be a zener diode for protection on that line.

I kinda figured that's what they would be. I found a M7 (1N4007) type for my other power supply. I'm assuming I would need a 1N4007?

https://www.digikey.ca/product-detai...ICT-ND/3025854

Something like this?

[budm]

Re: Mini Max CT250 Spa Control/Power Board

What is the resistance reading in Ohms of the bad diodes?

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

What is the resistance reading in Ohms of the bad diodes?

I'll have to meter it when I get home tonight. I think it was around 5 ohms but let me confirm.

[budm]

Re: Mini Max CT250 Spa Control/Power Board

I'll have to meter it when I get home tonight. I think it was around 5 ohms but let me confirm.

Tested off the board, correct?

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

Tested off the board, correct?

Yuppers. I removed all the diodes in question and a good one for testing purposes.

[redwire]

Re: Mini Max CT250 Spa Control/Power Board

It's extremely rare for relay coil back-EMF diodes to fail. Either a cheap crappy part, or something else must have happened to the board.

A shorted (coil) diode would overload the relay driver IC, guessing ULN2003.
I would also check ohms on the relay drive and GND to see if the IC is damaged.
Not sure where the low voltage DC comes from, it has a 12/24VAC control transformer?

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

It's extremely rare for relay coil back-EMF diodes to fail. Either a cheap crappy part, or something else must have happened to the board.

A shorted (coil) diode would overload the relay driver IC, guessing ULN2003.
I would also check ohms on the relay drive and GND to see if the IC is damaged.
Not sure where the low voltage DC comes from, it has a 12/24VAC control transformer?

I'll be doing more meter checks. The unit is my friend's. Either the pump or heater blew and took this board with it. I had three broken solder traces around the two middle relays.

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

What is the resistance reading in Ohms of the bad diodes?

The resistance is basically a dead short. It's 1 ohm and when I short my meter leads, they are 1 ohm.

[dcapper]

Re: Mini Max CT250 Spa Control/Power Board

It's extremely rare for relay coil back-EMF diodes to fail. Either a cheap crappy part, or something else must have happened to the board.

A shorted (coil) diode would overload the relay driver IC, guessing ULN2003.
I would also check ohms on the relay drive and GND to see if the IC is damaged.
Not sure where the low voltage DC comes from, it has a 12/24VAC control transformer?

I tested the relays and they have the proper resistance and they triggered when I put voltage on them. It does have a 12/24 vac transformer. There is a LM2937ET but it seems to be operating properly. My buddy is going to order a new board if I can't get it working, so taking shots in the dark will be ok.

The whole story is, my friend got the hot tub for free. The people changed the pump and the heater when it died. The display board powers up with lights but only shows a 0. They replaced that board too. When you power up the tub now the main pump kicks in for a few seconds and then the circ pump runs. The heats works too. This was with the blown diodes and solder traces. I'm assuming when the pump or heater died, it blew the board. But not knowing them, I can't say for sure.