I am going to go with Max's suggestion that it is a Littlefuse S4008R SCR. (The R option means that it is non-isolated, i.e. the tab is connected to pin-2.)

https://www.littelfuse.com/assetdocs/discrete-thyristors-sxx08xsxsxx08x-series-datasheet

Pin 2 and pin 4 is common on both if that helps?? So if it is an SCR how do I order a replacement?? or do I need to do more testing?

 

There is quite a few videos on youtube for method of testing to see the switching action.
Mouser or Digikey stock them, among others.

 

There is quite a few videos on youtube for method of testing to see the switching action.
Mouser or Digikey stock them, among others.

Can you recommend a supplier where the shipping is a little more tolerable?

 

Sayal Electronics - free shipping with order over C$50.

S6015L SCR 600V 15A https://secure.sayal.com/STORE4/prodetails.php?SKU=167838
Q4008R4 TRIAC 400V 8A https://secure.sayal.com/STORE4/prodetails.php?SKU=142156

I am not sure if a TRIAC will also work in this application.

I can pick one up and send it by post to you.
Note that the MC-02 treadmill controller is not recommended for high power applications.

 

I would stick with an SCR, especially if this is like the MC-60, which it sounds like it is.

https://forum.allaboutcircuits.com/attachments/mc-60-motor-controller-pdf.80579/

 

Sayal Electronics - free shipping with order over C$50.

S6015L SCR 600V 15A https://secure.sayal.com/STORE4/prodetails.php?SKU=167838
Q4008R4 TRIAC 400V 8A https://secure.sayal.com/STORE4/prodetails.php?SKU=142156

I am not sure if a TRIAC will also work in this application.

I can pick one up and send it by post to you.
Note that the MC-02 treadmill controller is not recommended for high power applications.

Thanks MrChips I know the value of the MC-02 as you refer and a follower of the youtube channel you highlight. It is not my intent to spent a lot of money to repair this board but to increase my knowledge in; how to repair, things to look for and soldering skills in board repair. At this juncture in life it is something to keep the mind active. I have already learned a great deal thanks to you guys. Thanks for the offer to mail a replacement but that wouldn't be necessary. I have access to the following; K30502-01, MBR30100-DT and BT138-600E maybe you could tell me if either of these are close?? It is more about making it work than being able to use it. I may find a suitable replacement from China, cheep and free shipping

 

Thanks MrChips I know the value of the MC-02 as you refer and a follower of the youtube channel you highlight. It is not my intent to spent a lot of money to repair this board but to increase my knowledge in; how to repair, things to look for and soldering skills in board repair. At this juncture in life it is something to keep the mind active. I have already learned a great deal thanks to you guys. Thanks for the offer to mail a replacement but that wouldn't be necessary. I have access to the following; K30502-01, MBR30100-DT and BT138-600E maybe you could tell me if either of these are close?? It is more about making it work than being able to use it. I may find a suitable replacement from China, cheep and free shipping

Amazon has the BTA12-600 10Pc for $11.00 + tax, free shipping. Any good?

 

10pc for $11, you can't beat that.
BTA12-600 is a TRIAC.
A TRIAC is bidirectional where as an SCR is unidirectional. I don't know if this will work without seeing the schematics.
If the two TRIACs are in a bridge circuit then they will likely blow by shorting across the power supply.

 

Amazon also has 5 pcs S4008 for CAN$16.00.

 

Amazon also has 5 pcs S4008 for CAN$16.00.

Thanks MaxHeadRoom I did not see them. Fair price even with the $6.00 shipping.

 

If that is two SCR's then it is using the same method as the MC-60 board where the SCR's are part of a full wave bridge, there are two large diodes that complete the briodge.
D9 - D10 ?

If D9 and D10 are a part of the bridge are they also uni-directional? on D10 I get a reading one way of .478v the other way 3v whereas on D9 i get 0v and .5v. D8 is reading the same as D10 on the diode scale

 

No device in the bridge should be bi-directional.

 

No device in the bridge should be bi-directional.

Sorry should have read unidirectional

 

Merry Christmas to all enjoy the holidays season