Identify diode (SMD)

[spikey]

Hi,

I've been trying to identify the diode pictured below for several days without success. It looks like is made by ST and is marked 'EE 63 721". This diode is from the Tacx Vortex Smart bike trainer and is component D9 on the PCB.

This is the last faulty component to be replaced and am tearing my hair out as I so near in fixing this board. Please can you help before I go bald

 

[kellys_eye]

Have you tested the diode first?

 

[spikey]

Yes, I've tested a short in both polarity with my DVM with diode removed from PCB.

Since it's made by STM I thought it should be easy to find.

 

[kellys_eye]

Could be a transient voltage suppressor (63V). Can you show more of the PCB so we can get some context?

 

[spikey]

Could be a transient voltage suppressor (63V). Can you show more of the PCB so we can get some context?

 

[kellys_eye]

Hmmm, still can't find anything other than references to TVS (transient voltage suppressors). If it is such a device then the circuit could, theoretically, work without it being in place as it's only there to protect against spikes that 'may' occur. You could do worse than put in 'any' TVS (I'd go with a 63V version anyway given the limited coding we can see) and see what happens.

Your picture is 'too contextual' now! If you can see adjacent component identification (the main IC's device number etc) you can do worse than check out the appropriate datasheets which often give application data that include some related schematics that may show the recommendation for the use of a TVS at the signal input pins.

 

[spikey]

Thank you Kelly for your insight.

I've been doing further research. On the left of this diode is a 3.3V regulator and a microprocessor on the right requiring 3.3 or 5V supply. I've read elsewhere that the middle row marking is the relevant information which is "EE". I found this on SMD code website which indicates it's SM6T18A a TVS 15.3V 600W diode. I guessing this is the right one?

 

[kellys_eye]

I guessing this is the right one?

As good a guess as any - and with the value stated (15V-ish) it seems appropriate. Like I said, the circuit should work without it if all you want to do at this stage is to prove you fixed the fault (whatever that was).

 

[73's de Edd]

Sir Spikey . . . . . .

And finally, here is your confirmed, million dollar referencing . . . . . . of . . . .
Page 2/5

https://datasheet.octopart.com/SM6T15CA-STMicroelectronics-datasheet-8321715.pdf

marking code EE . . . . 18 Volt

Track down that nearby . . . . .what seems to be the sole and principal filtering for the low voltage DC supply for that circuit board.
I feel sure that your " mystery part" will be connected across that 100 ufd 25VDC mini canned cap with interconnecting foil traces .

Note the banded end marker, indicating that your unit is being unidirectional versus bidirectional polarity.

I very rarely see them fail as shorted . . . . . its usually just their " eating" themselves up, as being degraded with each experienced overloads internal "explosion" .

Otherwise, the principal DC supply for series connected MMM UUU LLL TTT I I I PPP LLL EEE DC modulated braking electromagnets working against mating large niobium magnet sets, ( located over on the OTHER half of the unit) is being acquired from the boards centrally located 4 E-caps , with their hefty capacitances and working voltages .
They are being controlled by the two larger power FETS on the board.

Tha a a a a s sit . . . .

73's de Edd . . . . .

 

[steve1418]

http://markingcodes.com/search/i/SM6T18A LOOKS LIKE THIS ,

 

[spikey]

Sir Spikey . . . . . .

its usually just their " eating" themselves up

Thanks Edd, love your funny description.

 

[spikey]

http://markingcodes.com/search/i/SM6T18A LOOKS LIKE THIS ,

Thanks Steve.