# Diode substitution for FMXG26S

I been hunting for an equivalent for a Diode in TV Power Supply - its a FMXG26S. Does anyone have any idea of an equivalent? Or where I can look one up? The datasheet advises the following for the device:- https://www.semicon.sanken-ele.co.jp/sk_content/fmx-g26s_ds_en.pdf

• Transient Peak Reverse Voltage - 600V
• Peak Reverse Voltage - 600V
• Average Forward Current - 10A
• Peak Surge Forward Current - 100A

All help greatly appreciated!

The critical parameters are:

• 30 ns 90% recovery time which requires low junction capacitance
• 1.5V@10A which implies an Rs of (1.5V-0.7Vth)/10A = 80 mOhms and raises junction capacitance
• Rth(j-c)=4 °C/W
• Ir = 100uA max @ -600V which implies 600V/100uA= 6MΩ

Diodes Inc and Cree etc will carry suitable replacements.

Here's a short list that may or may not contain the ideal replacement, then compare thermal and other specs

https://www.digikey.com/products/en/discrete-semiconductor-products/diodes-rectifiers-single/280

# update

closest so far was an ST diode. STTH1202 NO Good 200V instead consider this 600V
The Sanken part is still the best (but even those can fail if caps also degrade)

Sanken                  ST
30ns max. @ 0.5A 25°C   33ns max @ 1A 25°C
600Vrm                  600V
1.5V @ 10A              2.9V @ 12A typ **worse, may need bigger heatsink**
100uA @ 600V 25°C       20uA @ 600V 25°C (better)
20,000uA @ 600V 150°C   400uA @ 600V @ 125°C ( better but tested with lower heat stress)
4°C/W to case           2.4 °C/W to case  ( better )


also search "ultrafast 600V diode Sanken stock"

All these specs above are tradeoffs so Sanken in Japan were pushing the envelope.

My suggested replacement may still run hot and fail early unless heat rise is checked after unplugging. If burning hot to touch, a bigger heat sink may be needed. A DMM can check if voltage has decayed to a safe level before touching. Don't if unsure.

• Thank you so much for your help really appreciate it! As my daughter will when finally get this TV to work! – Neale Francis Mar 22 '19 at 9:45
• THat one s still not good enough – Tony Stewart Sunnyskyguy EE75 Mar 22 '19 at 18:01