Hi All!
Sorry if this is in the wrong area. Please move it accordingly if need be.
Currently I have a CRT chassis that uses 2SD1398 that has a damper diode. These components are notorious for having fakes and all genuine are NOS. So my idea, is to find a HOT that is made currently today and do a modification to act like a 2SD1398.
My plan is to get a BU508AF that does not have a damper diode, but is readily available on DigiKey. https://www.digikey.com/en/products/detail/stmicroelectronics/BU508AF/2043589
And to mimic the damper diode that’s missing, I plan to get UF5408 on DigiKey and on the solder side, solder the cathode of UF5408 to the collector and the anode to the emitter pad of BU508AF.
Will my plan work?
Hello @iBringsTheRuckus,
Your self-imposed restrictions appear reasonable given the state of NOS devices (I sure do miss NTE).
Yes, the idea has merit:
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Transistor specifications are in the ballpark, and both are designed for HOT application.
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Transistor pinout appears the same (do double and triple check this statement).
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The UF5408 may be on the weak side of current specification. Unfortunately, I’m unable to find the diode specification for the 2SD1398. Consider matching to the peak current of the HOT.
But will it work?
I’m unable to answer that question as there is always risk for something unknown. If I’m honest, I will say that there is a real risk that this substitution will damage the CRT.
However, given the state of NOS parts, it may be worth a try.
You decide.
Please let us know if you were successful as there appears to be high interest in this substitution. Pictures would be a treasure for other readers.
Happy soldering,
Aaron
P.S. There may be value in locating a schematic of a CRT featuring the BU508AF. This would provide a natural match for the damper diode.
Hello iBringsTheRuckus,
I see the 2SD1398 Datasheet says it is rated for 800V Collector-Emitter Voltage, and 120W.
The BU508AF is rated for 700V Collector-Emitter voltage, and 50W.
I did not find a 800 or higher to offer, but a better option to start with, is 497-7196-5-ND which is the same 700V, 8A, but is rated for 125W. This is a manufacture number of BU508AW. Has the same pin spacing, and pinout.
Please check the datasheet to help verify compatibility.
