# Chasing a modern alternative to the 2SK1250

#### BertyB

Joined Dec 18, 2020
11
Hi All. As per the title, I am looking for a modern alternative the the Shinden 2SK1250 Power MOSFET. These are a common point of failure in the power supplies that Sega used for their late 1980s moving arcade machines. The power supplies take a PCM input which controls forward and reverse power of a large DC motor which operates up to 60V DC.

From my experience in repairing these power supplies, failures are usually due to overheating of the 2SK1250, despite there being active cooling systems and an overheat circuit.

Here is a data sheet for the MOSFET;

https://datasheet.octopart.com/2SK1250-Shindengen-datasheet-8316814.pdf

And here is the MOSFET in relation to the power circuit - labelled Q19, Q20, Q21 and Q22

I am wondering if there is a modern, silicon carbide alternative that might be more reliable? Please let me know if you have any suggestions.

#### Papabravo

Joined Feb 24, 2006
19,591
So does that mean you think the part ratings are not sufficient for the application?
This is a less than useful schematic since many details have been obfuscated. Is there some reason why you think that it would be sufficient to understand the application and offer suggestions?

#### BertyB

Joined Dec 18, 2020
11
I think that heat dissipation is an issue. All four 2SK150s are on the one heatsink, along with large diodes.

Due to space limitations there is not much more that can be done in the way of cooling. Finally, although Alabama etc still has these parts, I am finding it difficult to acquire these MOSFETs.

In regard to your comment about the circuit diagram, you are right. There is not much detail there. I can most a more comprehensive overview soon.

#### Papabravo

Joined Feb 24, 2006
19,591
I think that heat dissipation is an issue. All four 2SK150s are on the one heatsink, along with large diodes.

Due to space limitations there is not much more that can be done in the way of cooling. Finally, although Alabama etc still has these parts, I am finding it difficult to acquire these MOSFETs.

In regard to your comment about the circuit diagram, you are right. There is not much detail there. I can most a more comprehensive overview soon.
The circuit looks like a kind of bridge driver and the L3, L4, L5 inductors represent motor windings. Is that correct?
You said the motors were 60V DC motors but that really doesn't tell me much. I need to know things about how much current they require under various conditions and what kind of loads are involved. There is just so much that is missing.

#### MrSalts

Joined Apr 2, 2020
2,617
And here is the MOSFET in relation to the power circuit - labelled Q19, Q20, Q21 and Q22
yes, but they are $17 each, that's the bad news. The good news, - they have on resistance about 10% of your current unit so heat lost to the mosfet will be minimal. Four on one heat sink won't be an issue. - they have same or less input capacitance and gate charge - they are much faster than your current units (5x to 10x faster rise snd fall times). - same package size. - immediately available - higher voltage capability - higher current capability - higher operating temp (175°C) but you'll never get close with the low on-resistance) https://www.digikey.com/en/products/detail/unitedsic/UF3C065030T3S/11587026 #### Papabravo Joined Feb 24, 2006 19,591 yes, but they are$17 each, that's the bad news.
The good news,
- they have on resistance about 10% of your current unit so heat lost to the mosfet will be minimal. Four on one heat sink won't be an issue.
- they have same or less input capacitance and gate charge
- they are much faster than your current units (5x to 10x faster rise snd fall times).
- same package size.
- immediately available
- higher voltage capability
- higher current capability
- higher operating temp (175°C) but you'll never get close with the low on-resistance)
https://www.digikey.com/en/products/detail/unitedsic/UF3C065030T3S/11587026
The quantity price is of course more manageable.