28th-Nov-23, 10:34 AM
Hi Drifter2 - yes the space around the parts does help us DIY repair enthusiasts :)
And, the space adds another dimension. These MOSFETs can handle a lot of power yet they have no visible heat sink to help keep them cool. Instead they use the electrical ‘drain’ pin as a heat sink onto the copper surface below. The drain pin is the one which sits alone opposite the other two pins. So larger spacing can provide a larger area of copper underneath for more effective cooling of the part.
As an aside, the above photos now clearly show the MOSFET and npn parts used by Hornby in rev G and rev H decoders at that time.
The original part for motor control for the rev H variant appears to be a Diodes manufactured DMN3404L. With reference to the Diodes datasheet we can see this part was manufactured in November 2017, with final assembly and test in Chengdu.
Global supply chains are all part of this great hobby!
c
And, the space adds another dimension. These MOSFETs can handle a lot of power yet they have no visible heat sink to help keep them cool. Instead they use the electrical ‘drain’ pin as a heat sink onto the copper surface below. The drain pin is the one which sits alone opposite the other two pins. So larger spacing can provide a larger area of copper underneath for more effective cooling of the part.
As an aside, the above photos now clearly show the MOSFET and npn parts used by Hornby in rev G and rev H decoders at that time.
The original part for motor control for the rev H variant appears to be a Diodes manufactured DMN3404L. With reference to the Diodes datasheet we can see this part was manufactured in November 2017, with final assembly and test in Chengdu.
Global supply chains are all part of this great hobby!
c
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