Transistor FBN-L287 / NSN 5961-01-379-3433 - UK Vintage Radio Repair and Restoration Discussion Forum

evingar · 2nd Jun 2018, 11:22 am

Hi,
I wonder if someone can help me ?
I'm currently trying to salvage a old 1980s Lambda power supply. I've found the reason it's distressed is a faulty power transistor type FBN-L287.
I can't find any data on it in Towers (update 5) or on-line, although I've found a reference to a NATO number NSN 5961-01-379-3433

The date code the device is F8317 (17th week in 1983 ?)

Argus25 · 2nd Jun 2018, 11:38 am

I've come across this sort of dilemma in the past too. There is one way around it , if you cannot identify the transistor, trace out the circuit that the transistor is in and the circuit configuration and see if you can find the rated voltage and current of the supply. Then it becomes a fairly easy task to select a suitable replacement transistor in the same physical package. So if you could provide that info, I could suggest the part to use.

But there may be an equivalents list out there too.

evingar · 2nd Jun 2018, 2:25 pm

Hi,
Thanks for the reply.
I suspect the part is manufactured specifically for Lambda, hence the "L" prefix to the 2nd block of letters and the lack of data in Towers (etc). Naturally, there is no service data available for the PSU, so it looks like I will have to resort to what you suggest.

evingar · 3rd Jun 2018, 8:21 am

For the record, in case someone else picks this up, When reverse engineering the circuit, it became obvious this part was a power MOSFET, which is quite unusual in equipment of this vintage. This maybe explains why it was a "special" while other components in the PSU were easily identifiable standard parts. Anyway, on knowing that, it measured out OK - the fault was further back in the control circuitry. The power supply is now working and on long term soak.

2nd Jun 2018, 11:22 am	#1
evingar Octode Join Date: Oct 2003 Location: Newbury, Berkshire, UK. Posts: 1,770	Transistor FBN-L287 / NSN 5961-01-379-3433 Hi, I wonder if someone can help me ? I'm currently trying to salvage a old 1980s Lambda power supply. I've found the reason it's distressed is a faulty power transistor type FBN-L287. I can't find any data on it in Towers (update 5) or on-line, although I've found a reference to a NATO number NSN 5961-01-379-3433 The date code the device is F8317 (17th week in 1983 ?) __________________ Chris

2nd Jun 2018, 11:38 am	#2
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Transistor FBN-L287 / NSN 5961-01-379-3433 I've come across this sort of dilemma in the past too. There is one way around it , if you cannot identify the transistor, trace out the circuit that the transistor is in and the circuit configuration and see if you can find the rated voltage and current of the supply. Then it becomes a fairly easy task to select a suitable replacement transistor in the same physical package. So if you could provide that info, I could suggest the part to use. But there may be an equivalents list out there too.

2nd Jun 2018, 2:25 pm	#3
evingar Octode Join Date: Oct 2003 Location: Newbury, Berkshire, UK. Posts: 1,770	Re: Transistor FBN-L287 / NSN 5961-01-379-3433 Hi, Thanks for the reply. I suspect the part is manufactured specifically for Lambda, hence the "L" prefix to the 2nd block of letters and the lack of data in Towers (etc). Naturally, there is no service data available for the PSU, so it looks like I will have to resort to what you suggest. __________________ Chris

3rd Jun 2018, 8:21 am	#4
evingar Octode Join Date: Oct 2003 Location: Newbury, Berkshire, UK. Posts: 1,770	Re: Transistor FBN-L287 / NSN 5961-01-379-3433 For the record, in case someone else picks this up, When reverse engineering the circuit, it became obvious this part was a power MOSFET, which is quite unusual in equipment of this vintage. This maybe explains why it was a "special" while other components in the PSU were easily identifiable standard parts. Anyway, on knowing that, it measured out OK - the fault was further back in the control circuitry. The power supply is now working and on long term soak. __________________ Chris