It looks like L1 & L1A are 2 coils (or a transfomer) in one package? input choke of some kind
Is that a dc input jack?
The diode looks like it is for reverse polarity protection for the LM317
I see some SOD-123 diodes marked A4 like the Vishay 1N4150W
or maybe this Rectron FM4004W-T (1 amp 400 volt)
So the power jack on that board is fed by 12VAC or 12VDC?
That is the common mode choke (it does not look like center pin on the right is used), the circuit will function without (bypassed) it, but is there any protection such as fuse any where on the primary side of the Transformer?
Can you do straight shot pictures of the whole board and how the board is connected to other boards/ components?
any of those fm4004w should work, or anything similar, it's not that special, that coil has 5 leads, where do they go? looks like 2 leads connect to the jack 1 connects to the diode. Is the coil actually bad? I would leave the coil alone and just replace the diode to start with.
BTW, looking at the pictures, I cannot see any burnt mark on D1.
The output side of L1A (that choke has two windings, L1 and L1A) connected to the Cathode of D1, it also feed the VIAs that goes to the bottom side of the board.
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