Repairing the power supply on a HD1200/1, think I have the FETs identified (original FDP8870 no longer in production, going with IRL7833), but I'm getting conflicting data on the driver transistors. The one marked "12W" is blown, from what I can tell it's either a PNP or an N-channel FET.
4 blown, the other 4 power supply transistors only have a single SOT-23 type device driving them which my meter says is a BJT. This is one of those odd power supplies like the 1000/1, except here we get dual full bridge power supplies (in parallel) with 2 transformers instead of one. So 4 FETs per transformer, driving a pair of transformers.
I'm not understanding what the power supply configuration is. Maybe someone else can help.
If you can't figure it out and no one else can help, I'd need a lot more questions answered (and likely photos).
If you can't figure it out and no one else can help, I'd need a lot more questions answered (and likely photos).
In other words the primary is not center tapped, it has an H-bridge arrangement like the Helix HXA's. 2 transistors turn on to feed power through the primary in one direction for one half of the drive wave, then it switches to the other pair to reverse current flow on the other half of the cycle. +/- then -/+. The secondary is conventional, full wave rectification.
Pretty similar to the 1000/1, but without drive transformers. I believe the extra transistor may be doing some level shifting for the high side FETs or something like that, but I haven't dug too deep into the circuit design. I just know that I have good drive before the 12W and nothing after it lol.
Pretty similar to the 1000/1, but without drive transformers. I believe the extra transistor may be doing some level shifting for the high side FETs or something like that, but I haven't dug too deep into the circuit design. I just know that I have good drive before the 12W and nothing after it lol.
I've been told the drivers are:
FMMT589 >> Q53, 54, 61, 62, 22, 25, 27, 46
FMMT489 >> Q63, 52
2N7002 >> Q57, 58, 59, 49
FMMT589 >> Q53, 54, 61, 62, 22, 25, 27, 46
FMMT489 >> Q63, 52
2N7002 >> Q57, 58, 59, 49