Prototype unit 1 (henceforth known as unit A) is complete, apart from the stud that holds down the mosfet.
Just need to insert the stud, grease the insulating washer, fit mosfet and top hat and secure with nut. Then need to solder the three mosfet leads. Tighten everything up, do a double check on the wiring, then it should be ready for test and initial bias adjustment.
As the M3 material won't be here till Monday I can do more on unit B tomorrow.
The only thing necessary for the triumph of evil is for good men to do nothing.
Nick wrote: ↑Sat Jul 04, 2020 9:48 pm
Out of interest what insulating washer are you using?
I'm very glad you asked that question Nick.
I sort of realised that a TO-247 was a different size to a TO-220 but I'd not realised the insulating washers were different. Bugger. I'll order some tonight, but probably won't get them till Weds/Thurs, still-never mind eh.
Mia Culpa.
EDIT. Some on Ebay are sold individually and cost more than the mosfet did, but that's probably the "free" postage.
Do I need anything special ?
The only thing necessary for the triumph of evil is for good men to do nothing.
Thanks Nick, If I'd been really desperate I could have driven to Colchester and collected some. As it is, I ordered some silicon ones on Ebay last night and paid £1 extra for first class post.Might be here Tuesday.
I did find some TO-3 ones in the spares box which could be cut to size, but I'd end up with 1 tiny hole in the material and I didn't want to risk it.
The only thing necessary for the triumph of evil is for good men to do nothing.
There was one detail on unit A that bugged me a bit, and I didn't really want to perpetuate it on unit B, so I've stripped unit A back to do some modifications.
I have the time.
The only thing necessary for the triumph of evil is for good men to do nothing.
If the prototype units pass muster, I'm going to have to make each monoblock a two box unit.
This is because the weight of the prototype is really too much to lift up, and put down. They are a gnats under 20KG.
So, I'd need to put the heatsink, choke (microwave oven transformer), circuit board and one (extra ?) PSU cap in a box of their own.
The boxes I already have would house the power supply and could cut down (height wise) if necessary, but I don't have to decide that just yet. I would like the top box (PSU is bottom box) to be more stylish, but without being gaudy, so clearly some thought is necessary. Initial leanings involve dark blue acrylic sheet in some form, and I hope the heatsink can be fixed (rather than the original hinged idea) and the bias adjustment pot accessible from underneath, with the top box turned on its side.
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The only thing necessary for the triumph of evil is for good men to do nothing.