Retro 100 watt power amplifier.

Thread Starter

nigelwright7557

Joined May 10, 2008
532
I took an old Maplin disco amplifier design and brought it up to date using modern transistors.
I kept the To3 output transistors which makes the heat sink bracket fun to make as the holes have to be spot on.
Puts out about 100WRMS
 

shteii01

Joined Feb 19, 2010
4,644
When you have transfer punches... you don't need to worry about being spot on. (small pilot holes also very helpful)
 

Thread Starter

nigelwright7557

Joined May 10, 2008
532
What I do is get the first 4mm hole in after lining up the heat sink with the pcb.
I then put a bolt tight through the hole in the heatsink and pcb then drill the hole at the opposite through the pcb into the heat sink.
I then bolt that tight up to hold everything in place.
The transistor leg holes are 2mm and I drill those with a hand drill to stop the drill making a new hole in the pcb.
Once I have the holes all drilled I unbolt the pcb and drill out all the holes to 6.5mm to fit plastic bushes.
 

MisterBill2

Joined Jan 23, 2018
18,173
Do the drilling using a milling machine with digital readouts, then getting the holes positioned to withing 0.001 inch is a simple matter. Having the right tool for the job makes it much simpler to do the job right.
 

LesJones

Joined Jan 8, 2017
4,174
Many years ago I used a dead TO3 device as a template. I cut the top off with a saw and removed the chip and punched out the insulation round the base and emitter leads. Now I would probably do it as MisterBill2 describes using my milling machine with it's DRO.

Les.
 

MisterBill2

Joined Jan 23, 2018
18,173
Many years ago I used a dead TO3 device as a template. I cut the top off with a saw and removed the chip and punched out the insulation round the base and emitter leads. Now I would probably do it as MisterBill2 describes using my milling machine with it's DRO.

Les.
Unfortunately I no longer have access to a Bridgeport or any other mills, although there is a "maker" shop a few miles away , and they have all kinds of good tools.
 
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