GB: Maplin lateral mosfet pcb derivative
I have taken the 1980's Maplin 75 WRMS lateral mosfet amp and brought it up to date with modern easy to find transistors. I also added extra decoupling at front end to get around the hum problem some had.
The pcb allows use of TO3 or to247 packages.
The pcb has no copper below where TO3 transistors sit so it doesn't get shorted out by heatsink.
I have 7 pcb's now and if there is more demand I will buy in some more.
PCB's come with parts list, circuit diagram, build instructions and power supply wiring diagram.
Power supply needs to be +/-35 volts
£6.99 per pcb.
p+p is £2.25 to UK and £9.99 rest of world.
I have taken the 1980's Maplin 75 WRMS lateral mosfet amp and brought it up to date with modern easy to find transistors. I also added extra decoupling at front end to get around the hum problem some had.
The pcb allows use of TO3 or to247 packages.
The pcb has no copper below where TO3 transistors sit so it doesn't get shorted out by heatsink.
I have 7 pcb's now and if there is more demand I will buy in some more.
PCB's come with parts list, circuit diagram, build instructions and power supply wiring diagram.
Power supply needs to be +/-35 volts
£6.99 per pcb.
p+p is £2.25 to UK and £9.99 rest of world.
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Hi Nigel,
Private message sent re a couple of these boards. It's an itch I have to scratch!
Cheers
John
Private message sent re a couple of these boards. It's an itch I have to scratch!
Cheers
John
Maplin took a Hitachi lateral mosfet datasheet from about 1980 and came up with the Maplin 75WRMS lateral mosfet amplifer. Many hundreds were sold.
They later came up with a higher powered version which was about 150WRMS.
About a year ago I came across an unbuilt Maplin lateral mosfet kit on ebay so I bought it. I adapted the circuit for my own needs by adding extra decoupling at the frnt end for better hum performance. I also added a DC offset trimmer.
They later came up with a higher powered version which was about 150WRMS.
About a year ago I came across an unbuilt Maplin lateral mosfet kit on ebay so I bought it. I adapted the circuit for my own needs by adding extra decoupling at the frnt end for better hum performance. I also added a DC offset trimmer.
i cant see the attached image..but i still have some pairs of k176/j76 TO-3's . how much for the pair? plus shipping in the philippines.
New batch of pcb's in due to demand.
£6-99 each or discount more multiple purchases.
£3-99 p+p to UK. £10-99 to rest of world.
This PCB has options of TO247 or TO3 mounting.
Exicon and Profusion have laterals to fit.
Comes with parts list, power supply diagram, circuit diagram and build instructions.
£6-99 each or discount more multiple purchases.
£3-99 p+p to UK. £10-99 to rest of world.
This PCB has options of TO247 or TO3 mounting.
Exicon and Profusion have laterals to fit.
Comes with parts list, power supply diagram, circuit diagram and build instructions.
Hi Nigel, I have purchased one of these boards. 3 questions please.
1. I have 134/49 fets. will they drop straight in?
2. At what voltage? the boards are marked 25v but also you sent me plans for 45v psu.
3. assuming i can use either...what output in watts may I expect?
I was going to pm you on ebay but thought others might like to know.
thanks Brian
1. I have 134/49 fets. will they drop straight in?
2. At what voltage? the boards are marked 25v but also you sent me plans for 45v psu.
3. assuming i can use either...what output in watts may I expect?
I was going to pm you on ebay but thought others might like to know.
thanks Brian
1/ Your mosfets will work OK if lateral mosfets. Dont use vertical mosfets, wrong pin out.
2. Power supply depends on mosfets, in your case I would go with the +/-40 volts DC but only into 8 ohms. So that means a 28 or 30 volt AC transformer with two windings.
Bridge rectifier and smoothing caps as in drawing I sent.
3/ You should get about 100 watts output into 8 ohms.
2. Power supply depends on mosfets, in your case I would go with the +/-40 volts DC but only into 8 ohms. So that means a 28 or 30 volt AC transformer with two windings.
Bridge rectifier and smoothing caps as in drawing I sent.
3/ You should get about 100 watts output into 8 ohms.
Great they are original laterals I ripped out of the 25w maplin amp I told you about some years ago. Thanks Nigel.
Thanks for letting me know about 25v markings.
They should be B++ and B-- as voltage changes depending on mosfets used.
They are quite easy to build only awkward bit is mounting bracket for the heatsink.
The mosfets need isolators between transistor and heatsink.
The transistor bolts also need an insulating bush between them and the mounting bracket to stop them shorting out.
They should be B++ and B-- as voltage changes depending on mosfets used.
They are quite easy to build only awkward bit is mounting bracket for the heatsink.
The mosfets need isolators between transistor and heatsink.
The transistor bolts also need an insulating bush between them and the mounting bracket to stop them shorting out.
OK Nigel that makes sense now. I will let you know how i got on when i finish. I am going to use the same mounting bracket mapllin supplied albeit sawn in half as Im building monoblocs. Of course I will mount bracket to heatsink. Cheers Brian.
After I mount transistors I always check with multi-meter that there are no shorts between any transistor pins or case and the heat sink.
No worries Nigel. I will do my best not to extract smoke from these mosfets.
the mono cases i intend to use have hs on each side. Iam intending to have wires from board to devices. Will there be any caveat in that? 50mm to 100 length max.
TIA. Bri.
the mono cases i intend to use have hs on each side. Iam intending to have wires from board to devices. Will there be any caveat in that? 50mm to 100 length max.
TIA. Bri.
hi Nigel ,i already received the boards. I will be using K176/J56 and try to increase the rails to +/- 50vdc which I already have, will there be no problem?
Just finished assembling Maplin on Nigel's boards. It is running from 28V toroid transformer with a pair of dual die Exicons ECW20N20/ECW20P20. No issues and sounds great.