Was given two Cirkit PA100 amplifiers brand new in box fully built and unused but minus heatsinks, I'm wondering if I used the wrong heatsink bracket size. I've used 1" x 2" angle bracket 3/16ths inch thick (75mm long to match the PCB width)
The construction sheet uses 4" 6BA screws to mount the Power fet to the heatsink with 10MM heat-shrink sleeve over the screws to to isolate them from the bracket.. The insulated bushes are on the underside fitted between these and the transistors casinga. 10mm sleeving is about 5mm too long? Thus the question about heatsink thickness.
I saw Maplins 100w amp. circuit is where I got the details from, it was very basically the same circuit their PCB width was 3.5" not 3".
Thanks, Dave
The construction sheet uses 4" 6BA screws to mount the Power fet to the heatsink with 10MM heat-shrink sleeve over the screws to to isolate them from the bracket.. The insulated bushes are on the underside fitted between these and the transistors casinga. 10mm sleeving is about 5mm too long? Thus the question about heatsink thickness.
I saw Maplins 100w amp. circuit is where I got the details from, it was very basically the same circuit their PCB width was 3.5" not 3".
Thanks, Dave
Thank you for quick reply, I didn't want to clog the post up, here goes-:
1) Maplins 100W PA see link and go to page 48 for full details https://worldradiohistory.com/UK/Mapelin/Maplin-Electronics-1990-12-01.pdf
2) Same amplifier with heatsink construction. from Muzik Magazine http://www.muzines.co.uk/articles/mosfet-amplifier/2651.
The Cirkit PA100 is slightly different but they don't give heatsink details
"Argh....", just realised Maplin amp. don't use any sleaving on the screws, Cirkit does say to cut the sleeving to 10mm lengths, I do suspect that means shrinking them on the screw, un-screwing then fit them in the heatsing.... because the sleeving don't fit the bush.
I'm going have to photocopy the building instructions, it simply shows the 4" 6BA mounting screw with a plastic bush then the 10mm sleeving fed from the bottom up to the top of the transistors - my problem is 10mm is 5mm too long thus my question about the thickness of the heatsink,
The transistors are insulated, but I questioned why my sleeving is 5mm shorter, no heatsink details are given in the construction sheet. I guess if they used bushes with longer necks that would be better.
Note:
Maplin provides solder tags rather than soldering the bolt heads instead of how its done in Muzic magazine. Just that I thought ashamed they weren't completed..
Dave
1) Maplins 100W PA see link and go to page 48 for full details https://worldradiohistory.com/UK/Mapelin/Maplin-Electronics-1990-12-01.pdf
2) Same amplifier with heatsink construction. from Muzik Magazine http://www.muzines.co.uk/articles/mosfet-amplifier/2651.
The Cirkit PA100 is slightly different but they don't give heatsink details
"Argh....", just realised Maplin amp. don't use any sleaving on the screws, Cirkit does say to cut the sleeving to 10mm lengths, I do suspect that means shrinking them on the screw, un-screwing then fit them in the heatsing.... because the sleeving don't fit the bush.
I'm going have to photocopy the building instructions, it simply shows the 4" 6BA mounting screw with a plastic bush then the 10mm sleeving fed from the bottom up to the top of the transistors - my problem is 10mm is 5mm too long thus my question about the thickness of the heatsink,
The transistors are insulated, but I questioned why my sleeving is 5mm shorter, no heatsink details are given in the construction sheet. I guess if they used bushes with longer necks that would be better.
Note:
Maplin provides solder tags rather than soldering the bolt heads instead of how its done in Muzic magazine. Just that I thought ashamed they weren't completed..
Dave
