I made a few photos of my PSU:
http://www.keprt.cz/sampsu1.jpg
http://www.keprt.cz/sampsu2.jpg
You can clearly see that D4 is missing (right-bottom), and there is a very
large old zener diode put there instead. It is Tesla 6NZ70 - 12V 1.5W Zener
diode which proudes a LOT of heat. (If I count correctly, a 2.5W diode should
be used instead.)
I am also suspicious about R1 (large grey resistor right beside D4) which is a
bit mechanically damaged (clearly visible on the second photo), and also C4
(one of the large capacitors) which seems to me a bit bloated.
So do you recommend me to put there 1N5349 instead of that old big boy? (Local retail
shop here offers me 1N5349, not 1N5349B, but I think it is the same and maybe it actually
is the "B" version.)
I don't use my Sam often, I just nostalgically keep it. So I don't want a whole
new PSU.
Best regards,
Aley
______________________________________________________________
Od: "Colin Piggot"
Komu:
Datum: 14.01.2012 19:15
Předmět: Re: Power supply circuit diagram
Aley Keprt wrote:
So I just need to know what was the original piece in the PSU and I am
going to replace it back.
For the 12V Zener Diode - I use 1N5349B when repairing old supplies. I would
also recommend replacing the wirewound resistor by it with a higher wattage
part - often see them burnt out when the 12V line fails. I still have a few
of these parts if needed.
Thomas Harte wrote:
You should sell those; some of us are pathologically incapable of
soldering but would love a quiet power supply.
I can supply switch mode power supplies with a little adapter cable to plug
into the SAM if needed. I also add a big capacitor to the 5v line in my
adapter cable as there can be a bit of noise on the output from the switch
mode power supplies.
Colin
=====
Quazar : Hardware, Software, Spares and Repairs for the SAM Coupé
1995-2012 - Celebrating 18 Years of developing for the SAM Coupé
Website: http://www.samcoupe.com/
