Hi,
I have started with recapping the Analog boards of my Mac 128K to Plus series.
I have just done 2x in the last days and there were obvious differences after replacing the capacitors.
On both, the brightness pot ( the one on the Analog board to set the maximum Brightness ) was almost fully open, after replacing the caps I had to turn it almost completely closed.
The other was from a Mac 512K and had an unstable display in the first 5 minutes, like there were fast rolling barrs on the background: it's completely gone now.
The remarkable facts is that none of the Radial capacitors actually looked bad and the ESR values were still good too.
Only the plastic housing of the 4700pf filter capacitors near the AC input was cracked.
I replaced all capacitors on the analog board, except for the Ceramic one's unless their values were out of spec.
I used high-grade Panasonic or Nichicon capacitors rater 105°C and 7000 hours. These are an upgrade over the original design as this still had a lot of 85°C capacitors and definately not 7000 hours one's.
It's not cheap to do a full recap of an Analog board, as the 7000 hours are expensive, so are the filter capacitors ( there are 3x of them: 2x 4700pf, 1x 0.47uf ).
However it's something I can recommand to all fellow collectors given these board are over 25 years old.
I have started with recapping the Analog boards of my Mac 128K to Plus series.
I have just done 2x in the last days and there were obvious differences after replacing the capacitors.
On both, the brightness pot ( the one on the Analog board to set the maximum Brightness ) was almost fully open, after replacing the caps I had to turn it almost completely closed.
The other was from a Mac 512K and had an unstable display in the first 5 minutes, like there were fast rolling barrs on the background: it's completely gone now.
The remarkable facts is that none of the Radial capacitors actually looked bad and the ESR values were still good too.
Only the plastic housing of the 4700pf filter capacitors near the AC input was cracked.
I replaced all capacitors on the analog board, except for the Ceramic one's unless their values were out of spec.
I used high-grade Panasonic or Nichicon capacitors rater 105°C and 7000 hours. These are an upgrade over the original design as this still had a lot of 85°C capacitors and definately not 7000 hours one's.
It's not cheap to do a full recap of an Analog board, as the 7000 hours are expensive, so are the filter capacitors ( there are 3x of them: 2x 4700pf, 1x 0.47uf ).
However it's something I can recommand to all fellow collectors given these board are over 25 years old.
