25:30 Yes you do, but only if it's dirty. I've fixed possibly over 100 floppy drives over the 30+ years I've been repairing stuff and I've seen a lot of Commodore drives (especially 1541) with some crap stuck on the head that scratched the disk. Some of them were so bad even IPA wouldn't remove it and I had to get my fingernail in there and get it off. So maybe the heads don't need cleaning as a general rule but it's a mistake to assume that they are clean without at least looking at them.
Check the resistor values in the emitter of the main switching transistor, the main resistor to the primary side -ve sets the current limit. Check the 220uF capacitor in the other PSU, I guess this capacitor is the one in series with the main switching transistor base, it should be an LESR type.
I disagree with not cleaning the floppy drive heads. If they have hardened gunk on them, you're going to destroy any disks you put in them. It happened to me a few times when I got lazy. Now I always have a spare floppy "scratch test" disk I put in any drive to check for scratching (even if I DO clean the head first), before I use any disk I want to try reading.
RIFA capacitors are Metalized paper. My advice is don't use any capacitors with paper in them. Use MKP metalized polypropylene or MKT metalized Polyester. Beware there are also MKP-P and MKT-P which contain paper, so I don't use these. For safety, make sure you use X or Y rated capacitors as appropriate for the application.
Thanks for the new videos, we were missing you.
Switch modes are a challenge but I saw Mr.C back feed from the output on the secondary to troubleshoot and wanted to try that procedure.
25:30 Yes you do, but only if it's dirty. I've fixed possibly over 100 floppy drives over the 30+ years I've been repairing stuff and I've seen a lot of Commodore drives (especially 1541) with some crap stuck on the head that scratched the disk. Some of them were so bad even IPA wouldn't remove it and I had to get my fingernail in there and get it off. So maybe the heads don't need cleaning as a general rule but it's a mistake to assume that they are clean without at least looking at them.
Bring me that PSU next time you're over. It's often a good idea to get a 2nd set of eyes on things.
Zork is a good test of the machine's graphics capabilities.
Check the resistor values in the emitter of the main switching transistor, the main resistor to the primary side -ve sets the current limit.
Check the 220uF capacitor in the other PSU, I guess this capacitor is the one in series with the main switching transistor base, it should be an LESR type.
Swapping the power supply, until you can repair the first, is a good solution, IMO.
I disagree with not cleaning the floppy drive heads. If they have hardened gunk on them, you're going to destroy any disks you put in them. It happened to me a few times when I got lazy. Now I always have a spare floppy "scratch test" disk I put in any drive to check for scratching (even if I DO clean the head first), before I use any disk I want to try reading.
What type of capacitor are RIFA's ?
RIFA capacitors are Metalized paper.
My advice is don't use any capacitors with paper in them.
Use MKP metalized polypropylene or MKT metalized Polyester.
Beware there are also MKP-P and MKT-P which contain paper, so I don't use these.
For safety, make sure you use X or Y rated capacitors as appropriate for the application.