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Mark
Good luck with that. I don’t do microdrivesredgatemodels wrote: ↑Mon Oct 23, 2023 11:12 pm Next job is to get those damn microdrives working …….
Yes.
I’m not sure what you are asking. The mains power supply unit is an unregulated type made up of a thermal fuse (which may be part of the transformer or under it), an isolating mains transformer, four diodes, and one or two electrolytic capacitors. Plus obviously a plastic case and input and output cables. They produce between 9V and 12.5V DC at up to 1.4A. Yes, if any of the diodes have become faulty, replace all of them. Yes, if the electrolytic capacitor(s) are life expired, renew it/them. Or, buy a modern PSU. A 9V type with a current rating of 1.4A or higher will do. But keep in mind most will have the output plug with the wrong polarity. Either get one with the correct polarity, or chop off the existing plug and fit a new one (2.1mm inside dia., 5.5mm outside diameter barrel type, some machines may need the long version).
DRAM faults are indeed the most common. The 7805 voltage regulator is actually fairly reliable. But they are cheap, so it is worthwhile having a spare.Pygmalion wrote: ↑Tue Oct 24, 2023 12:10 pm
- I also plan to make a spare set for emergencies. Since ULA has a large heatsink and is completely cool, I assume the weakest points of the ZX Spectrum are the lower memory chips and the linear regulator. Is there anything else I should have on hand as a spare?
If you remember, I once had 50Hz harmonics in the 12V line, which indicated that one of the diodes was not working properly.1024MAK wrote: ↑Tue Oct 24, 2023 5:59 pmI’m not sure what you are asking. The mains power supply unit is an unregulated type made up of a thermal fuse (which may be part of the transformer or under it), an isolating mains transformer, four diodes, and one or two electrolytic capacitors. Plus obviously a plastic case and input and output cables. They produce between 9V and 12.5V DC at up to 1.4A. Yes, if any of the diodes have become faulty, replace all of them. Yes, if the electrolytic capacitor(s) are life expired, renew it/them. Or, buy a modern PSU. A 9V type with a current rating of 1.4A or higher will do. But keep in mind most will have the output plug with the wrong polarity. Either get one with the correct polarity, or chop off the existing plug and fit a new one (2.1mm inside dia., 5.5mm outside diameter barrel type, some machines may need the long version).