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Early VIC-20 Voltage Regulation questions

Don't fret, you can use a DC power supply (unless the AC9V signals are used elsewhere within the VIC20)!

You just use two of the full-wave bridge rectifier diodes and let the other two sleep!

Dave
 
daver2 said:
Don't fret, you can use a DC power supply (unless the AC9V signals are used elsewhere within the VIC20)!

You just use two of the full-wave bridge rectifier diodes and let the other two sleep!
Click to expand...
I mean, yeah, its going to "work" but even though you cannot see it, those two diodes will be trying to dissipate 2x the heat. You may want to check the actual part they used for the bridge rectifier. The original PB101's were rated for like 4A, so from a power dissipation perspective 4A and 50$% duty cycle, so 2A @ 100%. If the actual part is rated higher, then you are OK.
 
>>> What is the A/C used for? Is it needed on the user port for modems / WiFi modems?

I can't see it wired up to anything else on the schematics. Not to any external connector. The unregulated +9V is used by the cassette motor, but I can't see any use for the AC voltage.

Dave
 
daver2 said:
>>> What is the A/C used for? Is it needed on the user port for modems / WiFi modems?

I can't see it wired up to anything else on the schematics. Not to any external connector. The unregulated +9V is used by the cassette motor, but I can't see any use for the AC voltage.

Dave
Click to expand...
Hmm I believe the c64 uses the A/C voltage for the internal clock (jiffies). I may have to probe around on the board later when I get time and see if it's going anywhere, the schematic shows it going off somewhere but ... to what? maybe nothing.
 
Divarin said:
On the bench I'm using one labeled as 9 volt AC but actually puts out 10 (no load), I also have another one I can use which is labeled as 9 volt AC but puts out 15 with no load. I haven't tried using this yet.
...
Maybe this VIC's power circuity simply assumes a higher input voltage?
Click to expand...
The old wall wart type adapters typically just contain a transformer and do not have a regulated output. They are rated for a voltage and a current. They will drop in voltage when you draw a current through them - so you can't really get a full picture by measuring the voltage at zero load. Typically they will measure high, but under the correct load they will drop to the correct voltage. All transformers have losses, but I think this is more apparent when trying to re-use the relatively inexpensive adapters that were designed for and provided with a specific piece of electronics in mind - and then trying to use that adapter under a different load.
 
bsd64 said:
The old wall wart type adapters typically just contain a transformer and do not have a regulated output. They are rated for a voltage and a current. They will drop in voltage when you draw a current through them - so you can't really get a full picture by measuring the voltage at zero load. Typically they will measure high, but under the correct load they will drop to the correct voltage. All transformers have losses, but I think this is more apparent when trying to re-use the relatively inexpensive adapters that were designed for and provided with a specific piece of electronics in mind - and then trying to use that adapter under a different load.
Click to expand...

Yeah if only I could find that adapter that was showing 15 volts under no load. Oh well I went ahead and ordered the one off Amazon, if it works well I may modify my ray carlsen to use that as the 9 volt A/C source. That way I can continue to use this one power connector for multiple machines rather than having a big-mess-o-wires under the desk. Well it's already a big-mess-o-wires but at least it's somewhat manageable. As long as this new adapter wouldn't end up over-volting the C64 or C128, which it shouldn't if it's a regulated output.
 
Just a quick update on this, the power supply from Amazon worked fine and the VIC-20 is now working normally. I guess if anyone else needs a power supply for one of these early VIC-20's that's not a bad one to go for as 9 volt A/C supplies rated for 3 amps aren't that easy to find and when you do find them they're not cheap.
 
I have some videos about reducing power consumption in the original two-prong VICs on my YouTube channel.

By reducing power consumption you also reduce the required size of PSU you need ... I've got my VICs down to under 1A.

I've recently designed a board to replace the internal RAM which reduces power draw by over 200mA

EzSBC also produce a "low noise" version of their LM323 replacement:
ezsbc.shop

PSU5 No Noise

5V 3A switch-mode voltage regulator, high-efficiency replacement for the obsolete LM323K. 20V Maximum Input This version of the PSU5 suppresses the loud noise at switch off reported on some pinball machines. The module has exactly the same functionality of the original PSU5 but includes extra...
ezsbc.shop
 
Old thread, but:

9V AC is connected to the user port. It might be used by some RS232 level converters, maybe some EPROM programmers and such. Check each user port accessory.

Otherwise the unregulated DC is used for the cassette motor, and obviously the 5V regulator.

There is an old thread at IIRC the denial/sleepingelephant forum with the conclusion that a VIC 20 with built in rectifier+regulator can run at 10-12V DC and at 10V it actually runs a bit cooler than with the regular 9V AC.

As for finding a transformer, I recommend going through the bins at thrift stores / flea markets. Just feel the weight of the mains adapters / wall warts. Anyone that is light weight isn't even worth reading the label on as it will be a switched supply that outputs DC (or worst case high frequency AC which I think is a thing for LED drivers).
If they charge like €1 or so for each adapter, I would kind of grab all of the ones that supplies various somewhat reasonable AC voltages as they might come in handy and will over time be rarer and rarer to find for cheap.

Otherwise, it's just a transformer. You can buy the transformer itself from most electronic components suppliers, and since it's not a super cheap thing also check surplus sellers, eBay and such. Then just put the transformer, a suitable fuse, mains intake connector or mains cord strain relief and maybe a mains power switch in any suitable box. Maybe add a LED with a series resistor (and possibly a small bridge rectifier) to indicate that output power is on.

For the European two prong VIC 20's, you can surprisingly use RCA female wire connectors! They fit on the prongs of the chassis intake connector on the VIC 20. I would recommend using two red connectors and put a warning label clearly stating that it's 9V AC for powering a VIC 20. That way you don't need to 3D print a connector or replace the intake connector (or back feed through the 9V AC pins on the user port).

Afaik the US VIC 20 used the same connector as some electric razors used for 110-120V AC mains. Sorry for being a tiny bit political but that being legal has a strong third world vibe. Like with a mains cord for a razor and the VIC 20 in the off position nothing would break but there would be a 50% risk that the signal ground of the VIC 20 would be connected to live mains power.
Either way, you should be able to find suitable electric razor power cords. IIRC these might have special wires with more strands than regular wires, but each strand being thinner, to allow for flexing a lot more as you'd move the cord each time you use your shaver. Don't know if that makes it more challenging to connect to or not though?
 
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