1541 won't work with VIC-20

Boray · Post by **Boray** » Sun Oct 31, 2004 4:59 am

Good news!!! A 9V DC 3A power supply would work just as well! Here is the words from Ray Carlsen (Commodore repair guru) (plus my question to him):

Ray Carlsen wrote: > Another question... It is very hard to get hold of a substitute
> PSU for the old 2-prong european vic20 (220v AC -> 3A 9v AC.)
> At least two people are looking for one on the "Denial" forum.
> If everything is rectified inside anyway - then would it work
> just as well with a PSU that generates 3A 9v DC???

Anders,
After looking over the schematic, I believe it would work fine
with a DC supply. All DC sources derived from that AC power pack are
indeed rectified and used as either 9VDC (cassette motor) or 5VDC
(everything else). The only other place the 9VAC shows up is at the user
port. Unless something is plugged in there that needs the AC source, it
shouldn't matter that it's missing.
I don't like to give out information when I've not tried it
myself, but in this case, I don't have a problem with it. Note the
polarity of the DC supply source would not matter because of the bridge
rectifier in the computer. Whichever way you connect a DC input, the
rectifiers would reverse it if necessary.
Lastly, I've never tried to buy a 9 VDC 3 Amp adaptor, but it
seems to me that would be as rare as a 9VAC power pack. If I couldn't
find one, I'd probably buy a 9 volt transformer and install it in a
metal case to power my VIC. Even so, a three Amp would be unusual.

Ray

On page 70 of Clas Ohlson's latest catalog, you will find one (or 3) suitable transformer(s). (Article number 32-8529) for 295 swedish crowns.

/Anders

Leeeeee · Post by **Leeeeee** » Sun Oct 31, 2004 8:06 pm

Boray wrote:Good news!!! A 9V DC 3A power supply would work just as well!

It won't, 9VAC will need to be replaced by a 12V DC (RMS VAC * root 2).

Lee.

carlsson · Post by **carlsson** » Mon Nov 01, 2004 2:36 am

I posted a question on ELFA user forums, and one replied me personally with his friend owned a VIC-20 and was certain it took 9VDC input. As we all know, it quite doesn't. Personally I'm too uneducated (or stupid?) to understand why a direct current would work the same was as an alternating, but if it does...

Someone else told me to look among transformers. I'm sure one can build your own PSU which delivers the right power - maybe even one with two connectors that delivers both 5V and 9V 3A. If I'm not mistaken, it doesn't do any harm if the PSU is able to deliver more current than the computer drains, only the opposite.

Boray · Post by **Boray** » Mon Nov 01, 2004 6:35 am

12V??? Can you explain that a little better? So that a novice like me would understand?

I actually thought that it would be the other way around if any difference... The sinuswave rectified would be as a lot of upward bows going from 0 to 9V at top right? And 9V DC would constantly be a top of 9V. So as a total, 9V DC would be more than a 9V AC????

/Anders

Boray · Post by **Boray** » Mon Nov 01, 2004 6:38 am

Anyway, here is a little more info from Ray Carlsen

Ray Carlesn wrote: > There is a "battery eliminator" that can deliver
> 9V/3A DC sold by a company here in Sweden (called "Clas Ohlson").

Anders,
I have to wonder what kind of equipment takes that voltage and
current. Battery eliminators here are usually 12V... to run a car radio
for example.

> They also have one that can deliver 9V/4A and one for 9V/6A.
> I guess they would work too? Because they only deliver as much as
> the computer needs - right? And there is a 3A fuse in the vic20
> anyway... Have I understood this correctly?

Exactly correct. The only exception would be the so-called "wall
wart" types of supply (generally ones under 2 Amps). They are usually
unregulated, and a larger (higher current) unit might put out quite a
bit more voltage under the same load than a low current one. However, I
suspect the power supplies you mentioned are switchers and therefore
inherently regulated to put out no more than the rated voltage.
Switchers tend to be very small and light weight for the amount of
current they can supply in comparison to the C64 black brick which is a
conventional linear type.

Ray

Leeeeee · Post by **Leeeeee** » Mon Nov 01, 2004 9:40 am

Boray wrote:The sinuswave rectified would be as a lot of upward bows going from 0 to 9V at top right? And 9V DC would constantly be a top of 9V. So as a total, 9V DC would be more than a 9V AC????

/Anders

Nope, 9VAC will go from zero to plus 12.7V through zero and down to -12.7 and so on. The Root Mean Squared value of this waveform will be 9V which is the equivalent DC voltage into a resistive load.
The problem starts when you rectify the AC as the current is only drawn at the wave peaks so it becomes about 12VDC after rectification.

Lee.

Boray · Post by **Boray** » Mon Nov 01, 2004 10:01 am

But why would the vic-20 need 12V when only 9V and 5V is used inside? wouldn't it work with a 9V DC suplly anyway?

Hmmm..... Well, I measured, and out of my power supply comes 10.5V AC. After the rectifyer, it's 11V DC.

Could this be because they have increased the voltage of the
power outlets from 220 when the vic20 was built into
more like 225-230V today?

Maybe it's more healthy for the vic to buy one of those DC power packs....

I don't think there is anything wrong with the AC measuring of my multimeter. When I measue the power outlet, it's 225V and that's probably right...

/Anders

Boray · Post by **Boray** » Mon Nov 01, 2004 10:26 am

Hmmm..... I think I will buy a better multimeter. It doesn't seem very accurate.... Or the power outlet is varying quite much... But I think I will buy a new one anyway. A digital one....

/Anders

Boray · Post by **Boray** » Tue Nov 02, 2004 4:43 am

Leeeeee wrote:It won't, 9VAC will need to be replaced by a 12V DC (RMS VAC * root 2).

Lee.

Ray Carlsen wrote: > "It won't, 9VAC will need to be replaced by a 12V DC (RMS VAC * root
> 2)." Any idea what he talks about?

Anders,
I might agree if I had not had a look at the schematic of that
particular VIC20. After the rectifier, the only thing there is a 5 volt
regulator and a pass through to the cassette regulator circuit (six
volts). A conventional regulator needs an input about three volts
higher than its output to regulate (not drop out). A 9 volt DC input
meets that requirement. The AC input does provide a higher DC input
voltage, but the excess is just converted to waste heat.

Ray

Ray Carlsen wrote: > I have now done some measuring... My Vic-20 PSU delivers 10.5V AC.
> So 10.5V goes into the rectifyer, and out comes 11V DC...!?
> Can this be because they have increased the voltage of the
> power outlets from 220 when the vic20 was built into
> more like 225-230V today?

Good questions, and you've got it right. The voltage is "nominal"
9VAC, but what you actually measure will indeed be higher (or lower)
depending on how you measure it, whether the transformer is loaded or
not(computer connected), the line voltage (which varies a lot from place
to place and even in the same location at different times of the day).
With 9VAC input to the bridge recfifier and filter capacitor, the
unloaded output will be somewhere in the neighborhood of 12.7 volts DC.
That's because it's the peak to peak (RMS times 1.414) excursions of the
line that are actually being measured. On one half cycle, the AC voltage
goes above zero about six volts, then crosses zero and goes below zero
about six volts. Loading has a lot to do with what the actual voltage is
at that point. Note that there is not a lot of energy in those peaks, so
when you load down a capacitor input filter (what they call a standard
rectifier and filter cap circuit), the running voltage is something less
than the peak reading. The "effective" voltage (loaded) is something
they call RMS (ratio means square). It has to do with how much actual
power is available (expressed in Watts or Volts times Amps).

> Could this be the cause of the heat problems I have had?
> (I have moved the rectifyer out of the vic20 case etc...)

The rectifier and regulator in the early VICs do run pretty hot.
That's why the later design uses the "split" supply like a C64... the
regulator is in the supply to keep the heat away from the computer.
Waste heat is a consequence of linear regulation. That's why switchers
are the supply of choice nowadays... greater efficiency means less waste
heat.

> Would it be more healthy for my vic-20 if I bought one
> of those DC power packs we talked about to use 9V DC instead?

Probably not. The regulator in the VIC is where most of the heat
comes from. Notice the enormous heat sink. Using DC instead of AC as an
input still requires the internal regulator that converts the input (AC
or DC) to +5VDC for all the chips.

> If you remember, I have a vic-1020 expansion box (which I sent
> you the scematics for once). The power goes from the PSU into the
> vic-1020 to power it, through a "master" on/off switch and then into the
> vic-20 (which always has the power switch on). Would it work to
> use 9V DC for it all? To just replace the original PSU with it so
> to say...? If you don't still have the scematics, then I can send
> it to you.

I do, and I put them up on my schematics site for all to use. I
did notice something odd however. The 1020 power supply diagram seems to
be incorrect. They show what is called a full wave rectifier (two
diodes) instead of a bridge arrangement (four diodes). Their full wave
circuit has no ground return. Such a circuit usually has a center tapped
transformer, but a standard VIC supply has none. So, I suspect the
schematic is incorrect and the actual circuit is a bridge. I can't
verify that without seeing the unit. But, to answer your question, I
think a DC supply would power the 1020 OK too.

I would like my vic20 to live as long as it can, and
> running it on 11.5V instead of 9V seems a bit unhealhty, don't
> you think?

Well, the higher the input voltage, the harder a regulator has to
work to drop the excess voltage. However, it's made to work that way
unless you're ready to modify it to make it more efficient. That would
mean getting the 5 volt regulator out of the box. Then you would feed a
regulated +5VDC to the computer directly. 5 volt supplies are even
easier to find, but this mod would require a bit of work to implement.

Ray

Boray · Post by **Boray** » Tue Nov 02, 2004 11:04 am

Sorry for this double post with the buy&Sell forum, but this concerns this thread too...

---

I just bought a better multimeter and made some measurements. And
Lee is absolutely right: 2A is clearly enough.
My vic-20 uses 1.64A while running and more like 1.75A at startup.
Vic-20 + vic1020 uses 1.79A while running and something like 1.95A
at startup. These ampere measurements has an accuracy of
+-(2.5% +5). I don't know what the +5 means (maybe someone can
explain), but if it's just the percent, then the real value for a
vic-20 should be in between 1.60A and 1.68A.

Some more measurements:

The power outlet varies in between 228V and 231V.

The vic20 PSU without load: 11.4VAC (49.9Hz)

Over the rectifier while the computer is running:
in: 10.3 VAC, out: 10.9 VDC

Over my old rectifier without load (I have replaced it):
in: 11.4 VAC, out: 9.73 VDC

(AC accuracy +-1.2% +3)
(DC accuracy +-0.8% +3)

Interesting?

/Anders

Boray · Post by **Boray** » Tue Nov 02, 2004 11:09 am

Woops... The c64 PSU can only deliver 1A of 9V (right?) so maybe I was right anyway.... it's not enough!

/Anders

ChristopherT · Post by **ChristopherT** » Wed Nov 03, 2004 7:06 pm

Boray wrote:Woops... The c64 PSU can only deliver 1A of 9V (right?) so maybe I was right anyway.... it's not enough!

/Anders

I swap my C-64 PSU between my C-64 and my VIC-20 just fine. I don't
think that would be a problem. I think the problem is wether or not you
are getting good clean AC to the PSU. I just used my DVM on my outlet,
I got a good 122.0 volts and it never varied. Try eliminating anything
between the wall outlet and the PSU, maybe you have a surge suppressor
that's getting old and flaky?

Christopher

carlsson · Post by **carlsson** » Thu Nov 04, 2004 2:45 am

I think you may have a VIC-20CR, the newer one with a 3 or 5-pin DIN connector providing both 9VAC~ and 5VDC=. It draws equal power as the contemporary C64 does, so it is not an issue here. We're speaking the first generation VIC-20 with its two-prong connector, which only gets 9VAC~ input.

Boray · Post by **Boray** » Thu Nov 04, 2004 8:45 am

Yes... and it's not me having the trouble either.... But it seems idrouge (the original poster) isn't reading this forum anymore or he would probably had replied...

Btw, running the tape takes futher 0.1A (playing) to 0.2A (rewinding). Anyway, a total of 2A should be enough for a normal 2-prong vic20...

/Anders

carlsson · Post by **carlsson** » Thu Nov 04, 2004 2:02 pm

Phew. Did you measure if different colour combinations or size of writable screen draws more power too?

What about with and without a cartridge plugged in, or for that matter a joystick, disk drive (which the thread originally was about) or with Shift Lock depressed?