How to : 4 pin psu to 2 pin vic adapter chord DANGEROUS?

[R'zo]

I made a chord to power my 2 pin Vic-20 from a 4 pin Commodore power supply. I took photos and made an instructional video for anyone who might be interested.

https://youtu.be/_U4Ar8ev7lA

[eslapion]

VERY VERY BAD idea!!

The 2 pin VIC-20 requires up to 30 VA to operate properly from a 9-11 VAC source while the 4 pin VIC will usually draw no more than 2 VA from the 9 VAC source since it draws most of its power from the 5Vdc source.

A Commodore 64 4 pin PSU can deliver up to 9 VA on the 9 VAC source, still far from enough.

[R'zo]

It's enough. I use it almost every day. The 2 pin vic itself only needs 9v to run the extra voltage in the 11v 2 pin is for periphials. With this chord you can power the vic, just not alot of extra hardware. I can still run my tape drive and sd2iec just fine.

[R'zo]

VERY VERY BAD idea!!

I am curious as to why you say this. I would understand if the power source were to high, you would run the risk of blowing out the vic. With it being less than the 11v psu made for it the worst that would happen is that the vic would just not work. Like i said it works just fine with my vic.
I also would not have posted this if i had not tested it out first, that would just be irresponsible.

[Mike]

I have to concur with eslapion. You're *overloading* the PSU!

The 9VAC transformer of the wedge is rated for 9VA, i.e. you can draw 1 A from it for any indefinite time.

Now the 2-prong VIC-20 draws at least around 2 A from the transformer. Not enough to trigger the fuse, but there is an increased voltage drop over the PSU, the regulation of the 5 V inside the VIC-20 becomes worse, and the 2 A produce excess heat inside the transformer, up to the point that the isolation is damaged and you get a short inside the transformer.

And *that* will kill at least the fuse, but also the PSU and any connected VIC-20 as well!

[eslapion]

... The 2 pin vic itself only needs 9v to run the extra voltage in the 11v 2 pin is for periphials. ...

And where do you think it takes the 5V it needs to run internally? From air?

No, it rectifies more than 1 amp from the 9VAC and feeds it to a linear (very lossy) regulator.

The voltage is right but your 4 pin PSU CANNOT FEED THAT MUCH CURRENT! It won't be long before you destroy your PSU.

[R'zo]

I understand what you are saying and am checking other recources. I know some one who has been using a similar method for some time.

[R'zo]

From the info that I can find you are correct. Although I am having a hard time finding info on the 2 pin vics actual power consumption.

I am currently posting warnings on the pages that I have posted this on.

My electronics knowledge is novice and I would like to thank eslapion and Mike for calling me out on this and warning me.
I would like to hear other input and opinions to join in on this. 2 pin psus are getting harder to find and more expensive for there rarity. I would like to see more done on alternate power supplies but not at the risk of the vic.

[eslapion]

Very early VIC-20 2 prong PSUs sold in north america were in a black metal case.

They were rated for 11Vac @ up to 38VA. Later ones were in a black plastic case. They were rated for 9Vac @ up to 30VA.

Strangely, even if there were differences in the external transformers, the diode bridge, capacitor and regulator were identical in their specifications. This indicates the VIC will work fine wether you have a 9Vac, 10 Vac or 11Vac transformer.

AFAIK, the VIC will only produce more heat with a higher voltage, so 9Vac is better.