Help installing cooling fan on VIC-20

Modding and Technical Issues

Moderator: Moderators

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Help installing cooling fan on VIC-20

Postby ral-clan » Mon Oct 06, 2014 8:19 pm

Now that I've finally had a VIC chip go bad due to heat buildup (even with a heat sink installed), I'm very interested in installing a small fan onto the back of my VIC-20. Fortunately, I've salvaged many old computer fans from PCs over the years. I have some 5v ones that are about 5cm square, and some very small fans that might be 3v (I'd have to check) - the latter were salvaged from an old Plextor CD-burner.

I'm very handy with a soldering iron, and doing case modifications using a dremel, etc. I've had my VIC-20 opened many times to do chip swaps, install a reset switch, and do repairs to the joystick port...but I don't have strong electronics theory knowledge...so I would just need some help and advice on where would be the best place to power a fan from the VIC-20 motherboard.

Are there any safe locations to power a 5V fan from? What about a 3V fan?
Is it even advisable to power a fan from the motherboard, or would that stress the power supply or other components?

Also, any advice on the best location for a fan? I'd preferably like it installed on the back, where it wouldn't be highly visible.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
highinfidelity
Vic 20 Afficionado
Posts: 391
Joined: Thu Jul 28, 2011 2:34 am
Website: http://www.hirtel.it
Location: Torino, Italy.

Re: Help installing cooling fan on VIC-20

Postby highinfidelity » Tue Oct 07, 2014 2:43 am

I know you're not interested in comments from people that wouldn't do that, but here I go: I wouldn't do that.

Heat dissipation was fairly well calculated for the VIC20 chips (their longevity speaks for it) and, although a passive radiator may always help, a fan is really pushing the tweaking too far IMHO and will turn your dear old vic into a Frankenstein.

By the way I don't think your VIC failed because the chip was not cooled enough. All the contrary, I suspect that the chip overheats because something else is not working properly. Some current leaking capacitor is the first suspect, followed by some out-of-range resistor.
GOD is REAL. Unless declared DOUBLE PRECISION.

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Tue Oct 07, 2014 6:19 am

Well, thanks for that tip. But that opens a whole other can of worms. How do I even begin to tell which component is operating out of range? Seems like a very large job and the only tool I have at hand is a multimeter - and I'm not entirely sure what the process is for checking components (i.e. resistors, capacitors and that damn bridge rectifier) on the motherboard.

Is it not the case that other people's VIC-20s get hot around the cartridge port?

It also makes me worry because any VIC chip I put in this machine may eventually suffer the same problem until it is rectified.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
highinfidelity
Vic 20 Afficionado
Posts: 391
Joined: Thu Jul 28, 2011 2:34 am
Website: http://www.hirtel.it
Location: Torino, Italy.

Re: Help installing cooling fan on VIC-20

Postby highinfidelity » Tue Oct 07, 2014 7:07 am

ral-clan wrote:It also makes me worry because any VIC chip I put in this machine may eventually suffer the same problem until it is rectified.

Exactly, that's the point. Your VIC replacement will probably overheat just as well. Also, I personally don't remember my VIC20 getting especially hot anywhere, and in particular near the ports.

A multimeter is often sufficient to check a circuit board if you know what you're doing. There is people here that seem to know every single voltage at every pin inside the VIC20 (not me, unfortunately) and hopefully they will kick in into this conversation.

Otherwise, I think that replacing all of the electrolytic capacitors is a good starting point. They age not well in any case, and VIC20s are now in their thirties... :wink: Ceramic capacitors are instead usually OK and can be left untouched.
GOD is REAL. Unless declared DOUBLE PRECISION.

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Tue Oct 07, 2014 7:29 am

Well, I hope one of those knowledgeable people do chime in eventually. I would really like to find out the source of the heat.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Wed Oct 08, 2014 6:30 pm

Still thinking about installing a fan.

I have a very small one (like 2cm x 2cm) from a Plextor CD burner.

12V 0.05A

Thinking about powering it off the datasette port.
Could I still use a datasette while the fan is in operation, or will this draw too much power?

I will only do this if it can be done absolutely discreety (i.e. hidden internally with fan holes not visible from the front) and if the fan is quiet.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
RobertBe
Vic 20 Guru
Posts: 1825
Joined: Sat Jul 14, 2007 2:48 pm

Re: Help installing cooling fan on VIC-20

Postby RobertBe » Wed Oct 08, 2014 8:09 pm

ral-clan wrote:Are there any safe locations to power a 5V fan from? What about a 3V fan?
Is it even advisable to power a fan from the motherboard, or would that stress the power supply or other components?

Which version of the VIC-20 do you have? Version 1 with the two-prong power input or version 2 with the round DIN input?

Truly,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

User avatar
RobertBe
Vic 20 Guru
Posts: 1825
Joined: Sat Jul 14, 2007 2:48 pm

Re: Help installing cooling fan on VIC-20

Postby RobertBe » Wed Oct 08, 2014 10:22 pm

I sent a message to C= hardware repair tech, Ray Carlsen, and this is his answer to this thread:

--------------- Forwarded message -------------------

From: Ray Carlsen
Date: Wed, October 8, 2014 9:02 pm


Hi Robert,

I'd answer his questions this way...

A small fan can't move much air if put at the rear of the computer unless a large enough hole is drilled so airflow is not restricted. I would still put heat sinks on the chips that run hot such as the VIC and Kernal to get the heat away from the IC's and into the surrounding air where a fan can remove it. My website shows how I do that. As far as a fan, the small ones used in a PC to cool the CPU are usually 5 volts. If there is such as a thing as a 3 volt version, you would need to drop the 5V source to power it. Perhaps a tiny light bulb in series would work to drop the voltage... don't know since I've never seen such a fan.

There are two versions of the VIC20 and both use a regulated 5VDC source to power the chips. That's where I would tap off the fan voltage, right at that source. Small fans typically draw around 100mA which is no more than a game cart would impose. The early VIC20 uses a single transformer type of PS which has a two pin plug that fits the computer. The regulator IC inside the computer is VR1 and its output is 5 volts. On that same line are filter capacitors C44, C45 and C3 as well as resistor R28 that feeds the power LED. There should be space on one of those components to attach the positive fan wire but the large heat sink will probably be in the way. One convenient place to tap off 5 volts is at the B/2 terminal of the cassette port. A/1 is ground.

The later version VIC20CR (cost reduced) uses the same power supply as a C64 so its 5 volt regulator is inside the PS. There are several filter capacitors inside the computer on that 5V line, namely C33, C34 and C40 as well as a resistor R23 that feeds the power LED. As with the earlier version computer, 5 volts for the fan can be taken off somewhere on that line. One easy place to tap it off is either side of inductor (just a small coil) L3, and negative to ground. As with the early VIC20, you can also get +5V at the B/2 terminal of the cassette port and A/1 is ground.

As far as where to mount a fan, I think I'd keep it completely internal to simply circulate the air inside the case and thereby eliminate hot spots. Normal convection should vent the warm air. If there is enough room, set the fan upright at one end (perhaps at an angle to make it fit) to blow air across the board. If that's not possible, locate it centrally to flow air around inside the case. Keep in mind that both sides of the fan must be clear so air can easily flow through it... the reason I think an upright position might be best, if that's possible. All this is guesswork since I've never done one, but those are my thoughts. Good luck!

Ray

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Thu Oct 09, 2014 6:03 am

Thanks, Robert, for sending that e-mail off to Ray. His answer was (of course) extremely helpful and his level of knowledge unparalleled.

The VIC I'm trying to improve cooling in is a 2-prong modem.

I know he's an expert, but I'm not sure about the idea of just circulating the air within the case. Hot air is hot air whether it's cirulated or not. I was thinking about putting the fan at the back of the case, blowing air out (and thereby sucking cold air in through the slots at the underside of the case.

I'm going to do a complete capacitor swap on the motherboard first, to see if that helps the issue.

Actually, Ray might be helpful here - does he or anyone else already have a capacitor list for a 2-prong? Would save me a little time...

I'll see if I can find Ray Carlsen's e-mail on line.

PS: I've seen a lot of your pictures and videos on-line. Your videos of the Commodore convention presentations are very useful to us who cannot attend these conventions. Thanks.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
RobertBe
Vic 20 Guru
Posts: 1825
Joined: Sat Jul 14, 2007 2:48 pm

Re: Help installing cooling fan on VIC-20

Postby RobertBe » Thu Oct 09, 2014 10:26 am

ral-clan wrote:I know he's an expert, but I'm not sure about the idea of just circulating the air within the case. Hot air is hot air whether it's cirulated or not.

Well, there is the other method of drilling bigger vent holes in the top of the case. :)
...does he or anyone else already have a capacitor list for a 2-prong? Would save me a little time...

I'll see if I can find Ray Carlsen's e-mail on line.

His e-mail address is right there at the top of his website.
I've seen a lot of your pictures and videos on-line. Your videos of the Commodore convention presentations are very useful to us who cannot attend these conventions. Thanks.

Thanks for looking at them! I still have to get BIOS to post my video the August Classic Gaming Expo in Las Vegas.

Which reminds me to announce more of my pics from that show,
Robert Bernardo
Fresno Commodore User Group
http://www.dickestel.com/fcug.htm

User avatar
RobertBe
Vic 20 Guru
Posts: 1825
Joined: Sat Jul 14, 2007 2:48 pm

VIC-20 blacking out (Was: Help installing cooling fan on VIC

Postby RobertBe » Fri Oct 10, 2014 8:26 pm

While e-mailing Ray about your VIC-20 problems, I told him about my VIC-20CR problem, and he responded.

RB> every once in a while, the VIC-20 would go to a black screen. I would power it off and on, and it would function
RB> normally for several hours before it would black screen again. I blamed the black brick p.s....

As far as the VIC20 blanking out, it's hard to tell what's happening. Chips can be marginal and can go temperature sensitive. With the VIC20 that's failing, I'd sink the VIC chip for sure since they are hard to get and are frequent failures sitting inside that metal box with no way to vent waste heat. The Kernal ROM runs warmer than the others and should be sinked as well. I've not worked on as many VIC20's but those two IC's get replaced more than the others in my experience.

RB> time to do a multi-hour test of the VIC-20CR with your universal power supply. I'll have to buy or make some heatsinks
RB> for the those chips, too.

The VIC is the most important and the easiest. One strip of metal that sits on the chip with the ends bent up to touch the metal cover is all you need. I'll show you a photo. I attach the metal strip to the IC with fast set epoxy so it can't move and perhaps dislodge and short something out. The best "glue" I've found is J B Quik from the JB Weld company. I rub sandpaper on the sink bottom and the IC top to clean and roughen the surfaces, then apply a tiny drop of epoxy and spread it around. I then apply the sink and move it back and forth slightly while pressing it down to squeeze out the excess. It sets up in 10 minutes. If an IC is already on its way out, sinking may give it a bit more life but there are no guarantees. Most store-bought heat sinks have very small fins which don't help much since the air flow inside a closed computer is minimal. That's why I make my own sinks with large fins. The Kernal ROM UE12 also runs very warm and I've had to replace a few of those too.

Ray

User avatar
Boray
Musical Smurf
Posts: 4016
Joined: Mon May 03, 2004 10:47 am

Re: Help installing cooling fan on VIC-20

Postby Boray » Sat Oct 11, 2014 3:47 am

Here are some pictures of fans I used in a Vic-20. One of them is blowing air into the user port from outside. The other one is blowing out air from inside (by the power led)
http://www.boray.se/commodore/vic/index.html

I think the most important thing is to remove the paper shielding around the board (I'm not sure if it even exists in NTSC machines though). Remove the lid on the box around the vic-chip (if any) and then put a heat sink on the vic chip.
PRG Starter - a VICE helper / Vic Software (Boray Gammon, SD2IEC music player, Vic Disk Menu, Tribbles, Mega Omega, How Many 8K etc.)

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Sun Oct 19, 2014 7:15 am

Hi guys,

I installed the fan in my VIC-20 (pictures below). It is an internal installation, blowing air out at the back top of the case. So this should mean it sucks air from the slots at the front bottom of the case, providing good convection (however, in reality it will probably get a lot of air from the datasette and user port openings.

There were not a lot of good places where this fan would fit, even though it is small (about 1-inch or 2.5cm square). But I think the central location, right near the VIC chip should be good. This fan is also very quiet. You can hear it in a quiet room, but it is just a murmur.

I was reluctant to physically alter the VIC-20's case, but I feel I did it discretely and when you are sitting in front of the VIC-20 you cannot even see the fan opening. I would rather a carefully modded case rather than a dead VIC 6560 chip.

This a 12v fan pulled from a Plextor CD burner. Ray Carlsen gave me advice on where to find the voltage points on the motherboard of a two-prong power connector VIC-20. The positive and negative solder points at the large 4700uF capacitor (at C39) provided approximately 11.4V.

Pictures below (click to make them bigger):

Image

Image

Image

Image

Image

Image

The red button is a reset button connected the 555 timer chip.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com

User avatar
Boray
Musical Smurf
Posts: 4016
Joined: Mon May 03, 2004 10:47 am

Re: Help installing cooling fan on VIC-20

Postby Boray » Sun Oct 19, 2014 7:56 am

Nice!
PRG Starter - a VICE helper / Vic Software (Boray Gammon, SD2IEC music player, Vic Disk Menu, Tribbles, Mega Omega, How Many 8K etc.)

User avatar
ral-clan
plays wooden flutes
Posts: 3509
Joined: Thu Jan 26, 2006 2:01 pm
Location: Canada

Re: Help installing cooling fan on VIC-20

Postby ral-clan » Sun Oct 19, 2014 3:14 pm

The pictures of the opened VIC-20 I posted raise another question: why did a lot of the chips have a blue circle stuck to them? Indicators that they were burned in?

One of the 6522s in the picture doesn't, but that's because I replaced that one last year. The original VIC chip from this unit also had a blue sticker.
Image Music I've made with 1980s electronics, synths and other retro-instruments: http://theovoids.bandcamp.com


Return to “Hardware and Tech”

Who is online

Users browsing this forum: No registered users and 0 guests