1541 won't work with VIC-20

idrougge · Post by **idrougge** » Wed Oct 06, 2004 9:04 am

Hello, I'm a new VIC-20 owner (since two days). Due to it lacking a suitable PSU (it's an old model), I had to spend yesterday evening hacking a DIN connector onto it in order to use a C64 PSU instead. After fixing a video cable as well (net instructions were no good, VIDLOW is not connected on my machine), the machine started without problems. Runs BASIC programs just fine, PEEKs and POKEs work as expected.

But I can't get it to work with the 1541! The drive works fine both with C64s and with Amigas (using Easy1541), but when I issue a command such as:
lO"$",8
the drive lights up and the VIC20 says "SEARCHING FOR $", then just sits there. Usually, STOP-RESTORE won't even break it. I get the same results when trying to load "*" or a named program.
What could be wrong? Is it some difference to the C64 which I've missed, have I got a dead VIA or what?

vic user · Post by **vic user** » Wed Oct 06, 2004 9:42 am

i wish i could give you an answer that would help.

the only times i have ever had the problem you mentioned, is when i had my 40/80 column cart. in the vic, and my printer and drive on at the same time. some kind of conflict i guess, which gets resolved as soon as i turn off the printer (which is last in the chain) and then my drive works fine again

carlsson · Post by **carlsson** » Wed Oct 06, 2004 10:00 am

I guess you don't have another unit connected in the other end of the 1541? It may be a broken VIA. While I never tried it myself, it should be possible to replace or switch the two - one handles joystick/diskdrive and one handles user port/keyboard scan?

When it comes to "hacking a DIN connector onto it", I thought the incoming power requirements were slightly different between the models, but maybe you replaced more components than just the connector?

idrougge · Post by **idrougge** » Wed Oct 06, 2004 10:11 am

I did switch the VIAs yesterday, at least I think I did (could have mixed them up). No good. I think I'll try cleaning them up a bit - there's 20 years of "ärg" on the pins.
The VIC is supposed to take 9VAC, it says so all over the place. The C64 supplies 9VAC at the two upper pins. I just added a DIN7 connector above the old two-pin one. The VIC has worked for several hours this way, so I can't be doing it all wrong.

carlsson · Post by **carlsson** » Wed Oct 06, 2004 4:06 pm

Oh, ok. I just remember the internal fuse is quite different between the two models, but maybe it is due to internal design rather than the current supplied. I'm quite unskilled when it comes to those kind of things, so I'm sure you know what you did.

I believe the 1541 also has 6522, but those normally are soldered to the board so not possible to remove from a spare unit. Otherwise, I think Ray Carlsen and/or the C= Hackers email list could guide you where to look for faults if the disk drive still doesn't work. By the way, does joystick work? I got the impression those two functions should be in the same chip.

idrougge · Post by **idrougge** » Thu Oct 07, 2004 5:56 am

I've tried swapping the left and right VIAs several times, tried cleaning them, the 1541 still won't respond correctly.
If I try to handshake using OPEN15,8,15,"I:":CLOSE15 the drive will hang with its access light on and refuses to answer another handshake.
I've tried using the datasette, and it works just fine, so the VIAs can't be entirely cooked. Could it be just one output/input pin which is disfunct on both chips? That sounds silly, doesn't it?
I'll try to write a joystick tester tonight.

idrougge · Post by **idrougge** » Thu Oct 07, 2004 5:56 am

I've tried swapping the left and right VIAs several times, tried cleaning them, the 1541 still won't respond correctly.
If I try to handshake using OPEN15,8,15,"I:":CLOSE15 the drive will hang with its access light on and refuses to answer another handshake.
I've tried using the datasette, and it works just fine, so the VIAs can't be entirely cooked. Could it be just one output/input pin which is disfunct on both chips? That sounds silly, doesn't it?
I'll try to write a joystick tester tonight.

carlsson · Post by **carlsson** » Thu Oct 07, 2004 6:31 am

No idea, maybe there are minor logic gates somewhere who play a part too, or the connector or some traces are bad, or the Kernel ROM?

I have observed similar behavior when I connect another computer in the other end of the 1541 daisy chain. It is something you shouldn't do, but there is a POKE for each C= computer to set high CLK IN and DATA IN and thus "release" the chain:

C64: POKE 56576,PEEK(56576) OR 192
VIC: POKE 37137,PEEK(37137) OR 3
Plus/4: POKE 1,PEEK(1) OR 1

Maybe you will observe a different behavior if you try that VIC POKE?

Boray · Post by **Boray** » Thu Oct 07, 2004 8:40 am

Look at Ray Carlssen's symptom/repair text:
http://personalpages.tds.net/~rcarlsen/cbm/vic20.txt

I had diskdrive problem on a newer Vic20 (the one with the din power plug) - and it was a logic chip that needed to be replaced. After that, it works great. I first unsoldered the old chip and replaced it with a socket that I then put the new chip in. For jobs like this it's great to use solder wick (tenfläta / avlödningsfläta). You just put a bit of it over the place and put the soldering iron on top of it and the "lödten" is sucked up beutifully. A "tensug" can ripp the metal off the card...

/Anders

Boray · Post by **Boray** » Thu Oct 07, 2004 8:46 am

It was UB4 I replaced. You can buy it here: http://www.elfa.se/elfa/produkter/se/2012856.htm

/Anders

Boray · Post by **Boray** » Thu Oct 07, 2004 2:03 pm

Forget what I just said... The old model vic20 has a 3A power supply. The 9v of the C64/(or new vic20) power supply is only 1A. So maybe your vic20 just gets too little power to work 100%. Before doing anything to the vic, I would try with a 3A power supply. You should be able to buy one somewhere (9v 50Hz AC that can provide 3A (27W) or more). Maybe on Elfa or Claes Ohlson.

On the lable on the vic20 it says 25W. So how would a 9v 1A power supply be enough? 9*1=9W. While 3*9=27W. So.. at a minimum (without any external gear), 25/9= 2.78A would be enough. Still 2.78 times more than the C64 power supply can provide.

Then when you have a 3A power supply, and it still doesn't work... then you can begin to suspect that there is something wrong with the vic....

/Anders

carlsson · Post by **carlsson** » Thu Oct 07, 2004 4:20 pm

Hm, my broken VIC-20CR is still at my parents' place, so I can't check it, but my C64c says 15W, while its power supply says 5V 1.7A and 9V 1.0A, a total of 18W effect is printed. The 2-prong VIC-20 PSU just says 3A, so I guess only runs on 9V while the VIC-20CR uses both currents at the same time.

I have an old, probably broken brown brick from my first VIC or C64, and it says 9V 1A, 5V 1.5A but also says 33 VA (voltampere, i.e. watt), which I'm not sure how it can become. In any case, the 9V current should be too weak.

Anders, I think you may be onto something! Iggy, if your VIC still has the 2-prong connector intact and you find absolutely no other ways to test it, you would be welcome to come by although I live a little more than an hour away. I don't know when I'm scheduled to go to Stockholm, but maybe you can find a closer VIC owner.

Boray · Post by **Boray** » Fri Oct 08, 2004 5:10 am

carlsson wrote: I have an old, probably broken brown brick from my first VIC or C64, and it says 9V 1A, 5V 1.5A but also says 33 VA (voltampere, i.e. watt), which I'm not sure how it can become. In any case, the 9V current should be too weak.

I saw that too on my vic-20-CR PSU... And I think the 33W is how much the PSU uses itself from the 220V (It was stated together with the 220V) while it's only supplying 9*1+5*1.5=16.5W. The rest is losses in the conversion (that's why the PSU gets hot).

Maybe an old Märklin train PSU would work if you measure and set it to 9v. (It is AC and hopefully 50Hz). I don't know how many amps it can provide but I remember that they were quite powerful and could drive many trains at the same time (while my Lima PSU only could drive one)...

/Anders

Boray · Post by **Boray** » Fri Oct 08, 2004 5:39 am

Märklin PSUs seems to be too weak as well. A 10W (VA) can only provide 0.62A. I saw some marked 32VA, but if they have the same "verkningsgrad" then it would only come up to 1.984A. I saw one 9v AC PSU on Claes Ohlson, but it could only handle 1A... Maybe it's harder to find a suitable PSU than I first thought... Maybe some electonics junkyard? In some old printer or something....

/Anders

carlsson · Post by **carlsson** » Fri Oct 08, 2004 8:29 am

It reminds me, I have a portable Casio PB-700 with expansion kit FA-1 which includes a micro cassette and a four colour plotter. The computer itself is driven with batteries, but the expansion kit uses a power adapter.

http://www.mds.mdh.se/~dal95acn/tidning ... iofa10.jpg

When I bought it 2nd hand (auction, 50 SEK) there was a Canon replacement power adapter of 5.8V, 600 mA or something like that. On the bottom of the expansion kit, it says 6V, 15W which theoretically means I need a PSU which can deliver 2.5A at 6V. So far I haven't found a such adapter, and people knowledgable in this field doubt that the printer really needs 15W to run. The micro cassette runs, albeit too slow, with the current adapter. The printer refuses to start, but maybe the pens have dried up many times since 1984.