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Replacing Computer Chips on a 1541 Drive

Guybrush3pwood

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Jun 19, 2015
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155
Never done this before, so I'm hoping to understand better before I make a move. Recently, I hosed up my 1541 drive and determined that, most likely, the VIA 6522 chips needed replacing. Of course, this is just my best guess, but whatever. Here are the chips in question.



So what my question is, can I just replace it with any old 6522 chips, or does it have to be EXACT?

I'm pretty sure this would work:

http://www.ebay.com/itm/6522-VIA-Ch...62457096?hash=item43dc842708&autorefresh=true

but would this also work?

http://www.ebay.com/itm/R6522AP-R65...P40-PACKAGE-/161045852724?hash=item257f14b234

Also, anyone know of a place to find these chips cheaper and not so...out of country?
 

car88fan2

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Aug 4, 2015
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Temecula,Ca
By no means am I expert on this but I believe they need to be replaced with the MOS chips. they are proprietary Commodore chips and the need to be the same ones. For the money they are selling the MOS chips for I would look at just buying another 1541 and using it as a parts drive. Are you in the states.? I see many Buy it Now with free shipping within USA for around $40 or less.

Also have you looked up the 1541 drive troubleshooting guide by Ray Carlson. Loads of info on a lot of C stuff.

http://personalpages.tds.net/~rcarlsen/cbm.html

Bryan
 

Guybrush3pwood

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Jun 19, 2015
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I actually recently got a 1541-II to replace this drive, but I thought if I could get a couple chips on the cheap, it might be worth trying to salvage this one.

Can you guess how I broke my drive? I think it happened when I tried plugging my 3DO controller into my C64. Don't know if that's what actually caused it, but shortly after, my drive stopped working correctly. I'd get a "searching for" message after inputting a load command and it would just hang there. I took the cover off and I could see that round metal part spinning. From what I found online, this was indicative of both the 6522 via chips going bad. Sad part is, I just bought that drive a couple weeks ago.
 

tipc

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the 2nd link has what appears to be a Rockwell product. My guess is both will work, but your mileage may vary. Similarly (or not) I replaced an 8272 in a Tandy 2000 w/a Rockwell 6765. I sat on a rock and pondered for a while and came up with the conclusion that the Rockwell part # corresponded to the NEC version of the 8272 (upd765). See the resemblance? My hunch payed off, and the Tandy booted up fine. Now this doesn't mean it'll turn out that way in every case. But if it were my predicament, I'd readily bet on the Rockwell chip working in place of the original.
 

tipc

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I left out part of the story. The 6765 was pulled from another pc compatible (ITT Xtra XP) after I concluded it was an 8272/upd75 clone. The 8272 in the T2K, if memory serves me, was a -5. How many variations (if any) of the 8272 (or the 765) there are I couldn't tell you. But I ignored all that and just plugged it in. I don't remember if either had to be desoldered. I want to say they were both socketed, or at least 1 was.
 

Guybrush3pwood

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You can buy a new 6522 here
http://www.jameco.com/webapp/wcs/stores/servlet/Product_10001_10001_43254_-1 or plenty of other sources, and they will all work just fine.

I highly doubt the 3DO controller had anything to do with it, and my suspicion is there's nothing wrong with the VIAs. It could be bad RAM or a number of other things.

I used this guide to troubleshoot it. I get a solid red light and the round metal piece inside just spins and spins. When I try a "load" command, I get "searching for" and then nothing. Seemed to match to the VIA chips.

http://personalpages.tds.net/~rcarlsen/cbm/1541/1541chip.txt
 

Chuck(G)

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I left out part of the story. The 6765 was pulled from another pc compatible (ITT Xtra XP) after I concluded it was an 8272/upd75 clone. The 8272 in the T2K, if memory serves me, was a -5. How many variations (if any) of the 8272 (or the 765) there are I couldn't tell you. But I ignored all that and just plugged it in. I don't remember if either had to be desoldered. I want to say they were both socketed, or at least 1 was.

The primary source was NEC for the uPD765, cross-licensed with Intel (8272). After that, there were lots of vendors of the chip, including Zilog, UMC...
 

Guybrush3pwood

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Any tips on how to figure out which chips exactly need to be replaced? I'd hate to spend the money on replacement chips only to find they weren't the ones with the problem.
 

geoffm3

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The best thing to do generally is to swap the two chips (since they are interchangeable) and see if the symptoms of the failure change any. That can help pinpoint which chip is bad or eliminate them as the problem altogether.

What sort of symptoms are you having?
 

geoffm3

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Sorry.... just watched your video. I have had a bad VIA chip cause the symptoms you're having, but it could be caused by a few other things as well.
 

Guybrush3pwood

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Jun 19, 2015
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Sorry.... just watched your video. I have had a bad VIA chip cause the symptoms you're having, but it could be caused by a few other things as well.

Yeah, that's the conclusion I arrived at as well. Oh well, hopefully the 1541-II I bought is a little more sturdy.
 

Dean7878

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Location
Baker City, OR, USA
I have all of the chips and other parts for the 1541 for sale.

MOS 6522 $2.99
MOS 6502 $7.99
MOS 901229 $2.99
HM6116P-4 $1.99
325572 $9.99

US shipping is $2.70 plus $0.10 per chip. International shipping is $5.70 plus $0.70 per chip. If you are interested PM me with your paypal email address and I will send you an invoice in paypal.

I would swap the 6522 chips in UC2 and UC3. If one of those are causing the problem then your symptoms will change. Also if you have a working VIC-20 you can swap the 6522 and the 6502 in the VIC-20 with those in the 1541.
 

Guybrush3pwood

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Jun 19, 2015
Messages
155
I have all of the chips and other parts for the 1541 for sale.

MOS 6522 $2.99
MOS 6502 $7.99
MOS 901229 $2.99
HM6116P-4 $1.99
325572 $9.99

US shipping is $2.70 plus $0.10 per chip. International shipping is $5.70 plus $0.70 per chip. If you are interested PM me with your paypal email address and I will send you an invoice in paypal.

I would swap the 6522 chips in UC2 and UC3. If one of those are causing the problem then your symptoms will change. Also if you have a working VIC-20 you can swap the 6522 and the 6502 in the VIC-20 with those in the 1541.

Problem with swapping is that my drive exhibits symptoms that arise when both of those chips go bad, so I'm not sure swapping them would get me anywhere.

I'd love to buy your replacement chips, but without knowing which chips need replacing, I'm not sure what I could do except buy all of them, and that's not a very economical solution.
 

Dean7878

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Oct 28, 2014
Messages
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Location
Baker City, OR, USA
UC2 is the motor controller interface. When the drive is powered on if this chip is faulty it will cause the red light to come on and stay on and the spindle motor will run continuously.

UC3 is the serial interface. When this chip is faulty the drive will power up normally. When LOAD is attempted, screen may indicate "SEARCHING FOR ...", but no motors run and red LED does not light. Computer will be locked up until reset or turned off.

So if the symptoms change you know you have a faulty 6522. If they remain the same the 6522 isn't the problem.
 

Guybrush3pwood

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Jun 19, 2015
Messages
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UC2 is the motor controller interface. When the drive is powered on if this chip is faulty it will cause the red light to come on and stay on and the spindle motor will run continuously.

UC3 is the serial interface. When this chip is faulty the drive will power up normally. When LOAD is attempted, screen may indicate "SEARCHING FOR ...", but no motors run and red LED does not light. Computer will be locked up until reset or turned off.

So if the symptoms change you know you have a faulty 6522. If they remain the same the 6522 isn't the problem.

Right, but like I said, the red light comes on and stays on, the spindle motor runs continuously and I get the "searching for.." message. So wouldn't swapping the chips just get me the same results since both seem to be faulty?
 
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