Commodore 1541-II diagnosis and repair

[@pizza665]

Thanks mate! Just checked my 1541-II with your analysis and it has the same problem. The PSU worked for the last few days. Just ordered a 2-in-1 PSU for my C64C and the 1541-II as replacement which will save room as well.

[@digitalarchaeologist5102]

Literally I watched this video and my 1541-II had the same problem the next day. I'd already ordered a combined replacement PSU for the C64 and 1541-II (I know the C64 PSUs go bad and kill the system) which finally turned up and of course resolved the issue. I wouldn't have had a clue otherwise because the PSU seemed to show normal voltages otherwise

[@ingodiekmann8321]

You did a nice job finding the issue. I would have changed all the ICs and caps in the 1541-II before thinking that the power supply might be the issue. Thumbs up 😀

[@TheRetroChannel]

Funny you say that, this drive did have a prior issue with a faulty ROM. If you look closely you can see that I've already socketed all the ICs and replaced the caps. I didn't troubleshoot the issue, so instead just pulled out everything, I think the ROM was the last one I checked! But my intention is to use this drive as a test bed, like the ZIF socketed C64

[@michaelcarey]

I ended up with two 1541II drives without power supplies. I repurposed a couple of switchmode power supplies that were originally for USB HDD cases (dual output 12V/5V). A quick check on the output wires and the addition of a 4-pin DIN plug made for a nice replacement.

[@TheRetroChannel]

Yep, I picked up one designed to power a HDD and also a cheapie off 5/12v supply off Banggood. Now it's just a case of figuring out which one will work better

[@wallacebrown3151]

You might be able to get 2 small power supplied fro Aliexpress or Banggood to fit side by side in that case. I used one for my C64 power brick rebuild and was able to salvage the transformer for the AC. Since you want dual DC voltages, the tiny switching power supplies I got a short while ago should fit safely side by side I side the original enclosure

[@TheFurriestOne]

Ha, your C64C has the same keyboard feature as mine, a single keycap from a Breadbin! XD Wow, that's a lot softer potting material than the C64 bricks! (at least on the surface?) I find de-soldering all the components makes it fairly easy to remove the PCB intact. (oh, you did!) I don't think it's expansion so much as heat and chemicals from the potting that bows the cases like that. The real pain is getting the epoxy brick out and chipping the transformer free, if you choose to rebuild the original design instead of replacing fully with a modern switching unit. (no judgement either way, it's just preferences) Good informational video! Seems people might want to use 'saver' circuits to protect their drives from these bricks.

[@wimwiddershins]

My old 1541-II started doing the same thing. I think I tracked it down to a bad rom socket, but after this I'll have another look at the power supply.

[@TheRetroChannel]

Could well be just a bad socket, but always worth checking these old potted supplies when under load

[@uwelanski5376]

Good work,thx.

[@leeselectronicwidgets]

I believe that the bad cap is 2200uF at 25V. It may have been possible to leave the bad one in situ and parallel a couple of 1000uF caps (or even 4 x 470uF) in space beneath the lid? (hard to tell from the video if there’s enough space)

[@leeselectronicwidgets]

(And disconnect one leg of the bad cap of course)

[@TheRetroChannel]

There's very little space, even for a few 470s. I've got a couple of different switching supplies on the way so at least one of them should fit

[@Jimblefy]

Thanks

[@taltechchip5827]

I fixed my 1541 II old power supply. Solder a new cap on top of the old one will do the trick. The drive will freak out when it receives too much AC ripple. Put your meter in AC mode and check the 12v DC out. There should be no AC on the 12V DC out line.

[@DrDavesDiversions]

Hi Mark! If you want to keep using that old C= PSU case (for appearance sake?), I bet a Meanwell IRM-10-5 (especially the through-hole model, instead of thee screw terminal one) and an SD XMDZ DC-DC boost module, for 12V (like Keelog and Electroware use for their dual PSUs) would fit in there. If you recall, when you helped me by measuring your 1541-II motor current draw, we found that the SD XMDZ can provide more than enough for the 1541-II motor (since it also worked for my original 1541, which drew 2/3 an amp, peak, on 12V).

[@TheRetroChannel]

Ah yes of course, I totally forgot about the boost module. I've already got another switched mode supply that delivers the 5v and 12v but if that doesn't work out I will certainly try your way

[@DrDavesDiversions]

@@TheRetroChannel I think those components cost is < $10... ~9 + ~0.50 USD.

[@akira808state4]

A word of caution: never plug the serial cable into the drive when it’s on. It could destroy one or more of the chips.

[@jussikuusela7345]

The DIN plugs are stupid in that very often the signal pins mate before the sheath. If there is a potential difference between the device chassi, it wil try and equalize through the signal path.

[@TheHighlander71]

Whoever thought of that epoxy potting solution will not make it on to my christmas card list. Apparently the stuff dissipates heat very well, but it sure doesn't attract christmas cards.

[@TheRetroChannel]

Yeah I've heard similar things about the potting actually helping dissipate the heat. I guess everything is built to a cost, and putting a linear PSU in a sealed potted brick was likely the cheapest way out. Good ol' Commodore!

[@MrRobbiepee]

how about modifying something like a pico psu? they should have more than enough power, and are tiny

[@TheRetroChannel]

As far as I know the pico PSU still requires an external power supply

[@rayvansteenderen5372]

Drilling out the bad cap is an easy solution.

[@blackterminal]

Are the power supplies for these ok?

[@iamdkk]

RPD-60A might fit diagonally

[@TheRetroChannel]

Thanks, I think that's one of the ones I looked at. There were a couple that would fit daignoally but the components on either edge would be too tall. I've got something on the way that should fit, had to think outside the box a little, no pun intended

[@alessiodesideri6154]

WOW AMAZING! I found the Commodore 64 and the Commodore 1541 II in the cellar, but they were immersed in total humidity, do you think i should wait before trying to connect them to the current and turn them on? It counts that the discs with the games are full of mold, but it is generated by the paper labels ...

[@TheRetroChannel]

Maybe wait a couple of days before powering them on, but chances are the damage has already been done. For your sake I hope they still work, good luck

[@senilyDeluxe]

I've had quite a few 1541-II where that SONY IC would hold the CPU in Reset, but everything else is OK with the drive and I can't get it to work no matter what. PSU is not the issue, I don't even have one and made my own from a thin client PSU. Also it stays in reset no matter if the motors are connected or not. I have ONE SINGLE working 1541-II...

[@TheRetroChannel]

Yeah it seems the Sony IC is very sensitive and it doesn't take much to hold the CPU in reset. Seeing as you've ruled out any other issues , lift and isolate the pin on the Sony IC that holds the reset line, the drive should work just fine

[@senilyDeluxe]

@@TheRetroChannel The chips on my drives were made by Motorola and Sanyo respectively - and the drives do not work. All I can do is load a one file demo that blinks the drive LED, hook up the defective one with the reset line lifted, run the program and enjoy the blinking.

[@TheRetroChannel]

Intersting, yeah the Motorola and Sanyo are equivalents to the Sony. Sounds like there's a deeper issue...

[@donaldblakley6796]

Hello. I know this is an old video. My psu is fine. Replaced cpu.. stopped spinning problem.. however it won't read/ format. Head exerciser works with the world of Jani. The head reads fine and passes tests with another board. Strange eh? Any thoughts would be greatly appreciated

[@TheRetroChannel]

If the drive responds normally but won't read or format, it might be the read write amplifier has gone bad. It's the square surface mount IC

[@donaldblakley6796]

Ok bud thank you. I have another parts drive coming. Those beltless ones are more reliable than the newtronics. Probably couldn't find that square chip anyways. U are always responsive. I really appreciate it

[@damianscott431]

Similar issue with 1581 drives... using the same aged power supply.

[@TheRetroChannel]

Interesting, I have a 1571 with a bad lower head but it has a internal switched mode. I didn't realise they went back to an external brick with the 1581

[@terosaarela4555]

There are schematics available for the power supply. How about a new transformer and making a custom PCB that would fit inside the original casing?

[@senilyDeluxe]

what's wrong with the old transformer? (unless of course the replacement will be a switch mode PSU) (don't get me wrong, putting a new PSU in and developing a retrofit PCB is a great idea - just... Transformers don't usually go bad... ever. It can happen though - but here the culprit was clearly a dead capacitor) I'd probably drilled the old cap out and stuck a new one in.

[@TheRetroChannel]

In theory if I could seperate the transformer then it could be reused. But then I'd still need to design and put in a linear supply (there's no way I could design a switched mode myself) so again heat build up would be a concern...

[@TheRetroChannel]

Yep the old transformer should be fine assuming it could be seperated from the rest. As for drilling out the cap it was certainly considered, but then I'd just have the same issues with heat buildup. I think I've found a switched mode that should fit, fingers crossed

[@senilyDeluxe]

@@TheRetroChannel Considering the heat buildup you should consider how much you're gonna run the drive. Way back when, it was used for hours on end. Nowadays it can be compared to a vintage car - you won't be using this as a daily driver. So with one or two hours of operation every once in a while instead of hours and hours of use daily, I'd have just replaced that cap. Had I planned on using this thing all the time, I'd have gone Tero Säärelä's route, removed the potting, replaced the circuit board and sawed some vents into the case.

[@tenminutetokyo2643]

DOOD! You can get a dual CPU/Drive 3rd party replacement power supply off Amazon for $70. One brick drives both units.

[@TheRetroChannel]

Yeah, I've seen the Keelog version but I don't trust their PSUs. They're probably fine for the 1541s but I've seen them introduce noise in the video output on certain C64s. This is for an older C64 only version so I hope they have improved them since

[@vhfgamer]

Just find a 5v wall wart and a 12v wall wart, and stick the guts in the commodore brick. That's what I did for my C64 (just the 5v).

[@vhfgamer]

Oh and PS... my 1541 mark ii had the same issue as yours. My 12 volt rail died just like yours.

[@ematech]

80% of the problems are the power supply

[@Adam-rt7lp]

@TheRetroChannel kzbin.info/www/bejne/eGfWaGaPZr-cmqM My 1541-II is making loud noises like the video above. Do u have any tips or is it done?

[@TheRetroChannel]

First thing I'd check is the resistance between the read/write heads. I happen to have a video going public tomorrow that will show how to do it

[@Celcius1]

You need more music in your videos

[@TheRetroChannel]

Thanks Paul, I'll try and add some more tunes in the future

[@Celcius1]

@@TheRetroChannel also if you want to build a custom supply you could look at using TI’s power designer