Help with Pico PSU in CZ-600C

[paran01d]

Hi All,
      Im new to this forum and pretty new to the X68000 and hoping I can get some help. Over the past year on and off I have been trying to restore a CZ-600c. First thing i did was build a replace powersupply from https://github.com/mattsoft/X68K_Pico_PSU_v2.

Once I got it powered on I got a lovely loud beeping noise from the speaker and some garbled video.
I then did a full recap which helped with the video and got it booting, but still with the loud constant beep from the speaker. I read the articles here on the sound system and decided the opamps where broken.

Before the replacements arrived I actually figured out it was the pico psu I had chose not putting out -12v. Sure enough as soon as I connected a spare full size psu the sound was fine and the X68k we fully working.

Since then I ordered a different pico psu and before installing made sure it was putting out -12v.

Unfortunately upon booting I now get random read and crc errors from the floppy drives ((scsi2sd) seems to work fine). I also tried soldering the floppy wires directly to the drive socket on the pico psu and get the same result... any ideas on what I might be doing wrong or what I should be looking at to diagnose ?

thanks in advance

[Cyothevile]

Where did you order your pico PSU?

[paran01d]

I just purchased it of ebay:

https://www.ebay.com.au/itm/324245429549

[paran01d]

Actually i just saw the note:

`It's important to match the power output of your AC-DC converter with the power rating of the PicoPSU.`

I went with the BOM on the site which is a 75W step down converter and this Pico PSU is 90W, is that the issue ?

[Cyothevile]

No.

The issue is that you're using a fake pico I think regarding sound


Go to the x68000 pro repair thread on here. A gentlemen talks about how he used a fake one and the capacitor on the sound wire would constantly blow up until he got a real pico

[paran01d]

Sorry i already mentioned in the second part of my post that i fixed the sound with a different pico (the 1st one was not giving out the required -12v).

My problem now is that with the pico im getting CRC errors reading known good floppies.

Where can i get a genuine pico ?

[Cyothevile]

Using a 90w one wouldn't cause that I think. I'm using mean well one inside my computers.

This is the one I'm putting in the FMT power cards. Also the ones in all my X68 computers.


https://www.mini-box.com/s.nl?it=A&id=417&whence=

[dankcomputing]

Fun source of 3-prong AC cords: You know those brick PSUs that ship with the C64 that everyone hates? I usually smash em open to grab the DC cable and build a new PSU, but the AC cable will fit in the X68000 with just a little filing down on the strain relief.

[paran01d]

This is the one I'm putting in the FMT power cards. Also the ones in all my X68 computers.


https://www.mini-box.com/s.nl?it=A&id=417&whence=

Thanks for the advice, sadly $52 shipping to Australia... I'll try find a local alternative.

[paran01d]

Ok managed to find one delivered locally for around $70 us, for any aussies on the lookout

https://ebay.us/gAnNJz

[paran01d]

Just a quick update to let you know the new PSU arrived and when fitted fixed the CRC errors on the drives.

Thanks for all the help.

But just as everything was working fine, I tried booting a disc I haven't used before (and original afterburner), seemed to be booting then the drive gave out a horrible squealing sound. I ejected the disk and could see some massive scratches in it, guessing it had some dirt or something and my head is now screwed because it wont read any discs now ..

[Cyothevile]

Just a quick update to let you know the new PSU arrived and when fitted fixed the CRC errors on the drives.

Thanks for all the help.

But just as everything was working fine, I tried booting a disc I haven't used before (and original afterburner), seemed to be booting then the drive gave out a horrible squealing sound. I ejected the disk and could see some massive scratches in it, guessing it had some dirt or something and my head is now screwed because it wont read any discs now ..

Clean the heads very very well and then format an empty/blank disc. Then try to read it or something

I've learned the very hard way that the squeeling sounds is when there is mold spore or dirty heads. Ruined Present 2 for FMT when I try to dump it

[dankcomputing]

Can I get away with 90W for the PicoPSU or should it be 120?

[wolpi]

Can I get away with 90W for the PicoPSU or should it be 120?

I made bad experiences with the original PicoPSUs since they only deliver 0.05A on -12V which is (at least for my model) not enough. The Inter-Tech 160W would deliver 0.15A on -12V which results in a stable voltage - however, it is a little too large for the classic "Tetris"-brick. The Inter-Tech 120W (Rev2) version delivers 0.1A on -12V which drops to -11V in my machine - not ideal but it seems to work.

[dankcomputing]

The official specs of all the mini-box PicoPSUs seem oddly similar between the models. Max 5V amps doesn't seem to change much between the 90, 120 and 150 watt models, for example. Max -12v amps are all at 0.05 amps (with a peak of 0.1) too.

The "WI" models are a bit different though - they all regulate the 12V instead of just passing it through (so they can be run on a wider variety of voltages), and the manuals there all seem to list 0.1 amps as the max and the peak.

Do we have the amps/watts of any of the stock X68000 power supplies?

[paran01d]

Ok I tried this and still cant boot anything from floppy. Weird thing is i can backup and write images with mkimg and copy files to and from floppy with LHES.. when i try to boot i get

"It was not possible to start the system. Reboot" (with games i get the similar in Japanese)

And an address error is displayed (SR=$2019:PC=$0000DF42)

Clean the heads very very well and then format an empty/blank disc. Then try to read it or something

I've learned the very hard way that the squeeling sounds is when there is mold spore or dirty heads. Ruined Present 2 for FMT when I try to dump it

[Cyothevile]

There should be two capacitors in the rear of the floppy drive that are visible to you. Have you changed those?

[paran01d]

Ok figured out my soldering onto the pico psu was not as good as I thought as one of the 12v power wires had come of, fixing this and I can boot from floppy again, so the head clean worked!

No I haven't replaced any of the caps in the floppys yet, while I still have them accessible ill order
some low profile ones and get them done.

thanks for your advice

There should be two capacitors in the rear of the floppy drive that are visible to you. Have you changed those?

[dankcomputing]

By the way, I don't know how other PicoPSUs from other vendors behave but avoid the mini-box 120W unit if you're going to run it in an x68000. It will not soft-power on normally no matter what you do. You can trick it into powering on by having the front power button pressed as you turn the back switch on, but that's not exactly desirable. No idea why it does this, I've even tried adding resistors to +5 or GND of varying values to the PS_ON line and it doesn't change it's behavior. Every other ATX source I had on hand powered on normally. It's really perplexing.

The 90W is what you want, that will work fine.

[leonk]

Given you've got the original X68000, your PSU is very different from subsequent units; you have something that resembles a modern PSU rather than that lego piece that came after.

What I've found to be better for these systems, long term, is to install a microATX PSU and have an all internal solution. I used a commercial grade 1U PSU; they're pretty cheap on eBay and have a lot more safety features and make sure power is clean, safe, with over voltage, over heating, etc. protection all there. 

I transfer the new PSU guts into the old PSU shell.  I've also replaced the 2 prong wire with 3 prong wire for proper grounding.  Yes, it requires a lot more work, and you need to be good with this sort of stuff, but once done, the system will run much better for much longer.

Here's more wiring info for you: https://nfggames.com/nfg/x68repair/