I've got myself a failing recapped Quadra 610!

[fergycool]

My recapped Quadra 610 has started becoming a bit problematic. This all started when I'd been trying to get the CD Rom drive working (I'd recapped it but it still does not work) so the Quadra had been on all day.

A few times in the past there has been no boot chimes. Generally I'd found powering down, turning off at the mains, leaving five minutes then booting back up always worked. I guessed that it was the PSU that I knew needed recapping.

Since having the Mac on all day this problem had been getting worse. To the extent that it would never warm boot. If I restarted it was fine. But if I shut it down and turned off then I always had to leave it turned off for some time. Sometimes even overnight.

I thought it was time to recap the PSU. However, even though I know I should have recapped it myself I was quite daunted by the task and I saw this company selling refurbished vintage Mac parts,…. including a 6100 PSU, which also fits my Quadra 610. In an act of weakness I went and ordered one (far too expensive!) which I regretted as soon as I placed the order (please do not judge me for throwing money at a problem rather than putting the effort in to fix it myself! Lesson learned - I hope….).

Anyway it came on Tuesday. I put it in the Quadra. Same issue started happening immediately. Over the past few days it's become far worse and now there are very rarely any boot chimes at all!

So either I bought a failed PSU or the problem is not the PSU at all.

A few months back after I'd recapped this machine I still got the chimes of death. It turned out to be a leg of a chip (RP3), which is surrounded by three caps, that had corroded. I added a blob of solder which sorted the problem. But the rest of the board looked good. I'd previously checked that all chips legs are making contact and they are. For some months it worked almost flawlessly (except for the issue mentioned above).

My initial thoughts were some sort of short. Only when it's cold is there a space, but when it's warm whatever is causing the short expands and touches. However, it does not have to be on long before it does not restart. For example the logic board has been in an unheated workshop all night. This morning I plugged it in and I got the chimes! I left it running for twenty seconds then turned off, then back one again. The chimes had gone.

So what could it be? Is something storing a charge that is only being discharged over time? If so why did it not happen before?

In the absence of any idea what the problem is my plan is to go through every chip on the board that's near a cap and reflow each leg.

Anything else I should be looking for?
Thanks!

 

[fergycool]

Bizarrely since posting this the Quadra is mostly behaving. It was in my workshop so I brought it back into my office, reassembled into the case and it boots fine. I reread this post about a soft power Quadra that was failing to turn on as the caps were not being discharged, The Quadra 610 does not have soft power, but the rest sounds very similar.

 

[Byrd]

Check the voltages of the PSU at startup, in use and under load ... I'm betting the "refurbished 6100 PSU" had no recapping done?

 

[chiptripper]

PSU seems most likely still, yeah. That said:

Every 610 I’ve seen has had some amount of corrosion on IOSB from the adjacent capacitor. The pins and traces on that side should be inspected and solder reflowed where necessary. (Delicate pins so work carefully.)

Another possibility is the power connector on the logic board side. Three caps in close proximity can degrade the connector. The onboard RAM is right above and can also be hit.

 

[fergycool]

Thanks.

I tested from one of the two Molex connectors. I assume this is exactly the same as the logic board connector.

Unfortunately it's not exhibiting this issue at the moment. No matter how I boot it up the chimes work and it boots fine!

On boot (when chimes sound)
5.12v
11.94v

On boot (when no chimes sound)
To come

After boot.
5.12v
11.92v

Under load (unstuffing a large archive)
5.12v
11.92v

I'm betting the "refurbished 6100 PSU" had no recapping done?

I bet you are right. I regret this waste of money!

 

[fergycool]

PSU seems most likely still, yeah. That said:

Every 610 I’ve seen has had some amount of corrosion on IOSB from the adjacent capacitor. The pins and traces on that side should be inspected and solder reflowed where necessary. (Delicate pins so work carefully.)

Another possibility is the power connector on the logic board side. Three caps in close proximity can degrade the connector. The onboard RAM is right above and can also be hit.

Thanks! I've not checked the power connector at all. I will do so. You will have to help me identify the ISOB though. I'm quite new to this! Thanks.
BTW I did find a "pinout" for the 610 PSU. I guess with some wago connectors and an ATX PSU I can check if it boots fine or still exhibits the issue.

 

[fergycool]

Actually am I right about taking readings from the Molex connector? If I take a reading from it I get 11.92v. But from pin 1 and pin 4 of the main power connector I get 11.98v

 

[chiptripper]

You can take readings from the molex, yes. Your voltages are all within normal range.

IOSB is a TI chip located right above the CPU, U21. The leaky cap that damages it is C45.

 

[fergycool]

Well since taking those voltage readings the Quadra has behaved itself perfectly! It has not failed to boot once. I've put the case back on and will try and use it daily to see if the issue resurfaces. How annoying

IOSB is a TI chip located right above the CPU, U21. The leaky cap that damages it is C45.

Ah yes, thank you! It's the one with the label IOSB. Sorry I did not notice that before! Apart from lightly scrubbing the legs I have not done anything with that chip. However, I did gently "nudge" each leg with a probe and everything seemed secure.

 

[fergycool]

So I removed the case this morning to add a few files to the SDcard in the Blue SCSI.

After replacing the card and repalcing the case it stopped booting. So powers on but no chimes.

I tested the voltages and they are the same as before:

5.12v
11.94

So I guess this means that it's not the PSU that is at fault.

Also by causing this by moving the case, then I guess this could mean that something has been "physically" moved and this causes the issue.

I'll check the IOSB and power connector as the next steps now.

 

[fergycool]

I've just taken the logic board out to my workbench. I reflowed each leg of the power connector (with plenty of flux). Then I cleaned each side of the IOSB chip with a cotton bud and isopropanol. When dry I then added plenty of flux to one side (the closest to the cap) and reflowed each leg as best that I could with just a magnifying glass and no microscope. I think I know what I want Santa to bring me this Christmas! I then connected up a PSU and the speaker. At first I got the chimes of death. But after powercycling I got proper chimes! Yeah! At that point I thought I'd either fixed the problem, or just nudged the issue away. I popped it back in its case and booted fine from a floppy. Put in the SCSI cable and immediately got the problem. So does this mean to say it's possibly an issue with the SCSI bus?

 

[chiptripper]

Good on you for pushing ahead with this restoration. Looks like you’re narrowing it down.

There were two leaky caps in close proximity to the SCSI connectors and controller, I’d get the magnifying glass out again and see if you can spy some bad traces, and check the fuse there too.

 

[fergycool]

Good on you for pushing ahead with this restoration. Looks like you’re narrowing it down.

There were two leaky caps in close proximity to the SCSI connectors and controller, I’d get the magnifying glass out again and see if you can spy some bad traces, and check the fuse there too.

Thanks. I will do so. However, after making that post the Quadra has never failed to boot once! I'm sure I've not fixed the problem but for now I'll wait until it resurfaces again and just enjoy using it!