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Quadra 605 schematics?

Addicted

Active member
I have a Quadra 605 logic board that lost some solder pads during an aborted recap. Five, possibly six of eleven caps have lost one or both pads.

I completed the de-capping and am now assessing whether or not I have the skill to restore the board. I have limited tools and experience with such dense, small-scale rework.

So before I begin.. is the schematic archived anywhere?

Regards,
-A
 

Phipli

Well-known member
If there isn't, give me a list of caps and which pads and I'll beep them out and let you know where to run a wire to.
 

Addicted

Active member
Thanks. I was taking a break and thinking I would continuity-check them tonight or tomorrow - but I need a board vise, third hand, aide, something.

Some of these may be "second level" challenges. C137(-)'s loss for example breaks a trace - so I expect it will require at least two bodge wires.

I'm hoping to replace the most difficult of these (C137 and maybe C36) with SMT tantalums hot-glued to the bottom of the logic board - to avoid tricky soldering that a tin-can cap topside would cover and which may come undone while soldering that tin-can over them. C136/C137 may need (perilously long) bodge wires from the bottom layer coming around through the drillout ZH1 .

A couple of pads that remain are lifted only at one end. Heat damage, I think. I will epoxy them down - once I know they don't connect with anything below them.

Part(polarity)Status
C137(-)Gone. This severs a top-level trace from L12, across the pad, to a via under the cap.
C137(+)Gone. Seems to connect only to a nearby via.
C136(+)Gone. Seems to connect only to a nearby via.
C149(+)Partially lifted. OK unless there is a hidden via under the pad tip nearer to RP14. Continuous to via and C150(+) [which is gone].
C150(+)Gone. Hopefully this only went to the via common with C149(+).
C150(-)Halfway lifted at end nearer to U30.. Still good contact with via in center of footprint. I need to determine if there was a via buried under the end of the pad nearer to U30?
C36(+)Gone. Uses a via to connect on some inner layer, only. I hope it's just going to a power plane.

I'll keep searching this site for schematics. I found the LC II logic and the Mac SE/SE30 analog board schematics, so far.
 

Addicted

Active member
This is looking not-so-bad. Won't be any ugly and electrically iffy-longish rework wires running around the board edges as I feared.

Part(polarity)Rework
C137(-)Topside bodge to L12 near FD1.
Topside bodge to U30 pin 15.
C137(+)Topside bodge to C136(-). *Note A
C136(+)Topside bodge to L11 near D2.
C149(+)No hidden via that I can find. Tack it down with epoxy.
C150(+)Topside bodge to C149+.
C150(-)No hidden via that I can find. Tack it down with epoxy.
C36(+)Topside bodge to U1 pin 2 (PLL Vcc). *Note B

  • Note A: C136 and C137 must be bridging three potentials? Anyone can confirm that I got this one right?
  • Note B: I'm assuming from placement that this is decoupling for (half of) the SIMM, and should connect directly to Vcc on the SIMM if possible. Still looking for that one.
I was able to do the continuity checks using hi-res photos of the back of the board and looking for recognizable groupings ('constellations') of vias. This reduced how much probing I had to do. Then I cut two slots out of the sides of an old shoebox and voila; no-cost board gripper. Some raw searching for continuities was still required (namely, for C36(+) above, to find which power plane it touched).
 

Addicted

Active member
I found the perfect spot for the C36(+) bodge: the ROM SIMM socket is not populated, and very close to the RAM SIMM, and has two candidate through-holes very near C36. Now.. to craft the wires.
 

Addicted

Active member
I thought the rewiring went really well. The PRAM battery clip/holder is due to arrive today but hasn't shown up, so I tried testing it without a battery.

I got nothing. No video, no sound.

On the positive side, I got no exploding caps, no smoke anywhere, no clicking/squawking power supply, and no hot-to-the-touch components. The new fan is running.

Some of my 'continuities' must be wrong, unless the Q605/LC475 really won't even flinch without its PRAM battery.. which I think I've heard is true.. but I didn't think it would be absolutely flat-line DOA.
 

Phipli

Well-known member
I thought the rewiring went really well. The PRAM battery clip/holder is due to arrive today but hasn't shown up, so I tried testing it without a battery.

I got nothing. No video, no sound.

On the positive side, I got no exploding caps, no smoke anywhere, no clicking/squawking power supply, and no hot-to-the-touch components. The new fan is running.

Some of my 'continuities' must be wrong, unless the Q605/LC475 really won't even flinch without its PRAM battery.. which I think I've heard is true.. but I didn't think it would be absolutely flat-line DOA.
Video doesn't work without a battery on the 475 / 605. Thats the first thing to try.
 

Addicted

Active member
So true! I checked all my new caps for shorts, in case I'd bridged their leads underneath; all good. Reseated the VRAM. No boot.

Then the battery holder arrived; I installed it and a fresh battery and the Q605 booted right up. No sound, but that was the problem that the recap was originally hoping to fix. So it's back to 'normal'.

One good thing about having to do all this rewiring -- I've already given the board's topside a good inspection for corrosion. There may still be some hidden under a chip, though, U30 is the prime suspect. I'll check the underside of the board for broken traces and the like later today, after I read up on all the existing advice here about no sound.

This Quadra had seen a lot of damage - the case was basically shattered; there was rust on the EMI shield inside the case and on the video and external SCSI connectors shields; the plastic clips holding the components together were brittle and snapped off; the floppy also was rusted up. The bottom of the case had a big crack, a caved-in dent, too. The original HDD responds to SCSI, but never becomes ready. This may have been found in a dumpster dive. But the logic board, the VRAM and DRAM, the CPU, everything but sound is testing AOK. The rusty PSU even works, although I'll recap it soon. It's been rewarding to get it this far.
 

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Addicted

Active member
And lo, there was audio.

Before I recapped the Quadra logic board, I could hear faint system noises -- continuous white noise (faint), added chatter during SCSI activity (less faint), and a number of whirrs and buzzes depending on video and ADB activity. But nothing else. No beeps, no music.

I spent the morning recapping the weathered power supply that came with the Quadra. It was surprisingly clean inside. I replaced the paper safety caps, everything.

And to test the PSU, I needed a load, and the Quadra was right there, so I hooked them up.

And the Quadra played the starting chord. It has sound, speaker and speaker jack both. The background noise remains, but.. I could live with that. (I would love-love-love to remove it, however.)

I will have to check the voltages on the other PSU I was using before. I think it is the only one I have not yet recapped, and maybe it it faulty.
 

AwkwardPotato

Well-known member
Some amount of digital noise is to be expected on these systems but gauging how much is "normal" can be difficult. If the EMI shield/connector shields are severely rusted or missing altogether, the noise will be significantly worse. The fingers on the EMI shield must make good contact with all the connector shields as well as with the PSU (on this style of case, there may also be fingers that contact the bottom of the board, not sure).
 

Addicted

Active member
I think Apple never meant 'normal' to include 'can be heard by everyday casual users'. I don't know dBA, really, but I'd estimate that the background noise is in the 25-30 dB range. About as loud as a whisper - and constant.

This brings me back to the topic's theme. I'd love to see some schematics of the Q605/LC475 to learn where audio and data/addresses buses might be close enough for some goop/corrosion/solder bridging to produce this sort of interference. But I think no such info is in the public domain.

My uninformed, wide-angle guess is that before the recap, some filtering capacitor(s) was(were) failing to filter - and my rework left the replacement(s) for the(those) critical cap(s) unconnected.
 

Phipli

Well-known member
I think Apple never meant 'normal' to include 'can be heard by everyday casual users'. I don't know dBA, really, but I'd estimate that the background noise is in the 25-30 dB range. About as loud as a whisper - and constant.

This brings me back to the topic's theme. I'd love to see some schematics of the Q605/LC475 to learn where audio and data/addresses buses might be close enough for some goop/corrosion/solder bridging to produce this sort of interference. But I think no such info is in the public domain.

My uninformed, wide-angle guess is that before the recap, some filtering capacitor(s) was(were) failing to filter - and my rework left the replacement(s) for the(those) critical cap(s) unconnected.
The sound circuit on the LCIII and Color Classic is similar, but not the same. The 475 has line in instead of mic in. Possibly other differences. But it is informative about how the DFAC II sound chip is wired.
 

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