Posts Tagged fix

2009 Mac Pro with DVI and HDMI displays – restart problems

So I bought a new (old) Mac Pro; late 2009, 12/24 core, 64GB, NVIDIA GeForce GT 120 512 MB. It’s running macOS 10.12.3 Sierra. I hooked up one monitor to the HDMI port, and one to the DVI port. Seemed to work fine.

Until I rebooted the machine.

Then it refused to show the mouse pointer (Apple magic mouse), although It would warn of the mouse’s disconnect and reconnect if I powered the mouse up and down. Likewise, there was no response to the keyboard. It just sat there showing login options for me and a guest; it wouldn’t respond to anything at all I did with mouse or keyboard.

After trying power downs, pulling the plug for a while, pounding on the keyboard, powering the mouse up and down, I finally thought to pull a connection to a monitor. Specifically, the DVI-connected monitor. Immediately the mouse pointer showed up, and I was able to log in.

Up to this point, I had the machine set up so that the HDMI monitor was on the left, and was my home (boot screen) monitor. That’s the one you drag the menu bar to in the Prefs / Displays panel. But I noticed when the machine booted, it showed up on the DVI monitor first, then the HDMI monitor, and then it locked up.

So, still booted up after all this screwing around, I swapped monitor cables, then set the DVI monitor to be the home monitor, as the left monitor was now my DVI-connected monitor instead of my HDMI-connected monitor.

Now the machine restarts cleanly, or at least, it has a few times in a row.

So if you’re having this kind of problem, after the login screen shows, try pulling one or the other or both of the monitor cables to see if it will unlock the mess. And make sure the DVI monitor is your home monitor once you get things running again.

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Marantz MA700 troubleshooting

I have quite a few Marantz MA700′s; of the group, four of them exhibit random popping sounds of moderate energy at the speaker output with no audio input to the unit. Clearly this is a very common failure mode for the MA700.

I have opened one of the “poppers” up on the bench, and with the buffer amplifier signal cable to the power amplifier disconnected, the popping noise remains, so it’s definitely not in the audio path on the buffer amplifier board. The buffer amp is connected to the power amp via an electrolytic, so there’s no problem unplugging the buffer from the power amp.

There’s another problem with this unit, too: I see somewhat random engagement of the high power rail mode for the amp, but this is not co-incident with the clicking coming from the speaker.

When the high/low power state switches randomly, the associated relay clicks, which is audible at very low volumes, and this is obviously not the design intent. Erratic high/low power switching problems are going to be nearby QU05, very likely the electrolytic CU08, the diodes DU01 and DU02, or QU05 itself. I’d suspect CU08 first.

The main amp PCB shows evidence of excessive heating towards the front of the chassis, where the driver section is located. Unfortunately, it looks to me that the mechanical assembly is complex with regards to the main amp and attached heat sink; taking it apart looks to be quite a big deal, my vision has become very poor, and I don’t actually need the amp, so I’m just going to close up. However, at least this exonerates the buffer amp and provides a pointer as to how to troubleshoot high/low rail power issues.

If anyone locates a specific component that is responsible for the clicking and popping, I would very much appreciate hearing about it; I’m willing to hack in a replacement electrolytic from the component or solder side of the board if that’ll solve the problem. Likewise, if circumstances lead me there — if one of my working MA700′s fails and I really need to fix one of these “poppers” — I’ll post what I’ve learned.

I’ve put the service manual for the MA700 online here.

–Ben, AA7AS

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Revamping the Calendar

Why bother?

The yearly marching of month, day, and date is inconsistent, causes much confusion and migration of obligations and responsibilities, and is generally responsible for considerable angst and actual problems. Basically, the reason I think it needs to be fixed is because it is, in my humble opinion, very broken.

Most attempts at this severely disturb the cycle of months, weeks, or weekdays. Consequently, they face stiff opposition from people who have a use for those cycles. I don’t have any problem with that; my problem is with irregular cycles. I think that most problems arise from that irregularity, not from the various months or weekdays, which are quite functional in our society.

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