Macintosh Plus Making Hissing Noise...?

[PowerMac G4 MDD]

Got a Mac Plus here; the picture on its screen is a bit iffy, only appearing if the computer is shaken or hit on its side. Additionally, there's a constant hissing noise coming from the left side of the machine... perhaps a capacitor gone wild?

Is there a distinct way to troubleshoot this, or should I try replacing all the caps on the left-hand board? Looking on the inside, I don't see any visible issues.

 

[MacTech68]

If the display is giving you an image, albeit slightly odd, then it may be a loosely connected ground wire.

Looking from the back, there should be a green wire screwed to the chassis on the bottom right.

There is also a long black with white stripe wire that goes to the top left mounting of the tube.

Finally there should be at least one screw holding the bottom of the power/sweep board to the chassis near the bottom left (looking from the rear). It should have a folded, thin metal insert that folds front to back of the board.

Other possibilities are a loose connector on the rear of the tube, or loose connector on the other end of those cables where it plugs into the power/sweep board and associated solder joints.

 

[PowerMac G4 MDD]

Wow, thanks for this! I'll check on the machine when I get around to it. Currently curing some vintage Mac plastics to remove their yellowing. Such a painstaking process.

 

[PowerMac G4 MDD]

BTW, what about the hissing noise? Someone else told me that certain resistors may not have been cut, assuming that the RAM was upgraded (and done so improperly at that).

 

[MacTech68]

BTW, what about the hissing noise? Someone else told me that certain resistors may not have been cut, assuming that the RAM was upgraded (and done so improperly at that).

My previous post is in regard to the hissing noise - those are the easiest, first checks to make that may cause hissing noises.

There is NO way RAM resistors could cause a hissing noise, AFAIK.

 

[PowerMac G4 MDD]

My previous post is in regard to the hissing noise - those are the easiest, first checks to make that may cause hissing noises.

There is NO way RAM resistors could cause a hissing noise, AFAIK.

Okay, thanks for clearing it up. I'll update the thread when I get around to opening up the Plus again.

 

[PowerMac G4 MDD]

My previous post is in regard to the hissing noise - those are the easiest, first checks to make that may cause hissing noises.

There is NO way RAM resistors could cause a hissing noise, AFAIK.

Back again - I will check out the Plus when I can, but I have a more important machine, now, which is suffering from a similar issue, albeit possibly from some other cause: I just got an original (non-upgraded) 128k a couple days ago, and I noticed that it would sometimes bong and ask for the floppy, while, other times, it would power on without a bong and display a screen with faint, white/gray lines and general noise on it. Since I noticed that it would sometimes work, I went and serviced the floppy drive so that it could accept/eject properly again. In the process, I noticed that movement of the drive's connector on the logic board would determine how the Mac would behave once turned on.

After getting the drive working and packing up the Mac, I was able to successfully boot from a system disk. However, the issue came back at half force. I would momentarily see line-pattern spasms on the screen. It was not like it was with the Mac Plus - not distorted or momentarily flicking off and needing to be hit on the side - it would just show spasms on and off and get worse at certain points. I also heard that similar churning noise from the top of the case, but, unlike with the Mac Plus, there was no whine, and the noise was more subtle. While the symptoms don't exactly match, do you think that both Macs have a similar issue? It's rather odd, though, that the floppy connector seemed to be triggering it (although I never touched the connector whilst the Mac was powered on). I will check the Plus with your original instructions in-mind, but I am more concerned with the 128k because it is of more value. Do you know what could be wrong?

 

[MacTech68]

Regarding the 128k:

This gets a little more complicated - there are many potential causes.

You may need to disassemble the machine and take some good, in-focus pictures of the analog board, as well as getting hold of a multi-meter to check voltages.

A few questions to begin with,

does the computer have a programmer's switch installed?

does the problem occur when the computer is cold (from being off overnight) - or does it also do it when it's been switch on for a while and rebooted?

are there any strange smells or small wisps of smoke coming from the top?

A recording of the sound, or a video of the machine's screen (with sound) may help in diagnosis.

 

[PowerMac G4 MDD]

Regarding the 128k:

This gets a little more complicated - there are many potential causes.

You may need to disassemble the machine and take some good, in-focus pictures of the analog board, as well as getting hold of a multi-meter to check voltages.

A few questions to begin with,

does the computer have a programmer's switch installed?

does the problem occur when the computer is cold (from being off overnight) - or does it also do it when it's been switch on for a while and rebooted?

are there any strange smells or small wisps of smoke coming from the top?

A recording of the sound, or a video of the machine's screen (with sound) may help in diagnosis.

I believe there are programmer's switches on it, and I believe that the issue can happen at any time. It seemed to first go away (as in, let me at least boot) once I adjusted the 400k drive's cable on the logic board, but then it would come back intermittently. Above all, it was present into booting, as I mentioned about the lines appearing on the screen.

I'm healing from a recent surgery, so I will not be able to check back on it for some time. However, once I'm more well, I'll disassemble it, take pictures, and see if I can record that sound. Thanks for your willingness to help.
[doublepost=1466280178][/doublepost]Okay, while I cannot take it apart yet, I did go up and try to turn it on and boot it. (BTW, no smell comes from the machine. I will record the noise later; but to give you a current idea of what it sounds like, it's a small electronics hum... I guess you'd hear it if you put your ear up to an old-school Gameboy or something.) Anyway, I turned it on and it showed the spastic floppy screen. Better than when I used to boot it cold and it was completely not discernible. Put a boot disk in and booted; it seemed to work, but there were lines coming in now and then, appearing on the screen. Got a video of that for later on. Seems like the lines would appear further into boot.

Then I tried restarting and it came up to the floppy screen fine. Upon booting to desktop, it was also fine. Didn't see any artifacts after that and gave up and turned it off. Still made that very quiet noise, but nothing on the screen. Seems like the floppy screen stops acting up once the computer is no longer cold; however, the artifacts upon boot seem to happen later on, once the computer is hot. That second time, I would likely have seen them if I had waited longer. However, it hurt my body to kneel down like that. I'll show footage later, as well as a sound recording and detailed documentation of the innards.

 

[PowerMac G4 MDD]

Good news! Turned the machine on without the rear casing on and found out that the buzzing noise is actually coming from the speaker, which could mean that the issue is less serious than it may have initially seemed(?) Still testing it for the screen issue.

 

[MacTech68]

I'm loathed to say what I'm thinking, but it might be the Flyback Transformer.

 

[PowerMac G4 MDD]

I'm loathed to say what I'm thinking, but it might be the Flyback Transformer.

I haven't seen the issue in a bit, though (I'll test the Mac again), and that noise was discovered to be coming from the speaker, not the CRT.

 

[havokalien]

noise maybe from the speaker, but whats giving it the stray voltage to make the sound? no screen most likely bad flyback, which has stray voltage due to failure causing speaker noise.

look up mac dead sea scrolls for the step by step fixing of compact macs.

 

[PowerMac G4 MDD]

noise maybe from the speaker, but whats giving it the stray voltage to make the sound? no screen most likely bad flyback, which has stray voltage due to failure causing speaker noise.

look up mac dead sea scrolls for the step by step fixing of compact macs.

Is the flyback easy enough to replace (and to obtain)?
[doublepost=1466385224][/doublepost]BTW, I would hate to do this, but if I never can find a replacement one for my 128K (which I probably will, but this is as a last resort), could I steal the analog board from my working Plus? I am not referring to the Plus that I originally asked about - I'm referring to the working one I have... unless the one that you have stated just needs to be grounded correctly can have its analog board used.

 

[havokalien]

yes the ananlog fro 128 to plus are interchangeable. the flyback can be found pretty easy. Has quite a few pins to desolder and desolder, but they are big and well seperated so a big clumsy iron would make it pretty easy.

 

[PowerMac G4 MDD]

yes the ananlog fro 128 to plus are interchangeable. the flyback can be found pretty easy. Has quite a few pins to desolder and desolder, but they are big and well seperated so a big clumsy iron would make it pretty easy.

Where can I get a new flyback transformer? Is there a good site at which I can order one? Also, I read somewhere that people usually put in modern ones that are the less susceptible to breaking. Are you aware of which kind people usually use? (BTW, I would't gut my Plus for this, so I guess I'll buy a new flyback transformer).

 

[havokalien]

I have not bought one lately. You would definitely want to do a google on that. I have enough compacts that swapping boards was never even a question. The time involved is crazy when you have a bunch of machines. The craze is dying down so people trying to get tons of money for orignal 128's unmolested and stuff is pretty over IMO. I have a 128 board that needs the memory replaced , but I have a 512 board in it until I have that done as I can not do chips. I can do everything but that. I just cannot wrap my head around it.

When the flyback goes out it matches your symptoms. 68kmla dot org has had some info on good updated flybacks, but again I have not messed with one in decades.

 

[MacTech68]

Depending on your location, this one is suitable and is the highest revision available for 128K thru to the Plus:

http://www.ebay.com/itm/121655780759

HOWEVER - there are some checks that should be done before replacing it - although it won't hurt to have a spare for the future too.

 

[PowerMac G4 MDD]

Depending on your location, this one is suitable and is the highest revision available for 128K thru to the Plus:

http://www.ebay.com/itm/121655780759

HOWEVER - there are some checks that should be done before replacing it - although it won't hurt to have a spare for the future too.

Great, thanks! And, by checks, do you mean making sure that it actually DOES need the flyback transformer replaced?

(Also, any difference with this cheaper one?: http://www.ebay.com/itm/157-0026B-Flyback-1570026B-Replaces-Apple-HR-42031/400922654856?_trksid=p2047675.c100010.m2109&_trkparms=aid=555012&algo=PW.MBE&ao=2&asc=36862&meid=05f85a5273aa4c48975202c15ee30182&pid=100010&rk=5&rkt=24&sd=121655780759)

BTW, is it possible that the floppy drive's connection to the motherboard could be causing it? Not sure if just a coincidence, but it seemed as though the issue would alter itself a bit after I'd adjust that cable and then turn the Mac on again and boot it. Granted, it does seem to not want to boot from cold. (Someone else had mentioned reflowing the solder joints.)
[doublepost=1466401746][/doublepost]Just thought I'd add a picture of what it looks like when I try booting cold:
[doublepost=1466402357][/doublepost]And here's a video of the Mac displaying those screen spasms. You can see that, after re-booting, they aren't seen again; however, if I turn the machine on cold, it gives me the screen shown in the picture above. Then, after a re-boot, it will boot fine, yet it may (or may not) exhibit those spasms - spasms which vary in intensity.

 

[MacTech68]

OK, now this is a little different - IMHO.

There seems to be a 16 bit gap at recurring points during this fault. I'm no longer calling it an analog board fault.

Without looking up a circuit, I'm calling RAM or video buffer. Maybe it IS just noise from the Analog Board, but I'm really not sure now.

See cropped frame grab from your video:

 

[MacTech68]

I seriously recommend that we check the voltages are near spec before going any further.

 

[PowerMac G4 MDD]

I seriously recommend that we check the voltages are near spec before going any further.

What is that voltage dial on the analog board? Is that unrelated to everything? (I know that's not what you were referring to, but could it make a necessary adjustment?)

Really hope it's not the RAM.... I bought the machine specifically because it had its original 128k of RAM in it. Very disappointing. I'm hoping it's merely noise; however, it shouldn't be enough noise that the whole machine doesn't turn on at cold boot.

Here, let me open it up later on and jiggle the floppy drive cable while the machine is running. I still have a feeling that there could be a lousy connection going on.
[doublepost=1466451276][/doublepost]

What is that voltage dial on the analog board? Is that unrelated to everything? (I know that's not what you were referring to, but could it make a necessary adjustment?)

Really hope it's not the RAM.... I bought the machine specifically because it had its original 128k of RAM in it. Very disappointing. I'm hoping it's merely noise; however, it shouldn't be enough noise that the whole machine doesn't turn on at cold boot.

Here, let me open it up later on and jiggle the floppy drive cable while the machine is running. I still have a feeling that there could be a lousy connection going on.

(BTW, if RAM does end up being the issue, could I steal RAM from my other 128k, whose board had RAM added to it from a 3rd-party vendor? I have been meaning to remove that module that activates the extra RAM, since I want it to also report 128k.)
[doublepost=1466451913][/doublepost]Okay, floppy cable is fine. Should I just give my logic board a good cleaning? It's only dusty, but maybe cleaning could help. In fact, I could even use the Macintosh Classic motherboard method and wash it in the sink, unless that's a bad idea. [I'll also send you pics of the mobo before doing anything else.]

Oddly enough, the lines issue seems intermittent. In fact, other than the fact that the machine only boots correctly on the second try (from a cold boot), I haven't seen lines yet on the desktop. I'm browsing through the GUI now without any issues.
[doublepost=1466453288][/doublepost]First off, here are photos of the motherboard:

 

[PowerMac G4 MDD]

(One last picture that couldn't fit with the rest.) Also, do you notice that odd little piece in between those two largest ROM-looking chips? It's just smack-dab there.)

 

[MacTech68]

What is that voltage dial on the analog board? Is that unrelated to everything? (I know that's not what you were referring to, but could it make a necessary adjustment?)

That's what you would use to make an adjustment - but you'll need a multimeter to make the adjustment.

Really hope it's not the RAM.... I bought the machine specifically because it had its original 128k of RAM in it. Very disappointing. I'm hoping it's merely noise; however, it shouldn't be enough noise that the whole machine doesn't turn on at cold boot.

Here, let me open it up later on and jiggle the floppy drive cable while the machine is running. I still have a feeling that there could be a lousy connection going on.

The board looks fine to me - nothing glaringly obvious. You'll be pleased to know that it has one of the earlier ceramic CPUs. Just for reference, the latest chip I can see from the photos has a date stamp of 1984 week 28.

(BTW, if RAM does end up being the issue, could I steal RAM from my other 128k, whose board had RAM added to it from a 3rd-party vendor? I have been meaning to remove that module that activates the extra RAM, since I want it to also report 128k.)

You could, but it would be MUCH easier to buy a chip. MUCH easier.

Okay, floppy cable is fine. Should I just give my logic board a good cleaning? It's only dusty, but maybe cleaning could help. In fact, I could even use the Macintosh Classic motherboard method and wash it in the sink, unless that's a bad idea. [I'll also send you pics of the mobo before doing anything else.]

NO - don't wash it - it doesn't need it - the caps don't leak on these boards in the same way a Classic or Classic II.

Oddly enough, the lines issue seems intermittent. In fact, other than the fact that the machine only boots correctly on the second try (from a cold boot), I haven't seen lines yet on the desktop. I'm browsing through the GUI now without any issues.
[doublepost=1466453288][/doublepost]First off, here are photos of the motherboard:

That might be because the background image is slightly different from boot screen to desktop. - maybe.

(One last picture that couldn't fit with the rest.) Also, do you notice that odd little piece in between those two largest ROM-looking chips? It's just smack-dab there.)

That's a factory modification of resistors (in a resistor pack) that was introduced fairly quickly by Apple after introduction. It's quite normal.

 

[PowerMac G4 MDD]

Okay, thanks for the info. BTW, the lines on the screen have appeared at the desktop before. I'm just not seeing them as often / at all anymore. However, it does take two tries to get it to boot, from a cold start-up.

So how do I troubleshoot the memory, then? I'm assuming it would be expensive (and take lots of time) to replace every RAM chip. Also, could it be a possibility that the voltage and only the voltage is off? I'll see if I can find a multimeter.