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Mac Plus video issue

K

KenEG

Experienced Member
Joined
Oct 20, 2016
Messages
440
Location
Cincinnati, Ohio USA
I just picked up a Mac Plus cheap. No keyboard or mouse. Insides look fairly clean so I turned it on. I get a vertical bar about 1/2 inch wide that does look to have an image in it. The computer gives one long beep when turned on. I tried putting a System 6.07 options disk in it and turning it on. The drive doesn’t do anything. Maybe I need a mouse or keyboard before trying that? It looks like some of the solder joints are fresh especially around the transformer that the high voltage cable comes out of. Please help me fix this.
 
I've posted these before but it's always worth reposting:

Classic Mac Repair: http://www.ccadams.org/se/classicmac2.pdf
Dead Mac Scrolls: https://archive.org/details/TheDeadMacScrolls

The Dead Mac Scrolls has pictures that will guide you to your possible issue and possible solutions. I've not had your exact issue but if others have, then i'm sure they'll comment as well. As for the Mouse and Keyboard, they don't matter for a working system. When I was repairing mine I didn't have a working keyboard. I did have a mouse but not hooked up. The sad part is that finding a cheap mac plus is easy, finding an affordable keyboard to go with said computer is going to be the challenge. You'll likely pay more for the keyboard and mouse then you did for the computer itself.

The drive should do something, but if it's been sitting, it's almost guaranteed that you'll need to open it up and oil most of the moving parts. The mac drives used this grease that basically turns to concrete over time so lots of oiling and moving parts around might help that. Assuming it works at all. Obviously cleaning the head while you're at it.
 
Thanks. I actually found those two after I posted. My first try seems to be re-soldering a connector and the coil for width adjustment. I also have to find my plastic tool for adjusting coils. I was afraid it was the fly back transformer, but that isn’t one of the suggestions for my symptom. If I can get the display working, I will pull the drive and work on it. I have cleaned and lubricated drives before, so that shouldn’t Be a problem. Yes, buying a mouse and keyboard are likely to be much more than the $25 I paid for the Mac, but worth it if I get it working. If I can’t fix it, I won’t need them. LOL
 
KenEG said:
Thanks. I actually found those two after I posted. My first try seems to be re-soldering a connector and the coil for width adjustment. I also have to find my plastic tool for adjusting coils. I was afraid it was the fly back transformer, but that isn’t one of the suggestions for my symptom. If I can get the display working, I will pull the drive and work on it. I have cleaned and lubricated drives before, so that shouldn’t Be a problem. Yes, buying a mouse and keyboard are likely to be much more than the $25 I paid for the Mac, but worth it if I get it working. If I can’t fix it, I won’t need them. LOL
Click to expand...

That was my thinking as well which is why I didn't bother finding a keyboard til i fixed it... and when i did find one, it didn't work. Eventually found a few locally that took care of the 512k and the Mac Plus I have. I mostly did adjustments the 'lets try and not kill myself' method, with the exception of L2 because you need to do that with a special tool or with the machine off (I chose the later since I didn't have a tool or the inclination to make one). Though your issue doesn't sound like an adjustment problem. I found following the info in the classic mac repair first will get all the basic issues out of the way and get things calibrated, then follow the dead mac scrolls f you still have specific issues that didn't get solved in the earlier troubleshooting.

KenEG said:
I took another look. Capacitor C1 has a definite bulge. So I guess I order a replacement and start there.
Click to expand...

Ironically I've had C1 look kinda bad on both of mine and still work fine. It's not something I had in stock so I didn't bother looking for a replacement since my board worked anyway, but it is a common issue from what i read. That said, if you have to get capacitors anyway, you might want to replace the RIFA's at C38 and I believe C37 / C33... assuming it's not a newer board or they've never been replaced (still gold plastic covered paper caps). Replacing won't fix any of your issues but worth doing if you're working on the board anyway and will keep family members from disowning you when they blow. :)
 
OK, I will look at the RIFA caps, but I tend to only replace what id needed to get them working. Maybe as I gain confidence in my abilities I will do more. I'm not sure what C1 does, but if it is causing low voltage in the horizontal sweep circuit, it would explain my issue. The solder joints for it are definitely newer than most of the board. Someone has worked on this before. The capacitor looks the same as the one next to it, so maybe someone refreshed the solder joint but didn't replace it.
 
What is the difference between a high frequency capacitor and a regular one. The first ones I ordered say bipolar, but not high frequency. Through a lot of googling, I discovered that I really wanted a horizontal deflection high frequency capacitor. I ordered one of those at a price that was similar to 5 of the regular bipolar capacitors. Is this a difference in ESR?
 
I decided to try a couple of things today. I unplugged and checked the yolk connector J1. It looked OK. When that didn’t change anything, I reflowed solder joints on the width adjust coil, J1, and the flyback transformer. Again, no change. I tried adjusting the width with the computer off since I don’t have a non-metal tool right now. I can change the width a little. Does this rule out the coil as a potential cause?
 
KenEG said:
I decided to try a couple of things today. I unplugged and checked the yolk connector J1. It looked OK. When that didn’t change anything, I reflowed solder joints on the width adjust coil, J1, and the flyback transformer. Again, no change. I tried adjusting the width with the computer off since I don’t have a non-metal tool right now. I can change the width a little. Does this rule out the coil as a potential cause?
Click to expand...

If you don't have a plastic tool handy you can use a wooden BBQ skewer. I just whittle down the end until it fits snugly.
 
KenEG said:
What is the difference between a high frequency capacitor and a regular one. The first ones I ordered say bipolar, but not high frequency. Through a lot of googling, I discovered that I really wanted a horizontal deflection high frequency capacitor. I ordered one of those at a price that was similar to 5 of the regular bipolar capacitors. Is this a difference in ESR?
Click to expand...

HF capacitors are designed for operating at high frequencies, like present in flyback or deflection circuitry. You don't want to replace a HF capacitor with a general purpose capacitor because such a capacitor will generally break down and not work, or fail and potentially take out something expensive. HF caps should be low ESR, but it depends on the capacitor.

Polarized capacitors also shouldn't be replaced with bipolar capacitors or even nastier things could happen.
 
If a HF capacitor can't be found you can often take the capacitance and divide by say five and use 5 smaller capacitors in parallel. The smaller value work better at higher frequencies.
Don't fiddle with the adjustments. You have a major failed item. Miss adjusting the controls won't make it better.
I hate blanket replacing capacitors myself but replacing the RIFA capacitors is really just fixing a faulty design. These early capacitors had a design flaw and will fail with lots of stinky smoke. Since they really are not functional, I often just clip them out of the circuit.
Dwight
 
GiGaBiTe said:
HF capacitors are designed for operating at high frequencies, like present in flyback or deflection circuitry. You don't want to replace a HF capacitor with a general purpose capacitor because such a capacitor will generally break down and not work, or fail and potentially take out something expensive. HF caps should be low ESR, but it depends on the capacitor.

Polarized capacitors also shouldn't be replaced with bipolar capacitors or even nastier things could happen.
Click to expand...

I was initially having trouble finding high frequency capacitors. Once I figured out to search for horizontal deflection capacitors. I was able to find what I needed although at 4.7µF not 3.9µF. I believe that the tuning coil should be able to be adjusted for the difference. I found out today that it is called an LC circuit and calculated that the inductance will need to change by about 2µH. I believe that than isn't a problem for the coil.
 
Dwight Elvey said:
If a HF capacitor can't be found you can often take the capacitance and divide by say five and use 5 smaller capacitors in parallel. The smaller value work better at higher frequencies.
Don't fiddle with the adjustments. You have a major failed item. Miss adjusting the controls won't make it better.
I hate blanket replacing capacitors myself but replacing the RIFA capacitors is really just fixing a faulty design. These early capacitors had a design flaw and will fail with lots of stinky smoke. Since they really are not functional, I often just clip them out of the circuit.
Dwight
Click to expand...

I saw in once of the repair guides the suggestion to use four 1µF ceramic capacitors in series as a substitute, but I prefer to keep things close to original when possible.
I only adjusted the width control to test the coil. Since it made a difference I am assuming it is working for now.
I thought the RIFA capacitors were there for over-voltage protection. Newer designs use a device that I don't remember the name of that shunts the voltage to ground and blows a fuse. Are there better replacements for RIFA capacitors?
 
KenEG said:
I saw in once of the repair guides the suggestion to use four 1µF ceramic capacitors in series as a substitute, but I prefer to keep things close to original when possible.
I only adjusted the width control to test the coil. Since it made a difference I am assuming it is working for now.
I thought the RIFA capacitors were there for over-voltage protection. Newer designs use a device that I don't remember the name of that shunts the voltage to ground and blows a fuse. Are there better replacements for RIFA capacitors?
Click to expand...

You can use the newer RIFA capacitors. They work fine. These are not intended to act as MOVs, They are to isolate spikes from the outside and noise from the inside. The older ones had cases that cracked over time. The newer ones use better potting material.
Dwight
 
Everything dwight said about the Rifas is, as usual, correct. the only difference i might add is that while they aren't as important as they once were, and you can definitely to run your system without them (which is preferable to smoking up your whole house), i do suggest not leaving them out of the circuit design permanently. X2's are super cheap so order some from China and leave them out while you work on things. If you start leaving them out on everything, you just might start getting odd behavior with certain older tech or tech that uses the powerline for various things (like powerline networking devices) so best to try and put them back in to avoid that variable when you have other issues.

As for the HF capacitor, i doubt the capacitance will make a huge difference with such a small number. The only thing i would suggest is possibly a higher voltage capacitor. It doesn't *need* higher voltage but that stupid fanless mac design will get hotter and a thicker capacitor will be less affected by the heat and less chance of the esr going up to unacceptable values. I believe one of those manuals mentioned something about that as well.
 
Dwight Elvey said:
You can use the newer RIFA capacitors. They work fine. These are not intended to act as MOVs, They are to isolate spikes from the outside and noise from the inside. The older ones had cases that cracked over time. The newer ones use better potting material.
Dwight
Click to expand...

Yes, MOV was what I was thinking of.

So if you remove the RIFA capacitors the only issue might be increased noise out of the power supply and may back into the mains?
 
ngtwolf said:
Everything dwight said about the Rifas is, as usual, correct. the only difference i might add is that while they aren't as important as they once were, and you can definitely to run your system without them (which is preferable to smoking up your whole house), i do suggest not leaving them out of the circuit design permanently. X2's are super cheap so order some from China and leave them out while you work on things. If you start leaving them out on everything, you just might start getting odd behavior with certain older tech or tech that uses the powerline for various things (like powerline networking devices) so best to try and put them back in to avoid that variable when you have other issues.

As for the HF capacitor, i doubt the capacitance will make a huge difference with such a small number. The only thing i would suggest is possibly a higher voltage capacitor. It doesn't *need* higher voltage but that stupid fanless mac design will get hotter and a thicker capacitor will be less affected by the heat and less chance of the esr going up to unacceptable values. I believe one of those manuals mentioned something about that as well.
Click to expand...

OK, I will remove them if a new C1 fixes my issue and see if I want to bother replacing them. I bought a 50v capacitor as suggested in the Dead Mac Scrolls. I doubt if I will ever have this on for an extended period. I always shut off my vintage computers when I am not using them. No point in tempting fate.
 
KenEG said:
OK, I will remove them if a new C1 fixes my issue and see if I want to bother replacing them. I bought a 50v capacitor as suggested in the Dead Mac Scrolls. I doubt if I will ever have this on for an extended period. I always shut off my vintage computers when I am not using them. No point in tempting fate.
Click to expand...

If your experience with the Mac Plus is anything like mine, you'll spend a lot more time fixing it then you'll ever spend using it. :)
 
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