512k sweep/power supply help

This might help: http://68kmla.org/files/classicmac2.pdf

If not, feel free to e-shred it.

Thank you I was having trouble finding much of anything.

While nothing as detailed and sophisticated as Tom Lee's excellent technical guide, I have confirmed the following analog board information:

http://spreadsheets.google.com/pub?key=pOzKVtKz19Ab2BDc-g73ndA

Dang, that's an awesome PDF on classic Macs Tom. I've never seen it before but I'm glad to have it now. Thanks!

Dang, that's an awesome PDF on classic Macs Tom. I've never seen it before but I'm glad to have it now. Thanks!

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Thank you for the kind words. If you find any errors or have suggestions for improvement, let me know. One of these days, I hope to update it with the excellent information contributed by the folks on this forum (with proper attribution, of course).

I only noticed today that my Google docs spreadsheet (link posted above) had the first note missing. I've added that back.

I also found a Revision-J 630-0102 analog board on EBAY, which the seller claims to have come from a Mac Plus.

hey I know its been a while for this post but thank you for the information I am finally on my way to fixing it.

Quick stupid question I am in need of C6 and its a 22uf 50v and I have 2 10uf and a 2.2uf that are 50 or higher volts will the extra 0.2uf going to be too much extra tolerance for the 512k if I install them in parellel? I can always use 2 1uf ones but I would like to put as few in there as possible and I do not want to order one capacitor online and get charged a bunch for shipping. Radioshack has them but only in 35v (they are so lame) I do not think it will be but I just wanted to check.

10% tolerance is typical, so for C6, anything between 19.8uF and 24.2uF is perfectly safe to use.

While in theory you may likely be able to get away with a 35v spec part from Radio Shack, it's always best to err on the side of "higher voltage" when it comes to caps, especially caps used in power supplies or old Mac analog boards.

cool Thank youl I like to use what I have and not have to make a special order, I am going to be using nails for j1 until I get a real one. And I think I found a way to repair the battery holder, I used vinegar to neutralize the acid on it and I am going to solder in some metal plates that should work well.

I think it was doing this before, when I turned it on I saw the disk ? as expected but then the picture faded off. I could hear some small cracks or sparks at the start of the power abruptly ended shortly after, does this just sound like bad caps? I seep to recall it not fading off before but I do seem to remember a cracking or sparking.

Take a look at the pdf doc I linked to earlier. It describes the "no raster" problem, its common causes, and the simple cures. The short version: Resolder the four-pin yoke connector on the analog board, check C1 (I'd just replace it, even if it looked good), and freshen up all the solder joint on the flyback transformer. These simple steps clear up the vast majority of the disappearing/flaky/distorted display problem in the classic macs.

ok sorry i did not see it before . I need sleep soon too much excitement getting my lisa fixed and on for the first time in about 2 years since I found it. Thanks for pointing out what I should search for.

So strange, I left it unplugged for over a day to dissipate opened it up today and discharged the crt. then I took the paper cover off from the analog board. I see and hear a spark from around the transistor that is located by c40 and r41 on the back of the board and shortly after another. It seems like something that would happen with bad caps.

So strange, I left it unplugged for over a day to dissipate opened it up today and discharged the crt. then I took the paper cover off from the analog board. I see and hear a spark from around the transistor that is located by c40 and r41 on the back of the board and shortly after another. It seems like something that would happen with bad caps.

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Or from bad solder joints.

you know I read about the solder joins and did not even think about it, but that would make a lot of sense since it seems to only spark when moved around to much. I will redo the solder on the board and see if it is better or worse.

I re soldered what I could, and it did the same thing as last time I turned in on after being unplugged for a but. When plugged in then turned on it makes a crackle then I can see the screen come on then slowly fade off and turning it off and on will not bring the screen back also when turning it off I hear a squeak, (my old crate amp use to do this too).

it does not seem like Q11 is working when I test it. The one I removed is C2810 the sheet says 2SC2810 and Q11: 7A, 4-500V, 50W, 18MHz. I do not have either one here is there another equivalent that might work so I can for sure tell if that is the problem. I wish I had the transistor equivalences book right about now The Fairchild pdf says KSC2335 is the closest match but I do not have one either.

According to page 332 (Appendix C) in Larry Pina's Macintosh Repair and Upgrade Secrets, Q11 is the following type of component:

T-NPN, 12A, 100W, TO-220

Apple OEM Replacements:

2SC2827

2SC3039

2SC2810

3rd Party Replacement:

Philips ECG 379

(12A, 100W, High Voltage, High Speed, Switching NPN-Si transistor)

thank you I might have to get that book.

it does not seem like Q11 is working when I test it.

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How did you test it?

(And Pina's information about the 2SC2810 seems to be in error. I am looking at the datasheet now, and it says that the 2810 is a 50W device; 7A peak Ic, and 500V BVcbo; it's the same info that I had at the time I put together my own schematics, and summarized there -- patnukem, see the schematics at the end of that pdf; this info is there for every semiconductor I could identify)

Multimeter with transistor tester. it worked to correctly test the bad one in my lisa. yeah I was confused because I mentioned the Q11: 7A, 4-500V, 50W, 18MHz up top from your pdf as you said. Id rather use one I have here to see if that is whats wrong for sure then have to order something.

Tom, I wouldn't be surprised if Pina was in error because I've spotted other errors in his books. But for the most part, his information is quite accurate.

Pina says Q11 is to be rated at 12A. So when I looked up those Apple OEM "replacements" listed in his book, I too thought he would be in error because the data I see shows them to be rated at only 7A. However, I believe Pina is simply saying that those 3 parts are "what he himself has seen in various Apple analog boards through the years," and he therefore deems them "OEM replacements." Pina then offers the Philips ECG379 part as a proper 12A replacement.

So I think going with the Philips part or similar is the most prudent choice.

http://www.moyerelectronics.com/ seems to agree that ECG379 or NTE379 (they have a sheet for this one) is the replacement. they have a nice cross reference for ecg and nte, I had been looking for one this is very helpful. I may just stick with buying a new analog board since I do not have one that will work here and if I have to order anything I may as well just get the whole analog board. I will keep looking I may have one buried.

I replaced the two 100uf 200v caps. and reinstalled Q11 then started it up and It sparked just like before but dimmed slowly. I also noted that the brightness knob on the front seemed bad and would flicker brighter and then darker as it faded slowly, I also noted that the sides were waving in and out (like water) I will replace more caps I have here and see if it gets better.

Tom, I wouldn't be surprised if Pina was in error because I've spotted other errors in his books. But for the most part, his information is quite accurate.
Pina says Q11 is to be rated at 12A. So when I looked up those Apple OEM "replacements" listed in his book, I too thought he would be in error because the data I see shows them to be rated at only 7A. However, I believe Pina is simply saying that those 3 parts are "what he himself has seen in various Apple analog boards through the years," and he therefore deems them "OEM replacements." Pina then offers the Philips ECG379 part as a proper 12A replacement.

So I think going with the Philips part or similar is the most prudent choice.

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I heartily agree that Pina is to be trusted in most matters. I suspect that he was subtly (or not so subtly) guiding the user to an upgraded part. In switchers, however, there is a tradeoff among the various parameters, and it's not always better to seek a higher-current part. In switchers, there is considerable dissipation in the transition between states, so switching speed is important. Higher-current parts can be more sluggish, and using them can actually be self-defeating. Given that Q11 seems not to have any unusual failure modes, I'd normally be inclined to leave well enough alone.

That said, it appears, from what you've found from Pina, that Apple used a variety of transistor types for Q11 (I myself have not noticed this, so thanks for letting me know), so evidently any of the ones he cites have been proven to work well.

Multimeter with transistor tester.

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Yes, but how did you use it? Did you remove the transistor first? Or did you leave the transistor in circuit? The only reliable way to test a transistor is out of circuit. If you do it in situ, the test can be confounded by other things tied to the device.

From the intermittent behavior you are reporting, it's highly unlikely to be a transistor problem. Transistors rarely "fade out" repeatedly in this manner; they either work, or die.

I removed the transistor completely and used it as the instructions say to and it had no response at all not even a blip, I used it to test a good one the day before so I know it works and its only 4 days old (the multimeter). It is odd though my board did not have a connector to the Collector or middle pin is was just in a hole on the board with no solder or leads anywhere near it so I assume it is not meant to be connected. is there a proper schematic for this analog board, that pdf shows Q11 having all 3 pins connected.

Yes, all three terminals of the transistor are used.

The middle terminal is electrically connected to the tab.

I still have lingering doubts about the test. It is very rare for a transistor to behave in the intermittent way you describe. As I mentioned, either a transistor works, or it is dead. It is extremely unusual for a transistor to go back and forth between these two states. I cannot recall ever having encountered this myself. Indeed, I can't recall even hearing about anyone else encountering such a phenomenon. Depending on the precise method used by the multimeter, it is possible to get a false result. In the case of power devices, it is frequently adequate to do the following:

1) Check for a good diode between base and emitter.

2) Check for a good diode between base and collector.

3) Verify that there is no continuity between collector and emitter.

You also mention sparking. Is this something you see, or is it something you hear?

And have you looked very carefully at C1? Is there *any* bulging on the top?

Have you carefully inspected the yoke connector? Not only should the connections on the analog board be resoldered, but you should also unmate the two connector halves and inspect all 8 of the pins for signs of arcing, melting, oxidation, etc.