I had to reread the manual to my multi-meter to make sure I was reading AC when checking pin 6 on the TDA4605. I confirmed that I was reading AC, but this time, the measurement was a little lower at 8.23V.
I have replaced DP3 & DP4.
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Need guidance on Classic II repair
- Thread starter sixsevenco
- Start date
I had to reread the manual to my multi-meter to make sure I was reading AC when checking pin 6 on the TDA4605. I confirmed that I was reading AC, but this time, the measurement was a little lower at 8.23V.
I have replaced DP3 & DP4.
Hi Everyone,
Thanks to all of you that have helped me along the way. My Mac Classic II is still down. In searching the forum for answers, I came across this post. I am going to try some of the testing and replacing components as described in the post. Do I hit a point where it's better to find a different Analog Board? I'm not giving up on this Mac. I just received my SCSI2SD to replace the hard drive....
Any thoughts or suggestions?
Thanks to all of you that have helped me along the way. My Mac Classic II is still down. In searching the forum for answers, I came across this post. I am going to try some of the testing and replacing components as described in the post. Do I hit a point where it's better to find a different Analog Board? I'm not giving up on this Mac. I just received my SCSI2SD to replace the hard drive....
Any thoughts or suggestions?
Mouser looks like the place to buy my replacement capacitors but I could use some buying advice. I'm planning to replace all capacitors on the Logic and analog boards but I'm not sure what replacements are suitable, for example one of the existing capacitors is a Nichicon, 470uf, 25v, marked with the codes; M9037 and VX(M) plus a temperature of 85℃. Does this refer to the max operating temperature? Are the codes important? Using the filters on mouser (including the size filters) I have whittled to 8 matches but none appear to be exact (https://www.mouser.co.uk/Nichicon/Passive-Components/Capacitors/Aluminum-Electrolytic-Capacitors/_/N-75hqt?P=1z0wrk5Z1yx4awyZ1z0zlbmZ1z0x27uZ1z0x0wm). Are all/any/none of these suitable replacements?
I am not an expert, so take my advice with a grain of salt...
I don't know what the codes mean, but I don't think they matter much. I think so long as you're hitting the key specs (470uf, 25v, size), you'll be ok. You might want to consider the capacitors with a longer life. (e.g. 7000 hours) I think some models or versions of the capacitors are intended for different uses (automobile, audio, etc.) Not sure which one is best choice; I think automobile may be more durable. Also, I think you will want 105C instead of 85C if available.My advice would be to look through this thread and buy all of the items listed in on shot. (Capacitors, Diodes, CNY17G, etc.) Maybe buy spares just in case... Generally speaking, I think I've spent way more on shipping than on the parts. Mouser probably wont have the TDA4605. I had to go to ebay to find that.
Huzzah! I may have figured it out. Funny thing is, I didn't change a thing. Here's my theory. Initially, I only replace the capacitors on the motherboard and the analog board. After doing this, I my Mac still wouldn't chime. In trying to troubleshoot, I started messing with the PP1 voltage adjustment. I probably cranked it to the max! Thanks to the wonderful advice I received here, my next step was to replace DP3, DP4, CP4, CP5, TDA4605 and CNY17G-3. My Mac immediately chimed after replacing these. I was so thrilled, I never tested the voltages on the floppy port, and again, they were likely still cranked to the max. After a few hours, the screen started getting wavy, and eventually everything failed. I think I triggered the "CROWBAR"!
Now the Classic II's analog board doesn't have R56, but it does have PP1. I figured it would be designed to behave the same way. So I made the adjustment as described in the quote above. It chimed on the first try! The screen was wavy, so it was clear the voltages were off. From there I dialed in pin 6 on the floppy to a 5.00V, and it's been rock steady for about three hours. I loaded After Dark, and I'm going to let this baby run for many hours. I think I'll do a new post as a summary of all of my lessons learned. This was a tough one for me, but I think I am finally seeing the light at the end of the tunnel.
I would like to offer my thanks to everyone that helped me, and a special thanks to bibilit and dochilli!
Now the Classic II's analog board doesn't have R56, but it does have PP1. I figured it would be designed to behave the same way. So I made the adjustment as described in the quote above. It chimed on the first try! The screen was wavy, so it was clear the voltages were off. From there I dialed in pin 6 on the floppy to a 5.00V, and it's been rock steady for about three hours. I loaded After Dark, and I'm going to let this baby run for many hours. I think I'll do a new post as a summary of all of my lessons learned. This was a tough one for me, but I think I am finally seeing the light at the end of the tunnel.
I would like to offer my thanks to everyone that helped me, and a special thanks to bibilit and dochilli!
This looks similar to an issue i'm having with my fully re-capped Classic II.
On a cold boot up, no bong at first, and a dim glow from the screen, then a few "clicks" (from the flyback transformer?) and then the screen lights up normally.... and a few seconds later a bong!
But, the screen has a noticeable *wave* / squiggle along the vertical axis of the left and right of the picture.
After the computer being on for a few minutes, a reboot happens perfectly, no delay or picture "wave".
Caps on the Analog board and logic board have been replaced... should I try measuring the voltage outputs to rule out any other possible component failures?
View attachment IMG_2104.mp4
On a cold boot up, no bong at first, and a dim glow from the screen, then a few "clicks" (from the flyback transformer?) and then the screen lights up normally.... and a few seconds later a bong!
But, the screen has a noticeable *wave* / squiggle along the vertical axis of the left and right of the picture.
After the computer being on for a few minutes, a reboot happens perfectly, no delay or picture "wave".
Caps on the Analog board and logic board have been replaced... should I try measuring the voltage outputs to rule out any other possible component failures?
View attachment IMG_2104.mp4
You up should definitely measure the voltages on pin 6 of the floppy port. The acceptable voltage ranges are listed earlier in this post/thread. I bet your voltages are low.
Have you replaced DP3, DP4, CP4, CP5, TDA4605 and CNY17G-3?
PP1 is a bit tricky to reach. I bought this kit to make adjustments to the other controls on the anaglog board. The longest tool will safely reach PP1.
https://www.amazon.com/dp/B005M6BY2A/
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That is one of the most well worn tool kits in my arsenal! (Mostly used on Plus and under machines, for me.)
Measured pin 6 and it's reading about 4.73 V. Quite below 5V. Is that well within range of adjusting PP1?
Haven't replaced anything but caps, none of the Diodes or the DIPs have been replaced, just all of the capacitors.
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Definitely adjust it, but then check the 12V supply as well, if that is applicable to the Classic II (I know it works on the earlier compacts). If you can't adjust to 5V without throwing 12V out of whack, something is wrong on the component level.
From what I gather a voltage reading that far off is not uncommon. Hope a simple adjustment fixes it for you!
From what I gather a voltage reading that far off is not uncommon. Hope a simple adjustment fixes it for you!
I think you need a minimum of 4.85. I’ll bet you could get there by adjusting PP1. Do you have a tool that can safely reach it?
I checked the 12V lines too, and it's also low. Pin 7 & 8 are reading about 11.5 V
I don't but i'll look at buying one! The same item from Amazon Canada is over $33 8-o . Pffffft
I suppose as long as it's non-conductive and the same size as the longest one in that ST-13 kit, I should be good to go.
Will having low 12V cause issues too? It was reading about 11.5 V on the 12v line...
Arg. That's a ridiculous price, especially for what it is... Try searching for "Universal Color TV Alignment Tool" or something similar. Maybe there's a different product that will accomplish the same thing. I read somewhere that someone carved a bamboo kabob skewer for the task too.
I was able to whittle a bamboo kebab stick and adjust the P1 so that the voltage on the 5V line is reading about 4.8v now... however, the problem persists after a cold boot.
Guess next thing I'll have to do is replace the components mentioned in this thread earlier,... any thoughts on what one it might be.... guessing TDA4605 and [SIZE=9pt]CNY17G-3[/SIZE] as i've already replaced all of the caps.
I did notice that the 12V line is also reading higher since I adjusted P1, around 11.7 v, still well off from 12v, but an improvement from 11.5 I suppose.
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You should be able to get DP3, DP4, and CNY17G-3 from Mouser or Digikey. I'd just get all of them. With shipping, it would be less expensive to get all of them and maybe not use something. You might need to go to ebay to find a TDA4605. I couldn't find one in stock from a reputable online seller. From what I read, DP3 and DP4 are a common point of failure, so you should definitely take care of them.
I was just reading through "Mac classic & SE : repair and upgrade secrets" by Larry Pina, and I read the following which might be of help to you. Putting some fresh solder down on PP1 might just solve your problem!
sixsevenco good to hear you managed to resurrect your mac from the dead, there is hope for us all.
I am slowly filling my basket on mouser thanks for advice regarding the capacitors, how do I find suitable replacements for DP3 and DP4, what are they? They do not have any markings.
I am slowly filling my basket on mouser thanks for advice regarding the capacitors, how do I find suitable replacements for DP3 and DP4, what are they? They do not have any markings.
