Classic II re-cap

[mtm84]

I got a Classic II that just displayed a checkerboard pattern.  In the process of replacing the mother board caps with tantalums I managed to lift off both pads of capacitor C9.  Does anyone know where those traces go so I can wire it up?  Or should I just not bother now?  

 

[mtm84]

So I found some very nice and clear pictures in this thread, and I was able to get a very small wire connecting the cap to the via at the end of the trace for c9.  Trying to turn it on the first time after recapping the board, I got a start up chime, but then heard some electrical pops and decided to turn it off.  trying to turn it on again results in the same popping sound and no chime.  Before I re cap the analog board, is it possible I have a short in the motherboard?  What is the standard behavior for a classic II with not motherboard in it at all?

Another issue, when I took out the roms before giving it a soap bath, I ended up breaking pin 1 on one of them.  From everything I could find on the internet, pin 1 is only used for programming the rom, and from what I see on the board, all 4 chips have pin 1 connected to each other and nothing else.  The chips are AM27C010's if anyone knows if that is right or if I need to fix or replace that chip.

Tried powering it on without the motherboard, fan turned on, but no display.  Is that normal for a classic II sans motherboard?  On the plus side, no popping sound, so guess i need to double check my caps.

 

[mtm84]

Using a multi meter and probing the molex connector, i got the following voltages: 10.85 on the orange, and 4.68 on the red. Pretty sure that's well outside the normal range of 12 and 5.  Guess the analog board is up for a recap for sure.

edit: after letting it sit on for a bit I ended up around 4.75 and 11 volts.  Still to low.  Also the popping sound stopped, but it doesn't chime at all now and the screen is dead.  So I assume something burned out but I'm not sure what.

 

[bibilit]

Voltages are too low to get things going, a minimum of around 4.85 volts and 11.80 is required.

you can have a try and use an hair dryer, heating the capacitors area will increase voltages for a test.

When you say screen is dead, what does it mean ? low voltages will display garbage on screen (lines, a wobbling display) but will display something anyway.

 

[mtm84]

I mean exactly what it says on the tin.  Screen was blank, like it had no power at all.

I am currently waiting on new caps from mouser, and in the mean time have removed the old caps and cleaned up the board.  only a few of the caps were leaking but could be the cause. I'm not entirely convinced that I don't have a short in the board somewhere either from one of the replacement caps, but it will be a few days before I'll be able to try again.

 

[bibilit]

The Classic will display something as far as the Logic Board is connected to the Analog Board, even with a bad Logic Board.

Your Classic is acting as if no logic board was connected at all.

A Classic with no Logic Board, will be dead, no display, no sound, no fan, nothing.

 

[mtm84]

Guess I will have to see if I get more life after recapping the Analog Board.  Would be discouraging if I fried the logic board replacing its caps :/

 

[bibilit]

Reading your first post, the Classic displayed checkerboard pattern on the first run, so obviously the screen was working.

Can you post a picture of the work done in the Logic Board side ? 

 

[mtm84]

Not particularly pretty but as far as I could tell with a multi-meter all the solder connections were solid.  The bodge wire on C9 is embarrassing though and i just noticed some corrosion on the ADB port by C3.  so I will probably have to  clean under there and re-solder that, which I'm not looking forward to but it will give me a chance to take a better look at C3.

 

[bibilit]

C4 seems badly connected (minus side) apparently not enough heat was used on your soldering, i will touch all of them again.

I will also clean the board accurately.

 

[mtm84]

Re soldered C4, and recapped most of the Analog Board, still no boot chime, blank screen.  Volts from the hard drive connector still reading low. 4.50 and 11.50 with the motherboard hooked up, 5.12 and 11.10 without the motherboard hooked up.  Case fan turns on, and that's about it.  Not sure what I'm going to check next.

 

[bibilit]

Did you cleaned the Logic Board ?

Your Analog board is not outputing correct voltages anyway.

I will replace both diodes DP3 and DP4 (1N4148) the Optoisolator (CNY17) and the TDA 4605 (see my post below)

High failure rate on all those parts.

You won't get close with those voltages.

Any short detected in the Logic board ? (try at the capacitors points for shorts)

With the voltages you have right now, the display should show the sort of picture you see below.

 

[mtm84]

Yes I cleaned the LB with 99% IPA.  Checked all the caps on it as well and some seem connected to ground but without a schematic I have no idea if that's supposed to happen or not, so I'm kind of probing blind here.

Got some digikey or mouser part numbers I can look at for the diodes and IC's?

 

[bibilit]

All references given to you are still available today :

1N4148 (2 required)

CNY17G-3

TDA4605

 

[mtm84]

Small update, finally got around to ordering the parts, just waiting for them to get here.  In the mean time I decided to try starting it up, and managed to get a chime and a gray screen, but then there's some crackling from the AB and it goes blank again.  So not sure if that's more bad caps on the AB that I haven't replaced yet, or just related to the the power control IC.  But hearing a chime is good news to mean since it means the logic board gets as fair as reading the rom chips.  I think.

edit: I should add that while it did chime, the hard drive did not spin up.  I know the drive is good because I checked it in my IIsi.