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Trouble Shooting Color Classic Analog board

hyperneogeo

Well-known member
So I watched Techknight's video on youtube for troubleshooting the board...I got to the part where he was checking the main cap which turned out to be shorted on mine. I took it out and found the two areas to be shorted still. I'm wondering where I would move from here? (Mines been completely recapped, so the cap there is new as well) Oh I should also mention when I turn on the power switch, it immediately blows the fuse.

Any help would be appreciated !
 

SuperSVGA

Well-known member
It sounds like you have a short to ground on a component there somewhere.

I can't seem to find any good images of the analog board online, and I don't have one here to look at. Would you be able get pictures of the front and back?
 

hyperneogeo

Well-known member
I think I did find it. It was one of the ssp6n60a. As soon as I took it out, the short went away. So I ordered a few of them.
 

hyperneogeo

Well-known member
So update. Yes the SSP6n60A was bad. Popped a new one in and I heard high voltage and such go on. Next there's no sound on boot. So I made sure everything was in OK. . Connected to the output audio on the motherboard, *BONG*. Ok, so lets check that tda7052, it's getting voltage, so that's good. Lets check the input into a powered speaker *BONG*. Let's check the output into another speaker *nothing*, so yup...bad 7052, ordered. Now the monitor turns on and all that stuff and I do hear the hard drive booting up and loading Mac OS, however I the picture even if I put up the brightness is just lines and such? Nothing clear at all.
 

hyperneogeo

Well-known member
So yeah, TDA7052 was bad.

Next I'm getting high voltage on the CRT, monitor is turning on and there is a picture, but it's basically white with lines. I've been told it's because the Lm2418 isn't sending out the correct voltage to the CRT. Checked all of the inputs and outputs, inputs 1V, outputs 3V. Hmm, lets check the VCC, it's 6V. Looking at the schematics it should be 90V...so lets keep going further back in the circuit.
 

hyperneogeo

Well-known member
Well, the problem turned out to be the previous owner reversed a diode that was supplying that 90V. Thanks to Techknight for leading me to it!
 
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