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Thank you. I didn't know that these tiny inductors have colored bands like resistors. That would make it 100 µH, and probably not faulty.

I'm still trying to find the problem with my Color Classic analog board which I smoked a few days ago. I get no +5 or +12 volts, nor am I producing 22KV to the CRT. While looking for bad components I found what looks like a burned resistor. I remove it and it measured 0.11ohms. What's...

MOSFET IRFBC40PBF appears to be identical on specs and available from Mouser.

After smoking my CC analog board, I have no +12- or +5-volt outputs to the logic board. Diagnosing the problem is proving to be a good learning experience. Please correct me if I’m wrong, but it looks like the CC’s analog board uses a 4A full-wave bridge rectifier (DP1) on 60Hz AC line voltage...

I made some progress on my Color Classic. I was able to pick away the glue that was preventing me from adjusting the trimpot. I was then able to adjust it to get B+ to 71.0V. The resistances between the pot pins were 372, 372, and 0 ohms (previously the measurements were 517, 517, and 0 ohms)...

Thanks. I clearly need to get my B+ voltage up to eliminate the raster distortion. If a 500K trimpot doesn't do it, I can substitute a 1k.

The pot is turned to its limit as you say. I assumed counterclockwise (0 ohms) since B+ is only 68.5V. If I turn the pot clockwise (higher resistance), B+ should rise. Am I wrong on that?

Yeah, I did. 517, 517 and 0 ohms.

Thanks. The resistance between the outer two pins measured 517 ohms.

I measured the resistance across the terminals at 514 ohms, 514 ohms, a 0 ohms. I think that indicates a 500 ohm pot. Right?

I found a YouTube video that Techknight produced while trouble shooting a CC analog board. He showed how to adjust the B+ voltage level to control the CRT's high voltage. He said that B+ should be about 71 volts to produce ~22,000V at the CRT anode. B+ on my board was only 68.5V which could...

I reduced the horizontal width with only a slight improvement of the raster shape. Does anyone happen to know the correct B+ voltage for the Color Classic and which pot controls it?

Thanks for the suggestion. I'll try that.

Try as I might, I haven't been able to produce a nice clean rectangular raster shape. The upper right corner appears shrunken. Any hints would be appreciated.

It's not perfect, but I was able to improve the geometry of the CC's raster. It's all accomplished using the 7 right most potentiometers on the back of the analog board (once the yoke is adjusted to level the picture). The rings on the yoke are used for vertical convergence adjustment while...

Is there an advantage to staying with System 7.1, for example, in terms of performance?

I received my 27C400 EPROMs yesterday and programmed one with my XGecu T48 programmer to create a new HI ROM chip. Inserting the reprogrammed ROM chip did the trick. The CC chimed and showed the floppy icon with question mark. The display was way out of adjustment though. There were still...

Are you sure it's not booting? With a black screen, the only indication would be the boot chime. Have you reassembled the CC including the bottom RF shield? There are two ground planes on the CC. You will not hear the boot chime if the shield is not in place, or an alternative grounding...

I faced the same problem recently. The ROM data on the Color Classic (and other 68K Macs) are interleaved between the two masked ROM chips, and the order of byte pairs is reversed from their order in the .ROM file. I wrote a program to create the binary files for the HI and LO chips which can...

I have a similar situation with my CC except that I have a raster display with horizontal retrace lines, but it will not chime or boot. I have +12V and +5V from the AB to the LB. I've recapped both boards but the computer still won't boot. BV13 is not connected to anything on my AB either. I...