68kMLA Classic Interface

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More classic ii fun..
Posted by: imactheknife on 2023-11-14 19:21:12
Picked up two classics, one is a classic ii. Classic one works fine with tell recapped logic and original analog board. Classic ii was dead and still dead with recapped logic and analog. I replaced all caps except 220uf 250v ones, and reflowed all important areas on analog board. Still deader than dead. Any ideas? The analog was like brand new, zero cap leakage i could find, was a nice easy recap
Posted by: joshc on 2023-11-14 20:14:41
Still deader than dead. Any ideas?
Search for existing threads about this problem; there are a whole bunch of components that can go bad on these boards; a typical one is the optocoupler. Replacing that and a few other bits will probably get it going again.
Posted by: dochilli on 2023-11-15 00:38:05
There are a lot of parts on classic AB that can be defect. Most often: DP3 and DP4 (1N4148), TDA4605, CNY17G, IRFBC40.
Fuse is ok?
Did you measure voltages at floppy port? Means dead that you get 0 V?
Are the solder joints of the power connector cracked? Resoldered?
Posted by: imactheknife on 2023-11-15 06:02:39
Search for existing threads about this problem; there are a whole bunch of components that can go bad on these boards; a typical one is the optocoupler. Replacing that and a few other bits will probably get it going again.
Ok, have some stuff coming from mouser. Will see that cures it.
Posted by: imactheknife on 2023-11-15 18:35:54
Well, replaced mosfet, and cny17, still no dice. No voltages at all, like power isnt even getting past the plug
Posted by: joshc on 2023-11-15 19:17:05
Check the fuse, as already mentioned above.

Also read this

Posted by: dochilli on 2023-11-16 00:44:08
And check the solder joints of the power plug.
Posted by: imactheknife on 2023-11-16 06:21:10
And check the solder joints of the power plug.
I did all the solder joints, checked fuse etc when i recapped it. I just changed all diodes at dp3, dp4, mosfet, cny17 etc. no change. Will have to order the 4605?? Anyways, the actual switch may be borked??
Posted by: imactheknife on 2023-11-21 19:32:43
I did all the solder joints, checked fuse etc when i recapped it. I just changed all diodes at dp3, dp4, mosfet, cny17 etc. no change. Will have to order the 4605?? Anyways, the actual switch may be borked??
Changed the 4605, it now has power but voltages are all over and no crt coming on. Makes a little squeak like sound when i turn off

So, where does one order the tda 4605? I had to pull this from another classic ii analog board. All major places say it is obsolete now
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