Macintosh Plus Analog Board Optocoupler

[Paulo G Camara]

Hi!

I'm troubleshooting my Macintosh Plus power supply and I suspect that I have a bad optocoupler.

My analog board is the international version 220V. The original optocoupler is the GE H11AVX515R which I can't seem to find online.

I have a substitute optocoupler from Motorola (4N35) that I believe is similar, at least in terms of the pinout.

Can you please confirm if I can use the 4N35 in place of the GE H11AVX5151R ?

Thanks!

 

[feltel]

The BOM of the Analog Board replica (https://github.com/daanvdl/Macintosh-Analogboard) lists a 4N35 as a correct part.

 

[bibilit]

H11AA1 is still available

 

[pinto_guy]

I've had instances where the optocoupler was OK, but the connections to the LB was faulty. You might want to reflux some of these pins and see what happens.

 

[daanvdl]

Hi!

I'm troubleshooting my Macintosh Plus power supply and I suspect that I have a bad optocoupler.

My analog board is the international version 220V. The original optocoupler is the GE H11AVX515R which I can't seem to find online.

I have a substitute optocoupler from Motorola (4N35) that I believe is similar, at least in terms of the pinout.

Can you please confirm if I can use the 4N35 in place of the GE H11AVX5151R ?

Thanks!

4N35 is fine.

 

[Paulo G Camara]

I've had instances where the optocoupler was OK, but the connections to the LB was faulty. You might want to reflux some of these pins and see what happens.

Thanks for the advice. That's usually the case. But unfortunately, in this case that is not the problem.

I've recapped the analog board, refluxed all the connectors, that were indeed cracked, and the Mac worked fine for some time.

I don't know if its a coincidence or not, but when I bought an external BlueSCSI and did the diode mod on the logic board to power the BlueSCSI directly from 5v on the logic board, the Mac started to slowly get slow and wine down and the speaker started to get really low until it locked and i turned it off because it started to make a moaning like sound.

Now, when I turn it on, it gives the startup beep but very very low. Some seconds after, it starts to make a moaning like sound again and I always turn it off so that nothing bad happens.

I've already replaced 7905 -5V voltage regulator on the logic board, but the symptoms remain the same.

Now I'm gonna replace the optocoupler before I go into changing the logic board capacitors, or do the documented upgrades to the switching power supply.

The Mac has 4MB RAM and the CRT works perfectly when I turn it on.

Does anyone has more ideas on what can be the problem?

Thanks!

 

[Paulo G Camara]

H11AA1 is still available

Thanks! I'll order one in case the 4N35 does not work.

 

[Paulo G Camara]

4N35 is fine.

Ok! Should I regulate the 5V potentiometer to the minimum before turning it on with the new optocoupler?

 

[Paulo G Camara]

The BOM of the Analog Board replica (https://github.com/daanvdl/Macintosh-Analogboard) lists a 4N35 as a correct part.

Thanks!