Color Classic analog board re-design, needs community feedback.

[jonschultz]

Progress report:

I have started to move parts from one of the original boards, since not all parts are in yet, and it seems a safer bet as to start with fresh parts (except for all electrolytic capacitors)

not done yet, but work is in progress!

once it's populated i will run a test to see if the power supplies work, before trying it out inside the color classic. ill keep you all posted!

The board looks great, awesome work!

 

[ArjenCNX]

Progress is a little slow, life's getting in the way a little, I'll get back to it soon!

 

[ArjenCNX]

 

[ArjenCNX]

View attachment 28745

I'm about 95% done, and slightly nervous about the first power-up...

 

[ArjenCNX]

Well, got it all together, and on first power up the 5/12/-5 PSU side doesnt work, ill have to de-bug it to see what is holding it up. ill keep you posted on the progress

 

[techknight]

Well, got it all together, and on first power up the 5/12/-5 PSU side doesnt work, ill have to de-bug it to see what is holding it up. ill keep you posted on the progress

The amount of times I can count where I had issues with that PSU id be rich. I can say that I am not surprised, hopefully you iron it out.

Make sure standby voltage is making it to the TDA4605 via the opto circuit from the switchon stage.

 

[ArjenCNX]

The amount of times I can count where I had issues with that PSU id be rich. I can say that I am not surprised, hopefully you iron it out.

Make sure standby voltage is making it to the TDA4605 via the opto circuit from the switchon stage.

Yeah, you got that right! so the HV supply switchmode is working, the +5 +12V one isnt starting through the power on command from the keyboard, im going to find out why that is, i do have the +5V from that HV switchmode side, and that is supposed to power up and activate the main PSU.

 

[ArjenCNX]

Okay, i have +5 and +12 aswell now, but when powering on, and when it's time to turn on the CRT i can see from my AC power meter it's doing a hickup thing where the power goes from 25 to 35W and back to 25W again. so i may have to measure the CRT PSU under load and do some fine adjustments.

 

[techknight]

Yeah, you got that right! so the HV supply switchmode is working, the +5 +12V one isnt starting through the power on command from the keyboard, im going to find out why that is, i do have the +5V from that HV switchmode side, and that is supposed to power up and activate the main PSU.

Yeah that HV side runs 24/7, thats why those zeners get baked out.

That transformer on the 520/550/575 has a slightly different winding ratio, they knocked that 24V tap down to around 18V and did away with the zener diode. They also bumped up the B+ winding.