Sega Cd 1 power board recap (failure)

So, I attempted to recap the SUB BD EXPORT board of my model 1 (I have previously recapped the main board), and now It won't power on...
All the caps except C40-43 (100 mf) are 10mf 16V, correct polarity.
Sometimes the led's blink, sometimes not. I already replaced the fuse, just in case.

Any advice on where to start error searching? From the looks of it, only the 100mf caps are related to power, the rest are audio output related?

 

hi Star , i recently fixed my TOP 3000 USB Programmer as the power LED would not come on when the Programmer is switched on. Also the Power Supply brick LED would dimly flicker and flash on and off. I got to the bottom of the situation as one of the Caps was totally dead , after i recapped the whole Programmer it now powers on fine and works great.

you may find something in my situation to help yours.

best of luck

 

Thanks, but I'm not sure how helpful that is. Of course, a cap may be bad, but they are brand new.

 

Try to messure voltages on all of the caps. Might be a broken/ripped trace.

 

was the unit working before the recap ?. If it was it's most likely a bad new cap or as Oakleaf mentioned broken/ripped trace

 

Yes, working before the recap.
Measuring is damn near impossible while it is in use. Easier to test continuity, but I am not sure where some of the caps are supposed to connect-.

 

Coulnt you 'hang' the board outside while the rest is losley connected and try to messure that way? I know the soldermask on that thing sucks. The other way would be to use the not so good servicemanual and schematic that is out there and messure continuity.

 

That's not a bad idea actually. Tried it on a couple of caps, Voltage across C40-43 at least.
Tried a few points on the ribbon cable connector also. VCC on pin 11 shows 5V. M.vcc on pin 20 is 1V and VCC2 on pin 19 is 2V

 

Cool. But thats sounds a bit on the low side. As I understand it. The megadrive tells the cddrive when to turn on. If you have a scope u could try probing each side of every cap to se if a signal is passing through, but it might be overkill.

Might be unecessery but are you sure everything is connected tight? And also, when u have the top of and insert the megadrive, sometimes u might push it to far on the connector...

 

Had a look at IC6, aka the voltage regulator. It is not outputting 5v, and it is barely getting any input...
Am I correct in thinking there really isn't that much to the power section?
From TR4, voltage is sent to the input of the voltage regulator with 2 caps in parallel?
The schematic says C27, but that has got to be C43.

 

Test the 7805 voltage regulator. Any money bet its failing. It the thing screwed onto a heatsink.

 

Well as I said (we probably cross posted), the voltage regulator is not receiving the correct input. And neither is C43 it seems, just some trickle voltage on both.

 

The capacitor I wouldnt worry about, you wont see operating normally if the 7805 isnt working. There are cheap and modern replacements for them these days that dont even generate significant heat.

https://www.ebay.com/itm/1A-6-5-40V...377177?hash=item3f6f5e1819:g:QFYAAOSwKOJYK~P0

 

But that can/do introduce noise.

 

Soo Tr3 needs to be enabled from the mega drive or elseware for there to be voltage on the input of the regulator? Might be a connection problem?

 

That is good to know, but even if it was faulty it should still be getting the same voltage as the TR4 outputs, right?

 

You could power the console from a bench power supply and see if its taking excessive current (showing a short).

Is the 7805 getting hot?

 

Doesnt tr3 need to be pulled for tr4 to conduct? Its like your using the mega drive ad a switch to switch on the IC6 regulator on the megacd. Or am i reading it wrong? The megadrive is still working rigth? Thus the 7805 in that is alright?

 

I don't have a bench psu unfortunately.
Doesn't seem to be getting hot, but I haven't had it powered on for long each time, just enough to take some measurements.
Tr4 shows voltages from 8.2-9.6 volts, so something is happening between it and the regulator.

Yeah, both mega drives are working alright.

 

its just going to be the regulator. it should get hot fairly quickly.