Sega SC-3000 video daughterboard.

[natshaw]

Oh dear, yes that's the one.

This is next step up, in the budget range I guess:
http://bit.ly/Wf76SJ

[honestbob]

Hi Guys

I started a new thread for Desoldering Tools / Techniques discussion

viewtopic.php?f=11&t=961

[Mr Wojski]

Just a couple of other questions.

1. Does the RF output work? That *may* have a direct feed from the TMS9929A VDP chip and bypass the daughterboard.

2. Can you hear the audio working / music playing when you plug in a games cart?
If you hear music you know that the CPU, RAM, and cart slot is working correctly

3. Edit - do you get a black screen plus a medium tone noise when you connect the SC-3000 to your TV? ie. the SC-3000 is kind of working, but not running the code on the cartridge correctly

I'm just looking for parts of the system that are / aren't working to narrow down the problem.

Hi Sorry to bump this really old thread however I am having the problem Number 3. that honestbob has described here. It tunes in to the TV fine however I just have a black screen with medium tone noise when i switch it on, have tried many different cartridges that i know work. Would love to hear if anyone has any Idea's on how to fix.

Ta

[natshaw]

Hi Sorry to bump this really old thread however I am having the problem Number 3. that honestbob has described here. It tunes in to the TV fine however I just have a black screen with medium tone noise when i switch it on, have tried many different cartridges that i know work. Would love to hear if anyone has any Idea's on how to fix.

Ta

Hi there, sorry didn't realise this questions was lurking at the bottom there! I'd look at your cartridge connector on the motherboard. Dirty, bent pins, bad solder joints. Can of contact cleaner is probably easiest thing to start with if you can't see anything obvious.

[natshaw]

Hi all, am new here, nice to find this place! Am repairing a Sega SC-3000, (blank video output, using composite from video out 5-pin DIN socket), and think I have a faulty video daughterboard. There's no significant voltage present on the supply pins of the 3 x ICs on there. From what I can tell, there's a +9V feed from main board (red wire) - then some sort of DC-DC transformer using T101 and a few inductors, transistors, and diodes. I think that's where my problem is.

Has anyone worked on these before? I'd love to find a circuit diagram that covers that daughterboard, but can't locate one. Alternatively, anyone know what voltages I should see on the pins of the T101 transformer?

Machine is the Aus/NZ model.

Thanks in advance, any advice/questions/whatever much appreciated!

Problem traced to faulty transistor TR106. This is the one that does all the switching (@ 140 kHz) for the transformer. Measured voltages, base high, emitter tied to earth, should see 0V at collector. Not the case. Am seeing 9V (from the DC flowing through the transformer primary). Replaced transistor, boom! Working SC-3000H video/audio.