Dead Sega Dreamcast - No Power

[@LearnElectronicsRepair]

Hey thanks for the shout out!!!! 🙂🙃🙂😁
What's wrong with the donor PSU that couldn't be repaired economically?
9:45 Use a light bulb to limit the current in series with the mains supply when you power up a PSU you just repaired - then the worse thing that could happen if there is a short is that the bulb lights up 😉

[@RetroUpgrade]

Did you like the 3d spinning LER logo. The doner psu was fixed off camera to make the video shorter😁.
Yeah I have to make me one off those light bulb testers.

[@messageobliquespe100]

Very grateful for Learn Electronics Repair - I need to build that lightbulb circuit - I’ll have to see which video it’s on!
Thx retro gamer for the soldering methods you use - it’s where I’ve probably gone wrong as I’ve generally used lower values & not a heavy tipped soldering iron.
Some observations/tips (gained from LER / EEV & others) :-
Make sure you’ve dumped any voltage out of the boards prior to handling - you were picking up & prodding away - you might get a nasty shock one day!
(Deadly too so beware!)
Bending the mosfet pin - ok - it’ll “do” for what you’re doing - if a more expensive item then perhaps get the real one if possible as over time the bend you put in can weaken/cause a problem - (I’ve seen it fail in practice) they’ll be a reference at the end of the mosfet number designating the pin arrangement.
I would’ve been tempted to measure / replace the big cap with what you’ve done. As the mosfet - then later the bridge rectifier went shot - any over voltage to cap will degrade it. Having recently looked more into capacitors - the lifetime is generally so many 1000’s of hrs. 1000hrs is 6 weeks continuous use - so I can only assume most caps are well over their hours but continue to function many times over until there’s a fail elsewhere so best to replace.
Well done for keeping tripod fail in 😂
I think I’ve a Dreamcast sitting around somewhere - never powered it up - might have some Dreamcast games around too. I’ll have to look as I’m going to eBay remaining sega gear I acquired - I’m keeping just what I need for a Williams defender build I’m doing.
Thanks for the upload 👍

[@benjamindominguezperez5900]

Gracias a tu video por fin veo imagen en mi dreamcast, la compré sin funcionar y bueno, resumiendo, tiene una gran escabechina en las pistas de la fuente de alimentación y le falta un BJT o un MOSFET (ni idea porque no está jajaj) por lo que opté por cambiarla por una de las modernas preparadas para el mod del lector, aún así, seguía sin dar imagen, por lo que revisé el ventilador y en la placa de los mandos tenía una pata mal soldada, una vez arreglado esto, volvió a la vida. Saludos desde Vecindario. PD: Si quieres la fuente vieja te la regalo 😅🤣

[@perkulant4629]

Always the poor mosfets. They have a hard life.

[@carlosmechosobentancour6733]

Hola...parece tan sencillo cuando tu lo haces que uno se anima a hacerlo también gracias por tus videos !!!!!👍👍🐱‍🏍🐱‍🏍

[@RetroUpgrade]

Muchas gracias !!!

[@JrManPT]

Nice repair, and great video!
🤣🤣@ 23:56

[@RetroUpgrade]

Thanks a lot 😁.
now i need to make a video fixing the cell phone tripod holder, 3d printing to the rescue 😎

[@Maestro_kenobe]

Tu sabes por qué te conocen en todo el mundo? Por el acento XD. Fuera de bromas, muy interesante el fix. Buen trabajo, espero poder ver más vídeos tuyos.

[@RetroUpgrade]

Muchas gracias 😂😂🤣. Nuevos vídeos en caminó 😁

[@riansigit]

My 12v pin only reads 11.35v on multimeter, is that fine?

[@RetroUpgrade]

It's a little low but most system are tolerant +-1v ,
the mosfet could be switching slower due to age.
would order in some for the 12v rail just in case :D

[@riansigit]

@@RetroUpgrade my dreamcast have blackscreen after boot same like your problem, fan is spinning tough. is there anything causing this problem? could the 11.35v possibly the cause?

[@RetroUpgrade]

@@riansigit It can be a mosfet but won't be exactly the same issue . My guess is the 12V rail supply is not handling the load very well due to age .
here is the schematic for the PSU on the dreamcast , my guess would be that Q2 is about to fail and needs changing out
gamingdoc.org/technical-documentation/consoles/sega-dreamcast/independent/schematics/psu-837-13570/
does the light come on when you power up ?

[@riansigit]

@@RetroUpgrade the light is up, normal orange
Thanks for your reply, really appreciate it

[@riansigit]

@@RetroUpgrade for Q2 replacement can i use L7812CV volt regulator instead of 2SD1856?

[@sanelb1147]

hello , could you please help me.. I have issue with my power supply , same as yours 220v. I am not getting 12v on the connector. 3.3v connector is also showing around 4.8v and 5v connector around 4.6v..

[@RetroUpgrade]

Hi there could be several rezones why your 12v rail is gone one of being the mosfet i changed in the video .
there are a couple of other components that can fail diodes /caps / resistors are rare that they break .
there is a nice schematic on this page for the PSU: dcnigma.tumblr.com/post/101352326649/dreamcast-diagram-s
Hopefully this helps , its a little hard diagnosing not having the board in front of me .
Recommendation is to first measure all the caps so you don't have a shorted or leaking one .

[@sanelb1147]

​@@RetroUpgrade thank you for the reply, I have already tested all capacitors and MOSFETs, there's no short and the mosfets are functional. I have focused my attention on the mosfet that provides 12v the d1276 (q301) on the second pin it has voltage of around 20-22V, on the base it has some micro voltage. when I manually apply voltage on the base pin, the 12v pin is also starting to rise. so the MOSFETs is functional. now the question is why isn't the MOSFETs getting open with the BASE pin, why doesn't it receive voltage so that collector can forward voltage to the emitter which will then automatically give 12v as wel. could it be that the transformer T001 BE128A is maybe malfunction? if you have any further ideas I will be so happy , as I aim already 1 week bussy with this issue and unable to solve at my own

[@sanelb1147]

another note, my dreamcast starts up normally, it works, just the GDrom is not getting its voltage. when I manually apply 12v on the 12v connector the gdrom starts working as well, thou it has issues reading discs that's a different issues with the laser to be solved later on@@RetroUpgrade

[@RetroUpgrade]

@@sanelb1147 You have done your homework that's for sure 😂, ok so you have tested most parts i would have as well , you even self powered the GDrom with 12v and it works .
only culprit left is the Transformer. the 3.3.v rail being 4,8volts is a little worrying , 3.3v rail is derived by a separate winding and would be very weird if that got affected by 12/5v winding . maybe something wrong with the input winding or some of the passives around there because its affecting all 3 rails or i guess 4,6 on 5v is fine .
try testing the diodes before the transformer d1/d2 in the schematics , test Q1(guessing this works because you are getting voltage on some rails ).
let me know if you find some wired measurement
good Luck ☺

[@RaptorZX3]

I know that's not the point of the video, but personally, at this point if the original power supply fail, i'll just replace for a Dreamcast PicoPSU and an external 12V 3A power supply.

[@RetroUpgrade]

Agreed the picopsu dreampsu. Is affordable now and a great option only thing i don't like is that they used a barrel jack and not a USBC PD connector instead 😜