Turbo-Duo R's with BIOS screen not loading...is this common?

[Yoder]

This is my first post, but I've read lots of threads here :-)  This place is a great resource with lots of really experienced members!

I currently have a TG-16 that I brought back from the dead by bypassing the RF output and building an a/v cable based on Jibbajabba's website.  (Thanks Jibbajabba).  I also have a PC-engine that I ordered from Japan...it's super cool and I even Retrobrighted it so it looks like new :-)  I plan to do an S-video mod to each of these when I get some time...been wanting to do that for a while now.

I have a few HuCards for each and a Tototek flash card, but I really want to play some CD games.  I'm considering purchasing a Duo-R unit that functions on the HuCard side and has a tested good laser, but has no CD audio (which I hope a re-cap my solve) and an issue where the onboard System Card BIOS doesn't load (requiring a System Card HuCard to load CD games). This one stumps me a bit.

I have read the archives and I don't see this come up much, and the one thread that I saw on it, never had a resolution.  Have any of you guys seen this before?

If I get it, I'll check the traces, look for leaking caps, etc, but I wanted to see what you guys thought.

Thanks!

[Necromancer]

Welcome aboard!

I'd steer clear of that one.  It sounds like a Duo-R that fellow member Keith is selling; Keith knows his repair stuff well, so it's most definitely not going to be an easy fix.

[Yoder]

Thanks!  Such a cool family of consoles...always something to learn with these things with the different variants, Japanese versions, etc!

It certainly could be, and the guy selling them has been very honest and up front that he was intending for it to be for parts, vs to fix.  But, OTOH, he hasn't attempted a repair other than checking that the laser is good...if he had, I'd figure there would be no hope for me.  But you're right.  It might be risky.   He also has a Duo with no audio (at all) and at least a bad door switch ("Please close door" display)...maybe that one would be more straight forward. 

I do want to save some money, have a project, and have an opportunity to learn, but I would like to actually get something working too :-)

[GohanX]

The only time I've encountered a similar issue is when a duo-r has a really dirty cart slot and an Arcade Card plugged in, so it's like the system doesn't post a CD bios screen since it knows a hucard is there, but won't do anything since it can't read it.

Personally, I'd steer clear unless it was really, really cheap and if it doesn't work out you could keep/resell it as a parts system. There are always people who need good Duo R shells!

[Yoder]

Well, the work-around is to just put in a system card...not a huge deal.  Then I just have to deal with the lack of CD audio.  That could be an unrelated problem...hopefully a cap, a trace, an op-amp, etc.  Of course there could be a bad DA converter in there too, I guess.

The good thing is that it functions 100% on the HuCard side, so at worst, it would be an over-priced PCE.

It's not super cheap, but not super expensive, either, considering these go for $150 and up when they (supposedly) work.  Well against your advice, I'm gonna grab it  :-" 

Hopefully I'm not making a mistake.  I'll do what I can with it.  If I can fix the audio, I'll be happy.  I don't  mind having a system card in there to use the CD side of it.

[thesteve]

id suspect you have a related prob.
fix one fixes the other.
never seen one that couldnt load the bios, but worked right with a system card.
bios failure has been a problem with the system bus, and other CD related things didnt work either

[Yoder]

And I guess that could be a good or bad thing, depending on what's broken and how serviceable it is.  The console should be on its way now, and I just placed an order for a new soldering station with a few tips (got the CSI Hakko clone http://www.web-tronics.com/soldering-stations-csi-station1a.html), some decent desoldering braid, and a few other small tools, so I should be ready to work with it soon...or at least when I finish my last C project of the semester.

Should I go ahead and buy a logic probe?  I don't have a scope, so that may be the next best thing for looking at the digital parts of the circuit.  I can at least put one together on a breadboard...I think I have all the stuff for a simple DIY one for now...

[thesteve]

a logic probe will be a minimum for what your getting
scope is better but probe is quicker

[Yoder]

First of all, I appreciate everyone's responses    Steve, are you familiar with the velemann portable $150 scope? http://www.vellemanusa.com/products/view/?country=us&lang=enu&id=351263 If so, does it suck?  ;-)  Or would you recommend picking up an older Tek analog scope.  I see a few locally like a 464, 466, and a 561 for $100 to $150 sort of locally.  Would that be the way to go?  Space is an issue for me too, so the portable one would be great if it works.

I think the last time I used a scope was in 1995 in Physics II Lab...I'm gonna need to spend a few hours just figuring out how to use one before I even start :-/

[thesteve]

im not familure with that portable, but its specs say it wont work for you.
the pce runs at 11Mhz so your scope needs to be usable at or above 22Mhz

[Yoder]

Good catch, I didn't even notice it was that slow! You ruled that one out for me :-)

[Yoder]

Ok, so I got the unit today.  Exactly as described.  HuCards play perfectly.  CD games play but no CD audio.  No loading of BIOS/ROM, either.  I get a purple and or yellow screen (unless I insert a system card), exactly like I see flashing up quickly when  HuCard is inserted, but then the HuCard game loads after those two screens cycle.  So either the ROM is corrupt, the ROM data isn't making it through to RAM or wherever it goes next, or the signal that tells it to load it isn't right.  Almost looks like a region lockout effect that you see on NESs when the games don't load right due to a dirty 72-pin...you know, when you get a colored screen.

The CD audio definitely doesn't work, but I can see that the Sanyo LC7881M DAC has been replaced and it almost looks like there may a bad solder joint on one of the tiny legs.  I pushed down on it while playing an audio CD and I got crackles and popping but no real CD audio.  First thing I'm going to do is make sure that those legs all have continuity and then maybe reflow the solder on it.  I doubt that replacing it again would help...it may have been a failed attempt to fix it...or maybe it did fix it 15 years ago, only to fail due to a bad solder joint.

I looked around and the caps all look clean...all Rubycons, and no bulging, leaking or obviously loose ones. 

It's a nice system, overall.  At least it plays HuCards without any issues.

Let me know if you guys have any thoughts :-)

[thesteve]

look for any black traces or via's as they fail often
the system rom loads across the slot, so you can test the data there for a missing data bit (open pin?)
look for cda before the avc chip

[Yoder]

Excellent...thank you.  I googled and found that this is where audio mixing occurs and is behind the heatsinks.  I'll see if I'm getting a signal to and from it, and I'll make sure it's getting voltage.  Can you give me a hint on what to search on to find the data sheet?  I'm coming up with very little on this chip.

[thesteve]

for the AVC search the part number on the chip
I have a copy at home but not here.