About the interface unit...

[SegaCD]

Hey guys, I have an IFU and CD-ROM-ROM unit, but no PCE yet... I don't have the original AC adapter, but I took a recommendation for a 9V Radioshack one (with an adaptaplug "Q"). I'd like to see if this at least works before I move on to purchasing a PCE.

So my question is this: should the IFU's power light light up when I move the "power-lock" lever to the on position even when there is no PCE plugged in? Because on my unit its not lighting up and that is worrying me... The plug is pretty snug so I'm worried that the generic adaptaplug is not making complete contact either (even though the person in the other thread said it should work). I matched the polarity of the plug to the diagram on the bottom of the unit too...

[Samurai Ghost]

I don't have one on hand to check but you might need a PCE in there to complete the circuit.

[SignOfZeta]

It won't do jack unless there is a PCE installed.

[incrediblehark]

The IFU power led will light up when in the lock position, even without a pce or cdrom unit attached. My guess is either the polarity is wrong on the ac adapter, or the adapter isn't strong enough (uses 9v 1450mA) or something is blown in the IFU (fuse most likely)

[Frank_fjs]

+1 to the above. The power LED should still light up on the IFU even with no consoles connected.

[SegaCD]

Just what I was afraid of.

@incrediblehark Its a Radioshack 273-1771 AC adapter which is rated at 1.5A so it should work fine. I also tried flipping polarity on the plug but it did nothing.

Since I made that first post, I've opened the unit up and poked around inside with a voltmeter. I'm getting some weird 14v difference across the positive and negative wires leaving the AV-out/AC-in combo board when the switch is in the "lock/on" position and nothing when its off... Well at least the switch works! But is that potential difference normal? Lol... My voltmeter said that AC adapter itself is putting out a solid ~9v at the tip though.

Anyway, Is there a fuse on the IFU? If not, does anyone know of any resistors or caps I should check on the board that might be blown? I'm guessing someone plugged an incorrect AC adapter into this or something. Thanks Ebay!

[Samurai Ghost]

Well if it makes you feel any better loose IFUs can be had for a few bucks so if it's not something easy like a loose wire or fuse you could always keep an eye out for a cheap one. I might have a few spares. Had 10 or 12 of the things at one point...

[SegaCD]

Yeah I know...but this unit has the same serial as the CD-ROM unit so I'd like to keep them together if possible!
And also resurrecting a dead unit is just plain satisfying! ;D

[Samurai Ghost]

Yeah I know...but this unit has the same serial as the CD-ROM unit so I'd like to keep them together if possible!
And also resurrecting a dead unit is just plain satisfying! ;D

Agreed! Check the fuse as it might have been blown if someone plugged in the AC adapter with the wrong polarity.

[SegaCD]

Where is the fuse...?
I see a gigantor diode which seems to check out okay... Could that be it? If it is, then thats not the problem...  

EDIT: That 14V difference I'm talking to is now down to 5V. Makes more sense, but I don't know whats going on. haha

[Samurai Ghost]

Not sure where the fuse is as I've never had to replace one. If you are planning to get a PCE anyway I'd just try testing it with that one before tearing it apart.

[SegaCD]

*cough* *ahem* A little late now. Hahaha!
Well I'm trying to find a boxed PCE in decent shape for a decent price which is why I've been holding out... :/

@incrediblehark and Frank_fjs: Did you guys actually try this without a PCE even inserted into the IFU? I know the IFU is supposed to light when a PCE is plugged in but not turned on... But I'm following the traces on the main board from the incoming power and the negative seems to go directly to the PCE console connector in two different places and thats it. No other visible place. Maybe one of these just is a pass-thru for the power that goes through the console even when its not on. Before I delve deeper, can someone confirm that without a PCE in the IFU, the indicator on the IFU still lights? I know the question is sort of redundant, but I'm hitting a wall and I just need a complete confirmation.

[Samurai Ghost]

I wish I had my PCE stuff on hand so I can tell you, but I know the thing won't light up just because it's plugged in. At the very least you have to turn it on by lifting of that little bar/lever in the front and sliding it all the way to the right. I know it's obvious but just to rule that out. Can someone on here with an IFU handy pop their PCE out and see if it lights up with nothing plugged into it?

[SignOfZeta]

I just checked and the CDROM2 is fully operational with the PCE removed. I could have *sworn* it wasn't like that before...hmm...

FWIW; I have the later version that says "PC Engine" on the cover rather than "IFU-30".

[Samurai Ghost]

Well the CDROM2 should work if it gets power, so yeah that makes sense. You can plug the AC adapter into it directly and it will play audio CDs just fine. But obviously it won't play games without a PCE in there.

[incrediblehark]

Where is the fuse...?
I see a gigantor diode which seems to check out okay... Could that be it? If it is, then thats not the problem...  

EDIT: That 14V difference I'm talking to is now down to 5V. Makes more sense, but I don't know whats going on. haha

I believe it would be the 30D2 diode you mentioned that would act in a way as the fuse. But you say yours is fine. I know this is going to sound like a stupid question, but how about the LED itself, and/or the locking power switch? Also, even without the cdrom and pc engine you should be able to test the expansion pins on the ifu to see if there's any power going to them

[Frank_fjs]

Just to confirm, yeah my IFU definitely powers on with no consoles inserted.

[SegaCD]

Okay. Thanks guys... :/

I believe it would be the 30D2 diode you mentioned that would act in a way as the fuse. But you say yours is fine. I know this is going to sound like a stupid question, but how about the LED itself, and/or the locking power switch? Also, even without the cdrom and pc engine you should be able to test the expansion pins on the ifu to see if there's any power going to them

Yes, thats the one. (Labeled "D1" on the board) Its definitely being a proper, working diode. :/ And I've tested both... The plug where the LED's wire plugs in on the board reads zero when turned on and off. I found where the locking power switch plugs into on the board and found continuity when in the "on" position and nothing when its in the "off" position...so that works properly.
Also, people have been saying that their CD-ROM-ROM units get power when plugged in even without a PCE. Mine does absolutely nothing when plugged into the IFU. (The CD-ROM-ROM works fine when I plugged a proper AC adapter directly into it though)

Testing the expansion pins is my next course of action. I found this diagram online, http://www.gamesx.com/misctech/pcebp.php , and found exactly how this diagram is relative the position of the socket on the main board. Does anyone have any pins I should check first? If not, I'm just going to put my meter across one of the Vins to a random ground pin tomorrow when I can trust my shaky hands a bit more. lol

@SignOfZeta: Mine is also a newer "CD-ROM2 SYSTEM" (AKA non-"IFU-30", AKA IFU-30A) one.

[Samurai Ghost]

Yeah sad to say that you might have a bad IFU.
If you still have the cover for yours I might be able to give you a free IFU without a cover if you don't mind paying the shipping. Once my shipment clears customs I think I'll have a few extras in there.

[incrediblehark]

then you can always swap out the bottom of your broken one and keep your matching serials (although I know actually fixing the dead unit is more satisfying)

[Samurai Ghost]

Oh yeah he wanted to keep the serials matching. It seems like the IFU would be easy to fix as its not a very complicated piece of electronics, but maybe I'm just talking out of my ass as I've only done minor repairs on them.

[thesteve]

they are not that simple, as they contain the drive interface and sound processing.
that said the issues with them should be simple.
start at the beginning.
is the power getting to the board from the power adaptor, ect

[SegaCD]

Yeah, I tried going across the expansion port Vin->GND pins and I'm getting readings <1v which I'm pretty sure are incorrect.

Yeah sad to say that you might have a bad IFU.
If you still have the cover for yours I might be able to give you a free IFU without a cover if you don't mind paying the shipping. Once my shipment clears customs I think I'll have a few extras in there.

Oh man, you're too generous. I really appreciate that. I'll shoot you a PM.

I figure I can just swap the entire circuit board from a new IFU into my old one. I can tell it'll be an easy task. Then it'll still have the matching serial numbers and it'll work. I also wont feel too bad pulling capacitors or whatever off of the dead board if I have to. I'll figure this out if it kills me! xD

@thesteve: It is definitely getting power from the power adapter. Also, I'd be a little surprised if it was the more complex electronics causing the problem... I figure the IFU, like most gaming related items, is designed so that at the very least the power light will still light up even if the other electronics are fried. It usually seems that the power LED is dependent from the specific electronics and if it doesn't light, it usually points to power supply issues, but I'm just assuming this from past experience with other electronics.

EDIT: If anyone thinks pictures of anything will help, I got a camera that takes pretty good micro shots and I'd be happy to put some up. :3

[incrediblehark]

you should post up detailed pics of the ifu board just for the sake of reference... I was going to the other day when I was checking mine out to try and help you but in the process I screwed up my rgb mod and had to spend the next couple hours rewiring the whole thing!

[thesteve]

id suspect blown fuse
it could be something unplugged as well

[Charlie]

FYI, capacitor C141 is directly across the power input.  If you apply reverse polarity, you will almost certainly blow that capacitor.  Either check it for a short, or remove it to see if it solves the problem.  Of course, replace it when done.

Ummm, you did make sure to turn the LOCK switch "on", right?


Anyway, here's the power path:
1. From the power jack on the AVPower board, negative connects through a small jumper to the black wire, which goes to P103, pin 1, then to board ground.
2. From the power jack on the AVPower board, positive connects to the red wire, which connects to P103, pin 2.
3. From P103, pin 2, it goes to C141 (47uf, 25v) and also through L101 to P102, pin 2
4. From P102, pin 2, it goes to the Power Switch.
5. Back from the Power Switch, it goes to P102, pin 1.
6. From P102, pin 1 it goes through L102 to P404, pin 2.
7. From P404, pin 2, it goes to the Lock Switch.
8. Back from the Lock Switch, it goes to P404, pin 1.
9. From P404, pin 1, to goes to D101 anode (that's the "30D2"), which is the polarity protection diode.
10. Out D101 cathode it goes to C101, C102 and C103 (330uf, 25V) in parallel, then continues on to R101, R102, R103, and R104, which are actually jumpers.  These jumpers feed the separate parts of the actual power supply circuit.  This was done so each circuit could be powered individually during board design.

You should be able to trace the power to that point.  Make sure to check the voltage against both grounds, the one on the AVPower jack, and the common ground on the board.

Charlie

PS. I suppose, if there was a place to upload it, like say a sticky entitled "Repair Guide - Interface Unit", someone might be pursuaded to supply an abbreviated schematic of the above circuit......(I'm just saying..!)

Edit: Added reference to R103, R104.

[thesteve]

nice trace charlie
general note resistors designated R and inductors designated L might act as a fuse if reason arose

[Keith Courage]

Not to hijack the thread but I was wondering if anyone has ever come across a IFU that powers and and works until a CD games loads. Meaning hu cards work just fine but as soon as A CD game loads the system freezes and locks up. I have 1 on hand right now that does this that I was just going to use for parts unless I can figure out how to repair it. If it's repairable I can send it your way SegaCD.

[thesteve]

look at power usage/voltage drops
if a supply is caving that would do it

[Charlie]

>general note resistors designated R and inductors designated L might act as a fuse if reason arose<

Generally yes, in this case no...both the R and the L are not discrete components, but actual wiring.  The wire gauge is way too thick to be a fuse link.  (The L's are actually ferrite beads strung on the wire).


Also, since R101, R102, R103 and R104 are actually links of wire, you can unsolder one end of each (For R101, R102 and R104, the end farthest from the connector is recommended -- it allows you to use the wire link as a convenient voltage test point.  For R103, it's the end closest to the connector) to isolate the regulator circuitries, then quickly/temporarily reconnect one at a time to determine which "path" is the bad one.  Be sure to check all four.

Charlie

Edit: Added reference to R103 and R104.

[SegaCD]

Hey everyone, sorry I kind of disappeared for a bit. Things have been pretty busy around here...like a few household projects and trying to find a job. (Sadly, no hits yet. haha) So I haven't found much time to work on this... I'll get back to working on it as soon as things calm down a little over here!

@Charlie: Thanks for that trace! That really helps me out! I'll be sure you check it all out in the order you wrote it...and especially C141. I really didn't check any caps or resistors as I wasn't sure if the ones I were going to check were relevant or not to my problem. haha

@Keith Courage: Thats strange. Hmm...well someone else said that the RAM is stored on the IFU so perhaps thats fried... Then when it tries to boot the game and stores the executing code to RAM it becomes corrupted and locks. I'm totally pulling this out of a hat of course, but its possible.
And if Samurai Ghost ends up unable to send me an IFU, then I'd be happy to work something out with you. haha

[thesteve]

Yeah, I tried going across the expansion port Vin->GND pins and I'm getting readings <1v which I'm pretty sure are incorrect.

sounds like your input power is not getting there.
could be the switch

[Charlie]

>@Charlie: Thanks for that trace!<

No problem.
If you need the schematic of that part of the circuitry, including the actual regulators and control circuits, let me know.

Charlie