PDA

View Full Version : Optical output smoking



TTT
08-04-2003, 03:50 PM
I did a search on this and didn't find anything close to my problem so that's why I'm going to ask.

I have a Sony T-60 that I was hooking an IR plug to from my Sony VCR so I could record to VHS tapes (until I get a DVD burner and Turbonet) and while doing this I noticed smoke coming from the optical output . (Which I don't think had anything to do with one another but I could be wrong) So after further examination I found the end of the optical cable all burnt up and the Dtivo optical output fried . I went into the unit and tried pulling the little silver cover off the optical and S-video housing and the black plastic part of the optical broke . Well I figured it was already ruined. So I need to know what I should do here. I read in here that coax is better than optical but I think I probably need to get the optical fix first right ? So is there some where I can send this unit to get it fixed ?

GREEK
08-04-2003, 04:00 PM
I could repair this unit for you cheaply. You could send the whole unit, but the motherboard is all i need and is cheaper to fix. PM me and well discuss it further.

TTT
08-04-2003, 04:17 PM
Greek you have a PM

But also what do you think caused this ? Is this something that happens often ?

BubbleLamp
08-04-2003, 04:25 PM
I would just use the coax, it is better than optical, less "jitter".

TTT
08-04-2003, 04:34 PM
Yeah I thought about that but apparently something has shorted out in there and I'm alittle concerned about burning the house down. Do you think this is somthing I need to worry about.

BubbleLamp
08-04-2003, 04:40 PM
Originally posted by TTT
Yeah I thought about that but apparently something has shorted out in there and I'm alittle concerned about burning the house down. Do you think this is somthing I need to worry about.

I can't speak to your piece of mind, you'll have to make that decision yourself.

TTT
08-04-2003, 04:57 PM
Sorry let me rephrase that .....if that happened to your tivo would you feel comfortable leaving it plugged up ?

TTT
08-04-2003, 05:02 PM
Originally posted by BubbleLamp
I would just use the coax, it is better than optical, less "jitter".

Yeah but that doesn't pick up Dolby Digital does it ? My A/V receiver has Digital coax but don't I need the optical fixed so I can convert the optical over to digital coax ?

GREEK
08-04-2003, 05:06 PM
I personally have never seen or heard of this in particular, but have some sort of dust accumulate and short out the board by the tuners. I would plug it in if it was my tivo, AFTER pulling it apart and removing the motherboard and looking on hte underside. If the "burning" occured inside you dont know the true extent of the problem unless you fully inspect everything.

TTT
08-04-2003, 05:10 PM
It's working right now . Everything is working except the optical output of course.

AlphaWolf
08-04-2003, 05:50 PM
I am wondering, does anybody know the specific brand and model number of the optical module on the tivo?

I am thinking that one could just solder the ground and signal points from the optical port to an RCA cable and have a coaxial output as easily as that. This would be a lot simpler than the method shown in that other thread. I just did a similar thing to my xbox.

TTT
08-04-2003, 06:04 PM
When y'all say coax you are referring to digital coax and not just regular rca jacks right ? I see your talking about coming from the optical port so I'm assuming you are talking about digital coax. Just want to make sure I'm clear on this . I have the unit hooked up with the regular RCA jacks right now but that won't give me Dolby .

BubbleLamp
08-04-2003, 06:46 PM
Originally posted by TTT
When y'all say coax you are referring to digital coax and not just regular rca jacks right ? I see your talking about coming from the optical port so I'm assuming you are talking about digital coax. Just want to make sure I'm clear on this . I have the unit hooked up with the regular RCA jacks right now but that won't give me Dolby .

Yup, I'm referring to digital coax.

AlphaWolf
08-04-2003, 10:20 PM
GREEK: what all do you know about the optical receptacle on the tivo? I am looking all over, and I can't find any diagrams for its pinouts or anything.

GREEK
08-04-2003, 11:33 PM
Alphawolf: I have looked all over myself about 2 weeks ago and cant find a single thing anywhere. I assume the seven solder points on the bottom of the MoBo are split to both the s video and the optical. I am unfamiliar as to how the optical combines the 6 channels and then transfers the signal. I am sure DSP is in effect on the receivers end as the dtivo only passes thru the signal from available channels, it isnt a true 5.1 piece of equipment, as you already know.
The grounding idea should work, as I assume the voltage is extremely low to the solder points, and I couldnt see how a basic 5.1 signal couldnt be broken down to just L and R in coaxial or maintain its integrity on through to the next piece of equipment. If you look on the underside of the board, there are only 5 main support solders, and 7 actual necessary solder contacts with traces on the board. As far as the board is concerned the traces are as follows;
1 goes back to the tivo master processor, a second goes 1/4 " to a trace point back to the top of the board. Thats all for the underside. On top that trace goes directly to a small trace cap resistor, and the other five do as well, very near the actual connector. If I were to beleive simplicity by design 7 pins would be 5 channels the point #6 for the subwoofer, and the 7th pin as a master ground. I have not seen any schematics as I said, but the optical must combine the signal rather simply, to be passed down the cable to be decoded. I am sure DSP plays a part in separation of the sound parameters, the only hard part would be the expirementation of which signal would go to which channel. It would be an interesting modification, that could actually be of some use.

rc3105
08-04-2003, 11:39 PM
http://www.dealdatabase.com/forum/showthread.php?s=&threadid=20819&perpage=5&pagenumber=3


--
Riley

GREEK
08-04-2003, 11:42 PM
I am gonna pull apart a optical in the morning and see if I can come up with a model # and manufacturer. There has to be something to identify this part under the aluminun housing. It definitely looks and feels like a one piece unit, I may have to take out the dremel for some open optic surgery. Good thing I have an RN in a short white skirt to help me:eek:

GREEK
08-04-2003, 11:46 PM
thanks riley, I dont know how I missed the end of that thread. I guess I didnt read into it far enough. good call.

AlphaWolf
08-05-2003, 01:17 AM
Originally posted by GREEK
Alphawolf: I have looked all over myself about 2 weeks ago and cant find a single thing anywhere. I assume the seven solder points on the bottom of the MoBo are split to both the s video and the optical. I am unfamiliar as to how the optical combines the 6 channels and then transfers the signal. I am sure DSP is in effect on the receivers end as the dtivo only passes thru the signal from available channels, it isnt a true 5.1 piece of equipment, as you already know.
The grounding idea should work, as I assume the voltage is extremely low to the solder points, and I couldnt see how a basic 5.1 signal couldnt be broken down to just L and R in coaxial or maintain its integrity on through to the next piece of equipment. If you look on the underside of the board, there are only 5 main support solders, and 7 actual necessary solder contacts with traces on the board. As far as the board is concerned the traces are as follows;
1 goes back to the tivo master processor, a second goes 1/4 " to a trace point back to the top of the board. Thats all for the underside. On top that trace goes directly to a small trace cap resistor, and the other five do as well, very near the actual connector. If I were to beleive simplicity by design 7 pins would be 5 channels the point #6 for the subwoofer, and the 7th pin as a master ground. I have not seen any schematics as I said, but the optical must combine the signal rather simply, to be passed down the cable to be decoded. I am sure DSP plays a part in separation of the sound parameters, the only hard part would be the expirementation of which signal would go to which channel. It would be an interesting modification, that could actually be of some use.

I have done a coaxial mod on some other things besides an xbox, and generaly it always comes down to this (please excuse my limited knowledge because of the fact that I am not an EE):

All optical receptacles (or all made by toshiba at least, which is the only brand I have ever dealt with) need 3 things: ground, 5 volts, and the SPDIF signal. A coaxial receptacle only needs the ground and SPDIF.

Bearing that in mind, I saw this mod (http://www.pcmx.net/spdif/ddcoax.jpg), which my own personal experience tells me is overkill. (plus I don't like bare wires hanging around there like that :) ). IMO an easier solution would be to just take a two wire approach, so I want to explore that option before proceeding with this.

TTT
08-05-2003, 07:26 AM
Originally posted by GREEK
I am gonna pull apart a optical in the morning and see if I can come up with a model # and manufacturer. There has to be something to identify this part under the aluminun housing. It definitely looks and feels like a one piece unit, I may have to take out the dremel for some open optic surgery. Good thing I have an RN in a short white skirt to help me:eek:

Or you could just wait alittle while Greek until you get mine which is already broken. :D

captain_video
08-05-2003, 07:44 AM
quote:
--------------------------------------------------------------------------------
Originally posted by BubbleLamp
I would just use the coax, it is better than optical, less "jitter".
--------------------------------------------------------------------------------



Yeah but that doesn't pick up Dolby Digital does it ? My A/V receiver has Digital coax but don't I need the optical fixed so I can convert the optical over to digital coax ?

It most certainly does pick up Dolby Digital. Here's the schematic for the digital coax circuit shown in AlphaWolf's last post. I don't know that I'd call it overkill as it's an extremely simple circuit. It's just basically a pair of inverting line drivers and some filtering components. Whoever did the original mod did a pretty amateurish job. It would probably be a lot cleaner to get one of the small project boards from RatShack to mount the components instead of letting them stick out with the leads exposed.

TTT
08-05-2003, 06:35 PM
If I could just understand that schematic I'd probably be good to go :( :confused:

Do those converters (optical-digital coax) actually help or sound better ?

AlphaWolf
08-05-2003, 07:08 PM
Many audiophiles will tell you that coaxial sounds better than optical, and I tend to agree. But you don't acheive anything unless you ditch the optical port entirely, which you could do by connecting a ground wire to the outer ring of an RCA jack, and intercepting the logic line going into the optical port. I don't fully understand what the need for all of the other stuff in this mod is for though.

TTT
08-05-2003, 07:15 PM
AlphaWolf, Is there a pic of what your talkin about anywhere. I don't mean that other complicated stuff that's already been posted but just a simple pic of your way.

AlphaWolf
08-05-2003, 08:02 PM
Nope, but basicaly it would work like this: If you look at your tivos motherboard near the s-video/optical port, you'll see the "R6" (10k ohm resistor), you'll solder a wire from the side of it thats closest to the s-video/optical port, and connect the other end to the center of the RCA receptacle. That finishes the logic line. The other line is the ground, you can get that from just about anywhere, and it connects to the outer ring.

I don't know for certain whether or not this will work, but by looking at the tivo service manual, and judging by my past experience with doing this type of mod, I have no reason to believe that it wouldn't. Riley told me that all of the other stuff shown in the pictures is probably there to prevent a static discharge from damaging any of the tivos components, but by looking at the way the s-video port is done, I can't see how it would protect things anymore than they are already protected. If that is the case though, I don't see why you can't just add a single capacitor into the logic line.

GREEK
08-05-2003, 09:10 PM
I agree with you 100% Captain. This could have easily been a nicer finish with a small project board, and they bothered to make a hole and install a finished port instead of hanging cable out the exhaust port or whathaveyou. I still wonder about the reliability and integrity or the rig.
As far as Alphawolfs post, I wonder why he didnt choose the 2 wire route, for simplicity. He must know something about the dtivos behavior, or possibly overkilled the capacitors for static charges sake, as a precaution. Getting inside the svid/opt to see the trace routes would put a finishing spin on this for me. I will open one up and try to construct a schematic of the inners. The solder on the outer ring sounds functionable, I will try it, and see what I come up with.

AlphaWolf
08-05-2003, 09:48 PM
Originally posted by GREEK
I agree with you 100% Captain. This could have easily been a nicer finish with a small project board, and they bothered to make a hole and install a finished port instead of hanging cable out the exhaust port or whathaveyou. I still wonder about the reliability and integrity or the rig.
As far as Alphawolfs post, I wonder why he didnt choose the 2 wire route, for simplicity. He must know something about the dtivos behavior, or possibly overkilled the capacitors for static charges sake, as a precaution. Getting inside the svid/opt to see the trace routes would put a finishing spin on this for me. I will open one up and try to construct a schematic of the inners. The solder on the outer ring sounds functionable, I will try it, and see what I come up with.

I sent the guy who did this mod an email last night, waiting to see if he can give me any insight. I don't suppose there are any certified EE's among us who would know what the reasoning behind adding all of this extra stuff is?

EDIT: Well, after looking at the manual in a bit more detail, it looks like all lines going to the s-video are protected by a series of capacitors (my first look at the board indicated otherwise), whereas the SPDIF_OUT starts from pin 47 of the sti5505, passes through the 10k resistor, and from there goes strait to the optical port. But, I still don't see why you can't protect it with just a single resistor.

AlphaWolf
08-05-2003, 10:46 PM
Originally posted by rc3105

the ic driving the led may or may not be rated for anything besides a led, not to mention who KNOWS what'll be accidently plugged into the spdif port


Just the sti5505 is, the only other things going to it are VCC (5v) and ground.

AlphaWolf
08-05-2003, 11:19 PM
I just noticed something interesting...have a look at page 19 of the service manual, pins 55-57 of the STi5505.

Who wants to take a guess as to what those are? :D

DarkWing
08-06-2003, 04:01 AM
/me raises his hand. "Oooh Oooh Oooh!"

captain_video
08-06-2003, 08:04 AM
allways a good idea to implement line driver buffer circuits when entering/leaving a piece of equipment.

I concur. While it may be easier to connect using AlphaWolf's approach, adding the extra components is probably a wise move. Any time you expose a circuit to an external connection you need to isolate it from the external circuitry. The load imposed by an external circuit can change the overall impedance and functional characteristics of the Tivo circuit if connected directly to another component, not to mention that it could cause potential damage to the Tivo without sufficient protection.

BTW, I'm not a EE either but I play one at work. I actually have a degree in Oceanographic Technology but I've been working with electronics for over 26 years. I just deal with overall functionality of units and not the get-down nitty-gritty workings of the internal components.

mrblack51
08-06-2003, 09:47 AM
i havent looked at the schematic recently, but one other option for putting a resistor in the line would be impedance matching to 50 ohms, to prevent transmission line characteristics, signal reflections, etc.

GREEK
08-06-2003, 03:54 PM
Yep, this guy probably did the right thing going overboard. The extra 2 bucks in parts is a cheap life insurance policy. I havent had a chance to bust openthe connector, but I am gonna duplicate this unit with a little twist. I wan wondering if the guy ever got back to you Alphawolf? I am dislexic when it comes to Etronics, and I cant act either. I dont mind risktaking though, the tivo gods have been good to me lately. If anyone want to put all this info together for a proposed plan, I got a tivo thats been begging me for some abuse. I am thinking of going the 2 wire route and the outer ring connect, just for expirementing real quick first as the control group info, then doing a pcb board project all nice and tidy and all.

AlphaWolf
08-06-2003, 09:40 PM
Originally posted by GREEK
I wan wondering if the guy ever got back to you Alphawolf?

Not a word, we are probably on our own here.

chainsawbob
08-12-2003, 11:15 PM
My optical out died about a year ago, and I removed it from the
mother board. you gotta remove the s-video and the optical out
all at once (pain in the butt). and I dissasembled the spdif module
(read broke) and found that the componet inside had burnt out
im unsure what the componet is called ?? photo-transister ??
my only other choice is too take an old dvd player apart
and adapt its spdif too the tivo. does anyone know what the name of this part is, I could just order the componet from digi-key
and super glue it back together.

GREEK
08-13-2003, 03:40 AM
I ended up doing the swap for TTT and its back out to him. The 7 pins coming down to the board from the svideo/optical are competely separate. The optical and svideo piggyback eachother with a dovetail mount youd find on the back of your dresser drawers. there are only 3 pins that are for the optical( alphawolf good call) and the other 4 are for the s video. The thught about the 3 or 2 pin setup stated previously will work. The photo by the mystery man is definitely overkill. Had the person took the opt/svideo apart he would have seen the schematics. There is actually no name/part # anywhere on it, and its actually held together by the aluminum housing. The dolby coax now looks like cake to do, and I'll post back with my results in a few days

TTT
08-13-2003, 05:01 PM
Yep and I can't wait to get it back.:D I miss my tivo:(

Yeah Greek please let us known how to do the conversion (the right way) Don't know if I'll have the balls to do it but it will be nice to know in case I want to.

AlphaWolf
08-24-2003, 04:57 PM
Originally posted by GREEK
I ended up doing the swap for TTT and its back out to him. The 7 pins coming down to the board from the svideo/optical are competely separate. The optical and svideo piggyback eachother with a dovetail mount youd find on the back of your dresser drawers. there are only 3 pins that are for the optical( alphawolf good call) and the other 4 are for the s video. The thught about the 3 or 2 pin setup stated previously will work. The photo by the mystery man is definitely overkill. Had the person took the opt/svideo apart he would have seen the schematics. There is actually no name/part # anywhere on it, and its actually held together by the aluminum housing. The dolby coax now looks like cake to do, and I'll post back with my results in a few days

Anything new here?

cali
08-25-2003, 06:28 PM
the reason for the extra parts is insuracne as has been said already.

vega
04-15-2006, 03:33 PM
sorry to reply to an old thread. has anyone tried AW's suggestion? judging by what I see, the optical connector has a light converting unit only, nothing else (I took a failed one apart). so the spdif line feeding the optical out should work. the only caveat may be the circuit suggested may amplify / alter the signal to a usable format for coaxial output. Anyone have success with this?
thanks