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Post by justgreg on Feb 21, 2014 20:25:09 GMT -5
Mac you here? Anyone?
As the Subject state, the positive pad for C8994 is lifted/gone. I have the Service Manual schematic in front of me. Can I pull positive from adjacent cap C8993? Bought the AVR on eBay for a really good price and it's in excellent condition. Looks like somebody tried to DIY re-cap the problematic HDMI board and it was an epic fail. The HDMI board p/n is BCHDM-0471. The majority of the caps (SMD) on this board are wildly out of spec when tested in-circuit using a Fluke 233. I know out of circuit testing is best but until the parts come in I tested them in. From what I've read (limited experience) is they don't lend themselves well to removal for testing and reinstallation.
Thanks Guys!
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Post by mastertech on Feb 21, 2014 21:00:22 GMT -5
What page in your manual do you see those caps in the schematic?
Also, I assume you mean TX-NR708, correct?
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Post by justgreg on Feb 21, 2014 21:46:27 GMT -5
LMAO...yeah on the model. I have dyslexic fingers I guess.
CORRECTION EDIT: Page 23 (not 27) for the circuit and page 76 for the component layout.
I'm not convinced the f-ed up pad is the problem with the thing but it needs to be addressed first.
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Post by justgreg on Feb 21, 2014 21:58:39 GMT -5
Looking at the schematic it would appear that I could pull the 3.3v from the + leg of C8993 (same + bus as C8994) but continuity from the little smidge left of the trace for C8994 to + of C8993 tests open. ? I don't see any components in the path that would cause an open and the 3.3v for all the caps in this area are off a 3.3v rail. I'm still a newb to reading schematics so I'm probably miles off in my thinking. EDIT: The cap symbol for the polarized caps in this area of the drawing are new to me. Is it just a Japanese symbol for polarized caps? I can pull from + at L8965, or I can open up a new piece of the pad for C8994 to tack the cap to because it's a large placement pad that the cap sits on and had a small feeder trace to the missing pad. I got a tone from the trace remnant to the large pad when I scratched off a little spot of coating. Why they'd run a fine trace off this big pad to the + for C8994 makes me wonder why when traces are so east to damage. To cut down on copper??? Is there some way to edit the subject? Nobody searching is going to be able to find any help from this thread with a bogus AVR number. ooops.
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Post by justgreg on Feb 22, 2014 10:40:12 GMT -5
Mac have you had a chance to look at the drawing pg. 23 & 67? I'm thinking I can expose some copper of the large pad and solder in the cap? I have parts and the iron is hot.
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Post by mastertech on Feb 22, 2014 10:44:29 GMT -5
I will be in the shop in about an hour. I will respond then.
I will have the admin change the topic.
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Post by justgreg on Feb 22, 2014 11:09:26 GMT -5
I'll be here studying the svc man.
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Post by mastertech on Feb 22, 2014 12:22:07 GMT -5
Ok, looked it over and yes, these 2 caps are mounted in parallel. Once installed you just need to verify that the pos side is connected to the 3.3v supply and the neg end is connected to gnd.
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Post by justgreg on Feb 22, 2014 14:17:37 GMT -5
Got it. Can I scratch off a bit of coating from the big pad under the cap and mount to that> I couldn't figure that out by looking at page 67. It 'looks' like I should be able to. To me it looks as though the missing pad fine trace ran off it. Thanks again man. I'm having a blast with my $40 purchase so far! I bought a mini heat gun and am in the process of making a coffer damn around the dts chip to reflow it. I bought some no clean liquid flux. I'll take some pix of my 'rig' to share later.
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Post by mastertech on Feb 22, 2014 15:59:00 GMT -5
Yes, you can scrape the coating off and solder to it. Just verify with your DMM that the connection is the same as what the original pad should of been, 3.3v or gnd.
Just be careful when heating that DTS chip not to bump it or bump the board while it is hot. If that chip slides just a fraction it is then worthless. Just don't touch it while hot.
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Post by justgreg on Feb 22, 2014 17:58:29 GMT -5
WOOOOOOOOOOOOOOOHOOOOOOOOOOOOOOOOOOO!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
I found another broken solder trace and it paid off staying up until 4am studying the schematics and learning because I was able to run a fly wire. I also had a little glitch with a radial cap I used below the LAN connect block..it hit a heatsink directly under it. I had to repurpose an old but high quality one to get lead lengths long enough to lay it down.
Yup on the no bumping rule. I read a ton last night from different white paper sites and dipped my toes into thermal thresholds and profiling. Wait til you see the pics of the coffer damn (as I call it). I made it out of adhesive backed metal duct tape. Dropped a little ball of new solder on the top of the dts chip and heated the chip until the solder melted then called it quits with the heat.
Is it OK to post pics here or should I start another thread? There's quite a few pics...around 15 but they'd make a great pictorial for someone tackling the same or similar tasks.
Umma go change out my old faithful 7 year old Onk and see what damage I can do to the wifes hearing. muaaahaaahaaaaa!!
Thanks for your help yet again Mac...this time around though I learned how to fish instead of waiting for a handout.
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Post by mastertech on Feb 22, 2014 18:05:02 GMT -5
LOL, good job.
Yes you can post all the pics you want but there may be a limit per post. Just continue with another post with more if it will let you.
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nashou
Unmoderated Off Topic
Tech in Training.....
Posts: 1,239
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Post by nashou on Feb 22, 2014 20:34:08 GMT -5
Nice!!! please post the pics!!!
Nashou
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Post by justgreg on Feb 23, 2014 13:58:12 GMT -5
I ran the 708 for about 8 hours last night, not very hard because wife was sleeping. It's in a cabinet, second shelf without the back on the cabinet. I keep the glass door open when everythings running too. At the end of the night I felt the top cover and didn't feel what I would consider excessive heat as has been talked about around the net. I listened for the sound of the small circulation fan but didn't hear it, which doesn't mean much. I'm going to pull it out of the cabinet and run it hard to see when/if the fan turns on. Have to hit the schematics to see if there's a thermocouple controlling it. I didn't see the fan turn on when it was on the bench with the cover off right after getting it working but 'assumed' it was temp controlled. Now not so sure. I've got a repurposed 1" heatsink I'm going to add to the TI dts chip. If I can find a good way to secure the heatsink I'll make it active by adding a small 12v fan. As an aside, can anyone recommend a freebie software program to mark up pix to insert comments?
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nashou
Unmoderated Off Topic
Tech in Training.....
Posts: 1,239
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Post by nashou on Feb 23, 2014 14:28:09 GMT -5
Greg just use paint to add comments to your photos.
Nashou
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