Re: Onkyo TX SV727: Found bad transistors, what else?
Yes these are the same 2 that shorted.
Ok, yeah i was referring to the "bigger" ones as the "last" ones before the output stage.
When i plug it in now even with the blown fuse i hear a relay click on, which i dont remember getting before...
Zeppelin1007
Member
Last Activity: 12-11-2018, 11:00 AM
Joined: 02-17-2017
Location: Parma, Ohio
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Reivax so i understand better, the 2 transistors i replaced, is that the output stage? I thought it was the 2 bigger transistors next to itLeave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Well i screwed up royally. Not even sure how!!
I checked all my transistors. No shorts. Checked my new resistor, it was making continuity.
The one thing i did do was clean up the crud and grime around my solder joints.
Apparently. I screwed something up doing that because when i powered it on: POP!
Fuse is gone. Also, more troubling, i dont have standby it seems! Before when the transistors were shorted itd blow the fuse, but id still have standby.
Even worse, both of...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
I'll do some digging and probing. I recall doing a continuity test right after this happened on all the big transistors and none showed shorts. I know the 2 i replaced arent shorted...first thing i checked lol.
I have the 2SD transistor on the left, and the 2SB15560 on the right. Any chance i switched em?
I'm printing off the schematics tomorrow at work. Preferably on the plotter for ease of reading.
If i screwed up a track/caused a short id guess itd be by where my soldering was. I'm just still...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Ok guys.
Took her to work where the guys here have good Fluke meters.
We got a problem!
So i measured all the resistor legs with respect to ground. Starting from the front of the stereo, to the back.
R1->GND = 0.016v
R2->GND = 0.01v (center leg)
R3->GND = 0.003v
Now where i did my repair:
R4-> GND = 49.01V (uh oh!)
R5->GND = 49.03V (center leg)
R6->GND = 49V
R7->GND = 0.008v
...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
The unit stays on, just in protect mode, no matter whats hooked up to it. No heat on transistors or heatsink. Will measure voltage on the emitter resistors tonight.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Ok.
collector on the 2SD2xxx transistor was shotty so i resoldered it. I do get a secondary relay click quickly after powerup, but immediately back into protect.
I do believe i smelt the smell nobody wants to smell last night. Ie. Burn components :-( cause i dont smell it now.
Borrowing a thermal cam monday.
There isnt much on this damn board i should be able to check it out pretty quickly.
Is there a computer reset on this? I feel as if the service manual is a bit incomplete....Last edited by Zeppelin1007; 03-31-2017, 07:02 PM.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Nah testing will have to be done at I'm guessing the test point terminals on the board. But I'm guessing these arent even going to be active if its stuck in protect mode?Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Amp turns on normally.
I refer to the "secondary relay" as the speaker protect relay i guess. I turn it on, it goes click, the VFD powers on and a few seconds later another relay would click.
I took measurements at the speaker terminals for the Front Left (i think left) i'll check when I'm not at work. Didnt think a meter would cause it to short.
I agree with checking my solder joints.
Maybe i didnt short it and it was timing from another problem?
Thanks...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Nope. No DC output. No secondary relay click.
Edit: im a bit fuzzy on this automatically setting the bias current. Even if i check it, is there anything i can do about it? Ie instead of a pot is there a spot where I'd solder more resistors in?
I broke something lol. She sat fine until i hooked the meter probes up. Yes it was set to DC voltage, not amps. I need to get it out of protect mode before i can worry about biasing.Last edited by Zeppelin1007; 03-31-2017, 06:38 AM.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
I see nothing in the service manual about biasing. This does have the pin headers tibimaki mentioned. There's also no pots anywhere in here.
Welp. Tried to take the voltage from the output terminals. Bad idea. Its stuck in protect mode and the secondary relay no longer clicks on. Ive disconnected everything but same result.
Back to the drawing board.
Edit: the new transistors checkout ok. Whew!Last edited by Zeppelin1007; 03-30-2017, 10:18 PM.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Ok. Im just checking i take it from center to outter on the resistor pins?
What do i do with these numbers? Ie what am i looking for/to check? Is this like biasing a tube amp and making sure you're running within the proper current rating for the tube?
Edit: for anybody else wondering, this is a good read
[url]http://www.tnt-audio.com/clinica/bias_e.html[/url]
Do different transistors make a big difference in sound like tubes? I bought a second set of transistors in case the answer is ye...Last edited by Zeppelin1007; 03-30-2017, 10:39 AM.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Welp. I replaced the transistors, made a dual resistor, soldered it all in and she fired up!
There is a second relay on a delay that turns on after the thing powers up that clicks on.
Now, before I button it all up, should I be checking voltages/bias? If so, I hope its at the terminals and not on the board.
Thanks guys. This has been sitting on my "someday I'll learn how to fix this" pile. Easily 6 years.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Ok guys. Sorry ive been slow to respond. Works getting out of hand and I'll be out of town for the weekend.
So that means i ordered the transistors and mica so they'll arrive by the time i get back
Ok ok on eBay. Makes sense. Just didnt know if there was some secret stash online i didnt know about lol.
Anybody see a problem with me buying single resistors and pairing them up? I see plenty of 5W singles on ebay. Don't feel like waiting the month for the slow boat from china (nor do i trust...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Ok guys. I found the transistors, mica sheets the right size..turns out i have some non conductive thermal paste.
Struggling to find the dual 0.22ohm 5w ceramic resistors, or, find them at a reputable dealer. Does Farnell have them as well?
Ive read i can just put 2 resistors in manually. Any specific kind that must be had?Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Petehall, gotcha. Makes sense. Any kind of thermal paste you'd recommend? And what if the mica doesn't come with the transistors? Is there a generic supply somewhere i can grab more?
DC offset where?Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
That's actually what I'm looking at petehall. Was trying to pinpoint what makes a transistor substitute compatible. Id obviously assume voltage and current ratings equal to and greater than the existing ones.
Question: I saw a guy on youtube replace some transistors with NTE based ones, that came with a glass/plastic plate. Whats the purpose of this? the ones i pulled off had little sticky pads on the back for the heatsink. How is this different than me putting some thermal paste behind the transistors before i...Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
The old 2SB1558 and 2SD2387? yes. Both showed shorts from B to E in both directions both in and out of circuit.Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Success! She fired right up!
OK! Now the fun part: Transistors and resistors.
Thanks a ton guys!Leave a comment:
-
Re: Onkyo TX SV727: Found bad transistors, what else?
Jiroy, this is what the guy i know uses
[url]http://www.apple.com/shop/product/HJ102VC/A/flir-one-for-ios-personal-thermal-imager?afid=p238%7CsLXTwavx4-dm_mtid_1870765e38482_pcrid_52243358770_&cid=aos-us-kwgo-pla-btb-all--slid--product-HJ102VC/A[/url]
China is good for some things, but electrical components...ehhh little iffy on. There is a massive industrial surplus here in Ohio that's never let me down when i need ancient parts that arent made anymore. I'll give them a shot too.
Update:...Leave a comment:
No activity results to display
Leave a comment: