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Onkyo Tx-8500 Trouble

very cool Jon Logan I was thinking I would have to give up :thmbsp:
and no tunes is really starting to suck. I also use this receiver to play movies, so Ive been playing them through the flat screen speakers which is horrible :thumbsdn:

Ok so yes the resistor in question is R-30 (1w47ohm) I replaced it with a 5w47ohm will this be ok?

Im off to test every thing then, None of the components have to be out of circuit to test correct?

-Tim
 
Yes, the 5W size is okay for R-30.

So, with the outputs removed and speakers disconnected, if R-30 is getting hot (sparking), the driver Q-11 is probably shorted. Transistor tests on the drivers.

Testing in-circuit should get you an idea if it's really, really bad or not. I think you're looking for shorts first. The high current through R-30 indicates that.

You're kind of out of luck for tunes at the moment. It's more enjoyable if you just absorb the process and not rush it. Bad stuff happens when rushing.

If the bad transistors and/or resistors are found, replace the bad drivers and resistors. Leave the outputs out (for the moment), measure DC(V) from Base to Emmiter on Q-07. That is the bias transistor. It should have about 3.6V or less. If it's much higher than that, the bias transistor is probably bad. When you get that voltage, it's safe to put in the output transistors.

Anyway, the next step will depend on the next measurement. Look at the drivers and resistors.
 
well, went and got another multimeter, the 20 dollar one craped out on me so I exchanged it for the 40 dollar one. I took the parts that you listed out of circuit because I didn't realize that my meter was giving me false readings. I guess it doesn't pay to buy a cheap meter. all though my cheap analog one has been working flawlessly for years..

test results, tested out of circuit.

* Resistors
--------------------
{47 ohm 1w}
#1 (47.5 ohm)
#2 (154.7 ohm) R-30

{2.7 ohm 1w}
#1 (3.0 ohm)
#2 (3.2 ohm)
#3 (3.0 ohm)
#4 (3.0 ohm)

{10 ohm 1w}
#1 (10.2 ohm)
#2 (r-32 cracked in half before i pulled it out)

{0.47 ohm 5w}
#1 (00.6 ohm)
#2 (8.5 k ohm)
#3 (38.3 k ohm)
#4 (00.5 ohm)
------------------

* Transistors -diode test

q08 (.544 volts) (base) to (emitter)

q10 (cant get any reading, looks like it arched across the top on the metal tab that the bolt goes through)

q09 (.557 volts) (base) to (emitter)

q11 (.596 volts) (collector) to (base)

Should I go ahead and order these parts from mouser.com or digikey? or somewhere else?
 
Yes, replace those resistors that aren't measuring right. ....the low ohm resistors i.e. 0.47 ohm measuring 0.6 are okay. It's the meter leads that add error to the very low ohm measurements. Replace anything cracked in half.

R-30 measuring 154 ohms is bad.


A forward biased transistor junction measuring .5~.7 are probably okay. Keep in mind that a transistor is like two diodes in series. You should be able to measure diode values (0.5~0.7) in one direction only and these diode reading should only occur from Base to Emmiter, and Base to Collector only. Any reading collector to emmiter in either direction indicates a bad transistor. ...just don't have your bare fingers on the leads. Your body's resistance will produce a inaccurate reading.

It looks like things are progressing nicely.

P.S. A good meter definitely adds measurement confidence!!

As I said before, this amp can be run without the output devices installed, as long as the speakers aren't connected. I think with the spark you saw earlier, there's still a bad transistor in there. Look at those drivers and pre-drivers. Q-8~Q-11
 
thank you, that clears things up a bit. Both smaller q10, q11 transistors are getting readings from the collector emitter and are kinda burnt looking. Im not getting any reading from collector emitter with q08/q09. The measurements I took earlier should be correct.
 
Digi-Key and Mouser are both good. Digi-Key has so many items that it can be frustrating to use their search browser sometimes.
....you can get >1000 hits on "100 ohm resistor"

You might as well order all drivers and pre-drivers, outputs, resistors and extras.
They are cheap enough and you're gonna get whacked for $10 bucks shipping anyway. The 2SB554 and 2SD424's are good transistors. ....used in higher quality stuff of the past. Soundcraftsmen, Yamaha, Onkyo, Adcom (I think). Anyway, extra's are good. You never know when some party will cause Onkyo case removal.

It might be good to shotgun replace all of the drivers and pre-drivers. They are cheap enough and sometimes transistors measure leaky which are harder to troubleshoot.
 
Ive got replacements for the 2SB554 and 2SD424's. How do I find replacements for the rest of the transistors since there discontinued?
 
This will work for Q-10
http://www.mcmelectronics.com/product/DISTRIBUTED-BY-MCM-TOSHIBA-/2SC2238

...and this will work for Q-11
http://www.mcmelectronics.com/product/2SA968&cid=prodCrossSell

Double check Q-8 and Q-9. They might be okay, and it would be better to not sub too many parts.

The main criteria for subs is their pkg style, breakdown voltage, current and bandwidth. These subs will probably be fine. MCM (last time I checked) had a $25.00 minimum. You can probaly get the resistors and maybe more 2SD424's and ...554's from them.
 
Thanks thats perfect I have a bunch of parts to order for my pioneer sx-1010 so maybe I can make one go of it..

*Diode function selected on meter

Q-08 (.521 v) collector to base

Q-9 (.553 v) collector to base, reversed probe polarity
 
That looks good Base-to-Collector on Q-8, Q-9. It is important to measure them Base-to-Emmiter and Emmiter-to-Collector as well. But I think those pre-drivers (Q8/9) have probably survived.
 
Nice to find out these survived, did the Base-to-Emmiter tests on them and got similar readings. The collector to Emmiter tests showed no short.

Do you think I would be able to get Q-10 & Q-11 from mouser by any chance?
 
Hi Jon Logan. I made a mistake. the smaller predrivers q08 and q09 were the ones that are bad. The mains q-10 & q-11 are fine. Ill need to order them. can you recommend replacements?

(Q-08)
Toshiba Japanese Transistor 2SC1628(O) -


Si NPN Power HF BJT
V(BR)CEO (V)=150
V(BR)CBO (V)=180
I(C) Abs.(A) Collector Current=50m
Absolute Max. Power Diss. (W)=1.0
I(CBO) Max. (A)=1.0u
h(FE) Min. Static Current Gain=70
h(FE) Max. Current gain.=240
@I(C) (A) (Test Condition)=10m
@V(CE) (V) (Test Condition)=5.0
f(T) Min. (Hz) Transition Freq=120M
Status=Discontinued
Package=TO-202var
Military=N


(Q-09)
Toshiba Japanese Transistor 2SA818(O) -

Si PNP Power BJT
V(BR)CEO (V)=150
V(BR)CBO (V)=180
I(C) Abs.(A) Collector Current=50m
Absolute Max. Power Diss. (W)=1.0
I(CBO) Max. (A)=1.0u
h(FE) Min. Static Current Gain=70
h(FE) Max. Current gain.=240
@I(C) (A) (Test Condition)=10m
@V(CE) (V) (Test Condition)=5.0
f(T) Min. (Hz) Transition Freq=120M
Status=Discontinued
Package=TO-202
Military=N
 
I'll have to get back to you. ...I'm at work. I was going to say the
2sB647/2SD667, but they are a little short on Vceo @ 120V. Everywhere else they are plenty good. I'll get back.
 
off topic* musics back on for now!

picked up a integrated receiver on Local Portland craigslist for a song.

1987 Yamaha natural sound integrated stereo receiver 2 channel 130W+130W

The sound quality's on par with some of my older receivers but I dont think it looks as pretty and also dosent have a tuner which is a -. I guess I could look for a separate turner? Positive is that it simultainiously drives a set of CV re-30's and a set of Carver ALS very nicely :music:

1306649_1.jpg


612969_1.JPG


Quality's very good, maybe one of the last. I might let this one go after the Onkyos fixed. Or might keep It for the bedroom if I can Find a good tuner and another turn table. I thought it was a steal though, 100 bucks. No one called him at all for days on it. :scratch2:
 
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no, good guess though. I think its a bit older than the M series. Its a AX-900u

ax-900.JPG
 
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hey Jon Logan,back on track,so go with japanese transistor replacements? should I go ahead and replace q10 and q11 with the ones I ordered?
 
Hi, Sorry for the delay. It's too bad that those transistors are obsolete. There used to be a deep array of choices for subbing transistors, and that's only if you needed to.

If those specs are right that you posted for Q-8 and Q-9, they have a TO-202var package? Sort of a flat larger transistor with a metal tab through it's middle. Those are larger than I would have thought for that part of the circuit. Anyway, I think you can use Fairchild KSC2682 for Q-8
and a Fairchild KSA1142 for Q-9 both available from Mouser.
http://www.mouser.com/Search/Refine...tor-+Emitter+Voltage+VCEO+Max|1&No=25&FS=True
Download these datasheets and note the pinout and change the way the laeds are soldered as necessary.

As far as Q-10 and Q-11 go, check them thoroughly with your meter's diode test. If they measure okay, just use them. Keep the subs you ordered on hand.

I'd recommend, at this point, putting in the replacements for Q-8 and Q-9, keeping the original Q-10 and Q-11 (if good), removing the output devices, disconnecting the speakers and then making some DC offset and bias voltage measurements, assuming things don't smoke right away. If things smoke right away, there's still something not right in the output section area. ....maybe Q-10, Q-11, maybe bias, etc. Get the subs for Q-8 and Q-9 and we'll go from there.
 
Ill order them asap ty. The originals look exactly like Q-10 and Q-11 but they are smaller.

Heres pictures of the originals. See how the tabs on Q-08, Q-09 look burnt?

21bpug4.jpg



9s748n.jpg
 
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