Onkyo T-9990 Tuning Problem..?

[xmatrix]

I’m very sorry it’s been a while since my last visit here but unfortunately I had to deal with some family problems that I wouldn’t wish anyone to happen.

Anyway…finally I got some time to open my T-9990 again and try to do some alignment.

So, the plan was to readjust “Muting Adjustment” for wide, narrow and super narrow…and set the voltage values to 0V…since my tuner couldn’t tune properly into an FM station (mainly only left tuning LED would lit even if the tuner was properly tunes into correct (any) FM station’s broadcasting frequency).

Before I started readjusting…the voltage value between:
TP1A and TP2A was…..1.854 V
TP1B and TP2B was…..3.53 V

I applied 50db…1khz signal on 99.00Mhz frequency…and I managed to adjust the voltage between TP1A and TP2A to a zero value. (I had to “turn in” the ferrite bit inside the coil L107 for around 4-5 full turns (inside direction)…to achieve 0V.
Well, that looked good…but unfortunately it wasn’t the same case with the L159.
Before starting, the voltage between TP1B and TP2B was 3.53 V. And the ferrite bit was pretty much in the middle of the L159 core.
Now, when I screw it in…almost all the way down in…there was no change in the voltage value at all. It would stay 3.53V. When I screw it out (other way…outwards direction) the voltage dropped only to 1.8 volt…and at that point the ferrite bit was almost about to drop out of the coil.
So, in other words, from one end to another…the voltage could only be adjusted between 3.53 V to 1.83 V. It wouldn’t go further down…
(On the other hand, just to point out…on L107, I was able to adjust the voltage between TP1A and TP2A…from +3.5V to -2.8 V…(that much I tried, although I believe it would probably go to more than -3.0 V)…so, not very professionally said…but both sides of the curve…plus and minus. I hope you know what I mean!
And between TP1B and TP2B…the voltage would only go from +3.53 V down to +1.83 V…never reaching zero, nor going to the other side of the curve (negative side)….so just one side of the curve.
(Just for info…that was with “+wire” of the voltmeter connected to TP1A/TP1B and “-wire” connected to TP2A/TP2B…although I thing that’s irrelevant.)
So, that obviously wasn’t a good sign…the fact that I couldn’t adjust the voltage to a “zero” V between TP1B and TP2B.
Consequently, (I guess)…the 3 tuning indicator LEDs remain in the same state…left on fully lit, the middle one (tuned)…being lit very, very faintly (picture attached)…and the right one would never lit.

Since the tuner was opened and the service manual gives the voltage values on the Q106 and Q157 (LA1235 IF section)…I thought it would be good to check them out.
I have to say…there are some big voltage differences (I’ve attached a picture)!
For example, on Q 106…on pin 12 should be 6.1V…I measured 0V (zaro) volt…! Pin 13 should be 1.5V… I measured 3.16V, pin 15 should be 0.5V…I got 0.61, pin 16 should be 0.6V…I measured 3.28V…!
On Q157…pin 7 should be 6.3V…I got 13.33 V…! Pin 13 should be 0.9V…I got 4.44V, pin 15 should be 0.4V…I got 0.61V…and on pin 16 which should have 0.5V…I measured 3.3V…!
As you can see, there are some huge differences. It certainly doesn’t seen right…and I wonder what could be the problem. Are the IF chips Q106 and Q157 faulty…? Can they change their internal characteristics that much..? Or have the surrounding semiconductors (…maybe capacitors) changed their values because of the tuners age..?
I do understand electronics to some extend…but I don’t really know how these kind of circuits exactly work…and why are the voltage values so different to the one given as a reference?

Has someone maybe got an idea what might be wrong…or what might be the problem…?

 

[dr*audio]

I think it needs a proper alignment. Sorry, but without proper test equipment there isn't much you can do.

 

[xmatrix]

It's such a shame that I wasn't able to fix it.

Any idea how much would the alignment of these kind of tuner cost..? At least...some rough price?

 

[dr*audio]

It's such a shame that I wasn't able to fix it.

Any idea how much would the alignment of these kind of tuner cost..? At least...some rough price?

If it's just alignment, no more than $100 USD. Just my opinion.

 

[RxDx]

Here are what claim to be 'simple' directions for aligning the T-9090 II.

I haven't had the guts, or the need, really, to attempt them.

 

[sab11ra]

Hi,

I hope someone on this forum might be able to help me.

I recenty bought Onkyo T-9990 (same as T-9090II) tuner, but it seem it has some tuning issue/problem.
There are 3 main problems that I discovered so far (…they are all connected together).

The main problem (first) is that the tuner can not "fully tune" into the station's frequency.

Let say I'm pressing UP frequency button..and let say on "100.00 Mhz" is a radio station. When I reach 100.00Mhz, the sound is ok, etc. but the “TUNED INDICATOR LED” (D722) never locks in (…3 LED diodes on the front panel...”<” left, “TUNED”, right “>”).
Only "left diode" (D721) is fully blinking (working) while tuning (UP or DOWN).
"TUNED" LED diode (D722-middle one) only comes on very, very little bit…while the right LED diode (D723) never comes on!
(So basically, just the left side of the S-curve as marked on the attached picture – Fig. 14…but only, kind of, first 1/3 of it).

Since the tuner is not able to properly "LOCK IN" into radio station's broadcast frequency, the sound is always MONO, unless I switch it on manually to STEREO.

And also, consequently…because not properly "locking in" the APR button is not functional (second problem).

Normally, once properly tuned to a station, APR automatically selects best IF settings, HI-Blend ON/OFF, RF mode (LOCAL or DX)…and the stronger signal either on ANT A or ANT B input.

But when pushed, APR always chooses SUPER NARROW mode, HI-BLEND ON and STEREO-OFF. Always, even for a local station with maximum signal!
That is because APR only works once the station frequency is "TUNED or FULLY LOCKED IN"...and in this case, since the middle LED diode is never fully on (LOCKED)…the tuner (or APR circuit) always thinks that the station frequency is not correct...because only "<" LEFT LED diode is ON.

More over, consequently third problem connected to this TUNING issue, is that the "Automatic Tuning" is also not working. It searches/scans indefinitely through the band, from 87.50Mhz to 108.00 and than all over again.
It never stops, because the tuner can never "lock in" into a station.

I don't know what is the reason for this tuning problem but I think it is most probably the age...and some components need replacing. …

I got the service manual and looking at the schematics diagram, I think there are two chips (ICs) that might be problematic.

They are "Tuning Indicator Drive IC" which is LB1450 and "IF System IC" which is LA1235.

Maybe they need replacing...I don't know. Or maybe some capacitors or some trimmers only need readjusting..?!?

Regards,

Hi i own a t-9990 all you nead to do is turn a l-159 just a very little untill you see the center tune lit be sure to be on 99mhz at wide position than switch to s narrow, stay on 99mhz and see if you still centerd if not slightly ajust l-159 untill centerd is lit ,than seek up and down the dial and you will see the improvmennt

 

[sab11ra]

Ps it works perfectly on my onkyo t-9990
Kind regards
Michael

 

[blargh22]

Hello xmatrix, I have a 9090ii with the exact same issues as yours. I was wondering if you ever got yours working properly.

 

[Scubzi]

Hello all. Thanks for your great input. I have recently bought a T9090-II with the exact same issue, not able to tune. I am going to try the suggestion from sab11ra on mine. I will let you know if I find the I-159 and adjusting it will fix the/my issue.

 

[Scubzi]

Just to confirm that my T9090-II was fixed by adjusting L-159 which is located at the center of the pcb. So very easy job. Thanks for your help.