Onkyo T-9990 Tuning Problem..?

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,

So, the deal is the discriminator (or whatever the thing uses) might be misadjusted to one side of the S-curve, or the ceramic filters have drifted.
With the "Super Narrow" filter in there, you have lot's of IF sections with ceramic filters that need to be more or less matched. Matched in frequency and bandpass. You can imagine what can happen if one is tuned south of 10.7MHz and the rest are centered about 10.7MHz. The center of the bandpass is now south of 10.7. This can cause the offset tuning as well.

The ceramic filters (sometimes) just fail. Is it thermal stress? Is it mechanical shock? I don't know, but they do (sometimes) go bad and need to be replaced. Look for a set of matched devices if you're considering replacing the IF filters.

I was looking at the schematics, and...from as far as I can understand...the IC "LA1235" should act as a discriminator (demodulator)..? Is that correct..?

You mentioned that the discriminator might be misadjusted..? If you look at the attached pict9, there are two points that could be adjusted...TP1B and TP2B.
(They are, sort of, connected to LA1235)

Would maybe readjusting them solve this problem...? I mean, is it worth trying..?

The other thing, would replacing LA1235 maybe help, could that IC be faulty..?

I'm asking these questions purely based on my assumption that the LA1235 is in fact a discriminator circuit, but it would be great if someone can actually have a look at the schematics, and point out what is truly acting as a discriminator in this tuner...what are it's components..?

I have attached few extra picture.

Tnx,

The service manual with alignment instructions is at http://www.eserviceinfo.com/downloadsm/49362/Onkyo_TG10.html
(This is for the Onkyo T-G10, which is identical internally to the 9090II)



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Definitely get the full manual with it's alignment procedure.

L-159 (and/or L-107) looks to be the adjustment. You can confirm by getting the data sheet for the IF IC and confirming it's peripheral coil functionality.

Yes, the IC might be bad. Yes, it is possible that adjusting the IC, really the coil, might fix it. There is no real adjusting of the IC. It is a fixed block and relies on external components for tuning/adjustment.

Don't write off the ceramic filters.

It sounds like the tuner simply needs alignment. You need a stereo FM alignment generator and a distortion analyzer to do this properly. The distortion analyzer can be replaced by a detector probe and an oscilloscope. If you don't have the equipment, take it to a reputable tech with rf experience.

Thanks a lot to everyone, your answers helped me a lot to get some ideas how everything works.

I got the service manual for the T-G10, with detailed instructions. I spent quite a lot of time goggling, trying to fine some more information, and to learn about the stereo FM alignment generator and a distortion analyzer.
I also called few tel. numbers trying to find (not reputable, but any…) rf technician, but with no success. Croatia is a small country, so I guess I’ll have to search hard.
Anyway, the main Croatian state’s FM broadcast operator has a contact number on their website, so I’ll try to ring them next week, they must know and have some rf technicians.

I don’t have any of the equipment myself (stereo FM alignment generator/ distortion analyzer), but after everything I read I got some ideas.

They might be really stupid, but maybe they are not…!?!

So, from the alignment instruction, and from what I understand…one would need to apply a 1khz signal from a stereo FM alignment generator to the antenna input of the tuner. And than measure and adjust the voltage on pins TP1A/TP2A and TP1B and TP2B to a value of “0” volts…right?
I got the idea to use my iPod with the iTrip as an stereo FM alignment generator.
(…iPod with iTrip is basically used to listen to a music from your iPod on any FM tuner’s frequency, wirelessly. Transmitting frequency could be adjusted on iTrip itself, and could be anything from 87.5-108MHz. And iPod needs to be placed close to a tuner, as the transmitter power is very weak).

Than I downloaded 1khz signal from the internet, and uploaded that file to my iPod (as any song). I adjusted my iPod/iTrip to play/transmit 1khz signal on 99.00 Mhz.
And on the T-9990II tuner, on 99.00Mhz, I could hear 1kHz sound, at about 40db…(TEST1).
Than I measured voltage values on TP1A/TP2A and TP1B/TP2B…with all three (different) IF BAND settings…(WIDE, NARROW and SUPER NARROW).

I did three tests:

TEST 0: With outdoor antenna connected, I tuned to a various frequencies (mainly around 99.00MHz)…where some radio stations were/are broadcasting. (So, voltage measurements taken with the radio station’s signal.)

TEST 1: Outdoor antenna disconnected, iPod with iTrip used to transmit 1kHz signal on 99.00MHz…with signal strength at 40…(40db). Piece of wire used as antenna.

TEST 2: Same as TEST1, but this time I connected adjustable 20db gain antenna amplifier between the tuner’s antenna input and a piece of wire. Now I was able to amplify the 1khz signal from previous 40db to a 60 db.

You can see all the voltage measurements on pict15.

As you will notice voltage values between TP1A/TP2A vary slightly (1.13V-1.8V) with different IF BAND settings, while voltage values between TP1B/TP2B is everywhere constant (3.53V).
Also, voltages are very different from what they should be…the adjustment manual says that values should be zero “0” volt…?!?

I know these procedure I did is far away from the correct and precise (as taken with a proper stereo FM alignment generator and a distortion analyzer)…but maybe is enough just to give you/us some more ideas with what might be wrong.

Now, just to generally understand fm tuners a bit more, and because I like to learn new stuff…can please someone just confirm that the LA1235 IC, with it’s surrounding components is actually tuner’s discriminator…?
Also, in the T-G10 alignment manual, R101 and R190 should be also adjusted, but via oscilloscope. Fot them, it says in the manual “Adjust For: Variable Point.”
What does that mean…”Variable Point”…can please someone explain shortly??
Regarding the R101 and R190, on pict14 you can see they are adjusted very differently. From the schematics, I think they have 10k value, so from the picture, as how they are currently adjusted, I guess the difference among them is around 1k-2k ohm..? Is that normal…?

I hope I explained my measurements well enough for everyone to understand what I was doing.

Your idea will work, to use the Ipad and Itrip as a generator. You must tune to a point where there is no station broadcasting, so you will have no interference. Then adjust the first IF transformer, which should be in the tuner pack, for the strongest reading on the signal strength meter on the tuner. Then follow the directions in the manual for adjusting the discriminator. If you can post the manual somewhere for download, I'll take a look at it. You really should have an oscilloscope to make these adjustments, but you can use your meter on the output of the tuner (at some point the instructions will probably tell you to adjust for maximum output with minimum distortion.) For the minimum distortion you will have to go by sound. It is actually pretty easy to hear when a sine wave starts to distort. Not as precise as a distortion analyzer but it will be better than it is now.

Well, that sounds good.

With the iPod and iTrop acting as a transmitter, the 1khz signal is very strong and clear with no interferences from other real radio stations whatsoever.

I don’t know what is "the first IF transformer", so I’m afraid…you will have to let me know, and guide me.

What do you mean by “you can use your meter on the output of the tuner”…would that be a voltmeter connected to a TP1A/TP2A/TP1B/TP2B pins…?

You can easily download the full service manual for T-G10 from the link above…the one that “bobschneider” posted (post #4).

http://www.eserviceinfo.com/downloadsm/49362/Onkyo_TG10.html

It would be great if I can at least make it tune correctly, and than later, when I find a proper rf tecnician, I’ll have it adjusted with a proper equipment.

I can also send you the service manual via email, just let me know your email address (via personal message).

Got the manual.
Let me go through the adjustment procedure and see what has to be modified to use what you have. I won't get back to this until tomorrow evening at the earliest.

No worries at all, whenever you get a chance. Many thanks...

minor comment - I don't know how "digital" the 9990 is, but many digital tuners can't lock into stations unless they are at an odd .1 mhz frequency - i.e. 99.0 mhz won't tune, but 99.1 or 98.9 will due to the way stations are assigned and the controller is prorammed. (however, in Europe it shouldn't make a difference)

sregor said:

minor comment - I don't know how "digital" the 9990 is, but many digital tuners can't lock into stations unless they are at an odd .1 mhz frequency - i.e. 99.0 mhz won't tune, but 99.1 or 98.9 will due to the way stations are assigned and the controller is prorammed. (however, in Europe it shouldn't make a difference)

Click to expand...

That's true for most North American market digital tuners, but ones for other markets can tune to "even" decimals as well, since there are stations on those frequencies outside North America.

But my US Onkyo 9090ii (the US version of the OP's 9990) can tune in .025MHz increments, presumably so you can slightly mistune a station to avoid interference from a nearby stronger one.


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It looks like you can do the IF alignment steps, wide, narrow and super narrow bandwidth, by putting the IF mode in wide, and adjusting the L105 for the highest reading on the signal strength meter. Then do the same thing in the super narrow band mode, adjusting L152.
For the muting adjustment, wide and narrow, use the multimeter on DC as they say. I think the R101 adjustment is the muting threshold. Leave that alone, you don't have a calibrated level with which to set it. Later you can go back and set it so that it just mutes when you try to tune in a fairly noisy distant station.
Same for the Super narrow. The 0V adjustment is the discriminator, and that is the voltage the tuner uses to detect that the station is properly tuned in.

First, I will just mention...I'm not sure if I was measuring the voltage values on points TP1A/TP2A and TP1B/TP2B correctly...?!?
I connected one wire of the voltmeter to TP1A, and the other one to TP2A. And than same for TP1B/TP2B.

From reading the alignment instructions on the website link below...I was, I think...suppose to be measuring voltage values between

TP1A pin and (maybe) ground, and between...
TP1B and ground...for aligning the L105/L159.

TP2A and TP2B...(and, I suppose...ground for each one) are supposed to be measuring points for adjusting R101 and R190.

Link: http://home.iprimus.com.au/toddemslie/T-9090-alignment.html

I was doing it wrong, wasn't I...?

Is actually "ground" the "other point" (other wire on the voltmeter, so "+" on TP1A , and "-" on ground) when measuring values on TP1A, TP1B, TP2A, TP2B, TP7A, TP7C etc...???




Now, for these new procedure, just to double check, that I got everything right and not to make any mistakes…



Regarding the first adjustment…it says:

”IF adjustment of wide and narrow”….Fig.2..…point: TP7A….use Oscilloscope....DC 500mW…Maximum”

How do I do that..?
I apply around 10db strong, 1khz signal with my iPod…..ok?
It says to use oscilloscope…do I anyway use my Voltmeter/Multimeter..?
And where do I connect the Voltmeter’s wires..?
Adjustment manual gives only one point…TP7A. What is the other one…ground?
(Same for point TP7C...?)


Second adjustment...
As per muting adjustment of wide, narrow and super narr.….L159 / L107

I do that as described before…1khz signal / 60 db / use voltmeter on TP1A/ground and TP1B/ground and adjust that point's values to “0” zero volt…?
Both of them...? Correct...?


(As a matter of interest, the voltage needs to be zero volt on those points, and I measured between 1,5V and 3,5V. At the moment, is it really that much out of the proper alignment...?)



Third adjustment...
Do I need to touch R101..?
You first mentioned to leave it alone, and than to go back and set it so that it just mutes when I try to tune in a fairly noisy distant station..?

What is the function of R101…? What doest it do..?
Is it...when I tune into a station..I can hear sound...and than I adjust R101 to the point the station goes mute(no sound)...and than I re-adjust it again just a little bit back, so I can hear the sound again.

Please re-read my last post carefully. Most of your questions are answered there. You are supposed to put the meter on DC volts , 200mV range, but maybe 2V range to start, and measure between the 2 test points, NOT ground.
You are correct about R101.

Ok…so, basically when adjusting L105 and L152, I visually use tuner’s signal strength meter (green bar display 0-100) and look for the maximum signal.
(For this, I don’t use Voltmeter at all, and I don’t need to measure anything on points TP7A and TP7C…?)


For muting adjustment, I use points TP1A and TP2A (I connect voltmeter to these two points) when adjusting L159 and L107…and I need to adjust the voltage between them to a “0” volt.


To adjust R101 and R190, I can later tune into a radio station, and adjust the muting threshold, simply by listening the sound on the speakers.


I hope this it the right procedure.
I’m sorry to double check this again, but I just want to be sure that I’m going to do everything right…and not mess up things even more.
I do all sort of electronics, but I’ve never fiddled with the coils and adjustments before (simply because I thought one always needs special equipment to do that).

xmatrix said:

Ok…so, basically when adjusting L105 and L152, I visually use tuner’s signal strength meter (green bar display 0-100) and look for the maximum signal.
(For this, I don’t use Voltmeter at all, and I don’t need to measure anything on points TP7A and TP7C…?)


For muting adjustment, I use points TP1A and TP2A (I connect voltmeter to these two points) when adjusting L159 and L107…and I need to adjust the voltage between them to a “0” volt.


To adjust R101 and R190, I can later tune into a radio station, and adjust the muting threshold, simply by listening the sound on the speakers.


I hope this it the right procedure.
I’m sorry to double check this again, but I just want to be sure that I’m going to do everything right…and not mess up things even more.
I do all sort of electronics, but I’ve never fiddled with the coils and adjustments before (simply because I thought one always needs special equipment to do that).

Click to expand...

All correct. This is the only way you can do it without a scope.

Thanks a lot Warren. I'll try to do the adjustments sometime beginning of next week...to busy over the weekend, doing a loft conversion.