Pionner SX1980 No light fine tune, stereo, lock

[Halisson]

Hello guys. I am from Brazil and I maintain some receivers but the Pionner SX1980 is not very common equipment here. I searched for a lot of research before creating this topic.
Started with the 2SK34 with problems what solved with the tip of substitution (markthefixer) and some more repairs in the source and everything is with the tensions in order.
However, I do not have AM tuning (this does not interest me), but the FM has tuning but does not indicate anything and the three light fine tuning, stereo, lock function lights do not work, but I have FM tuning and it does not change with FM in mono or stereo and Fm Muting.
The voltages of the ICs are:
pa1001
1 - 2.0
2 - 2.0
3 - 2.0
4 -
5 -
6 - 5.7
7 - 5.7
8 - 5.7
9 - 5.7
10 - 5.7
11 - 12v ( wrong tension compare service manual )
12 - 4.09
13 -
14 -
15 - 5.6
16 - 4.2
pa3001
1 - 13
2 - 3.0
3 - 5.10
4 - 9.68
5 - 9.68
6 - 11.9
7 - 0
8 - 2.0
9 - 0.8
10 - 2.3
11 - 2.3
12 - 2.1
13 - 2.1
14 - 2.1
15 - 3.7
16 - 0.3
I still have not changed the capacitors and it was only a few hours ago than some kind of diagnosis. I note on the oscilloscope some kind of voltage variation on pin 1 and pin 2 on the PA3001 when moving the tuner.
I also tested with an external antenna, not changing the problem.
Thanks for any help.

 

[rcs16]

11 - 12v ( wrong tension compare service manual )

That is the supply, it can be off by a volt.
Search for turbotx threads on his troubleshooting of his sx-1980 tuner.

 

[kevzep]

I think first you need to establish if the Tuner has FM Stereo to start with.
What sort of RF test equipment do you have?

 

[Halisson]

I think first you need to establish if the Tuner has FM Stereo to start with.

kevzep, tks to reply.
I have FM tuning with good quality.
I did a troubleshooting with the transistors which were OK (q11, q14, q15) and discovered two new features:
1 - The inductor L5 (22uh) was fisical damaged, I made the substitution without alterations;
2 - Replaces the PA3001 IC for a HA11225 and I immediately had the Signal pointer working perfectly fine, but I still remain without the indication of stereo, fine tune and Quartz.
I have 13.5vdc on pin Q17 (collector).

What sort of RF test equipment do you have?.

I work with Audio amplifiers and I only have one Stereo FM Generator (home-made) capable of turning on the Stereo pilot lamp. Still, a simple 50mhz oscilloscope.
I have more than 10 local radios with strong signal to also provide strong signal reception, even with external antenna.

 

[Halisson]

That is the supply, it can be off by a volt.
Search for turbotx threads on his troubleshooting of his sx-1980 tuner.

Ok, tks.
I'm already looking for information.

 

[kevzep]

I work with Audio amplifiers and I only have one Stereo FM Generator (home-made) capable of turning on the Stereo pilot lamp. Still, a simple 50mhz oscilloscope.
I have more than 10 local radios with strong signal to also provide strong signal reception, even with external antenna.

This will be enough to work on this problem.

I had some quartz lock issues with the SX1980 I was working on so I will go back and have a look at my notes and see what I can tell you about this fault, it may be helpful.

 

[Halisson]

This will be enough to work on this problem.

I had some quartz lock issues with the SX1980 I was working on so I will go back and have a look at my notes and see what I can tell you about this fault, it may be helpful.

SOLVED!
Reading some comments in audiokarma, I detected that I could make use of some ICs, but without success. HA1137w, HA11225. But I detected that the CA3089E ( Replace to PA3001A ) could be a compatible item and so it was, it worked but without the indication of STEREO.
A brief retouch on the VR3 trimpot and Light Pilot Stereo Turn on!

Finally for an even more detailed adjustment of the Quartz Lock, a brief adjustment in TC ( APC Board ) (very, very thin) and was perfect.
Thanks for all the time dedicated to the help!

 

[kevzep]

SOLVED!
Reading some comments in audiokarma, I detected that I could make use of some ICs, but without success. HA1137w, HA11225. But I detected that the CA3089E ( Replace to PA3001A ) could be a compatible item and so it was, it worked but without the indication of STEREO.
A brief retouch on the VR3 trimpot and Light Pilot Stereo Turn on!

Finally for an even more detailed adjustment of the Quartz Lock, a brief adjustment in TC ( APC Board ) (very, very thin) and was perfect.
Thanks for all the time dedicated to the help!

Excellent result!!
Yes well, anything to do with the Quartz lock, is all on the APC board, in the unit I had which was faulty, it had a +5V power supply issue to the APC board, the 5V runs the 100khz oscillator, without the 100khz oscillator, no quartz lock....

 

[Halisson]

Excellent result!!
Yes well, anything to do with the Quartz lock, is all on the APC board, in the unit I had which was faulty, it had a +5V power supply issue to the APC board, the 5V runs the 100khz oscillator, without the 100khz oscillator, no quartz lock....

Thanks for the answers.
It's all working still perfectly fine, FM, stereo separation, etc.
But I noticed a slight imbalance: When touching the touch, (fine tune on) the Tunning pointer drops far to the right, and when you release the touch, center the tuning in the middle and turn on the stereo.
I could not understand the logic of this happening. Is it the fault of the integrated circuit I put in?

Please check Pictures :

Tuning Right on touch :
https://uploaddeimagens.com.br/imagens/49089b6f-de3f-424b-bba6-c6247fdf9a65-jpg
Tuning Center release touch :
https://uploaddeimagens.com.br/imagens/f28c53bd-2401-4a31-8fee-f0a951d1c33f-jpg

 

[rcs16]

Did you re-align the quad detector, since you replaced the PA3001A with a ca3089?
I am not sure if they are exactly identical.

 

[Halisson]

I am not sure if they are exactly identical.

I'm agreeing with you right now, I do not know if they're the same.
I did the alignment, but I did not recapitulate the capacitors.
I think of first replacing the IC with the PA3001A before a more complex troubleshooting, as I do not know where else there could be a problem after hours of component validation and settings.
However, in my country does not have this component and I will import.
I had a slight improvement in the VR3 setting on the APC board ( AWX 124 ), but nothing significant.

Tks,
Halisson

 

[Halisson]

I am again returning to thank you for all the help so far involved. I spent a long time without participating here due to personal problems, but now I'm back. Thanks for all.
Today the receiver has great tuning, I have a new IC PA3001, LEDs (functions) Tunning, Quartz Lock and stereo are ok.
I had an initial problem with little tuning I changed all the electrolytic capacitors, cleaned the variable capacitor, lubricated the middle of the shaft, replaced HA1201, checked the grounding of the block and had an excellent tuning capacity, better than Marantz 4400, Marantz 2110, Sansui 9001 for example. I had the opportunity to see another SX1980 working and I noticed that this one I'm working on, still has a small problem, but the tuning of this one is better than the old SX still all original.
The best signal amplitude is seen by the signal hand, but the tuning hand is not "dead center".
I made a video that can be seen below, and the photos can help to understand the relationship of the best signal and the display of the tuning (1) and the signal in the dead center and center and the smallest sign with less tuning capacity (2) .
The problem is not in the indication of the tuning pointer, but the whole reception circuit is showing the best signal reference on the right. I tried some adjustment on T1, TCA, TCR1, TCR2, TCR3, TC0, confirmed Q1, q2, q12 and q13 are functional, tested off the board, with a resistor between 12 to 25 terminal tuner assembly. I didn't do the test in q3 (Could it be the front end mixer?)
I have some radios with good signal and a Meguro MSG2161 to support the tests and MAK6571W.
The signal is set at 4.8 (80%) + -99dB.

Please check picture and video

Tuning Error

• Halisson
• May 31, 2020

Pioneer SX1980 problem tuning pointer - YouTube

• Halisson
• May 31, 2020

Pioneer SX1980 problem tuning pointer error deadcenter X best signal / dead center ok x smaller...

 

[Watthour]

My initial suspcion is that the 76KHz oscillator may be off. With a 50MHz oscilloscope, that signal should be measureable, The waveform will have to be carefully analyzed to determine its true wavelength, then calculate the frequency. Adjustment is typically made via VR1 for the PA1001-A IC.

 

[Halisson]

My initial suspcion is that the 76KHz oscillator may be off. With a 50MHz oscilloscope, that signal should be measureable, The waveform will have to be carefully analyzed to determine its true wavelength, then calculate the frequency. Adjustment is typically made via VR1 for the PA1001-A IC.

Watthour,
I am grateful for your help, every day I try to learn a little from these problems, and I appreciate the patience of those who explain.
I did the test that you suggested, as shown in figure IC1001 the reading result on pin 15 I managed to reach the minimum of VR3 at 64.5khz and the maximum 84khz ( autorange config the Tektronix TBS1052). Test with another PA3001 or HA1137, with no changes. In any setting in VR1 or VR3 there is no change in the signal pointer. Was this test what was this of recommended?
I did another test, when using the HA1137 ( but I can't get the STEREO light ) I made a comparison with no radio, see the result of the pointer in HA1137 and PA3001. When moving VR1, there is no change in the frequency read.

76khz

76khz

• Halisson
• May 31, 2020

1001 :

IC_1001

• Halisson
• May 31, 2020

Pa3001

PA3001

• Halisson
• May 31, 2020

HA1137 :

Ha1137

• Halisson
• May 31, 2020

I await further considerations.
thank you

 

[rcs16]

Did you re-align the quad detector, since you replaced the PA3001A?

 

[Halisson]

you may not believe it, but 1 minute before having the answer you wrote in my questioning, I read your tip and made the adjustment but underneath and everything was right at the time! I read your tip below:

Hi txturbo,

It is nice to see that you can confirm that your ckt is working properly.
While you are at it, tune to a part of the dial where all you hear is white noise, see what your meter reads to determine if you quad coil is centered, see if it is in proper alignment.
BTW how easy is it to access the lower core slug? without going through the top. If you have go through the top you will have to move the top slug which will throw that off.
I suggest if you have to go through the top, determine how much you turn the bottom slug, then once centered move the top slug back to where it was initially. Or if you have the proper low THD RF SG equipment, you can adjust the top slug for lowest THD.

I think before he changes U4 (PA3001-A), that he should try to see if he can adjust the quad coil for center. Lets hope that is all it is, so he does not have to do what you are suggesting.
We have no idea if there is something wrong with the quad coil, it could be a broken slug or something else as well

original post on https://audiokarma.org/forums/index.php?threads/1980-fm-tuner-dead.757802/page-3

I apologize for forgetting something simple, but I confess that I had already seen the adjustment from above (guidance 22 : Adjust T1 upper core to reduce distorcion in the AF output (REC Jack) to a minimum ), but I didn't know about the adjustment underneath

I thank everyone involved in sharing knowledge and solving the problem. The Tuner is now 100%

Definitely, now solved!

Regards,

Halisson