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Pionner QX949 - FM no sound

Halisson

Halisson

Member
Hello guys.

In Brazil it is not common receivers monsters. I will need to order the parts from another city, so ask your help, please. Sorry my bad English.

I received from a friend a Receiver QX949 in excellent condition, great original part, capacitors, etc.
Aux and other functions OK.
AM works well increases and decreased Signal meter, but the FM is silent all, at all times.
The mounting plate is ANP-334 and not AWE-027 as the service manual.
The capacitors are all unique, I think of all exchange.

Wafer switch is clean.

Tensions located:

HA1138 - AM
1 -11.37
2 - 2.75
3 - 11.28
4 - 11.98
5 - 4.7
6 - 9.97
7 - 1.98
8 - 0.87
9 - 0.00
10 - 3.54
11 - 4.1
12 - 13.1
13 - 2.65
14 - 2.58
15 - 2.62
16 - 0

HA1137 - FM FI

1-0
2-0
3-0
4-0
5 - 0,63
6 - 0.91
7 - 0.10
8 - 0.8
9 - 0.8
10 - 0.6
11 - 13.89
12 - 0
13 - 0
14 - 0
15 - 0
16 - 0

HA1142 / HA1156 - DECODER STEREO

1 - 13.4
2 - 0.5
3 - 0.6
4 - 10.15
5 - 10.11
6 - 5.50
7 - 0
8 - 2.34
9 - 2.34
10 - 1.66
11 - 2.42
12 - 2.4
13 - 2.4
14 - 3.22

Q1 - 11.2 3,07V
Q2 - 0.7
Q3 -7.7
Q4 -7.6


HA1201

1-0
2-1.46
3-0
4-1.46
5-12.74
6 - 14.1
7 - 14.1

pinout ASSEMBLY

3 - FM mode 14.1 (am mode, 0v)
4 - mode am 14.1 (fm mode, 0v)
5 - 0.4
6 - 0.4
7,8,9,31,10,32,11,12,13, - 0
14 - 1.69
15 - 5.45
16 - 10.17
17 - 10.26
18 - 1.67
19 - gnd
20 - 14.08
21-0
22 - the pin
23.24 to 0
25 - 12.2
26 - 11.6
27 - the pin
28-0
29-0

Mute key works normal.
No change signal on FM mode or FM Auto meter.

Best Regards,

Picture to ANP-334 Tuner board.

http://imgur.com/a/SBtQF



 
Last edited:
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chazix, tks for help.

By validating the information I had misspelled the HA1137 IC voltage on pin 5. I have made the correction. This correctly information is 0,65v.

There were no changes to the switch in the OFF position. continuity test with the multimeter showed the switch to be working well.

Tks to assistence.
 
Halisson said:
This correctly information is 0,65v.
Click to expand...

This leads me to believe that the HA1137 is probably defective, because several of the other voltages are abnormal. In particular, pin 10 should have an internally-regulated voltage of about 5.6 volts.

Another possibility is a capacitor that should be connected between pin 10 and ground. (In the schematic for the AWE-027, it is a 0.47 microfarad electrolytic capacitor, but your board may be different.) It seems possible that, if this capacitor had severe leakage, it could cause the pin 10 voltage to be low.
 
Dear chazix ;
Follow your help, the CI arrived today , did subtituição IC and work FM. changing the IC, and all eletrolitics, but after check
ESR / capacitance of the capacitor in OK .
I appreciate your help by set the problems HA1137 the tip , the receiver is play FM very well .
One problem is that the sound STEREO is very sensitive. I will read the setting process according to the service manual and return to the result .
I appreciate your time and your willingness to help me with a tip, I solved the problem.
 
Last edited:
Halisson said:
I solved the problem.
Click to expand...

Parabéns, Halisson!

Replacement of the HA1137 should be followed by adjustment of the detector coil, which is T6 on the AWE-027 schematic. It is important to use non-metallic hexagonal tools for the adjustments, and the service manual also calls for the use of a distortion meter to make one of the adjustments. I don't know if you have this equipment

If you don't have the correct hex tools, my advice would be to not attempt to adjust the coil at all. There is a risk of damaging the cores.

If you don't have a distortion meter, you can still make the adjustment to the bottom core as the manual recommends.

Cheers,

chazix
 
Chazix,
Still enjoying your help. Okay with STEREO, as standard service manual and your tip.
A small, last problem: I have the indicator, front and rear L-R L-R has with volume 0 a little sound still goes. volume potentiometer is OK to GND, and to increase the volume, I still feel a loss of 10% right rear.
The volume is the same for all outputs (4) of the oscilloscope analysis.
Photo 1 - Volume 0 http://imgur.com/a/svUsj
Photo 2 - Volume by 50%, with lower R-R in the statement. http://imgur.com/a/EaPhs
I open a new topic with a new problem?
There is some adjustment to be done?
I did the power setting on the power amplification board, but did not change.
Thanks for your patience.
 
Halisson said:
I open a new topic with a new problem?
Click to expand...

I think that's a good idea. I believe that more AKers are knowledgable about amplifier issues compared to tuner issues.

I assume that all the level controls that surround the oscilloscope are set identically. I don't think there are any other relevant adjustments for high-level sources. (There may be other adjustments for CD-4 phono, but I don't think that is relevant here.)

I think it would be helpful to connect an audio signal generator to all four inputs of one the "4CH TAPE", and check whether the signal that reaches the power amplifier inputs is identical.
 
IIRC there is a block on the back that changes the votlages (B+) on the amps on side being 2 channel and flip it over, and it's in 4 channel. If so, unplug the 949 and remove the block and DE-OXIT all the pins and scrub with a small stiff brush (tooothbrush is fine, just don't use the wife's or girlfriends, better if they didn't know of each other), then DeOxit the sockets and run the block in and out a few times to scrub the sockets. Re-Spray, and let drain and dry a couple hours. See page 11 of the Owners Manual. Recapping the Main Tone board or what ever board the volume pot is on, may solve the problems you are having with the volume. REPLACE the FOLLOWING Transistors on any board they are found. 2sa725, 2sa726, 2sc458, and 2sc1451. These are the TOP 4 in the AUDIOKARMA ABI(Audio bureau of Investigation) TOP TEN WANTED LIST for KILLING PIONEER GEAR. The 2SC1451 heads the list, with the 725&726 tied for 2nd, with the 458 in 4th place. They cause all kinds of problems and start with noises (I liken it to the Breakfast cereal "RICE KRISPIE's" Once you get the Snap, Crackle, Pop from the speakers, start hunting for transistors. As for the 1451, it's so bad that if an initial inspection of a unit once home reveals them, REPLACE IMMEDIATELY and don't run the unit before replacing it/them. They will take out a complete Amplifier board without remorse, and absolutely no warning. The other 3 aren't as bad but they can cause widespread damage. .

These are replaced with FAIRCHILD transistors as follows; All available @ Mouser.
2sa725 & 2sa726........KSA992
2sc458........................KSC1845
2sc1451......................KSC3503.

They are inexpensive, and shipping will cost more than the parts (especially to the Southern cone). Try and make one order of all parts needed or anticipated.

Owners manual, Color Brochure, Service Manual, Service manual supplement, and schematics are on this page. http://www.kallhovde.com/pioneer/Pioneer/Main scan page.html CTRL-F and type QX-949. It will scroll down to it. D/L all documents for it if you have not done so. Then bookmark the link for future purchases of PIONEER Gear.

I checked with pioneer parts and got a list of capacitors using the ANP-334 in their search and the results came back (using a partial number : ANP-33* and about 12 different cap numbers came up.) Considering the 949 came out in 74, it's probably one of the units pioneer is culling out of the database. The ANP-334 may have been a mid 80's replacement board. It's possible that PIONEER used the ANP-334 as replacement parts for both the AWE-027 (949) and the AWE-041 (949A).

Larry
 
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Larry,

First I apologize for the delay. I was sick and returned this week.
I am very happy to learn from the forum tips, people are not afraid to share knowledge. This is grateful!

I clean the key but had no effect 4 or 2 channels, but I confess that an improvement. The problem was intermittent.
With the oscilloscope has detected serious difficulties in adjustment plate and severe acute adjust if seen several cold welds, improved perfectly leaving the volume accompanied the channels.
The question of the meter with the altered light, just take apart and located one of the metal parts were poorly connected. I did a complete overhaul cleaning with clean spray contacts and adjusting the screw torque. It was 100%

I appreciate your help and your materials to help in the learning process and diagnose the problem.

Best Regards,

Halisson
 
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