Hello all!
I have a receiver Onkjy Tx-7430 with it is all right ?! Only it does not work stereo and automatic search channel . Please help in what may be a fault?
Thanks in advance!
Here's the schematic:
I have a receiver Onkjy Tx-7430 with it is all right ?! Only it does not work stereo and automatic search channel . Please help in what may be a fault?
Thanks in advance!
Here's the schematic:
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Is the signal strength strong enough ? These units often only work correctly with a decent rooftop aerial.
Have you checked the tuner is working properly and I hope you know what frequency to set the VCO if it has been twiddled.
The signal is just fine!
When I turn the stereo / mono, mono to hear music on the stereo does not have anything ?!
The indicator LEDs on the stereo does not shine.
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Referring to the manual, section 5 on page 11:
During FM reception, this is operated by the IF level detection and zero cross detection circuits included in the FM IF & AM system IC of Q103 and by the noise component detection circuit of Q113. When a station is tuned, the output of all outputs go to the low level so Q703 goes from on to off, causing pin 22 of the controller IC to go to the high level to complete auto search tuning.
I could be worth checking that the above behaviour is correct as your problem seems to be related. Note that Q103 is not a transistor, it's a 24-pin IC (LA1266), the FM IF and AM system.
During FM reception, this is operated by the IF level detection and zero cross detection circuits included in the FM IF & AM system IC of Q103 and by the noise component detection circuit of Q113. When a station is tuned, the output of all outputs go to the low level so Q703 goes from on to off, causing pin 22 of the controller IC to go to the high level to complete auto search tuning.
I could be worth checking that the above behaviour is correct as your problem seems to be related. Note that Q103 is not a transistor, it's a 24-pin IC (LA1266), the FM IF and AM system.
adjust FM IF
Tune to a station near 98 MHz.
Connect mV meter between TP1 and TP2.
Meter should indicate about 0 mV, carefully trim L101 to 0 mV.
Best regards, 968driver.
Tune to a station near 98 MHz.
Connect mV meter between TP1 and TP2.
Meter should indicate about 0 mV, carefully trim L101 to 0 mV.
Best regards, 968driver.
That is not really the best advice. Messing around with the RF alignment before exploring all other possibilities is illogical. It is highly unlikely that L101 has become misaligned by itself.
I would begin by checking the operation of Q703 in the auto search tuning circuit as described previously. Then the stereo multiplex decoder IC, Q201 TP-4 pin to see if the voltage changes when a stereo signal is being received.
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Yes, between TP1 and TP2 you have to measure about 0 mV DC (+/- 50 mV), when tuned at a station around 98 mHz.
Adjust L101 for as close to 0 mV as possible.
Turn the core slowly and watch the mV meter.
This coil gets misaligned over the years by itself. It is a very common failure in almost all FM tuners, so nothing very special.
Adjust L101 for as close to 0 mV as possible.
Turn the core slowly and watch the mV meter.
This coil gets misaligned over the years by itself. It is a very common failure in almost all FM tuners, so nothing very special.
Memory and stereo is not working and tuning does not work !?
the voltage at TP1 and TP2 set at +/- 3mV😉
This is what I understand you are saying:
1) The receiver operates in mono mode correctly when manually tuned.
2) Stereo FM mode doesn't work when stereo mode is selected - stereo indicator not lit.
3) The automatic channel search does not scan.
Select stereo FM mode. Connect a working FM aerial and manually tune to a known stereo station having a good signal strength. Note the current rotational setting of R201 before starting. This pot sets the 19KHz VCO frequency for the stereo demodulator. It may be a good idea to clean the pot using a suitable contact cleaning product. Slowly rotate R201 and see if the stereo indicator lights up at any position. If it does, reduce the FM signal strength by tuning to a weaker station or shorten the aerial and re-adjust R201 so that it is set to the middle of the point at which the stereo indicator illuminates. If the stereo indicator does not illuminate at any position of R201's adjustment range, connect a DC voltmeter between TP4 and ground and repeat the adjustment above by looking for a low voltage transition when a stereo signal is being received.
The channel search issue can then be investigated afterwards.
Hi, nations!
With Tere and tuning works OK!, memory now is not working and sound amplifier 1/3,what next?
Thanks!
With Tere and tuning works OK!, memory now is not working and sound amplifier 1/3,what next?
Thanks!
Did you follow my instructions in post #11?
So you have the FM stereo mode and its indicator lamp now working properly?
Please explain what is meant by "sound amplifier 1/3"?
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With stereo m and tuning is until! Configured for L101 DC voltage at about OVdc.
Now the problem is when I answer the Max sound cue is about 30%!? Where to look for problem?
Iso So I have a problem with memory? the receiver will memorize the FM channels?!😕
Thanks!
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It appears that english is not your first language and consequently I cannot clearly understand what you are saying. Exceptionally, you could try including your native language in a new post, stating the language. Thanks.
Native language is Serbo-Croatian!
Wednesday stereo and tunig with the L101, with him, I've set the voltage at TP1 and TP2 to 0V!
It remains now about the problem of amplification and memory.
When you turn a volume max, to weight gain is about 30%, the same does not work store channels. That's why I asked for help in order to solve this problem?
Thanks!
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Thank you for making your previous post clearer and for confirming your language Tony. So, you have realigned the FM quadrature detector by adjusting L101 and the FM stereo mode is now working correctly.
The other problems you report are: low volume and the radio stations are not being stored.
For the station storage problem, it could be that the controller IC, Q702 is not receiving the correct "station tuned" voltage level on its pin 22. This is necessary to allow the controller to complete its auto search tuning. To test this, I propose the following:
Using a DC voltmeter, connect the positive probe to pin 22 of Q702 (OR to the collector of transistor Q703). The negative probe goes to 0V/ground. Adjust the tuning such that a radio station is NOT being received. The voltage measured should be around +5.6V. Then tune to a strong radio station. The voltage should then drop to nearly 0V. Please confirm that this agrees with your measurements.
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There is nothing to adjust. The test will confirm that the correct signal reaches the controller IC. We are looking for the voltage on pin 22 to change between "radio station tuned" (0V) and "radio station not tuned" (5.6V) conditions.
Update:
Without the correct voltages on pin 22, the controller will not be able to perform the auto-search of the stations and will not know if it has found a radio station to save in memory.
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