SX-626 No Stereo Seperation
- Thread starter mcdmgb
- Start date
Register to hide this ad
The stereo decoder is a simple 1 chip circuit, the ha1142. It controls the stereo /mono audio and also the stereo lamp.
If pin 8 has about 12.8v on it (main power) and the 4.7 uF cap connected to pin 1 isn't shorted, it is probably the chip. There are a few other resistors and a pair of coils that might go bad, but it is unlikely and the coils will be hard to check.
I don't know what controls the stereo separation, and if it is adjustable.
It's an OLD chip, and there isn't much info about it out there.
acme-sales seems to have it for about 12 bucks (no affiliation).
If pin 8 has about 12.8v on it (main power) and the 4.7 uF cap connected to pin 1 isn't shorted, it is probably the chip. There are a few other resistors and a pair of coils that might go bad, but it is unlikely and the coils will be hard to check.
I don't know what controls the stereo separation, and if it is adjustable.
It's an OLD chip, and there isn't much info about it out there.
acme-sales seems to have it for about 12 bucks (no affiliation).
The two service manuals I have access to are in the database:
1) Lo-res 2 meg art-155, art-027 with AWE-031 board (HA1142)
2) Hi-res 55 meg art-155, art-027 with AWE-031 board (HA1142)
The 3 7060's and the 5109 are what you eyeball in your receiver ?
IIAC the 7060's are IF amp stages, and the 5109 is a diff amp probably used as a mixer to generate the 10.7 mhz IF freq, although it COULD be the fm detector.
So that doesn't account for the ( fm detector maybe or the ) sterero decoder.
1) Lo-res 2 meg art-155, art-027 with AWE-031 board (HA1142)
2) Hi-res 55 meg art-155, art-027 with AWE-031 board (HA1142)
The 3 7060's and the 5109 are what you eyeball in your receiver ?
IIAC the 7060's are IF amp stages, and the 5109 is a diff amp probably used as a mixer to generate the 10.7 mhz IF freq, although it COULD be the fm detector.
So that doesn't account for the ( fm detector maybe or the ) sterero decoder.
Both the unit that's on the kitchen table and the SM that I have shows board AWE-011 as the tuner unit. I haven't looked at every board in the unit but the SM doesn't show a AWE-031 board. I have shkimmed the parts list for each board and the AWE-011 board is the only one to use ICs. maybe two different versions?
Mike
Mike
PM sent last night...
Sorry, I just found the 7 pm resend.
I'm bombed by spam and the latest trick is a name with a cryptic subject
with a huge attached .PDF
so: mike S626
was probably in the dozens of spam I blew away this morning.
I don't open the spam, as I want to keep my computer operative.
If it had said sx-626 or something more relevent or less cryptic I would have zoomed in on it immediately. Instead it hid in the crowd.
The q6 7060 is the FM detector, while the 5109 is part of a discrete stereo decoder. This makes it harder to troubleshoot, as you just can't treat the IC as a black box with a few passive components.
A short lesson is in order;
there is a 19khz "pilot" tone broadcast to signify the presence of a stereo broadcast in the raw fm demodulated signal, the stereophonic information is centered at 38 kHz (19×2, the second harmonic of the pilot).
The receiver doubles the frequency of the pilot tone and uses it as a phase reference to demodulate the double sideband modulated L-R stereo information at 23-53 kHz. The L+R is the 50hZ to 15kHz audio.
This doubling is done by the circuits including the 2sk30, 2sc870 and the many 2sc711's. The 2sc968 with C61 does the stereo indicator light stuff.
So far it is probably working, because the light behaves.
After that the second harmonic is fed to the multiplier circuit of the 5109.
There is only one adjustment besides the T7 (don't touch T7) and that's VR2 which is probably a separation adjust. You can try moving it, but be sure that you can return to the original adjustment.
I have to guess at this point, as without deep thought, the mono signal path is unclear.
I think that if the chip is dead, then the audio is getting through on monoural.
Because Q20 drives both the Q19 the stereo lamp circuit and T7 transformer which feeds the 5109, I think it is ok up to those points.
The 5109 can be subbed by the nte 917 (mouser.com 526-NTE917 @ 4.37 ea) but without a scope and a full schematic I can't be sure of just how the sound of the mono and stereo (with no or nil separation) signals gets out to the amp.
In other words, if a new 5109 doesn't get it going, and the transistors individually test ok, then it is a shop job.
I'm bombed by spam and the latest trick is a name with a cryptic subject
with a huge attached .PDF
so: mike S626
was probably in the dozens of spam I blew away this morning.
I don't open the spam, as I want to keep my computer operative.
If it had said sx-626 or something more relevent or less cryptic I would have zoomed in on it immediately. Instead it hid in the crowd.
The q6 7060 is the FM detector, while the 5109 is part of a discrete stereo decoder. This makes it harder to troubleshoot, as you just can't treat the IC as a black box with a few passive components.
A short lesson is in order;
there is a 19khz "pilot" tone broadcast to signify the presence of a stereo broadcast in the raw fm demodulated signal, the stereophonic information is centered at 38 kHz (19×2, the second harmonic of the pilot).
The receiver doubles the frequency of the pilot tone and uses it as a phase reference to demodulate the double sideband modulated L-R stereo information at 23-53 kHz. The L+R is the 50hZ to 15kHz audio.
This doubling is done by the circuits including the 2sk30, 2sc870 and the many 2sc711's. The 2sc968 with C61 does the stereo indicator light stuff.
So far it is probably working, because the light behaves.
After that the second harmonic is fed to the multiplier circuit of the 5109.
There is only one adjustment besides the T7 (don't touch T7) and that's VR2 which is probably a separation adjust. You can try moving it, but be sure that you can return to the original adjustment.
I have to guess at this point, as without deep thought, the mono signal path is unclear.
I think that if the chip is dead, then the audio is getting through on monoural.
Because Q20 drives both the Q19 the stereo lamp circuit and T7 transformer which feeds the 5109, I think it is ok up to those points.
The 5109 can be subbed by the nte 917 (mouser.com 526-NTE917 @ 4.37 ea) but without a scope and a full schematic I can't be sure of just how the sound of the mono and stereo (with no or nil separation) signals gets out to the amp.
In other words, if a new 5109 doesn't get it going, and the transistors individually test ok, then it is a shop job.
I moved VR 2 around and there does seem to be some separation when I listen through headphones. If I listen closely, I can hear the sound stage collapse switching to mono, but there isn't much there in stereo. I wonder if this is the best it gets for this model?
Mike
Mike
Well, you could spend about 7 bucks (~$4.5 + first class shipping) and swap the chip and see if that helps, or get it to a well equipped repair bench (fm stereo generator and scope etc), where adjustments can be tried etc... They would need the whole service manual.
jetman1979
Member
tape mon has fm bleed thru.
I just got a little pioneer entry level SX-424 real cheap. I noticed with the tape mon button pushed in I get fm bleed thru (not very loud). Is this normal?
Also the only lights are the signal strength and the dial pointer. I dont have dial lights or a stereo light. Easy fix?
I just got a little pioneer entry level SX-424 real cheap. I noticed with the tape mon button pushed in I get fm bleed thru (not very loud). Is this normal?
Also the only lights are the signal strength and the dial pointer. I dont have dial lights or a stereo light. Easy fix?