Restored SX-1050 Issue

[ILikePioneer]

Hi guys haven't been here for quite some time, I just rebuilt an SX-1050, everything new, caps, transistors,diodes, filters, etc. I used the list from here to get it done. When I finished the unit sounded great for a few days then I lost the right channel on FM and the left channel on AUX. Upon further investigation I noticed that I was missing the two 33uf caps on the equalizer board AWF-020, C18 and C17, I installed them and got back both channels on AUX but the right channel on FM is not there. I replaced the transistors on the equalizer but to no avail, nothing looks cooked, resistors all look new, all voltages from power supply look good. I went ahead and rebuilt the control board but still have the same issue, no sound on the right channel on FM. A nudge in the right direction would be helpful. Thanks

 

[zebulon1]

Clean the FM selector switch?
Set your meter to AC mV's and with the set on, FM selected and tuned to a strong station; ground the black probe to the chassis and take a reading on pins 11 and 13 of the tuner board. The meter will be jumping to the station transmission. It should coincide too what you are hearing on the good channel. This is checking the tuner outs.

Glad to have you back!
We missed you.

 

[ILikePioneer]

Hello Zebulon, when I probe pin 11 I'm getting mucho fluctuation ranging from 500mv AC down to 200mv AC, pin 13 on the other hand is relatively stable at 0.5 mv AC.

Low pass filter? reed relay?

 

[zebulon1]

Possible but there are a few other components in the path.
I'm betting it's one of the coupling caps.
Pins 6 and 7 are the channel outs on the HA1196 chip. Pin 6 is the right channel.
There are the coupling caps C70? and C47. Check the path the same way you checked the signal at pins 11 and 13.

You could do this as well:
Remember the Poor man's Signal Tracer?
"Signal tracer is 0.1uf nonpolarized, into the TAPE 2 play input, remember the other channel will be silent unless the mono button is depressed to share the signal between the two channels.
Tape 2 is used so that tuner remains selected and powered up".
It's an RCA Patch cord with the cap wound around the center pin.
Looking for a image.

 

[ILikePioneer]

I pulled the reed relay ASR-005,and now get stereo from both channels, it was very rusty under the outer metal cover. Can I leave it removed and be safe, or can I replace it with a reed relay from a SX-1250 spare tuner board?

 

[zebulon1]

If it's working it should be good. Hit it with a bit of Fader 5 to protect it.
Maybe something spilled on it?
Look the board over for any other rusty, corroded pieces.

 

[ILikePioneer]

If it's working it should be good. Hit it with a bit of Fader 5 to protect it.
Maybe something spilled on it?

Gonna try with the 1250 relay I'll let you know how it goes.

 

[ILikePioneer]

Replaced the original reed relay with the one from the donor 1250 tuner board and now both channels sound great. Yes this wasa basket case when I got it, had heavy rust issues mostly on the chassis. Thanks for the help, that was easy..

 

[jeffpaletz]

What does the Reed relay do?

 

[zebulon1]

It's part of the "FM Muting" circuit. Cuts out the signal(s) to the preamp.