Pioneer SX-838 - Only noises from Phono 1 or 2??

[Farducci]

Hey all, great forum. Time for me to come out of the shadows and become and active participant. Thanks in advance for all the great information shared over the years, but I can't solve this one by reading alone.

Recently got a '74 Pioneer SX-838 back that I had loaned out for a few years to a friend. Sounds as great as the day I lent it out aside from no Phono output. Phono 1 or 2 both produce intermittent thumps, gurgles and cracks but NO music. Is it safe to assume the Phono Preamp is not functioning correctly? I'm sure the TT and connections are all fine.

After a thorough clean and visual inspection of boards and connections I put the receiver back into service... when listening very closely on phono, I can actually hear relay click on the left side of the unit after a few seconds... then I hear what sounds to be another relay click on the right side of the unit.

Is there something I can check with a decent multimeter? I have no other test equipment.

I was considering the replacement of the EQ Amplifier board as a whole unit?

 

[Ylli]

You cleaned the function switch, right?

The 2SC1313 and the 2SA725 used in the Phone Preamp (EQ Amp) are on the list of the 10 worst transistors. https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/. If you don't want to do a lot of troubleshooting, I'd suggest you just go a head and replace all 6 transistors on the board with those recommended in the link. This may or may not fix it, but would be the easiest place to start.

 

[Farducci]

You cleaned the function switch, right?

The 2SC1313 and the 2SA725 used in the Phone Preamp (EQ Amp) are on the list of the 10 worst transistors. https://audiokarma.org/forums/index...ilure-prone-whatever-and-replacements.731653/. If you don't want to do a lot of troubleshooting, I'd suggest you just go a head and replace all 6 transistors on the board with those recommended in the link. This may or may not fix it, but would be the easiest place to start.

Yeah, everything has been cleaned with De-Oxit and all knobs and switches work perfectly without a hint of static or crackle. I have the transistors on order... I'll replace and see what happens and go from there. Cheers.

 

[Skywatcher]

Hey all, great forum. Time for me to come out of the shadows and become and active participant. Thanks in advance for all the great information shared over the years, but I can't solve this one by reading alone.

Recently got a '74 Pioneer SX-838 back that I had loaned out for a few years to a friend. Sounds as great as the day I lent it out aside from no Phono output. Phono 1 or 2 both produce intermittent thumps, gurgles and cracks but NO music. Is it safe to assume the Phono Preamp is not functioning correctly? I'm sure the TT and connections are all fine.

After a thorough clean and visual inspection of boards and connections I put the receiver back into service... when listening very closely on phono, I can actually hear relay click on the left side of the unit after a few seconds... then I hear what sounds to be another relay click on the right side of the unit.

Is there something I can check with a decent multimeter? I have no other test equipment.

I was considering the replacement of the EQ Amplifier board as a whole unit?

As Ylli says, replace the transistors, though I doubt they all failed at the same time. But more importantly replace the two light blue Sanyo capacitors. They are notoriously well known to fail and become "resistors", and have been dubbed "capsistors". You can use either film (preferred), or electrolytic to replace them with. In fact replace all the other electrolytic capacitors on that board while you are in there (if they are still original). No sense in doing just a "partial repair" and have to go back in later. Also, the SX-838 has some of those Sanyo capsistors throughout other boards and would be a good idea to target those as well before they cause the magic smoke to be released.