Occasional random pop from Pioneer SX-1010

[Chuck S.]

I recently, via my son's purchase, find my self having a Pioneer SX-1010 back in the house. The good news first, everything works. The unit was serviced in 2013 by Stereo Lab Service in Columbus Ohio. I contacted them and was told they replaced "about a half dozen small signal transistors". At easy listening levels it will play all day without incident. At moderately loud levels it occasionally emits a nasty pop out of the speakers, more often the right channel. I don't want to hurt the receiver or the attached HPM-200 speakers. Since it is both channels, I'm suspecting the power supply. Has anyone encountered the same or similar problem? Any and all thoughts on the matter will be appreciated.

Thanks in advance,
Chuck S.

 

[Renegade]

I had a receiver doing this, though at any volume level, and it turned out to be a transistor installed incorrectly. Some very good people here helped me sort it out, so hopefully they'll step up for you as well.

 

[petehall347]

first suspect outside interference .. ruled out by moving to somewhere else .
its odd that it does it in both speakers but not at same time ..
in my experience which is less than lots of folk here it is mainly bad transistors that cause popping noises .

 

[zebulon1]

You can separate the per from the main.
Try it as an amp or as a pre only. See/hear what happens.
Maybe some other "Signal" transistors are acting up. There known stinkers, 2SA725's and 2SC1312's in the pre. 2SA726's and the 2SC1451's in the main that could be causing the pop's.
The 2SC1451's are a time bombs. Not trying to scare you but the set may need more than whats apparent.

 

[HVHiFI]

Like zebulon1 said above lots of failure prone transistors in the 1010. I'd check to see if the input pair of 2SA726 was replaced on the power amp and the transistors in the preamp. Most 1010's I usually recommend a recap at this point if it hasn't had one.

 

[markthefixer]

go on a search and locate mission for any 2sa725, 2sa726 and 2sc1451 in the unit.

The 2sc1451 really stretches the definition of small signal transistor.

There are quite a few pre-emptive replacements, that still test ok, but have demonstrated a tendency to fail eventually. And a half a dozen is NOT the number I think of when doing a SX-1010, which includes the preamp circuits, the equalizer amp and even the tuner. It LISTS 2sa763 in the tuner, yet the 2sa725 IS an alternative in the BOM.

There are six 2sa725's in the two power amps, as well as four 2sc1451's as well.

 

[Chuck S.]

I've been reading a lot of old posts on the SX-1010. It seems that there are several known problems in the receiver requiring several dozen components to be replaced. While I used to do component level repair in the 70s and 80s, I no longer have any of the test equipment and don't feel up to doing what seems to amount to a rebuild. Are there quality repair services available? If so, I'd appreciate recommendations. I live in Oklahoma but willing to ship anywhere in CONUS to get quality trouble shooting, repair, and alignment of this great old box.

Thanks, Chuck S.