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Pioneer SX 1980 Trouble

M

Marivic

New Member
Hello All…Questions here, if anyone can help. My Pioneer SX 1980 have an intermittent problem as the right channel have lower signals. Besides being lower, it also have less treble or highs than the left channel. The left channel sounds awesome when its working right but sometime sounds like the right channel with lesser highs. Sometimes they both work perfectly and its sound so good but it does not last long. I hear this problem clearly with both Phono inputs. The rest of the inputs (aux, tape 1, fm, am) seems ok but only with lower volume. I dont have any electronic knowledge. I had a couple of vintage repair tech but really did not fix the problem. Can anybody recommend any experienced tech in the san diego/Los Angeles area. Im willing to drive to get this monster working right.
By the way, im also using a Pioneer SG 9500 EQ but it doesn’t seem to be the problem because the problem still happens when i have the EQ completely disconnected. I would appreciate any advice…
Marc
 
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The thing to do is make measurements comparing channels for gain from in to out on both the preamp and power amp sections.
My speculation is corroded switch contacts which might be cured by cleaning them.
I can’t recommend anyone in your area but I would see if you can find someone with experience with this unit
 
I'm going to add to Rick's reply.
I think your main complaint is the Phono?
The EQ (Phono amp) is a wonderful circuit. Although it uses some problematic transistors and some suspect capacitors. It should be restored to get the best from it.
Deteriorating 2SA726 transistors and several input and output coupling caps would cause sound quality issues..
 
rcs16 said:
The thing to do is make measurements comparing channels for gain from in to out on both the preamp and power amp sections.
My speculation is corroded switch contacts which might be cured by cleaning them.
I can’t recommend anyone in your area but I would see if you can find someone with experience with this unit
Click to expand...
Thank You very much for the reply and I appreciate it very much. I hope you or someone would be able to recommend an experienced tech..Thank you much. Every advise counts
 
zebulon1 said:
I'm going to add to Rick's reply.
I think your main complaint is the Phono?
The EQ (Phono amp) is a wonderful circuit. Although it uses some problematic transistors and some suspect capacitors. It should be restored to get the best from it.
Deteriorating 2SA726 transistors and several input and output coupling caps would cause sound quality issues..
Click to expand...
Thank You for the advise..Im really having a hard time figuring out if all inputs have the same problem. It seems like it because of the right channel but I surely hear it clearly from both phono inputs...thanks again...ill continue to look for an experience tech. Pacific guy have me on que for 4 years from a couple of month ago :(
 
rcs16 said:
The thing to do is make measurements comparing channels for gain from in to out on both the preamp and power amp sections.
My speculation is corroded switch contacts which might be cured by cleaning them.
I can’t recommend anyone in your area but I would see if you can find someone with experience with this unit
Click to expand...
By the way, could the power supply have anything to do with the problem along with the corroded switches, faulty transistors and caps?
 
Of course don't sell it...... I like you have no electronics repair skills. My SX-1280 (purchased new by me in 1979) has acted up several times over the years and it's frustrating. Luckily there are skilled hi-fi technicians 90 minutes away that have always bailed me out when needed. There has to be a qualified shop or technician located in the San Diego/LA area of over 15 million people. Hopefully someone here can help. I almost bought the SX-1980 but it was $100 more than the 1280 ($440) and I was tapped out as a PFC (E-2) in Okinawa....... Good luck!
 
Does it do the exact same thing when you select FM or a Tape monitor? Those selector switches for FM, AUX, PHONO1, AM, PHONO2 cause the problem you describe when they need to be cleaned, but they will each behave a bit different.

The scratchy sound you hear when engaging each selector switch is an indication they’re getting dirty. Long periods of no use will cause these switches to act up, as will living in an area with high humidity over time.

Unfortunately you have to take the unit’s face plate off to squirt the specific cleaner into these switches to clean them, and it’s important which cleaner you use or the switch will be ruined.
 
James Linder said:
Does it do the exact same thing when you select FM or a Tape monitor? Those selector switches for FM, AUX, PHONO1, AM, PHONO2 cause the problem you describe when they need to be cleaned, but they will each behave a bit different.

The scratchy sound you hear when engaging each selector switch is an indication they’re getting dirty. Long periods of no use will cause these switches to act up, as will living in an area with high humidity over time.

Unfortunately you have to take the unit’s face plate off to squirt the specific cleaner into these switches to clean them, and it’s important which cleaner you use or the switch will be ruined.
Click to expand...

My 980 had the same issue, and it was the tape monitor switches. It's not super hard to remove the front panel, and while I was in there I carefully cleaned the dial, and the backside of the display window glass.
 
James Linder said:
Does it do the exact same thing when you select FM or a Tape monitor? Those selector switches for FM, AUX, PHONO1, AM, PHONO2 cause the problem you describe when they need to be cleaned, but they will each behave a bit different.

The scratchy sound you hear when engaging each selector switch is an indication they’re getting dirty. Long periods of no use will cause these switches to act up, as will living in an area with high humidity over time.

Unfortunately you have to take the unit’s face plate off to squirt the specific cleaner into these switches to clean them, and it’s important which cleaner you use or the switch will be ruined.
Click to expand...
Hello and thanks for the reply..but my 1980 is fixed about a month ago. It wasnt any of the switches or selectors. It was the phono amp. Both phonos 1 and 2 needed to be recapped and all that good stuff. I was able to find a good guy locally..its been playing really good so far..thank you..
 
drjim said:
My 980 had the same issue, and it was the tape monitor switches. It's not super hard to remove the front panel, and while I was in there I carefully cleaned the dial, and the backside of the display window glass.
Click to expand...
Ill keep that in mind….but the 1980 is a lot different. You can find cleaning videos on you tube how complicated it could be if youre not experienced..thank you tho’
 
I’ll I want to say is these receivers are getting old. Like us. They now need a good going through. One thing leads to another.
I’m glad the guys see this and are putting the money into keeping them running because it not cheap and components are getting harder to find.
Note:
I’ve been struggling with my Concept all day and I have a bad attitude. Hopefully it improves with this local brewery Barley Wine!
 
Hello again everyone..i have a post about my 1980 being fixed a few months ago in this thread. unfortunately, my 1980 acted up again after a couple of months ( worked on by a local repair shop) .. it surely needed a complete restoration. Zebulon1 on the rescue and completely restored my dying 1980 and now sounds better than before, fuller sound, even signals between both channels I dont have to check if one channel sounds better than the other, they’re both perfect now, no more crackling on knobs and switches, no more distortion because of dirty buttons, even to the small details..FM blue light indicator is now even and bright (it was slightly uneven), the window lamps are complete, not dark on one side. Zebulon1 even picked the perfect lamps for it. Looks original but modern. There are more things too many to mention. Its pretty much brand new now. He’ll even give you weekly updates. IF EVER ANY OF YOU VINTAGE LOVERS NEEDS TLC ON YOUR GEAR, LOOK NO FURTHER AND CONTACT ZEBULON1 (and see if he can work on your gear) HE WILL GET YOU OUT OF YOUR MUSIC MISERY!!!
 
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