Pioneer SA-706 -Trying to bring back from the dead

Almonds

Almonds

Active Member
Hey there-

So, I've decided to start learning how to fix my audio gear as a hobby.

I've got a Pioneer SA-706 That has two problems right now, that may or may not be related.

1) There is a persistent buzz that sounds like a ground issue. The buzzing changes when I touch the chassis. It gets louder with volume increase.

2) There is a black cube shaped piece pictured below, that if it gets jiggled, will cause sound to either entirely drop out, or for it to drop out of one or the other channel. Tapping it can get the sound back.

Something else that may be related, the meter lamps are out. I don't know if this could contribute to the buzzing noise at all?

This seems to be a great little unit if I can get it working. I bought it off of craigslist to learn on. Someone on AK said the SA series were kinda easy to work on.IMG_3667.JPG IMG_3667.JPG IMG_3652.jpg IMG_3653.jpg IMG_3654.jpg IMG_3655.jpg IMG_3656.jpg
 
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The relay (Black cube) is for the protection circuit. Find a service manual and bone up on the circuit descriptions. Pioneer manuals are very informative.
The relay might need to be resoldered to the board, I would try that first. The relays are available new. The set looks crusty and looks like it has been worked on before.
Check all the grounds and look at that shoddy work closely for visual signs.
Hifi engine or (http://www.kallhovde.com/pioneer/Pioneer/Home.html) has manuals.
 
As I was about to get started, I noticed these:

Looks like some bad soldering and a lead that's drilled through the board but not soldered?

IMG_3670.jpg

it appears to me to be on the other side of the white rectangular thing sticking out of the boardIMG_3671.jpg
 
zebulon1 said:
That ceramic resistor is not factory.
Some butchery is present.
Click to expand...

That’s kinda what my untrained eye thought.

Do you have any idea what that resistor would be for?
Should I try to remove it or just leave it be?
 
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Follow the blue and yellow wires from the top leg. I wonder if its for the lighting? Looks like they wanted a fused power feed for something.
The one image shows some open holes on the board. What goes there? (First image in post# 4 lower portion of image)
Your new to this but its a good lesson in reading the schematic and trying to put this set back together properly.
Images on google will help a little.
I would get this amp back to OEM condition and worry about the hum/buzz along the way. That issue may iron itself out in the process.

Take an image of the trace/back of the board where the relay resides. They are around $12 to 15 dollars new.
 
here's an image where the relay is attached:
IMG_3669.JPG

They are the 10 leads directly to the left of the drilled hole.
There are 4 pairs stacked vertically in this picture and then 2 more to the left of them .

I removed the relay and tried to clean the contacts and then re-attached it. The relay doesn't work at all now. I used a chop stick and pushed them together and sound comes out when pushed together, but there's still a buzzing.
 
I also think you're right that the resistor is there for the meter lamps.

The holes in the board that have nothing in them from the previous picture are next to pin 31 and 32 in the circuit diagram which are connected to the meter lamps.
It says R619 47(1w)

I'm thinking someone tried to install LEDs for the meter lamps or something, so they changed that circuit?
 
Another interesting thing I found:
IMG_3672.JPG
This the part of the board (center of photo) where I put the relay back in. the board has 10 holes, but the relay only had 8 pins, so I didn't solder those two holes. Is it possible the relay is not the correct one for the unit?
I should have taken a picure of the relay when it was out, but I forgot.

here's a picture of the relay with the top off
IMG_3673.JPG
 
Okay.
I wasn't paying attention completely about the relay. The first image was with the cover on. I thought you were probing with the cover on.
The relay is protecting the speakers from melting. If it is not engaged, something is wrong with one or both amp channels. DC current will destroy the speakers.
By circumventing the relay, damage will occur.

The manual has an amp adjustment procedure. You must do that. Only read the voltage from the test points indicated in the SM. (Idle setting)
Also read the DC voltage from the speaker outputs on the amp board. It will not read the voltage we need from the speaker terminals as the relay is not engaged. (DC Balance)

You may need to bone up on the operation of a volt/ohm meter (DMM).

The buzzing is most likely an issue with the bum amp(s).
You got some work ahead.
 
Ok, the thing is, the relay was working before I took it out. Then I cleaned it and now it's not working.

I have a DMM and should be OK using that.

The only replacement relay I can find by Googling doesn't look anything like my relay. It has 13 pins where mine has 8.
 
Ok, I received my new relay and put it in and now the relay works, but I still have a buzzing.

I don't know where to look next.:dunno:
 
Thanks Zebulon1 for all your help!

I've got this baby working wonderfully now. Just going to get the meter lamps working for my next project.

You were right, someone butchered this unit, maybe trying to do a LED retrofit or something. Thanks for your tips, you got me looking at the lighting circuit and helped me figure out what was going on there. I clipped the pins on my new relay and put it in and that solved the big problem, and then found a corroded or chewed ground wire from the RCA jack panel and replaced that and the buzzing went away.
 
Very good job troubleshooting the receiver. A good visual check will usually produce results.
What's the next audio unit in for repair?
Your on a roll.
 
Maybe a fluoroacan pioneer! I’m a sucker for meters.

Or actually, a recap of this 706. I feel it isn’t up to par with my kenwood ka-3500 and I feel it should be, so maybe it’s not up to spec.
 
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