Pioneer SA-706 mysterious issues

[GaryFreedom]

Hi!

My Pioneer SA-706 is acting quite weird. Sometimes it doesn't turn on at all (no lamps or anything works). Then after playing around with some switches (like the tape monitor) it's coming on and working perfectly. First the lights come on and then the relay switches on too.
Sometimes it does switch itself off again though just after a second and I have to start playing around with it again.

I recently sprayed all switches and potentiometers with contact cleaner and soldered in new lamps for the VU-meters. I just got this device the other day so unfortunately I don't know any history about it.

Anyone having or had similar issues? What could possibly cause this problem? Where do I start?
Any help is appreciated.
I had a SA-506 before and never had any problems with it so I would really like to get the 706 in proper working condition.

Edit: It also seems that this problem only occurs when the amp is "cold"!?

Thanks in advance

 

[avionic]

Welcome aboard. .I'd look for cold solder connections around the power switch and/or possibly a loose fuse holder clip..

 

[avionic]

Do you notice and flickering in the lights when it does decide to work? And arcing or bad power switch could also be the root cause.

 

[QSilver]

Also check connections around the transformer primary and secondary. Depending on your teritory, the voltage selection (220V/240V) is done by moving a fuse from one holder to another. It could be that either the fuse is fatigued or the fuse clamps are weak. This fuse would be inside the unit near the AC inlet.

 

[GaryFreedom]

Do you notice and flickering in the lights when it does decide to work? And arcing or bad power switch could also be the root cause.

Now that you say it, yes! After it finally comes on it takes a few seconds until the lights reach full brightness and they do flicker a little until the relay switches.

 

[GaryFreedom]

Welcome aboard. .I'd look for cold solder connections around the power switch and/or possibly a loose fuse holder clip..

Also check connections around the transformer primary and secondary. Depending on your teritory, the voltage selection (220V/240V) is done by moving a fuse from one holder to another. It could be that either the fuse is fatigued or the fuse clamps are weak. This fuse would be inside the unit near the AC inlet.

I will check on that, thanks a lot!
I still wonder though how that would connect to the tape monitor switches??

Here is what happens:

I switch on the power - amp is dead (it's almost not noticeable but I can hear the transformer humming, nothing else works)
I leave the power switch on and play with the tape monitor switches - amp goes on

Anyways, I will start with checking on cold solder connections and check the fuse clamps and the power switch.
Thanks a lot!!

 

[avionic]

I still wonder though how that would connect to the tape monitor switches??

A bad solder connection or loose electrical connection is sensitive to vibration or even thermal expansion. Messing with the switch may be all the vibration necessary to " make or break " a poor connection.

 

[GaryFreedom]

A bad solder connection or loose electrical connection is sensitive to vibration or even thermal expansion. Messing with the switch may be all the vibration necessary to " make or break " a poor connection.

Thanks! I will check everything during the next days and keep you posted

 

[GaryFreedom]

Hi guys!

I finally got around looking at the amplifier and found the cold soldering connections!
Seems like the previous owner changed a transistor but did a bad soldering job. I redid the connections properly now and everything is working as it should now.
Thanks a lot for the help. Now I can finally enjoy the full functionality of the amp