Pioneer SX-850 Phono Stage Question

[eddiel]

Thanks for those links. I finally had a chance to get replacement transistors (to make it worth the shipping costs I bought extra extras but also other times on the board in case I needed them).

Anyway, I replaced the transistors and made sure to connect them properly.

However, the problem is not fixed

Phono 1 has the same noise issues as before. But Phono 2 has no noise but also very little sound. All you can hear is what I would describe as something similar to channel leakage. So I can hear music out of Phono 2 (and 1) but the volume in Phono 2 is very very low.

I double checked the configuration of the transistors and they are in correctly. The soldered connections appear to be solid as well.

Since the noise on Phono 1 didn't go away I'm guess that maybe there's a problem with another transistor on another board. Not sure what the Phono 2 problem could be but as a guess I'd say maybe a faulty solder or connection??

Any suggestions would be most welcome.

 

[eddiel]

a little bump...

 

[GreyOwl]

If you are expecting a quick reply from Mark, it may be a while since he has been in the hospital. See sticky at the top of the Pioneer section.

Charles

 

[eddiel]

If you are expecting a quick reply from Mark, it may be a while since he has been in the hospital. See sticky at the top of the Pioneer section.

Charles

Yeah I've seen the thread. I was just hoping someone else might be able to give me some advice.

Just goes to show how much Mark did help out around here. Really nice guy and helpful.

In the mean time I've been doing a little research on my own. As it happens we have an engineer at my new work with a pro-audio background so he knows some of this stuff and he's answered a few questions I had.

 

[randallflag]

Did you do all the caps as well? Not saying that is the problem but the rebuild for this board is so dirt cheap I would have done it as a matter of ruling out the usual suspects. Also did you definitively rule out the the switch you operated on?

 

[eddiel]

Did you do all the caps as well? Not saying that is the problem but the rebuild for this board is so dirt cheap I would have done it as a matter of ruling out the usual suspects. Also did you definitively rule out the the switch you operated on?

I haven't ruled out the switch but I am looking for a replacement. There's one on ebay but at $30 I might wait for a better deal.

I have the caps (bought all the bits from mouser) so I'll do those as well. But I thought noise is usually due to transistors. The equalisation board (I think AW-011) has transistors on it so I thought I should replace those as well.

As for the no sound from Phono 2...I think the phone board is dead in that regard. The tracers (I think that's what they are called; those lines that connect all the connections) might be screwed. I was talking to an audio engineer at work and I mentioned that when I was soldering in the new transistors I noticed that the tracers around the holes were lifting up. He said that it sounds as if the glue holding them down has given way. In which case...might need a new phono board.

I don't mind spending a little cash on this unit (withing reason) as I see it as a learning experience. As long as I can sell it for what I spent (unit was free) I'm good. So I've been searching for bits on ebay.

 

[randallflag]

Lifted traces happen from time to time due to age or in my case, not fully de-soldering a component before trying to remove a component. They can be dealt with by a multitude of solutions from superglue to soldering jumper leads further up the trace ect.. Search for some solutions, I certainly wouldn't toss a board for lifted traces.

 

[Watthour]

As RF stated, the foil traces can be repaired. Excess heat usually weakens the bond between the copper and resin board, so work quickly with the solder equipment if possible. If glue and jumpers are not good repairs, you can always save a board by installing bushings:

http://www.circuitmedic.com/guides/5-1.shtml

Before going through the hassle of acquiring a switch that you might not need, measure the resistance of the switch contacts in circuit. If there are suspect contacts, you can temporarily install wire jumpers on the solder pads around the suspect switch contacts. Just be CERTAIN of the switch pinout and/or circuit diagram. If the problem is not corrected, move on through the circuit.

 

[tsd71]

exactly how did you determine the correct way to connect the transistors ? There are 6 ways to connect some of them, and only one will work. I need reassurance that they went in correctly.


function pushbuttons from ebay on the boards... there's a buy it now auction (360411448368) with the board.

you can press the straw up to the top holes at one end and squirt, which will fill the entire switch. NO OPENING NEEDED

opening switches is a skill, an acquired skill.

Are you sure you installed all these transistors correctly? :scratch2:

Also there are numerous threads on here that deal with how to go around lifted traces...