Pioneer SX-205 drops external speaker when it heat up

[flexxmi]

I'm a newb, so bear with me. I've had this amp a long time and I've really had it cranking 4-100w Technics speakers at times. But some time ago when I was playing it the left channel dropped out after only a short amount of time. I turn it off and after a half hour or so the speaker will work again, but only briefly. The headphones still play fine, so I'm assuming there's an issue with the amp somewhere or possibly a speaker relay. Any thoughts?

 

[Natsukage]

Hello.

The amplifier does use a relay for protection through which the sound passes through. It is the one labelled RY402, but if there is sound in the earphone there's almost no chance it is the problem.

Have you tried playing around with the Speaker switches? They may need cleaning and cutoff on one side.

But these amplifiers are usually riddled with bad solder joints. I suggest doing a full solder checkup before changing any relays.

 

[flexxmi]

Thank you for your reply Natsukage. When you mention 'speaker switches' are you referring to the A/B switch on the front of the unit? I've tried the most obvious solutions like swapping speakers and checking wires and inputs. I pulled this unit and replaced it with a new Sony and the rest of my system is working fine now, but this amp sounded much better than the new Sony I bought so I would like to save it if I can. In order to check all soldering I will have to pull the board and I was hoping for some direction before I have to really dig in.

 

[flexxmi]

I'm leaning more toward an intermittent component failure that, when a load is applied, fails.

 

[Natsukage]

Yes, I mean the A/B switch. If they are defective, sound can cut off from one side intermittently. Clean them by using a cleaner such as WD-40 directly on the switches and switching them on/off a few dozen times. Unplug the amp before doing this of course.

Usually, intermittent components due to load are very rare in these old amps. Solders are usually the issue with this amp, and I've seen many of them over the years.

But to test if it is due to heat, you can use a hair dryer and heat up the amp. If it shuts down, you can then freeze individual sections using a compressed air can upside down to identify the culprit.

Giving professional secrets...my boss wouldn't be too happy. ^^;

 

[flexxmi]

Thanks .. I may give those switches a spray tomorrow, but wouldn't a contact cleaner be more effective and leave less residue? My concern is that WD-40 leaves an oily residue and it would seem to me that it would attract more dust and dirt than contact cleaner would. ?? I have heard of isolating suspect componenets with a quick spray of compressed air but have never had a need to utilize that technique before. If the switch cleaning doesn't work that may be the next step.

 

[Natsukage]

I've used WD40 without problems for over 10 years.

The issue with switches isn't dust and dirt, it's corrosion of the contacts. There's nearly no dust in this amp's switches, as they're relatively dust-proof.

I usually use a contact cleaner beforehand and then use WD40 to prevent future corrosion. But WD40 can clean any contacts without issue as well, although not as effectively. I suggested it first because most people do not have a proper contact cleaner, but have access to WD40.

 

[flexxmi]

Thank you for your help. I'll give it a squirt tomorrow and see if it does the trick. I assume it's best to try to apply the contact cleaner/WD40 as close to the spring area as possible with the unit facing upward so the intended fluids can get into the switch contacts?

 

[Natsukage]

Usually, it's better spraying directly on the switches, not the spring area. The switches will absorb the liquid through the plastic. But spraying on the spring area and holding the unit upwards will work equally well.

 

[flexxmi]

Is a bad solder job always visible to the naked eye? If it goes that far, should I be concentrating on seeking out a bad solder on the main board?

 

[Natsukage]

Yes, bad solder joints are visible to the naked eye. Look out for something like this:

Especially in the amplifier section.

 

[flexxmi]

I would like to thank you, Natsukage, for today you've made someone very happy! I sprayed the A/B switches first with contact cleaner and followed up with a dab of WD40 and it WORKED! I've been listening to my SX-205 for nearly two hours now and everything is working perfectly!! I must admit that I was a bit skeptical with this suggestion seeing that I never used those switches and found it hard to believe that they could be the culprit of my dilemma for that reason alone, but as it turned out it was EXACTLY the problem! I can't thank you enough Natsukage - I've returned my Sony amp to the box from whence it came and the Pioneer is back in action. And to think that at one point it was destined for the electronics recycling heap! This may have been the easiest fix of the amps I have that need repairing. I have three more 'newer' amps (receivers) and one tube amp in cue. Thank you again for the expert solution to my problem!

 

[Natsukage]

Glad to hear that was the only issue! The A/B switches are common for this amp, since I've repaired a few over the years.

Anyhow, glad you solved it, and I hope you enjoy your amp for a long time. ^^

 

[flexxmi]

Well now you can add another to that total! I'm glad it was an easy fix and can't begin to tell you how happy I am that this amp is back on the job. Thank you again!