Crackling or sputtering coming from inside a Realistic receiver?

Hi folks, in my introduction, I related that I bought a vintage Realistic STA-85 receiver to use for my turntable. It worked great the night I set everything up and played records for hours, but then the next day I noticed a sputtering sound coming from inside the receiver that was audible through the speakers. Also, the left channel started going out intermittently when using the turntable, but would go away if I switched to the FM tuner.

I'm pretty sure that there should be no crackling or sputtering coming from inside the receiver, correct? If not, is that a potentially fatal malfunction? Is the loss of the left channel a result of this as well, or is that something that may have to do with the turntable?

I just wanted to play some records, now I'll have to be a technician too haha

Check the power switch. It's notorious in many smaller receivers for failing and causing a crackling / arcing due to undersized contacts. Easiest fix is to jump the switch out, proper fix is to clean the switch contacts and install a relay to take the load of the amp. Do an AK search for bad power switch, you will find lots of info on this problem. Take a look at the Kenwood forum if you can't find a thread on it, the KR-4070 and others have the same problem too.

A proper fix would be a total replacement. Usually quite easy to do, and switches are mostly readily available. Cheap, too.

As for the channel cutting out, seems unrelated to the bad power switch.

Take out of service until this is sorted - the thing is a fire hazard.

Proper fix would be the relay. The original Alps switches had undersized contacts that could not handle the current load of the amplifier which is why they fail in such enormous numbers across all brands. If the switch is properly cleaned it will be able to handle the load of a relay coil, that's about it. It's a pilot duty switch at best, don't know what they were thinking putting that in there but don't repeat the mistake.

Channel dropouts, tuner dropouts and other sectional malfunctions are often caused by the power switch failure due to the resulting "brownout condition" it creates. No telling what part of a receiver will cut out first when running at half the voltage (seen it happen, often that's what the complaint is about rather than the arcing noise).

I think I'll just look for another receiver, after reviewing the costs for all the materials to bring this one back up to par would buy me another, "better" one.
Maybe someday I will give it a shot just to prove to myself that I can do this, but not anytime soon.

Thank you audiojones and Baron K Rool for taking the time to help me. As a wet-behind-the-ears solid state and vinyl aficionado, I appreciate it!

It's a pretty good little receiver and worth fixing up at some point when you're up to it IMO. I've got one here and I like it a lot (it had the same problem as yours of course). Good looking unit with a fairly sensitive "auto-magic" tuner, something like 35 or 40 wpc, discrete TO-3 outputs instead of modules, wooden case, plenty of power for average listening. The only thing I don't really care for are the volume sliders but I'm kind of used to them at this point.

Anyhow, not a big deal to fix but you are right about there being many others out there. Just try to steer clear of smaller receivers that have the power switch as part of the speaker control, most will have the same undersized Alps power switch and eventually will develop the same problem with the contacts arcing out. Try to find one with a dedicated individual power switch.

ADD-ON: If you want to use it now but aren't up to fixing it so the internal switch works properly why not just jump the power switch out and plug it in to a switched power strip to control the on-off function. You could plug the rest of your gear into the power strip too with all the extra outlets.

It's very simple, just unplug the receiver first, then cut the two wires going to the power switch (gray plastic box located on the back of the speaker selector switch shaft) and wire nut them together using a small gray wire nut or butt-splice connector. Make sure they're properly joined and insulated because they will carry the full line voltage at that connection. You don't need to worry about connecting the spark arrestor (small square component with the two wires going to the switch) because you will not be using the switch in the unit.

This way you can safely enjoy your receiver now without going through a big hassle. Also clean out the switches with some contact cleaner while you're in there, they usually need it (especially the function selector switch and the tape monitor switch).

That's very interesting! I think I could pull that off. Which of the two wire connectors would be deemed safest? I assume the speaker selections would still work?

Personally I like the twist-on wire nuts best for this type of thing, that way you don't have to cut the wire again (making them too short) if you decide to fix it properly. Either one will work just fine though, so don't sweat it. The wires are a very small gauge so you'll need the smallest wire nuts you can find to get a good tight connection if you go that route. Speaker function will not be affected, you can just leave the old power switch right where it is.

I believe I will try this this weekend. I will post a photo of the wires in question just so I don't make a boo-boo and cut the wrong ones lol (seriously though, I've had moments)

Alright! I'm going to Home Depot today and will pick up this can of contact cleaner:
http://www.homedepot.com/p/CRC-2-26-5-oz-Multi-Purpose-Lubricant-02004/100398344#customer_reviews

Audiojones, when you mentioned a gray wire nut, is that because it is for a certain rating?

Ok, I took the cover off and I must say it is pretty dusty in there. I will get an air duster and spray it out. I see the wire you mentioned: one is purple (or lilac) and the other is white, which is a bit thicker than the other. So, cut those two wires at the base, and cap them securely with the wire nut, and use the power strip as the on/off switch.

I noticed the lights are burnt out, what type of bulbs would I need, and how to remove them?

I bought a variety bag of standard wire connectors with four different sizes:

#20 #16 Gauge
#18 #14 Gauge
#20 #12 Gauge
#14 #12 Gauge

Blue=300v max
Orange=600v
Yellow=600v
Red=600v

Blurry shot of the inside of the receiver

RodantKapoor said:

Ok, I took the cover off and I must say it is pretty dusty in there. I will get an air duster and spray it out. I see the wire you mentioned: one is purple (or lilac) and the other is white, which is a bit thicker than the other. So, cut those two wires at the base, and cap them securely with the wire nut, and use the power strip as the on/off switch.

I noticed the lights are burnt out, what type of bulbs would I need, and how to remove them?

Click to expand...

Yes, connect the purple and white wires together with a small wire nut and you're good to go. As I mentioned before don't worry about connecting the arc supressor (that little blue box), just connect the two wires together and you're done.

I don't know what bulbs are used in that receiver, you'll have to remove one and get a number or a voltage rating. I'm sure they are pretty easy to find, you can try contacting AK'er dwojo, he has 'em all.

That can you posted a link to is spray oil, not contact cleaner. Do not spray any oil or WD-40 type product into the controls! Use contact cleaner only, and I wouldn't recommend spraying anything into the volume sliders unless they absolutely need it. Don't spray the tuning capacitor gangs either, it can ruin the tuner - just blow out the dust with canned air. Read the sticky on how to clean dirty controls, there are some do's and dont's.

Ok, I'll give it a shot tomorrow after work...
I contacted dwojo earlier after doing a search here, I hope to hear from him soon.
Well, I did blow out the dust as best as I could, and vacuumed what I could. I knew from reading on this site to stay away from the tuning mechanism, I just blew the dust out from the area. I did, however, use that contact cleaner very sparingly on the controls and let the whole dry for awhile.... so far so good....:sigh:

The blue can marked CRC QD is the contact cleaner, that CRC 22-6 stuff that you posted a link to is lubricating oil. You really need to spray CONTACT CLEANER into the controls and work them back and forth a bunch of times to clean them, NOT OIL. I would suggest going back to HD and getting the proper CRC QD Contact Cleaner and thoroughly cleaning out the controls that you sprayed oil into, then follow it up with compressed air to dry everything out. Again, there is a sticky at the top of the general discussion forum that is an excellent guide to cleaning the controls.

Cleaned as best as I could and found some deoxit at a guitar store a few blocks away. Thanks for the heads-up regarding the cleaner, glad I didn't use much.

Dave (djwojo) gave me quote on the lamps, seems they need to be soldered to the board. I think I have an old soldering iron around here somewhere..

Cool. It's really a nice little receiver once it's all set up. A lot of that RS audio gear was decent sounding stuff at a reasonable price point.

Update:

Since I've deoxited the switches and such I've had no problems with the left channel going out, nor have I heard any arcing. So, Ive decided (for now) not to bypass the power switch.