Tony Sestito said:
-When you crank it, there's a distinct low-pitched hum you can hear through the speakers.
Hey Tony - know why it hums?
...
It doesn't know the words!
Has the volume changed over time? If not it just might be the output of the cartridge relative to the gain of the phono section. Might be totally normal to need to turn up the volume a notch.
Edit: Just reread your post and it sounds like it did change. Cartridge failures are rare, they're just a long strand of coiled wire, but it does happen. Are the channels balanced? I would probably start with checking the wiring from the RCA plugs to the cartridge connection pins, center pins and grounds, being careful not to do bad things to the stylus. The low output and hum might be due to a crappy connection. Assuming you have an ohm meter, also check the resistance from the center pin to outside ground. Should be similar, and you should find reference values on vinylengine.com
In reply to jwagner (Forum Supporter) :
I think my first step is to hose the cartridge wires down with some Deoxit. That stuff works miracles; it has saved a bunch of my stuff in the past. I will probably clean the RCAs too. They are hard-wired, so it might be a good idea to check those connections on the inside. Hoping it's just dirty connections.
Tony Sestito said:
This used to be a common scenario: in the 1970s or 1980s a young guy would buy some large, high quality speakers for their stereo system. Later, they'd meet someone and get married, and eventually their wife would decide those things took up too much space or didn't fit with the decorating scheme, and they would be relegated to the basement or attic. Eventually, the family would have a garage sale and the speakers would be put on the sale with a $10 or $20 price tag. I picked up a couple pairs of speakers that way, and since I'm single I decide the decorating scheme. 
This many years on, it probably doesn't happen as often anymore.
In reply to stuart in mn :
I don't know much of the history on who owned these ones, but they came in with a really junky Magnavox all in one stereo from the late 80's. It was one of those ones that looks like stacked components, but everything is attached. There was no way that thing could have effectively powered these speakers. So, I am guessing they did get relegated to garage duty at one point because 80's woodgrain was out of style in their fancy rich people house. 😆
Lately, my 1980's Gemini D.J.Q1200 turntable has been annoying me. Since I've upgraded my receiver and speakers, I've noticed that the volume output of the turntable was lower than it should be, and on top of that, there was some unwanted humming underlying everything, like it had a bad ground. So I decided to open it up and see what was going on.
I pulled the platter, and everything seemed fine here. This is a direct drive turntable made in Japan, BTW.
Underneath, there are a number of circuit boards for audio, power, and the motor. I mainly inspected two of them: the small board with the spring on one of the screws on the bottom, and the motor board. I wanted to make sure the solder points were solid and the connector on the motor board was nice and clean. I found some gunk on the latter and cleaned it up.
I also found this loose inside the case. Not 100% sure what it is.
Then, I focused my attention to the cartridge, which is a Stanton 680EL, BTW. The pins were severely tarnished and disgusting. I carefully removed the wires and cleaned the pins, sprayed contact cleaner inside the cart, and put it back together. I also cleaned the RCA cable contacts and the ground strap.
After I put it all back together, I tested it out with a few favorites. Definitely more volume and less hum with nice, clear sound. That's a win right there.
This morning, I was right about to leave to run some errands, and my wife messages me that someone in the neighboring town was giving away an old "silver face" radio and some "tall" speakers. So, I slightly altered my plans to see if I can snag them.
And snag I did.
It was a Realistic STA-2100D receiver and a pair of "Theater Research" TR-2810 speakers.
First, the receiver.
This receiver is a BEAST. 120W/2 channel power, and just about every knob and function you could ever want or imagine for something that came out in 1980. This was one of Radio Shack's top receivers back then. And it's the product of a lawsuit between Pioneer and Radio Shack! They had a model called the STA-2100 that was a straight-up Pioneer clone, and once they caught wind, they had to make some mods and this is the result. It retailed for $699 back then, which is over $2k now. And they still sell for north of $500 for a working example today. This one needs a deep clean and the top veneer is a little roached, but the guy said it still worked. Score!!!
Now, the speakers:
Ever been approached by a guy in a white van asking if you want to buy some speakers that may have fallen off the back of a truck? Well, that's what these are. Theater Research is basically a counterfeit brand from about 25 years ago and what you would have gotten if you bought into the scam. They look great, but they are not. I mean, check out these "Kevlar" cones:
That's FAKE Kevlar! It's glued onto a paper cone. Ridiculous.
These also have built-in subwoofers, but I'm sure they sound like garbage. I'll likely put these out on the curb.
But either way, my luck has been fantastic lately or find cheap (or in this case, free) gear! Can't wait to get this receiver cleaned up and see how it does up against my recent Onkyo find.
I've been doing some research on this receiver, and I think I scored a real gem. Check out this ad!
Compared to the Onkyo TX-8511 I recently picked up, it's going to be an interesting comparison. This makes 20W more power and has a lot more features from what I have been reading.
- It has TWO Phono inputs with 3 stages of sensitivity per input, which makes it a better partner for vinyl playback. This may solve my volume discrepancy.
- It does have one Aux input, but I may lose the ability to play my digital streaming stuff. I may be able to utilize the multiple Tape and Phono inputs for that, though.
- The EQ options are far more than what's included on the Onkyo, which just has Bass and Treble knobs. I have no complaints about the Onkyo's sound, but this gives me a lot more options. It has Hi/Lo filters, a Loudness button, and the Bass/Treble have frequency turnover buttons. That's cool.
-The thing even has Dolby decoding built-in, which is nuts for something of that era.
-It has 4 meters built-into the face, including L/R output meters, and it just looks super cool.
I'll be pulling it apart for cleaning/testing later this week. Can't wait!
I love the way those old receivers look, cool score!
If the compressed air won't get off the gunk, how does one go about carefully cleaning the inside so you don't damage anything?
In reply to z31maniac :
That's a great question. I was planning on using cotton swabs and a small vac that I use for my Vinyl Vac setup. I also haven't tried my garage compressor; I just used canned air which usually does the trick.
I brought it outside to try my garage compressor, and as you can see that made a difference. I cleaned it up a bit more on the outside as well, and brought it back inside to test. After plugging it in, I heard a ZAP and started smelling bad smells, so something must have failed. It sounded like it was toward the back of the unit, so I'll have to inspect it. No magic smoke, strange enough.
So this will become more of a project than I thought. That said, it was a freebie and it's worth sinking some effort into. I'll be revisiting this one later.
I really appreciate vintage audio gear. I had a Marantz 2220 that was given to me like 30 years ago. I kept it in the garage, and I would turn it on from time to time. Volume control was a bit scratchy, but hey--garage stereo. Several years ago, I pulled it out for a small neighborhood get-together and it worked for a while, then *PooF!* It quit working.
I've got a decent understanding of electronics, and I've built a few simple projects--I'm no stranger to soldering. But figuring out what went poof was going to take some doing, and the thing was old and dirty, full of overspray and grinding dust and all kinds of stuff. I offered it in trade when I bought the Pioneer turntable for my son. I think he gave me something close to 100 bucks for it, which made me more than happy. Hopefully he got it working again and sold it to someone who can enjoy it. I really like the looks of that old Marantz stuff.
Your big receiver is a beast! Nice score.
I just found this video on restoring one of these monsters:
I am dumb, so I put power to it again to see if it would power on. And it does. That's good.
Without hooking speakers/inputs up to it though, I have no idea what section had the issue. I don't want to make it worse than it already is, so I'll limit my messing with it further for now. I think I'll have to recap the whole thing at the very least. Again, it's well worth the time, given everything I've heard about this unit. It's basically the last hurrah for Radio Shack's classic receiver line and represents the best of that era. It apparently can go toe to toe with the Pioneer, Sansui, Marantz, and the rest of the heavy hitter brands from that era.
What's a good place to buy capacitors and the like these days?
Tony Sestito said:
What's a good place to buy capacitors and the like these days?
Parts Express, Mouser, Digi-Key. There are a few others.
https://www.parts-express.com/electronic-parts/capacitors
I made the mistake of posting this receiver and the issues on a FB group geared toward that sort of thing. One guy basically said I ruined it by using compressed air to clean it. I have no clue how else I was supposed to get that gunk off. The guy made a point though: I may have bent a post or blown something in a bad place that could have shorted something out. I was careful not to bend anything and do damage, so I am thinking it's more a 45 year old capacitor issue rather than me cleaning the thing.
In reply to Tony Sestito :
That guys a dummy. Unless you were blasting it with 1000psi air you're not going to bend something. No way.
In reply to dculberson :
I was using a leaky blow gun and about 100psi. No danger to be had here. That said, I did try brushing and vacuuming it up before that. This stuff was baked on from high temps and smokers tar. Air was really the only option at that point.
Sounds like the type that says you ruined a Miata by modifying it.
In reply to z31maniac :
"It'S nOt PuRe AnYmOrE!!@@!!!!!!!~$"
Yup, definitely the same guy. I mean, I understand the "theory" behind it. But in practice, I'd rather take the risk than ignite the thing (and my house) by heating up all that gunk dust to superheated levels.
To my surprise, the post has garnered about 300 positive reactions so far, with a few people chiming in with their own units, talking about how good the receiver is. A few people told me that I should keep bench testing it to pinpoint if anything did actually fail. It might be ok?
The funny part is the gear snobs that have come in there saying how crap Realistic stuff is, and people instantly coming in and defending the brand. And yes, they did make a lot of lower priced garbage over the years, but their high end stuff can absolutely hang with the big names. This was the most expensive receiver they made in 1980; the only one "above" it was their first unit with a digital tuner (the STA-2200 in the YouTube thumbnail above) which was $100 less.
Fun Fact: They usually sold these together with a pair of speakers called the Mach Ones.
These have a 15" (!!!) woofer and were supposed to emulate the kind of sound you'd get at a club or music venue. They were massive too, and handled 160W.
When it is fully functioning, this thing + those recently acquired Ohm speakers are going to make quite the pairing. By all accounts, the Ohms are better, and are meant for high wattage as well, so they should sound great. They easily handle the 100W coming out of my Onkyo without an issue, so I would expect the same here.
Tested the receiver for audio output this morning, and nothing. The line level meters show zero output, so I'm guessing that there's a problem in the power section. Probably looking at a total recap/transistor replacement for the power section. I still need to bust out the multimeter, though.
This is a time where I miss having an electronics store around like Radio Shack or the like. There used to be a great place called You Do It Electronics just north of Boston that would have had all of this in stock.
Guessing that this will end up being a winter project next year once I get my electronics workbench set up in my basement. Kind of a bummer, but it was free for a reason. It will be a nice unit once fixed!
Tony Sestito said:
Tested the receiver for audio output this morning, and nothing. The line level meters show zero output, so I'm guessing that there's a problem in the power section. Probably looking at a total recap/transistor replacement for the power section. I still need to bust out the multimeter, though.
This is a time where I miss having an electronics store around like Radio Shack or the like. There used to be a great place called You Do It Electronics just north of Boston that would have had all of this in stock.
Guessing that this will end up being a winter project next year once I get my electronics workbench set up in my basement. Kind of a bummer, but it was free for a reason. It will be a nice unit once fixed!
Tony, there is a set of RCA jacks on the back labeled MAIN IN and PRE OUT. They should have a jumper between them. The picture I looked at online had a black jumper but some stuff I've had in the past had silver (natural metal) jumpers. If they are missing, no sound. Can be replaced with RCA audio cables. This was a feature that allowed the use of an equalizer or other equipment.
In reply to triumph7 :
The jumpers are present on the back of the receiver. I did pull them out and re-inserted them, and no change. There's definitely something wonky going on. When I leave it on for more than a few minutes, fuzzy sounds happen out of the unit itself and the lights on the unit dim, along with the telltale smell of old caps failing. So yeah, it's definitely got issues. I do have a service manual PDF, so I should be able to ID what I need as far as parts go.
Tony Sestito said:
In reply to z31maniac :
The funny part is the gear snobs that have come in there saying how crap Realistic stuff is, and people instantly coming in and defending the brand. And yes, they did make a lot of lower priced garbage over the years, but their high end stuff can absolutely hang with the big names.
I remember the days when Radio Shack built high quality stuff...looking through their catalog when I was a teenager was just about as good as when I was a little kid and the Sears Christmas catalog arrived in the mail. 
I've done some more cleaning, tinkering and troubleshooting with that Realistic STA-2100D receiver. It definitely has some issues.
First, I did get the bottom open, and took a peek around. The only things that I can see that may be "wrong" physically are the spots on the big green audio board that have lots of flux residue/gunk on the connectors.
For example, there are a few spots on various boards that look like this. I don't think this is causing the issues I'm having, though. Through some research, I found out that there's a LED behind the power button that will change from red to green under power. When it is lit up red, that means it's in protection mode. It usually does this during initial power-on to protect the speakers from blowing out. Well, this unit never switches from protection mode, and that LED stays red all the time. I do hear the protection relay kick on immediately, which means that part of the unit does function.
What I am thinking is that there are issues with one or both of the power supply units. Each channel has its own power supply setup, and one or both must have issues. So the next step is to pull those and try inspecting the boards for broken joints or bad components. I don't want to start dumping money into this until I know what to fix.
