Technics st-c04 for 46 usd , too much ??

[allanmatters]

Hi all ,is 46 usd tooMuch for a 1982 tuner technics.? Model is st-c04 , i tried to look for someones review on using the tuner or comments on other audio sites but couldn't find anything . I did find technical into of it on hifi engine . Seems decent i need to know if its a keeper in picking up stations or how do we compare it with say a Marantz ST560 tuner ?

Wondering if 46 usd is too much for a tuner in a maybe 7 outta 10 condition

Would greatly appreciate any ones insight

Thanks
Allan

 

[allanmatters]

More than 3 years down the line since my first post about this technics st-c04, I came across it again. I decided to buy it as I did not want to pay much for a decent tuner. I like the fact that this one picks up stations very well for a very basic model from Technics. Clean sound so far. But I am not able to get the stereo light lit or even the tuned led light for that matter. Using a speaker wire where one is hooked to the 300ohm and the other to gnd. Read a lot of posts here on audiokarma about antenna connection guides. It's probably an issue with my location. Just by the way I picked this up for 34 usd

Problems with the tuner - after about less than 2 hours it starts auto tuning on its own (like a ghost is within the unit) . If you try to stop it by pressing the "up" tune button, it refuses to stop auto tuning.
Opened it up and came across 3 gold capacitors. Value - 1.8v 3.3f. One of them looks a little bloated from the top. It's got some light brown residue on the top around the sides. The other two seem ok. Any one know if these gold capacitors have a special function? And what could result in the tuner to auto tune after a couple of hours.

 

[amptramp]

These are probably capacitors that hold voltage on the preset memory so you retain stations when power is off.

 

[allanmatters]

So I am not able to get the quartz led and the FM stereo led lights lit up. I tried connecting a dual speaker wire (what's used for home theater speakers) Connected one end to the to the 75 ohms terminal and the other to the Gnd terminal.(also tried the 300ohm terminal)

The other end of the speaker wire is split into two in the form of a T dipole

I used a really long wire which I placed outside my house on the ground floor. Nothing worked.

Then I took the tuner upstairs to the terrace on the second floor and tried there too. None of the led lights lit up. It's happening to all stations too. Tried around 10 stations including a few from AM. In AM, the quartz led turns on at a particular frequency. But there's no signal or sound coming from that particular station.

I am pretty sure there is no stereo feel. There's a button to put it in mono. But when I push it to mono I find no difference in sound. I even fiddled with the stereo button on my amplifier. Absolutely no difference.

My question is, do I need to do an alignment? I've read a few threads on audiokarma about voltage from DC to discriminator should read as 0 volts in tuners and that there is a sort of pot which can be adjusted for alignment.

The gold caps don't really memorize the stations as I think their times up.

Can't seem to get a service manual for the tuner on the internet. Tried hifiengine.

Would appreciate if someone could help me with the service manual for this tuner.

 

[amptramp]

The only pot adjustment is for the 38 KHz oscillator for the multiplex IC on most FM tuners. You would have to be able to get a signal into the multiplexer to see if the phase locking works. But it sounds like your problems are coming from a point well ahead of that in the FM RF or IF or detector section.

 

[allanmatters]

I will try to locate the manual to see exactly what you are referring to. So far I have come across quite some pots like the vr 301 and others.

The other problem wirh regards to the ghost auto tuning (nonstop) after and hour or so is interrupting my listening experience.

It eventually shuts down if I try to stop it from auto tuning on its own. I tried powering it down and then powering it up again after several minutes, but it's the same. Just auto tuning nonstop. I guess something is getting hot in there

 

[allanmatters]

Interestingly I found a transistor D880 at an extreme temperature. It's pretty hot. You can touch it for barely 2 seconds from the top.

The tuner is off. However, it's still connected to the mains while the mains is on and this transistor won't cool down until I disconnect the unit from the mains

 

[allanmatters]

So I pulled out a resistor reading as orange, orange, brown, gold which to my understanding is 300ohm. The color of the resistor was darkish looking. Seemed like the odd one out. After taking it out it read as 220ohms.

I put a new one which read as 229ohms

The tuner was able to run longer than usual. Also spotted another resistor looking darkish faded and that's running hot too. However, I am not able to find a replacement in terms of the same value from my other junk radio sets circuit boards.
It reads as brown grey brown gold. As far as I know it's an 180ohms resistor. Does any one know a substitute for this one I can use?

Edit : so I put in a 220ohm resistor as a substitute. The tuner was running well for just 5 mins until it started switching between AM and FM continously, with no music playing.

I put the old one back. It reads as 171.00 on the multi meter. I am guessing thats supposed to read 180ohms.

I also added a 21 ohms resistor connected parallel to the faulty old one which I added back. So it's now a total of 192ohms. The unit did start switching between AM and FM after some time.

I am having a hard time trying identify the color codes on the faulty one as I got no service manual to double check and th w faulty one is dark and the colors look confusing.
Does the value of this particular resistor need to be exact? If any one has this service manual, the number on the board is R709. I am looking at identifying what is the exact value of the resistor on there.