Newbe and excited to find AudioKarma.org

My name is Scott and I recently took the plunge to get back into vintage music. I have a lot of great memories of being a kid in the 70's and early 80's when I first really began to notice music. Our home stereo's were monstrosities with knobs and dials and waving needles. We used to spin records backwards to freak ourselves out when having a sleepover with friends. Jukeboxes blasted Foreigner while we pumped quarters into pinball machines, Mrs PacMan and Kung Fu at the arcade. Went on roadtrips with the family in the giant wood-paneled station wagon down Hwy 101 on the Oregon coast listening to John Denver on 8-track. Man the world was good back then....

I now of two teenage boys of my own who are into music, but all they've ever known is what comes out of an iPod. I want them to experience what music was meant to sound like. But since my wife would have strong words with me if I went out and dropped $1000 on some decent audio equipment, I decided to be patient and see what I might come up with from Craigslist, Goodwill, yard sales, etc. and the wait was worth it. For under $150 i picked up a beautiful Marantz 2216B (works flawlessly), a Toshiba SA-304 (that needs LOTS of work), and a Pioneer SX-680 in near perfect cosmetic condition but with a shorted left channel.

The Marantz needed replacement bulbs, but otherwise was fully operational when I got it home. Goodwill was selling it as "non-working, for parts only", but all that was wrong is they had the tape monitor button pushed in so couldn't hear the radio play.

The Toshiba had something spilled on it/inside of it and really did a number on some of the circuitry. It's a 4-channel unit that is in fairly good condition minus the deep half-inch scratch on the face-plate. It does operate but only has sound from one of the four channels.

The Pioneer is face-plate is near mint. The wood housing has two small areas on the edges where the veneer has been damaged but I think it can be repaired enough to look decent. Unfortunately the left channel appears to be shorted out or something. The left channel needle maxes out when powered up, and when I connected my speakers up, it immediately fried them (yeah...I was not happy to lose a $200 pair of speakers. Hard lesson to learn that when testing equipment it's best to hook them up to some cheap cannon fodder first).

I'm comfortable around electronics, and smart enough to know how not to electrocute myself, but I'm no technician. I can change out capacitors just fine when there is an obvious bulge or leak and I know what I'm looking for. For the Toshiba...I'll probably just list it on Craigslist and see what I can get for it. The Pioneer is too nice looking not to try and fix it up and possibly keep it. I'd be curious to know if any members have experience with the SX-680 model, with a channel shorting out and blowing speakers, and if it's a home repair remedy or if I'd be best to drop it off with a technician.

I will look to add photos of all three units tonight.
 
This unit does not have a protection relay, it just has fuses. So some previous owner must have "fooled with the fuse" to have left something behind that would destroy a speaker.

(hmmmm a channel's out... blown fuse...
get a fuse... damn, the fuse blew again...
AH HAH!!!I KNOW!!!! I'll get a BIGGER fuse!!!
arrrrrgggghhhhhh smoked the speaker...
get this thing OUTTA here!!!)

Chances are it's the stk-0039 module, it is a socketed, screw mounted with white (goop) thermal transfer compound module. New modules from the manufacturer are not available, but there are plenty of "replacement" modules that vary in quality (was the designer out for a quick buck or did they do it right?).

While it is out, check R351, R353, or R352, R354 (whichever is appropriate, located right next to the dead module's socket) for 0.22 ohms, to see if the module killed them during it's demise.
 
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If you want to fix it yourself you're in the right place. The SX680 is simple enought that you can get it working not matter what's wrong. The brain trust here is phenomenal. What you lack in knowledge can be offset by precisely following instructions, precisely answering questions, and being patient enough not to jump ahead. The first project might require you to buy some instruments (good voltmeter), but it's still be less than hiring a tech. Welcome to the forum.

Twodogs
 
Welcome. Yer last name ain't GRISWALD is it??? The references to
roadtrips with the family in the giant wood-paneled station wagon down Hwy 101 on the Oregon coast listening to John Denver on 8-track.
was too much to pass up.
 
Not Griswald, but that's sometimes what it felt like. Not only could the "tuna boat" haul about 47 people, we had a giant rack on the roof that was always loaded up with inner tubes, coolers, tents, etc. My little brother and I would sit in the far back on a blanket spread out with our toys and games (who the heck needed seat belts in those days?). Older sister would sprawl out on the middle seat and the folks would just be pleased when we weren't yelling or fighting with each other.
 
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Photos attached

I know it's important to include photos of your gear, so here they are. For the Marantz I included a before photo and an after photo with the blue LED bulbs inserted. Also note that on the Pioneer you can see the left channel needle maxed out.

Also including my Polk Audio Monitor 5A's I bought for $40. The only thing wrong with them was the external fuse was blown on both making the tweeters non-functional. Cosmetically they are in near mint condition. The photo flash makes the 6.5" look ragged, but it's perfect.
 

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If you want to fix it yourself you're in the right place. The SX680 is simple enought that you can get it working not matter what's wrong. The brain trust here is phenomenal. What you lack in knowledge can be offset by precisely following instructions, precisely answering questions, and being patient enough not to jump ahead. The first project might require you to buy some instruments (good voltmeter), but it's still be less than hiring a tech. Welcome to the forum.

Twodogs

Awesome. The tech would charge $50 just to look at it, but that amount would be applied to the total bill. He said on average repairs would be between $90 - $150. I spent $60 on the receiver without knowing the functionality and am planning on selling it once I get it working, but don't think I could get my money back if I end up shelling out another $100+ on repairs.

I do have a voltmeter but am not real skilled in using it. Non of the caps show any obvious damage, and no scorch marks on any of the circuitry that I could find. All glass fuses are intact an seem to be of the correct amps. I'll have a couple hours this weekend to dive into it so would love some initial suggestions, what to take photos of to post, etc.
 
This unit does not have a protection relay, it just has fuses. So some previous owner must have "fooled with the fuse" to have left something behind that would destroy a speaker.

(hmmmm a channel's out... blown fuse...
get a fuse... damn, the fuse blew again...
AH HAH!!!I KNOW!!!! I'll get a BIGGER fuse!!!
arrrrrgggghhhhhh smoked the speaker...
get this thing OUTTA here!!!)

Chances are it's the stk-0039 module, it is a socketed, screw mounted with white (goop) thermal transfer compound module. New modules from the manufacturer are not available, but there are plenty of "replacement" modules that vary in quality (was the designer out for a quick buck or did they do it right?).

While it is out, check R351, R353, or R352, R354 (whichever is appropriate, located right next to the dead module's socket) for 0.22 ohms, to see if the module killed them during it's demise.


We'll...on the schematics diagram it does list STK-0039, and looks like there are two of them. I'm reviewing this at work so am not sitting in front of the unit at the present time. Are then any signs I should be looking for before attempting to remove them? And since the issue only seems to be with the left channel, do I need to focus any attention on the module for the right channel? R351 & R353 are associated with the left channel module.
 
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This unit does not have a protection relay, it just has fuses. So some previous owner must have "fooled with the fuse" to have left something behind that would destroy a speaker.

(hmmmm a channel's out... blown fuse...
get a fuse... damn, the fuse blew again...
AH HAH!!!I KNOW!!!! I'll get a BIGGER fuse!!!
arrrrrgggghhhhhh smoked the speaker...
get this thing OUTTA here!!!)

Chances are it's the stk-0039 module, it is a socketed, screw mounted with white (goop) thermal transfer compound module. New modules from the manufacturer are not available, but there are plenty of "replacement" modules that vary in quality (was the designer out for a quick buck or did they do it right?).

While it is out, check R351, R353, or R352, R354 (whichever is appropriate, located right next to the dead module's socket) for 0.22 ohms, to see if the module killed them during it's demise.

Pulling the cover off, the STK-0039 are indeed large modules and should be fairly easy to access. Before removing though I was wondering if there is a recommended way to test to see if they're faulty or not. I assume the thermal transfer compound is dried up and would crumble to pieces when pulling the module out.

Also...in just some very brief internet pricing looks like I'd be hard pressed to even get a $100 for this unit in fully working order, meaning I'd need to make repairs for under $40 just to break even. This may not be worth repairing at all.
 
Problem solved!! Thanks AK!!

I looked on eBay for a replacement of the STK-0039 pack and found one shipping from Hong Kong for $5 plus another dollar for shipping, bring the total to $6. I payed through Paypal figuring I wasn't worried about losing $6 if the part was crap. The thing arrived in 7 days (I live in Oregon, USA) and it was packaged superbly well so that all pins were in perfect condition. I pulled the old component out, popped the new one in and the unit is now working perfectly. It took me all of about 4 minutes to do the swap. Nothing else was done for this unit other other then a good cleaning and a little deoxit on the knobs. The sound is brilliant.

Here are the before (with left meter pinned) and after photos...
 

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Just for the sake of keeping the STK-0039's happy and healthy there are some emitter resistors (should be 2 dual's or 4 singles) with a value of .22ohms 2 watts. With the unit turned off test them with an ohm-meter. If they are dual, no problem, the center leg is common between the two.

Procedure.
1.) Turn on ohmmeter, set to ohms.
2.) Touch the probes together and let the meter settle down. Write down the result. This is the internal resistance that is added to the results and you need to subtract from the resistor reading to get a true reading.
3.) If singles, touch the probes (One to each end of the resistor) so the resistor is between the probes. Let it settle down and write down the reading. Repeat for each one.
3A) If DUALS. Put one probe (black) on the center pin and probe the outer pin with the other probe(red). Let it settle down and write result. Do the same with the other side (red probe outer pin). write down result. Repeat for the other channel.

Now subtract the 1st reading you wrote down by touching the probes together, from each reading. Look at the resistors for a percentage. Normally 10%. If the readings variance's are less than the percentage you're ok. If one is out of spec replace it and it's mate. As cheap as they are you can replace all 4 and keep both STK's happy. And drop your anxiety level as well.

I couldn't find any @ Mouser. But did find 7 @ Digikey. All Wirewound, 5 of 7 are flameproof. All are small enough to fit in the area. And they are all 3 watt, which means they will dissipate heat a bit better than a 2w, staying cooler in the process.
http://www.digikey.com/product-sear...=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

This style would fit better, but ohmite doesn't make it in a .22 in any wattage. PHOOOIE!!!
TWM5J30KE.jpg

Larry
 
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