Whelp....screwed the pooch and torched an output on SX-680.

[streckfu]

Backstory:
As described in my bookshelf speaker thread, I picked up the Overnight Sensation speaker kit to build and put them together. I tested the crossovers with the drivers out of the enclosures after building them with a small Kinter amp I have. They seemed to work fine so I put them in the cabinets and went to test them using the SX-680 in my son's room.

Immediately upon power up the left channel meter spiked and a second later went to zero....blown channel fuse. After making certain that I connected the speakers correctly, and hoping that it was just a short in the speaker, I removed the OSs and connected the previous speakers then replaced the fuse. No change with no output on the left channel while the right is just fine. And to add icing to the cake, the woofer driver is seized.....

I have the service manual and will start investigating this weekend.

I am hoping (but it doesn't look good) that the STK0039 is not fried. In case I need a new STK, is Ebay still the only source? I am not finding anything via Google searches that are not Ebay auctions.

Should I check anything before moving the good STK0039 to the other position to verify the left one is bad? I am hesitant to do that out of fear of damaging it as well...If I need to replace the STK, which thermal grease/paste should I use? Will something like this work: LINK

Any advice in how to proceed is appreciated.

 

[Watthour]

I'm not going to be much help on the replacement STK modules, other than the more expensive ones found through Amazon: http://www.amazon.com/American-Micr...e=UTF8&qid=1464928564&sr=8-1&keywords=STK0039

However, I can advise you to NOT use that thermal compound on SS devices. It likely has metal in the compound. Use only a pure (metal-free) zinc oxide paste or silicone grease such as GC Type 44. Electrical conductivity of metal-bearing compounds may not be a big problem for computer CPUs running at a core voltage of 3.2V, but power output transistors with hot collector tabs or cases hooked to ±90VDC supplies will not like it at all.

 

[streckfu]

That is a big help and thank you! I'll be sure to get teh GC Type 44.

Have you used the STKs from that source? I'm willing to pay more for what works and is not a poor fake import. For now, I did take a chance on an Ebay source that is domestic and offers a warranty (at least advertises one.....).

 

[ZOOM]

There is no source. ALL STKs for sale are fake, every single one. It's a common strategy to sell fakes at a very high price, to give the illusion that they sell rare, hard-to-find genuine parts. All fakes will blow up either instantly or if you try to turn up the volume a little bit. Some people here tend to recommend using fakes anyway, but that will only hurt you in the end. You'll waste time, money and you'll be disappointed and angry. In short, there is no way for you to fix this amplifier, aside from taking a STK from another. Sell it for parts or chuck it in the trash. There's no other solution.

The thermal compound you wanted to use (Arctic MX4) is among the best there is, and is certainly not conductive.

 

[streckfu]

"Sell it for parts or chuck it in the trash. There's no other solution."

I am not ready to go that route. There is a local tech that I will take it to if I can't fix it myself.

 

[gpounce32768]

Dunno, I just repaired a Technics 5360, uses two stk0182 units. The ebay replacements I bought are used- markings and serial #'s are at least plausible, they match the originals very well wrt font & printing density; front and back. The amps both work, sound fine, DC offsets are pretty close. So buyer beware for sure but I'm not buying the all fakes proposition, though some may well be.

 

[streckfu]

Just confirmed that it was a bad amp circuit by swapping them. Replacements should be here next week.

 

[elvi]

Just confirmed that it was a bad amp circuit by swapping them. Replacements should be here next week.

Take an extra moment to sand off the black plastic extrusion for the external cover, as it can interfere with how well the rear heatsink mates to the larger heatsink.

FYI.. I located NOS GCC parts.. All true Sanyo if I remember correctly

 

[streckfu]

Are you willing to share?

 

[elvi]

Are you willing to share?

There are companies that advertise here on AK, and I've also located a set VIA a post in general solid state forum. The reseller was out of stock last time I asked, unfortunately. I have stopped purchasing and taking in units that need a module.

 

[streckfu]

Replaced STK is working for now. Even if fake, I happy to have it running.

 

[zebulon1]

Good deal.
I like to sand down the back and test fit the module to the back making sure most of the metal back of the module touches the heatsink surface. Then apply the thermo paste. Some of the newer modules have a ridge of plastic that keeps the module a good distance from the heatsink.
Those modules get HOT! Even in a min volume setting.

 

[streckfu]

After a little bit of use, the replace STKs started inducing weird noises that made the receiver unusable.
I did buy a NTE1282 which is proven to be excellent. The NTE seems to be NOS and was in the manufacturers packaging.