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JVC R-K100 Repair, STK Swap possible?

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Metal_Rott

New Member
Hey guys, I am repairing a toasted JVC R-K100. I mainly wanted to ask if it is okay to replace the STK4141ii with a STK4149ii?

Although I did it anyway and it turns on fine and but... still does the same thing. After turning it on within 3 seconds the g2z-222p-us relay trips. It doesn't shut down the receiver, it just doesn't produce any sound.

Well either way, I'm reppacing the relay and hoping that's the issue but I'd still like to know if it's perfectly Okay to swap the STK's that way. Can anyone throw me a bone here? I'm new to restoring vintage receivers. Thanks!
 
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So are you saying that when you click the reciever on and wait about 2-3 seconds, you Can here a relay click?

If this is the case then this is a GOOD thing. You should be getting a relay click after two - three seconds when you turn on the unit.
 
ELzekio said:
So are you saying that when you click the reciever on and wait about 2-3 seconds, you Can here a relay click?

If this is the case then this is a GOOD thing. You should be getting a relay click after two - three seconds when you turn on the unit.
Click to expand...


Yes I get the click but no audio output. Not even a buzz or scratch. The caps aren't bloated and I can't see any obvious burns or burnt hardware. My eyes tells me one thing but my nose tells me another.

I removed and opened the relay and it looks flawless. No corrosion and coil leads are intact.
 
I'm seeing some discoloration on these 2 resistors. Both are 68ohm but both only read 33ohm on the meter. Could that be the issue?
 

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Metal_Rott said:
Hey guys, I am repairing a toasted JVC R-K100. I mainly wanted to ask if it is okay to replace the STK4141ii with a STK4149ii?

Although I did it anyway and it turns on fine and but... still does the same thing. After turning it on within 3 seconds the g2z-222p-us relay trips. It doesn't shut down the receiver, it just doesn't produce any sound.

Well either way, I'm reppacing the relay and hoping that's the issue but I'd still like to know if it's perfectly Okay to swap the STK's that way. Can anyone throw me a bone here? I'm new to restoring vintage receivers. Thanks!
Click to expand...

Why? you can still get the original.
http://www.bdent.com/stk4141ii-sanyo-audio-sip-integrated-circuit.html
 
they are probley in parallel. Measuring resistors in Circuit can very commonly yield off results.

Are you able to find where the pre amp section connects to the amp section? I would check which part is giving the problem by injecting a signal into the amp section (from something like An iPhone). To verify the amp section is working.

Can you give some more pictures of the circuit boards?
 
In my experience its very rarely the STK pack which is at fault, its everything else around them ! Of the machines I've worked on with STK modules, only one had a shorted output and that resulted in fuses blowing.

Why were you looking at replacing the pack ? Have you checked the pinouts ? They often vary so substituting a different model is risky.

Did you verify voltages being supplied to the STK module ? Those resistors look like fusible types and could be burned up.
 
+1 to injecting a signal and tracing it - I use an audio probe that I made for that purpose.

Verify your voltages first though, starting with the power supply.

Caps can fail, especially in the signal path, without any obvious bloating.
 
I got the 4149 for dirt cheap at a local electronic store (they didn't have the 4141) and It gave me the idea of modifying this receiver to output a higher wattage. I couldn't tell you if there is a difference, It didn't work with the 4141...but....strangely enough guys! It's working now! I put everything back together and was going to call it a day but I tested it with a pair of different RCA's and... It works! That's not to say it was working before, not even the radio worked before, but now everything works perfectly!

It was the STK4141, I knew my nose knows whats up .

The 4149 seems to be working great in this arrangement, sounds great! Gonna post a video tomorrow of it powering some Sansui SP2000's on youtube.

Thanks for everything guys! If i didn't come here I would have just gave up and taken it in to a shop.
 
Changing STKs or for amps that use discrete outputs will not yield higher power. This is determined by the power supply voltage and the ability to deliver required current... It all starts with the power transformer. Putting in a higher voltage transformer is not really an option either. You would have to re-enginer everything downstream.
 
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