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HARMAN KARDON 430 - Right Channel Blowing Fuses

JB8

JB8

Well-Known Member
Hey all, it's been a while, back at it!

I'll keep this brief. When I first tested the unit it had a blown right channel fuse (the fuse that sits next to the main filter caps) along with the fuse on the underside for the same channel (FU3), both 3A. I replaced both fuses, removed and tested the output transistors, reinstalled them and swapped out Q421-422 (458's that I would eventually have swapped out regardless). Using a DBT everything looked good but I didn't fire up the unit under load... I then swapped out the Main Amp caps (6) along with the main filter caps (4). DBT after the new components were installed looked good so I hooked up some test speakers and fired it up still through DBT. Everything seemed fine but I hadn't engaged the speakers. I then pulled it from the DBT and powered it up, all good until I engaged the speaker button and "shortly" thereafter both fuses blew again. Dead right channel, left channel sounds fine.

The speaker fuse for the right channel has not been blowing and testing the transistors across the main amp and tone preamp with DMM didn't reveal any glaring issues but I know those 1344's can be problematic at times. It's been a while since I've attacked this kind of issue so I'm reaching out to this squad for some help. The issue is typically right there in front of my face but I always appreciate the assistance, thanks in advance!

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Ok, let's try another tact!

Three quick questions:
  1. The three fuses on the underside of the unit, should they all be slow blow? I've never had to replace these before. Currently the .5A fuse (middle) is slow, but the other two are fast. This seems like the others I've seen but checking nonetheless.
  2. Based on the fact that both right channel fuses are blowing (speaker fuse is not), but only once the speakers are engaged, should I primarily focus on the main amp and tone board specific to tracking down the culprit? Assuming since it's only one channel it's likely not PS but would appreciate confirmation.
  3. If after replacing a component on the right channel during troubleshooting, I'm assuming I should still test by using the DBT first and see if when engaging the speakers I get the light to glow? And while on DBT, should I be checking any specific voltages to establish any disparity between the channels?
 
After so many of you clamored to help I feel guilty saying this, but, I fixed it!

Even though this post received zero responses, I'll be back, maybe next time with something more interesting.

Still the best forum out there, very appreciative! :thumbsup:
 
JB8 said:
After so many of you clamored to help I feel guilty saying this, but, I fixed it!

Even though this post received zero responses, I'll be back, maybe next time with something more interesting.

Still the best forum out there, very appreciative! :thumbsup:
Click to expand...

I'm curious, but what was the fix?
 
All I can say is that there was a knuckle involved and a counterclockwise swirl...
 
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