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B&K ST1400 II with distorted left channel

crazy-in-az

crazy-in-az

Uhhhh....
I bought this amp about three weeks ago, and until last night it has been flawless.

Last night I turned it on following the proper order of pre-amp first, then power amp. As soon as a I tried playing a record I could hear a fuzzy sound coming from the left speaker, and the volume was fluctuating rapidly. I also could visually see the woofers on my Marantz Imperial Six's pumping in and out, as though there was some bad feedback from my turntable. The right speaker doesn't seem affected.

Here are are the things I tried-

-I swapped sources to my Technics CD player
-I changed speaker wire
-I tried different speakers
-I swapped interconnects
-I tried the amp on both outputs from the pre-amp (a Nikko Beta 30)
-I exercised all the buttons and switches on the pre-amp
-I tried to clean the amplifier control muting switch with deoxit
-I tried the same record and same turntable on the Nikko with a different amplifier and there was no distortion

I'm guessing something else is going on, something that requires more than a cleaning or swapping of cables. Outside of a complete overhaul can anyone give me some pointers or ideas?
 
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Oh yeah, I also made sure the subsonic filter was engaged on the pre-amp. I got the same distortion and woofer pumping with the switch on or off...
 
Check the speaker fuse on that channel. My ST140 had to have the springs in the fuse holder stretched out so they push harder on the fuse. They made an awful noise if they are loose.
 
NeilBEN said:
Check the speaker fuse on that channel. My ST140 had to have the springs in the fuse holder stretched out so they push harder on the fuse. They made an awful noise if they are loose.
Click to expand...

So I checked the fuses, but there weren't any springs in the fuse holder, just clips. And I accidentally shattered one while trying to re-seat it! So after waiting for a new 4AMP 250V fuse my problem still persists- scratchy distortion from the left channel only.
 
You should know better. (no cookies for you) these amps when sourced unknown.. it's best to open the box and inspect, bring up on a dbt.
 
Binkman said:
You should know better. (no cookies for you) these amps when sourced unknown.. it's best to open the box and inspect, bring up on a dbt.
Click to expand...
I know... Bad llama!

When I bought it a few weeks ago I inspected everything before power up, and used a pair of cheap speakers to test it. After that I added it to my main system. It worked fine for about two weeks before it started distorting.
 
Did you try either a different power amp or different pre-amp?
 
LOL no worries :D.. mate. We're not exactly any kind of rush on anyone's schedule... no sm for the topic.. 2nd series wattage? Thinking diff. may be more in the output stages. The 1430 @ 125W?
 
crazy-in-az said:
Okay, it looks like the 1430 has a different layout. I can't find a schematic for the 1400 II anywhere.
Click to expand...
Hello, I’m curious if you ever figured out the problem with your amplifier, ironically I have a B&K Ref 2220 that just started doing the identical thing, low volume ok as volume raises woofer start pumping in and out with distortion on left channel only, I have also tried everything you did and nothing, it still persists til present day, and I need it fixed I love love love this beast, and I’ll add its worse with 4 ohm speakers than 8 ohm
 
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