Hey everybody. I've got a kba 60 here I've got an issue with I'm hoping someone can help me with.
All the functions on the amplifier work, all knobs and switches do their appropriate jobs. The problem I'm having is if I go through channel one or Channel 2 of the amplifier it seems like the output of the amplifier is half, of course that reduces the bass response drastically along with the overall output.
When I first plugged it up and was listening to it it (line out from computer) it sounded fine I thought, then about 5 minutes into listening it popped in full bore normally obviously. So I cleaned all the knobs and switches with contact cleaner, all the inputs and outputs as well. Amp continued to play fine again for another 5 to 6 minutes and then it dropped out again and hasn't returned. So I took the line out of my computer and put it to the power amp input on the amplifier and it works fine. So it's something in the preamp stage I'm guessing. There's no Distortion coming through the speaker going thru the amp when either channel is used, it's just the power output seems in half which I'm assuming is due to the lack of drive from the preamp stage. Any idea what could cause this? I have used freez spray, tapped every component, Flexed the board and nothing seems to make a difference. Could possibly be one of the op-amps? Any insight is greatly appreciated.
Kb/a 60 issue
Re: Kb/a 60 issue
Since this post was so informative I figured I'd follow up in case some poor soul encounters this issue or a similar issue.
I'm not sure exactly if the target problem was a loose solder joint on a potentiometer, a bad capacitor, or a combination of both. After receiving no input here I decided just to go farther on my own intuition that it was possibly a bad cap in the input stage or a cold joint, so I shot gunned it
I recapped the entire amp as well as reflowed all the solder on every connection. It works just fine now. However whether it was a solder joint or the capacitor I'll never truly know. But the important thing is its working. After putting the op amps on a curve tracer they all checked out fine. So I am assuming it was probably a capacitor in line on the input stage as no real solder issues stood out.. The kb/a 60 is unfortunately at that age where the electrolytics need to be replaced simply due to age I usually always replace with 10,000 hour capacitors of good quality.
I'm not sure exactly if the target problem was a loose solder joint on a potentiometer, a bad capacitor, or a combination of both. After receiving no input here I decided just to go farther on my own intuition that it was possibly a bad cap in the input stage or a cold joint, so I shot gunned it
I recapped the entire amp as well as reflowed all the solder on every connection. It works just fine now. However whether it was a solder joint or the capacitor I'll never truly know. But the important thing is its working. After putting the op amps on a curve tracer they all checked out fine. So I am assuming it was probably a capacitor in line on the input stage as no real solder issues stood out.. The kb/a 60 is unfortunately at that age where the electrolytics need to be replaced simply due to age I usually always replace with 10,000 hour capacitors of good quality.