Odd problem in GK-1/55N

cmscott6 · « **on:** 13 Oct 2003, 01:44 am »

I seem to have an odd problem that crept up yesterday in my GK-1/55N combination: with no sources turned on I get an intermittent scratching sound from the left channel, almost the sound of turning a dirty pot, and the woofer randomly jumps. I'm a little concerned that this is not a healthy thing for my speaker. I tried switching tubes and checked for loose connections, but nothing seems to affect this. Is this the sound when dc is somehow getting into the speaker? Or does this sound more like a loose connection/bad solder joint suddenly creeping up? If anyone has any troubleshooting connections, I'd love to hear them!

Thanks!

Chris

AKSA · « **Reply #1 on:** 13 Oct 2003, 03:18 am »

Chris,

Disconnect the GK-1 from the amp, leaving the input to the amp not connected to anything.

With the amp on, and the speaker connected, listen over a period to see if this problem is coming from the amp.

If not, then connect the preamp, and listen again. This obviously lets you know where it's originating - we have to know this first up of course.

Cheers,

Hugh

cmscott6 · « **Reply #2 on:** 13 Oct 2003, 02:23 pm »

Hello Hugh.

The problem is definitely in the left channel of the pre-amp. The amp itself is dead quiet without connection to the pre. I made sure that the lid of the pre was not touching any of the bypass caps on the top of the pcb - that seemed to take care of the scratching noise.

There is still a barely audible (i.e. you have to have your head up to the drivers) white noise sound, which is the same regardless of volume. This may be just background noise from whatever and doesn't really concern me.

The problem with random thumps and jumps of the woofer does have me baffled. Again it only does this with pre-amp on and is entirely random as to frequency and volume. The problem started suddenly, and I had not moved or disturbed any of the components beforehand. Strange.

Thanks for the help, Hugh.

andrewbee · « **Reply #3 on:** 13 Oct 2003, 04:27 pm »

I'n certainly not Hugh

Try swapping the tubes around and see if the sound follows the tube. Check the tube sockets / pins as well to see if they are clean.

Andrew

PSP · « **Reply #4 on:** 13 Oct 2003, 05:20 pm »

A wise sage once told me that intermittent connections / bad solder joints can sometimes develop at the tube sockets... if the soldered connections get hot enough they can over time anneal, oxidize, and generally cause trouble. Maybe you want to carefully re-heat all the soldered connections to the left tube socket?

good luck,
Peter

AKSA · « **Reply #5 on:** 13 Oct 2003, 09:38 pm »

Hi Guys,

Really good advice.

I'd do the tube thang Peter mentioned, Chris, and would affirm that Andrew's point is often the case; heat from the tube will over time boil out the flux from the solder eventually causing a dry joint. This may be a pre-existing problem, it may be something which has developed; either way, it sounds thermal in origin and the advice on resoldering is excellent.

Hope this helps, thanks guys,

Cheers,

Hugh

Oz_Audio · « **Reply #6 on:** 13 Oct 2003, 10:21 pm »

I have had this problem as well.

It is bad solders on the tube holder to the pcb, not the easiest thing to solder as the tags are large and take a time to get hot for the solder to stick.

Try re soldering each leg again.

Mark

cmscott6 · « **Reply #7 on:** 14 Oct 2003, 02:04 pm »

Thanks folks!

I tried swapping tubes, and that didn't affect anything, so I'll try resoldering. Muchas gracias!

Chris