Tweaker hiss issue

[7elephant7]

Hi,

I've had a Tweaker 15 head for a few months, and everything worked fine until one day it started to make a hissing noise. Let me be more precise. Whenever the amp is on standby and I put it in ON, it starts making some crackling (like frying bacon) noises, for about 1 or 2 seconds, which then fade away. Then after that there is a constant, permanent hiss/static noise. This noise reacts to both the master volume control and the gain control. With both dimed there is a LOT of hiss, but that would be expected. What bothers me is that the hiss is present at more normal settings (even bedroom volumes). It doesn't change if I plug in the guitar, if I unplug it, etc. Also, whenever I switch from ON to STANDBY, I can also hear a slight crackling like before, that vanishes fairly quickly.

Now, the first thought was tubes of course. So I bought new tubes. I have three preamp tubes on the amp, and two brand new Tungsol preamp tubes, and I swapped the new ones in all possible combinations, the noise is still there. I definitely do not think that the three preamp tubes can be bad!

I did the same with power tubes, got myself two brand new matched Tungsols, popped them in and the noise is exactly the same as before.

Do you know what else can I try? It's not under warranty AFAIK (I bought it used from a private seller). I don't want to shell out too much money in a tech. In fact I was just about to sell the amp (I'm moving abroad and don't have the room to take it with me) when I discovered this issue, but I want to sell it in good condition.

 

[shimmilou]

The "sizzling bacon" sound is a classic symptom of a bad tube(s), or sometimes a socket with poor connections, either solder joints or the socket pins themselves. If you are sure that your tubes are good, you can try wiggling each tube in its socket to see if the noise is affected. Check the socket solder joints closely and maybe try re-tensioning the tube sockets.

Here is a good site with a brief tutorial of how to re-tension the sockets. Keep in mind that each amp is different, so you want to be safe, and sure that the amp is unplugged from electricity and the caps are discharged before poking around inside.

http://billmaudio.com/wp/?page_id=171

 

[7elephant7]

The "sizzling bacon" sound is a classic symptom of a bad tube(s), or sometimes a socket with poor connections, either solder joints or the socket pins themselves. If you are sure that your tubes are good, you can try wiggling each tube in its socket to see if the noise is affected. Check the socket solder joints closely and maybe try re-tensioning the tube sockets.

Here is a good site with a brief tutorial of how to re-tension the sockets. Keep in mind that each amp is different, so you want to be safe, and sure that the amp is unplugged from electricity and the caps are discharged before poking around inside.

http://billmaudio.com/wp/?page_id=171

Thanks. Yesterday I played a lot with the tubes, swapping one each a time (including both preamp and power amp), so I'm positive they are ok. I didn't wiggle them when the amp is on of course, but I did swap them with brand new ones.

I will have a look at the tutorial to re-tension the sockets, perhaps there is a problem there. How do I make sure that the caps are discharged?

 

[shimmilou]

Always verify that caps are discharged by checking the DC voltage across the caps with a meter. After the amp is unplugged from electricity, you can check from pin 3 of each output tube (+) to the chassis (-), looking for very low DC volts. The voltage won't be zero, but probably less than 10 volts or so.