Amp Help - Laney Cub 12 valve replacement

Teetonetal

At practice last night my amp suddenly changed sound, it became much more saggy a fizzy sounding, especially in the 1w input. When I checked around the back I could see that the middle 12AX7 was not lighting up. Metal clip that holds it at the base has discoloured slightly.

So does this mean the valve needs replacing?

Is it easy to do and how do you do it?

Do I need to replace all valves or just 1?

What is a good replacement valve

Thanks, all help appreciated

ICBM

Yes, replace that valve first. You only need to do the one.

Try a JJ or Chinese-made ECC83/12AX7 (any brand, including Mesa). Avoid Sovtek or any other Russian-made 12AX7 - that position is a cathode follower they have a high failure rate in that type of circuit.

It is possible it isn't just the valve, but try replacing it first anyway - it's always good to have a spare in any case.

Teetonetal

Thanks - anything special I need to do or is it just pull out the old, plug in the new?

ICBM

Teetonetal said:

Thanks - anything special I need to do or is it just pull out the old, plug in the new?

Yes, just that. Just be careful not to bend the pins, that's all.

Teetonetal

sweet, thanks for your help! Will order a couple of tubes

Voxman

I have a Cub 12R that had a similar problem and the amp was repaired by DV247 under warranty. The problem wasnt the valve but a loose connection on one of the valve sockets giving distortion and reduced volume.

Took the opportunity of replacing all the valves with JJ hand tested premium valves including a matched set of power valves. Sounds terrific with the JJs..massively better than the stock Ruby tubes that were dull by comparison. Amp is now louder, brighter, with way better and more organic and harmonic gain tone, warmer vibrant cleans, and even a little more volume and clean headroom. Delighted with the change.

Teetonetal

Voxman said:

I have a Cub 12R that had a similar problem and the amp was repaired by DV247 under warranty. The problem wasnt the valve but a loose connection on one of the valve sockets giving distortion and reduced volume.

Took the opportunity of replacing all the valves with JJ hand tested premium valves including a matched set of power valves. Sounds terrific with the JJs..massively better than the stock Ruby tubes that were dull by comparison. Amp is now louder, brighter, with way better and more organic and harmonic gain tone, warmer vibrant cleans, and even a little more volume and clean headroom. Delighted with the change.

Worth knowing, this is 2nd hand amp though so no warranty. If replacing the valve doesn't work I'll take it to a tech.

Teetonetal

Cheers ICBM, new JJ tube arrived today inserted and seems to be working properly again, proper test at band practice later in the week, but thanks for the help and advise! Always nervous about amp work