Valvestate 8080 bass bug

[BrainDamage]

Hello all,

First I'd like to thank the creators of this site and its members.

I've recently received amp Marshall valvestate 8080 bought in 1996 in Canada.

Since I haven't used it much, the amp seems to be in a very good condition. Still I don't know why it can't produce good basses anymore. I can only get a crunchy, dirty, powerless, unplayable sound.

Here's my personal diagnostic:

1. It's not a 6L6 tube matter, because the trouble concerns both channels, clean and overdrive. (while the tube only works when the OD channel is selected)

2. I supposed the speaker could have been damaged during its transportation from Canada to Morocco. I've checked the Celestion G12T speaker which seems almost new.

3. I've also plugged different guitars and jack just to make sure it's an amplifier problem and nothing else.

Questions:

1. The amp reposed in a frisky locker (probably at an average temperature of -10 degree C) for more than a year. So is this a possible reason?

2. Is it about circuitry? How could I fix it?

Thanx for helping an authentic Moroccan rocker.

PS: If I had to change the speaker, I've read in some forum that the Celestion Vintage 30 works a lot better with the Valvestate 8080, producing a nearer vintage sound. It sounds good, since I'm a Jimi Hendrix fan.

[korhipt]

valvestate 8080 bug

Hi,

First i would check the printboard for bad soldering etc.
Then give every pot and all switches a good spray of contact cleaner.
It is often that bad sound, low sound, dip in sound etc is caused by bad contact in switches and pots.

[Enzo]

OK, how did you "check" the speaker? Can't tell anything by looking. The very first thing I would do is connect the amp to a different speaker. It does not need to be the speaker you like a lot, just a speaker to determine if the other speaker was bad.

Does the speaker cone move freely and without scraping?

It is not a 6L6 issue because the amp is solid state. There is one lonesome 12AX7 in the preamp.

Check ALL the cement power resistors with a meter. Especialy R120. That is a 0.33 ohm 5 watt type, and it is in the round return of the speaker jacks. AN open one there would weaken the output a lot. But check the solder on them all as well. They are larger and can shake enough to crack their solder.

Plug a spare cord into the effects send and the other end right back into the effects return. If this restores the sound, the return jack needs service.

In fact, here is another test. Plug your guitar into the effects return. You won't get a ton of gain, and the controls will be bypassed, but does it sound clear and potentially strong?

You could also plug your guitar into the front like always, an dplug a spare cord into the effects send jack, and the other end into the input of another amp.. THat way we can listen to your preamp from the other amp. That lets us determine which parts of your amp work.

It is my opinion that cold won't hurt it much. AFter all, on a cold winter day when the temperatur is -20 degrees, the electronics in my car work perfectly well from the first cold instant. That includes the speakers and sound system.