AD30VT - loud hum for first 10 minutes

[tjcurtin1]

Hmmm... (or maybe I should say 'hum'). My ad30vt hums at startup for several minutes - level depends entirely on the attenuator knob, but it's quite loud if the attenuator is up. It eventually fades away to nothing, but the fade time seems to be taking longer with time. Any thoughts?

EDIT: A thought just came to me - could it have anything to do with humidity? Seems to have come with the summer, which has been very humid here, and the amp is in the basement which while not soggy is cooler and damper than the rest of the house.

[Plank_Spanker]

Post this in the amp forum. If Tung sees it, I'll bet he'll have some good words.

[tunghaichuan]

Hmmm... (or maybe I should say 'hum'). My ad30vt hums at startup for several minutes - level depends entirely on the attenuator knob, but it's quite loud if the attenuator is up. It eventually fades away to nothing, but the fade time seems to be taking longer with time. Any thoughts?


The first thing I would suspect is the tube. If it is going south, it could be taking a while to warm up. Do you have a spare you could try?

It could be that the attenuator circuit is going as well. One thing you might try is cleaning the pot, can you get to it easily and squirt some electronics cleaner in there?



EDIT: A thought just came to me - could it have anything to do with humidity? Seems to have come with the summer, which has been very humid here, and the amp is in the basement which while not soggy is cooler and damper than the rest of the house.

Could be. Where is the amp made? My guess is in Asia somewhere, probably China. They do not use the best components available. It would have to be the PCB, though. I don't know of any components that would absorb moisture.

This can be a big problem in old Fender amps. They have carbon-impregnated eyelet boards which can absorb moisture in a humid climate. The way to fix those is to desolder the leads, pull the board, and bake it in the oven for a few hours. I wouldn't suggest doing that with your amp, though.

Sorry I can't be much more help, I don't think I've ever even seen one of those amps up close. Report back and let us know.

tung

[marnold]

The first thing I'd try is to reset it. A large number of gremlins have been reported to be solved just by doing that. The manual p. 15 shows how.

[tjcurtin1]

Thanks, guys. Reset didn't work. Called Music 123 - fortunately, when I bought it I had allowed the salesperson on the phone to talk me into the 2 year extended warranty (I never buy those things...). They are just going to take the amp back and refund the purchase price.. Guess that means I get to...errr, will have to shell out a few more clams and get a VT30 to replace it!

[marnold]

Guess that means I get to...errr, will have to shell out a few more clams and get a VT30 to replace it!
That sounds like a real shame. You'll probably want to report back, just so that we can make sure you're OK and stuff :)

[Duff49]

Those Vox Chromies have been known to have a lot of problems, probably because they are so extremely sophisticated. Possibly the new version has addressed the main concerns in regard to performance and reliability.

I have a Fender Super Champ XD modelling amp that has an actual tube section, preamp and power tubes, and a modelling chip that is inserted into the circuit. The SCXD is a highly regarded amp.

I know the Vox Valvetronics amps have quite a dedicated following; but I personally would play a few other amps before I got another Vox VT30. Just to see what the other ones sound like and how the price format is. Personally, I thought the Peavey Vypyr 15 was cheaply built but it did sound okay but not really good or close to great. I bought a little two channel Marshall MG15CDR, with a real mini tank reverb and a closed back that sounded way better and I like it very much and use a Korg AX5G multipedal in front of it. Sounds great with or without the multipedal.

Too bad they don't replace the amp with a comparable Vox model.

Good luck with your new amp, whatever it is.

Duffy

[tjcurtin1]

HI Duffy - thanks for the suggestions. I had thought about the Fender Super champ the first time around - it does seem like an excellent alternative. I did like the sound and flexibility of my Vox, and the new version seems to be improved in several ways, so I just thought I'd stay with it. If I had the time to fool around, I would try out the Fender for sure.

[ibanezjunkie]

same thing happens to my teacher's TSL 100 when he changes the mode (25w/50w/100w)

dunno why it happens, it sounds like its raining inside the speaker cabinet for about 10-15 minutes.