problem with AC30CC2.......(who would have thought)

ball ox · 02-02-2009 09:19PM #1

Today I re-valved my Vox for the first time, much thanks to Eoin Madsen whos tube threads I dug up for advice

The AC30CC2 has a quad of EL84's, 3 12AX7's and a rectifier tube. I took out the stock ones and stuck in a Harma rectifier & quads. I replaced the 12AX7's with electro harmonix (not the best I hear).

After I stuck it all back together and switched it on I noticed a hum from the amp, not even the speaker, as soon as I took it off standby. Not good. Next, I cranked up the volume.... thankfully, the crackle which made me change the valves in the first place had gone. It had been replaced however by an oscillating hum. Not good. The oscillating pattern sounded familiar so on a whim I cranked up the tremolo which, it appears, seems to control the rate of said hum:eek: I also noticed the little green standby light fading on and off in time with the tremolo style hum............not good

Anyone any idea what could have happened? Gonna get rid of this after I fix it methinks :mad:

spoonbadger · 02-02-2009 09:35PM

Sounds like a problem with the preamp tube that controls the tremolo. I'm not familiar with the AC30 circuit though, so i'm kinda confused as to what that tube is. Normally there'd be 3 preamp tubes which power the basic circuit and the tone controls, and something like tremolo would be controlled by a 4th tube (or a transistor circuit)

.

Another possibility is a bad rectifier, which would better explain the standby light.

Alternatively, since the standby light is connected to the heaters for the quad of EL84s, it might a problem with the power tubes.

And yes,i realized this post was actually in no way helpful

.

Perhaps it's time for professional help?.

ball ox · 02-02-2009 09:57PM

ok, feeling mildly retarded now............. unplugged the jack lead and cranked up the volume............no hum

There is still the issue of the standby light though. If I turn the tremolo depth up full the light will fade in and out in sync with the tremolo rate. I'm not sure if this has always been the case as I never use the tremolo channel anyway

Just ran the tele through her there and I'm quite surprised at the difference in tone, much better. The stock valves were stamped '04 so maybe it was about time they got swapped out anyway......
Still thinking of getting rid of it though, the weight thing is becoming a bit of an issue when gigging. I have also had a bit of a nightmare with support acts not knowing how to use it properly due to confusion over the standby & power switches (i.e. flicking the the power switch on & off with the standby on when trouble shooting a dodgy lead - which incidentally is what I think destroyed the old rectifier). Can anyone recommend a similar sized/sounding tube amp? I'm think Fender or Orange. I've had a few Fenders before but never tube. I've never played an Orange but have heard plenty........ think it's GAS time again :pac:

Eoin Madsen · 03-02-2009 09:55AM

I assume the three ECC83s in the CC are for normal/brilliant input, 2nd gain stage/tone stack, and phase inverter - as per most amps. In the original AC30, you use another half an ECC83 for the tremolo input, and a full ECC82 for the actual tremolo circuit. I thought they'd omitted the tremolo circuit entirely since they cut those valves. It must be a solidstate component in the CC?

Power light is usually off the 6.3v heater current, I can't remember how the standby indicator is powered. I'll ogle the schematic later if Paolo or Voodoo don't show up with the goods in the meantime.

In terms of similar to an AC30 but less heavy... how about an AC15? :pac:

Paolo_M · 03-02-2009 10:48AM

The stand-by led runs from the 30V tap. Basically HT switches, turning on the base of the transistor and draws current from +30 through the dropping resistor and through the stand-by LED (or the other way if you like!!). That 30Vdc/15Vdc supply is also used for the switching circuitry so it must be "stealing" current somewhere in sympathy with the tremolo when it's turned on. This may not be a fault.
Not too familiar with the new AC30 circuitry but are you sure this is not simply a "feature" of the amp?

Eoin, spot on, the preamp uses a stand 3 X 12AX7 setup, parallel input gain => DC coupled cathode follower => PI. The oscillator, reverb and all the switching is SS driven.

Marshall 18Watt clones are a cool option to look at as an alternitive.

Glassheart · 03-02-2009 11:14AM

Fix it and sell it mate.

Those amps are a disgrace.And way overpriced too.

ball ox · 03-02-2009 06:18PM

Eoin Madsen wrote: »

In terms of similar to an AC30 but less heavy... how about an AC15? :pac:

I have certainly been thinking about this. I like the look of the heritage version but am a little worried about reliabilty. Anyone know if these are reliable enough for regular gigging?

seachto7 · 17-02-2009 09:24AM

on a side note, has anyone played the voxac30 CC head? any problems with it?

Beastieboy · 20-02-2009 05:23PM

having the exact same problem word for word as the OP....... going to have a second look at the amp now..... random....

ball ox · 20-02-2009 06:50PM

A friend of a friend who has the same amp tells me that the standby light thing is actually normal......... maybe its just something I never noticed before seeing as I rarely used the tremolo channel

Beastieboy · 20-02-2009 06:58PM

ball ox wrote: »

A friend of a friend who has the same amp tells me that the standby light thing is actually normal......... maybe its just something I never noticed before seeing as I rarely used the tremolo channel

I don't know. I had used the tremolo and never seen that happen before. Also mine is buzzing also which i know isn't normal.......

ball ox · 20-02-2009 07:03PM

Never got a buzz out of mine but I did notice a very slight hum after replacing the rectifier. However, again, this could always have been the case and I just didn't realize it until I went poking around looking for problems.

edit: as i mentioned above, at first I was getting a bad hum but it was just from a crappy lead exaggerating the existing hum. Try different leads and see if there is much difference.

Beastieboy · 21-02-2009 04:10PM

its buzzing without a guitar plugged in

ball ox · 21-02-2009 04:30PM

crap, maybe it might be worth trying a different brand rectifier.

Maybe Eoin or one of the other guys on here might be able to help you with troubleshooting the problem.

Beastieboy · 21-02-2009 04:58PM

I think i'll take it to be looked at by someone on monday.... hopefully won't cost too much...

problem with AC30CC2.......(who would have thought)

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