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Vox Ac30CC2 Rectifier...smashed
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Kellebot
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#1
29th February 2012
Old 29th February 2012
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Vox Ac30CC2 Rectifier...smashed

So i opened up my vox to replace out the valves, and i find the rectifier smashed and wrapped up in gaffer tape.

It looks as if the bottom of the rectifier is still there and (sort of) intact.

Is this insanely unsafe?

Can you run an Ac30 without a rectifier?

Im no expert with these things.
Kellebot
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29th February 2012
Old 29th February 2012
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Ngr
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1st March 2012
Old 1st March 2012
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without the rectifier the amp will not produce an sound but it is of no harm for the amp. replace with a working one and you are done. simple as that.
be sure to unplug the amp from mains power and take out the tube grabbing the base and rocking it with circular motion until it comes out. absolutely avoid touching the contacts that were into the glass.

I imagine you have never used the amp before, otherwise I can't figure out how you could produce any sound without a working rectifier.
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1st March 2012
Old 1st March 2012
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Weird..
maybe someone built a SS rectifier in there - like a Weber copper cap? Otherwise, no idea how that could work.
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Kellebot
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1st March 2012
Old 1st March 2012
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That's why i'm baffled, i have been using this amp for nearly a year now!

It's possible that someone built a SS rectifier in there, it looks as if someone has tampered with the insides.

Either way ive opted to get a new rectifier just to be safe.


This was the last thing i expected to see!
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1st March 2012
Old 1st March 2012
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Ngr
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mmmm...
if the amp was working with the smashed rectifier it means that there must be a solid state one installed directly on the tube base (it's just a few diodes).
pic is not very clear. I have one that is just a tube base with a black resin cover masking the diodes installed inside the tube base itself.
you can take off the insulating tape (unplug the tube base from the amp first) and see what's inside. You should see 4 diodes soldered on the tube pins.
No need to change to tube rectifier. Modern tube rectifier (AC30 uses a GZ34) are not very reliable.
So keep your SS one and replace your preamp and power tubes. Just remember to use standby switch with solid state rectifier to avoid wearing tubes too fast.
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1st March 2012
Old 1st March 2012
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Quote:
Originally Posted by Ngr View Post
mmmm...
if the amp was working with the smashed rectifier it means that there must be a solid state one installed directly on the tube base (it's just a few diodes).
pic is not very clear. I have one that is just a tube base with a black resin cover masking the diodes installed inside the tube base itself.
you can take off the insulating tape (unplug the tube base from the amp first) and see what's inside. You should see 4 diodes soldered on the tube pins.
No need to change to tube rectifier. Modern tube rectifier (AC30 uses a GZ34) are not very reliable.
So keep your SS one and replace your preamp and power tubes. Just remember to use standby switch with solid state rectifier to avoid wearing tubes too fast.
I'm going to second this recommendation and appraisal of what is under the tape.

Definitely check under the tape to see if it's a tossed together SS rectifier made up of 4 diodes. If those components are not in there, I would venture to guess that somebody installed an SS rectifier under the plate somewhere - especially since you say that it looks like somebody has done some work inside.

Obviously, if you take it apart to check, you need to be super-extra careful not to touch ANYTHING in there. I have an AC20CC1 (the 1x12) and it's the same amp. I've gone through mine and they have sectioned off the power caps and power transformer leads into a separate compartment, basically to keep folks from accidentally killing themselves via electrocution. Given the seriousness of the voltages lurking around in the power section of an amp, I feel compelled to always mention the warning of caution. If you're not already experienced with discharging capacitors, then I'd just have someone qualified to take a look at it.

The SS rectifier will definitely be more reliable and quieter provided the diodes used are quality components. The amp will be a little smoother and ever so slightly less "angry", perhaps, as is typically the case with an SS rectifier. But then again, as with mic preamps, it all depends on where the circuit is being "leaned upon" to get it's character. I won't venture to hypothesize beyond that.

Hope this helps,
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1st March 2012
Old 1st March 2012
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I'm into Voxes and I am a big fan of natural amp power supply sag when a rectifier can't keep up with current demand from a push-pull circuit. However, a good (meaning, vintage Mullard/Philips) GZ34 rectifier barely sags anyway, so you aren't missing much in an AC30 by running a solid state rectifier.

I use a 5V4 in my old AC30; it is a safe sub for a GZ34 (because it is indirectly heated and doesn't draw any more current than a GZ34) and it sags a little and also puts out slightly lower plate current, which is good for that amp. The old ones run hot, particularly if you use the 115v tap with about 125-127 volts AC like most of us have in the US.
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#9
2nd March 2012
Old 2nd March 2012
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This is a common problem with AC30CC2, the amp blows tube rectifiers. To be safe, just put a Weber Copper Cap there and you don't have worry about it anymore.
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