Thanx, i really want to learn- i have huge passion for guitars and I am
surviving fourth-stage cancer so music is very important to me.70's Vox AC30 won't make sound
Moderators: pompeiisneaks, Colossal
70's Vox AC30 won't make sound
About a year ago my Vox AC30 started taking a long time to warm up and make sound. Then it stopped making sound but the light comes on. On the advice of my friend Barry who is a great bass player too, I bought a JJ tube kit and replaced the 4 el84's, and six Ax7's but came up short two of those so I have to get two more. THey actually sent me five ending in 83, and one ending in 82. Also, the kit included a Tube rectifier but I guess my model doesn't have one. Anyway it didn't fix it, still won't make sound. Barry says I should replace the blue can caps. Should I see if that fixes it?
Thanx, i really want to learn- i have huge passion for guitars and I am surviving fourth-stage cancer so music is very important to me.
Thanx, i really want to learn- i have huge passion for guitars and I am
surviving fourth-stage cancer so music is very important to me.You do not have the required permissions to view the files attached to this post.
Re: 70's Vox AC30 won't make sound
That's an unusual model AC30, has it got reverb? If so, this schematic may be useful but your's may have been built much earlier, maybe mid 70s
https://el34world.com/charts/Schematics ... 30vrev.pdf
Also https://el34world.com/charts/Schematics ... 30vrev.pdf
Are you (or a buddy) competent and resourced to work inside a live amp chassis, eg taking fairly high voltage measurements?
The issue is that I don't think just replacing this or that group of parts has a good chance of success (though it might, and the high voltage ecaps would be a good start), as something specific has failed.
Some clearer, better lit photos would help too
How does the vib/trem/speed control work, eg is there a potentiometer with a pull switch ?
I assume that all 3 channels are dead?
If you put your ear to the speakers, can you hear any hiss when the amp's on and warmed up?
If so, the tone control should affect the hiss level a bit (?), but do any other controls have any effect / cause any change?
https://el34world.com/charts/Schematics ... 30vrev.pdf
Also https://el34world.com/charts/Schematics ... 30vrev.pdf
Are you (or a buddy) competent and resourced to work inside a live amp chassis, eg taking fairly high voltage measurements?
The issue is that I don't think just replacing this or that group of parts has a good chance of success (though it might, and the high voltage ecaps would be a good start), as something specific has failed.
Some clearer, better lit photos would help too
How does the vib/trem/speed control work, eg is there a potentiometer with a pull switch ?
I assume that all 3 channels are dead?
If you put your ear to the speakers, can you hear any hiss when the amp's on and warmed up?
If so, the tone control should affect the hiss level a bit (?), but do any other controls have any effect / cause any change?
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!
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Stevem
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Re: 70's Vox AC30 won't make sound
Both of those schematics show a internal or second fuse for the amps DC voltage besides the main AC fuse which is good and is why your seing atleast the pilot lamp come on!
So most likely this .500 amp D.C. Fuse is bad or the standby switch is bad.
I will bet that you had a output tube short out as this is what 98 % of the time blows this D.C. Fuse, and now that you have new tubes in it changing this fuse out should get you back up and running.
So most likely this .500 amp D.C. Fuse is bad or the standby switch is bad.
I will bet that you had a output tube short out as this is what 98 % of the time blows this D.C. Fuse, and now that you have new tubes in it changing this fuse out should get you back up and running.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
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pompeiisneaks
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Re: 70's Vox AC30 won't make sound
I agree with what's been said here, and repeat be careful inside these amps, they can store 500 volts and can kill. Make sure you know how to drain the capacitors safely before sticking anything besides a wooden chopstick inside.
Go watch videos on safe amp work to be sure you don't kill yourself! . Otherwise, have fun!
~Phil
Go watch videos on safe amp work to be sure you don't kill yourself!
. Otherwise, have fun!~Phil
tUber Nerd!
Re: 70's Vox AC30 won't make sound
The blue can caps look newer and shinier than the rest of the amp. Can you see any logos or other printing on them?
Re: 70's Vox AC30 won't make sound
Just to note that the Dallas era amps don't look to have a HT fuse http://schems.com/schematicheaven.net/m ... 30dals.pdf
Sorry for any confusion
It may be that a HT dropper resistor has gone open circuit; the hiss status mentioned earlier may help identify which is the last working stage.
Sorry for any confusion
It may be that a HT dropper resistor has gone open circuit; the hiss status mentioned earlier may help identify which is the last working stage.
https://www.justgiving.com/page/5-in-5-for-charlie This is my step son and his family. He is running 5 marathons in 5 days to support the research into STXBP1, the genetic condition my grandson Charlie has. Please consider supporting him!