Having an issue with my VTA120, had it playing yesterday and it was working great. Fire it up today and now I don't have any sound. Where is a good starting to track down what the problem is?
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Sound stopped working on VTA120
Pezcore67- Posts : 8
Join date : 2021-01-02
Bob Latino- Admin
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Join date : 2008-11-26
Location : Massachusetts
Pezcore67 wrote:Having an issue with my VTA120, had it playing yesterday and it was working great. Fire it up today and now I don't have any sound. Where is a good starting to track down what the problem is?
The most common cause of "the tubes light up but no sound" is a bad rectifier tube. If your amp also has no bias voltage, then that is another clue that the rectifier is bad. Just because a tube lights up is not always an indication that it is working properly.
Bob
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Pezcore67- Posts : 8
Join date : 2021-01-02
Thank you, Bob. Just checked the bias and I do not have any voltage.
Pezcore67- Posts : 8
Join date : 2021-01-02
Purchased a new tube rectifier and installed it. I fired up the amplifier, tubes lit up. After about a minute I heard something like a tube rattling sound and all of the tubes went out. I try to turn it on and nothing happens. Did I blow a fuse? What would cause this? Is it as easy as replacing a fuse?
Bob Latino- Admin
- Posts : 3279
Join date : 2008-11-26
Location : Massachusetts
Pezcore67 wrote:Purchased a new tube rectifier and installed it. I fired up the amplifier, tubes lit up. After about a minute I heard something like a tube rattling sound and all of the tubes went out. I try to turn it on and nothing happens. Did I blow a fuse? What would cause this? Is it as easy as replacing a fuse?
It could be a bad output tube OR you could have blown one of the 10 ohm 2 watt resistors on one of the output tubes that goes from pins 1 and 8 to chassis ground. Check that all four of these resistors (one on each output tube) do measure about 10 ohms each. If they measure ZERO ohms or some high value, then that resistor is bad. Note > That new rectifier that you put in may now be (unfortunately) bad now ?
Bob
Pezcore67- Posts : 8
Join date : 2021-01-02
Bob Latino wrote:Pezcore67 wrote:Purchased a new tube rectifier and installed it. I fired up the amplifier, tubes lit up. After about a minute I heard something like a tube rattling sound and all of the tubes went out. I try to turn it on and nothing happens. Did I blow a fuse? What would cause this? Is it as easy as replacing a fuse?
It could be a bad output tube OR you could have blown one of the 10 ohm 2 watt resistors on one of the output tubes that goes from pins 1 and 8 to chassis ground. Check that all four of these resistors (one on each output tube) do measure about 10 ohms each. If they measure ZERO ohms or some high value, then that resistor is bad. Note > That new rectifier that you put in may now be (unfortunately) bad now ?
Bob
Can I check those from the top or do I need to open the amp up? Which are pins 1 and 8? Also I checked the fuse and it is definitely blown.
Pezcore67- Posts : 8
Join date : 2021-01-02
I believe I successfully located pins 1 and 8 on each of the output tube sockets. All are showing around 10 ohms on my meter for all four tubes.
Bob Latino- Admin
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Join date : 2008-11-26
Location : Massachusetts
Pezcore67 wrote:I believe I successfully located pins 1 and 8 on each of the output tube sockets. All are showing around 10 ohms on my meter for all four tubes.
Good .. Those resistors should all measure about 10 ohms
The VTA ST-120 should have a 5 amp slo-blo fuse. Check to see if this fuse has blown. If it has, buy a few 5 amp slo-blo fuses.
Try turning the amp on with no rectifier in it. The amp won't play and you will get no bias voltage BUT if the amp stays on, the problem is with the high voltage system of the amp or a bad output tube.
When you get new fuses, try starting up up just ONE CHANNEL of the amp (pull the two output tubes from the other channel). If the amp stays on and that channel plays, you probably have a bad output tube in the channel that you pulled the tubes from.
Get another rectifier tube also.
Bob
Pezcore67- Posts : 8
Join date : 2021-01-02
So, good news. Not sure what happened but it's playing very well after I replaced the fuse and the rectifier tube. The new rectifier tube that I thought might have been wiped out is still good. The bias is set, I guess I'll see after it's playing for a little while.