Hi
Someone send me this amp and told me that the rectifier tube has blown and the amp has been modified using solid state rectifiers (Diodes). Since then it has been running very hot. He wanted the diodes removed and put back the GZ34 rectifier as before. I have replaced the diodes with the GZ34 and the amp is working fine. The problem I noticed is that, whenever I switch ON the standy switch, there is a bright arc inside this rectifier tube. I guess that this arcing will eventually blow the tube as before. Can the standyby switch be removed or is there any other way about it. I cannot post the schematic as it is 1.95 MB bytes
Please advice.
Thanks
Someone send me this amp and told me that the rectifier tube has blown and the amp has been modified using solid state rectifiers (Diodes). Since then it has been running very hot. He wanted the diodes removed and put back the GZ34 rectifier as before. I have replaced the diodes with the GZ34 and the amp is working fine. The problem I noticed is that, whenever I switch ON the standy switch, there is a bright arc inside this rectifier tube. I guess that this arcing will eventually blow the tube as before. Can the standyby switch be removed or is there any other way about it. I cannot post the schematic as it is 1.95 MB bytes
Please advice.
Thanks
I own an AC30 CC2 and it's a great amp.
The SS rectifier will raise the HT voltage and as such the OP tube bias.
Re install a new GZ34, your amp will sound better and run a little less current.
Be aware that most Vox AC30's I have worked on run the OP tubes way
above their max rated dissipation. You need to check this. If you don't know
how to do it, find a service tech that can. The most robust OP tubes are the
Russian 6P14P-EV if you can find them.
Good luck
TCD
The SS rectifier will raise the HT voltage and as such the OP tube bias.
Re install a new GZ34, your amp will sound better and run a little less current.
Be aware that most Vox AC30's I have worked on run the OP tubes way
above their max rated dissipation. You need to check this. If you don't know
how to do it, find a service tech that can. The most robust OP tubes are the
Russian 6P14P-EV if you can find them.
Good luck
TCD
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The pre-heated rectifier tube is charging up the empty filter capacitors. Unlikely to be good for the rectifier.
Some put a bypass resistor across the standby switch - passes some HT when open, full HT when closed.
Others do not fit a standby switch. The warming up rectifier does not have a sudden current surge.
Some put a bypass resistor across the standby switch - passes some HT when open, full HT when closed.
Others do not fit a standby switch. The warming up rectifier does not have a sudden current surge.
My son has a CC2. One of the mods I did was insert a 1N4007 in series with each GZ34 plate - this is a common mod that is done nowadays to avoid any rectifier tube arcing - especially for this kind of standby switch operation where diodes are hot switched. The power transformer winding is circa 300V-0-300V.
You will also need a bias adjust insert to check the EL84's are sharing ok.
You will also need a bias adjust insert to check the EL84's are sharing ok.
I read somewhere that Leo Fender introduced the standby switch to protect the HT filter capacitors from the current inrush at power on. In those ancient times the capacitors were expensive parts and had a shorter lifespan. Nowadays it's the tubes of course that we want to protect, so I would suggest not to use the standby switch or get rid of it.