I was on the hunt for a nice original Vox AC30 from the 1960′ s and it got me thinking on why I wanted it and what work it would need. Now I have worked on AC30’s in the past and my first AC30 was GIVEN to me as it was considered beyond repair. The player had sat a pint of beer on top of the amp, by all accounts the pint glass was almost […]
Amplifier valves get hot and there are very high voltages present, so make sure the amp is switched off and and the valves are cold. Hot amp valves can give you a bad burn ! The output valves , the rectifier, and ECC99’s all get especially hot ! My most recent burn was off the little output valve in the picture above, the EL84 output pentode The first basic question is how often to replace
Steps to follow when changing your valves in your amp Read More »
I offer 120 day warrant on valves ( tubes) . Why is this so great and why dont valves have a one year warranty like everything else?
“Why don’t valves ( tubes) have One Year warranty ?” Read More »
Rectifier Valve ? Many of the vintage amplifiers such as the Vox AC30 , Fender Twin Reverb use a rectifier valve. Other amps use modern silicon diodes. The rectifier valve ( or diode) is a key part of your amplifier’s power supply. Its job is to “convert” or rectify the AC voltage coming from the transformer into the high DC voltage needed by your valves in your amplifier. The output valves need the highest voltage
I thought this looked like a really useful table on bias current for output valves. The top of the page allows the super techie types to do an exact calculation based on measured voltages in your actual amp and the configuration of the circuit. The featured picture is actually all the tools ( apart from the right screwdriver). It is simply a multi-meter and a special adapter. You plug the adapter into the output
Here is a good video on Youtube on how to bias a valve /Tube amp. It is a good introduction on what is involved for those with basic electric skills. How to Bias a Tube Amp Part 1 – YouTube.
Resistor Drift and Noise While a lot of people like carbon composition resistors in their vintage amp, there is one issue you need to watch out for. This is especially true in amps where the valves hang upside down as in the original black-face and silver-face Fender amps. In these amps the heat goes upwards and straight into the components. The output valves are the hottest lace in the amp. The result is that the
New valve testers now installed. Click here and see how we are ensuring you get the best quality valves.
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