trouver sur le site rivera... j'espere que ca peut aider j'y comprend rien
Tube Changes
It is normal for tubes to wear with age. The tubes and their function and physical location are shown on an accompanying chart. Tubes are accessible by removing the top cover. To remove the top cover, first remove the side Phillips screws, and carefully unplug the fan.
The power output tubes are selected by us for best performance. Substitute tubes are shown in the Bias Voltage chart. If 655OAs (GE or Sylvania) are used in place of EL-34s, the power output will increase, but the timbre will be different.
The preamp and phase inverter tubes are 12AX7A/7025/ECC83/6681. All of these part numbers are for similar twin triode hi-mu miniature 9 pin tubes. We select these tubes for low hum noise, low microphonics, and high gain. Try to replace these tubes with the best you can buy.
A word about tube quality: There are only a handful of tube manufacturers worldwide, and there are no Western European or British companies manufacturing any longer. Marketing companies such as Groove Tube, Fender, and Mesa Boogie purchase their tubes from the same sources we do. Every tube you buy from us, whether in an amplifier or as a replacement part, has been thermally and electronically cycled for at least 12 hours. After this burn-in period, tubes that fail to meet our rigid specifications are either discarded or sold to other shops. If you wish to purchase replacement tubes from us directly, we will be pleased to assist you. Contact the factory for price and ordering information.
Warning: Never ever use Chinese EL-34s, 655Os, or 6L6GCs. They are mechanically unstable and will shorten the life of your amplifier.
Bias Voltages
On the power supply/power amp printed circuit board there is a bias adjustment trim poten?tiometer for each power amp. To access the insides of the amplifier, remove the Phillips screw that hold the bottom panel.
NOTE: Removing the bottom cover exposes extremely dangerous high voltages.
If there is not enough adjustment In the range of the bias adjustment pot, you will have to change the resistors in the bias circuit to give you the proper bias voltage.
Model Tube Bias
TBR-1, TBR-3 6CA7 -39VDC
6L6GC -45VDC
6550A -52VDC
EL-34 (American) -39VDC
EL-34 (English or German) -37VDC
KT-77 -39VDC
Nasr Eddin Hodja... Tu dois te sentir bien seul...