The first order of business when restoring a tube amp or preamp is to rebuild the power supply – the main source of hum and noise and malfunction, as the electrolytic caps in a 50-year-old amp are almost guaranteed to be off spec if not leaky or worse — short. And if they are not yet, they will be soon!
Of equal importance is the biasing circuitry which usually has an electrolytic cap (see above) and a selenium rectifier – a fire hazard. It is essential that all parts in that portion of the circuit be right on specs so that your power tubes work properly without risk of red-plating, overheating, working with too high (or too low) a bias voltage applied to them — all risks of damage or life reduction for these precious tubes.
This kit includes all the parts you will need to completely rebuild the power supply section and the biasing section of one ST70 (set of newly made tubular electrolytic caps (German Authenticaps), axial electrolytic, diodes, resistors, film caps, all of the exact same values as the originals, all guaranteed to fit in place of old parts, and all audiophile grade.
Also included, a short instruction sheet and a copy of the amp’s schematic.
We are happy to help you in case of difficulty but note that it is essential that you possess solid soldering skills. These amps run at 450+ volts — Lethal voltages. Use at your own risk. And if you are not sure….do not do it but hire a properly trained tech. They should not need more than an hour or two to install the whole kit.
US shipping: $6.98 via Priority Mail
International shipping: $25.00 air mail