Recovery give in those tubes that have a faulty first diode connected to the output (F). To restore just before you need to carefully drill out the faulty diode.
Here's how: drill diameter 6...7 mm, departing from the edge of the multiplier 7 mm, on the side opposite to the inscriptions, drilled three holes to a depth of approximately 12 mm, as shown in the figure. When drilling is necessary periodically to remove the drill from the hole and to track the emergence of copper, or, if the diode is burned - burnt diode.
Then, drill another few millimeters further to drill out the remains of the burnt diode. Then the holes are filled with epoxy resin, glue BF or nail Polish. After drying of glue or resin to the terminals "-" and "+F" on the outside is soldered diode CCG or selenium column HEAT (anode to terminal "-"), and the multiplier is set to TV.
Thus I have restored about ten multipliers ON/27-1,3 who work for more than three years.
Author: A. Parfenovich (EU1DD), Minsk; Publication: N. Bolshakov, rf.atnn.ru