Our full service and Modification includes:Safety check, drill and fit a HT fuse* and a fused/switched IEC block for safety. We now fit a dual IEC outlet in place of the obsolete 2-pin sockets. Perform fault diagnosis. Replace all the out of tolerance and physically damaged resistors with modern high tolerance types. Replace the full set of small signal electrolytic capacitors and dual smoothing blocks. Replace the full set of paper coupling and decoupling capacitors with HV polypropylene capacitors. Check valve biasing and recommend what valves, if any, need replacing. Faulty valves will be replaced at cost if requested. Full performance check and adjustment. 24 hour soak test/retest. If the output or mains transformers are faulty we can replace them at cost plus fitting charge.
The images above show a typical full service and safety modification. The images upper left and middle left, show the rear of the Stereo 20 with the modified connectors. In place of the round pin Bulgin connector a switched/fused IEC block is fitted. The upper left image has professional speaker terminal posts, twin IEC outlets and an internal HT fuse fitted. On the lower right image the HT fuse is external and fitted just above the switch cable. The fuse is 315mA medium blow type.The schematic bottom left, shows the position of the HT fuse and GZ34 rectifier valve 'protection' diode mods. (Shown by red dots). The diodes help preserve the life of the GZ34 particularly if it is a modern reproduction type.