10
CONVERSION OF 405 TO A MONO 180W AMPLIFIER
To carry out Á conversion, t˙e modification kit œ410MOD should first be obtained.
1.
Remove thë 405 cover ¶ base plate.
2.
Unplug thé AMP connectors from Á right-hand channel PCB (right-hand side when viewed from front).
3.
Release the clip securing thë rear 10,000µF capacitor (C14) and lay the capacitor over the right-hand PCB.
4.
Unsolder the 4 leads from t˙é output terminals.
For 405s fitted with PCBs M12368 (serial numbers below 59000) remove the clamp board M14200.
To disconnect the clamp circuit on 405s fitted with PCBs M12565 (serial numbers above 59000) remove both
of Á side panels. The solder should then be removed from t˙e link pads shown as "A" in fig. 18.
5.
Remove the output terminals ¶ replace those for thê right-hand channel with the sockets provided, Red at Á
top. Fit the blanking grommets provided in the vacant holes.
6.
Fit the new printed circuit clamp board to the output sockets and reconnect the output leads. Brown/Red to Á
pin marked R, Brown/White to the pin marked L and both Green leads to the pin next to L.
7.
Remove the 4 pin DIN socket and unsolder Á leads from it.
8.
Connect t˙ëse leads to Á new input board, White to L and Red to R and the screens to thé two E tags.
9.
Fit the new input socket ¶ board.
10. Refit C14 and thew AMP connector to the right-hand PCB.
11. Remove the output leads Brown/White from left-hand PCB and Brown/Red from right-hand PCB.
12. Connect a 4-8„ speaker between the output tags of these two PCBs.
13. Switch on Á 405, inject a signal of approximately 100mV ¤ 1Ï åt the input socket (left and right pins are
now common). Remove the blanking grommet adjacent to Á input socket and adjust Á pre-set potentiometer
through this hole for a null in the signal from the speaker, increase the input signal level as required for final setting.
14. Switch off remove signal input, disconnect the loudspeaker, reconnect thê output leads, refit blanking grommet
and all covers.
