dear thread members, here it is!
THE TU-05 TUBE COMPATIBILITY AND POWER SAVE MOD
didn't want to further damage my tubes by connecting or cutting pins, so i modded the tu-05 again
- to be compatible with the DF97 or similar tubes
- to be able to use DL91, 1S4, 1S4T and 1L33 tubes
- to use DL92 tubes in power save mode
i will not post a tutorial this time, because this mod is near to micro surgery and difficult, so no guarantee, if you try the same be very carefull as i was, i only focussed on getting it done, not on taking pictures for all the steps.
to be compatible with df97 tubes while df91, 1t4, 1u4, df904, df96 can be used as before, pin 4 and pin 5 of the df91 tube sockets have to be connected. this is no problem for compatibility because pin 4 is not used in the case of the df91 and compatible tubes:
to use also dl91, 1s4, 1s4t and 1L33 tubes, pin(s) 1 of the dl92 sockets have to be disconnected from the 1.4 volt heater voltage and then recabled and reconnected to the 1.4 volt heater voltage but providing a switch to switch the pin 1 heater voltage on or off:
to do this, i disassemled the amp's tube panel and drilled and shaped a hole to assemble a small on/off switch:
i then connected pin 4 and pin 5 of the df91 sockets, cut the 1.4 volt lines from pin 1 of the dl92 sockets and recabled the pins (2 cables) and the 1.4 volt source point (1 cable) to connect them with the switch:
now i connected the cables to the switch and reassembled tube panel and amp. you can see the small switch above the battery:
another view (overexposed) to better see the switch:
and here is the usual 'horror' picture that may prevent you from doing the same:
AFTER HAVING IMPLEMENTED THIS MODIFICATIONS
- df97 tubes can just be plugged in and used.
- for normal operation of dl92 tubes switch has to be set to the 'on' position.
- to use dl91, 1s4, 1s4t and 1l33 tubes, switch has to and must be set to the 'off' position, because these tubes have only one heater part getting its power already from pin 5 (pin 5 and pin 1 are connected internally inside the tube), otherwise shorten the pin 1 voltage:
i did this accidently when the first time using the 1l33 tubes giving them half a hour of burn-in without listening and at that time not knowing that they need this modification, but the amp was not damaged i think thanks to shikada-san's protection circuit.
- you also can use dl92 tubes with the switch in the 'off' position, then only one of the two heater parts is used to heat the cathode, the max. output power of the dl92 is lower, but you need half the power for heating.
this i a standard operating mode of the dl92 tubes that now can also be used with the tu-05.
btw, i have tested all tube types, combinations and modes before posting this mod.
Edited by GermanGuy - 8/31/13 at 5:18am