Assembling a Dynaco PAS4 klonQuestions suggestions: tubular.well <( -at- )> gmail.com
As i never got my hands on a Dynaco PAS4 i will attemt to recreate one. A circuitboard from Roy Mottram is the starting point.
Pictures will follow Empty board Input selector mains transformer enclosure
Latest change: 200914
Double fault, removal of copper and addition of missing connection
E88CC internal screen connects to ground
I have no -3V bias, ground this ( Use a LED in cathode instead)
The use of odd component values forces me to build composit resistors
One of the ECC83 sockets
Higher powered resistors mounted higher for better cooling
As i have no -3V on board to use as bias to V2 and V5 i use a white LED. It is mounted in a free grounded hole and a wirewrap wire connects to pin 3 of the V2 and V5
LED soldered in place.
Wirewrap wire inserted before mounting tube socket
A long forgotten technology : wirewrapping. It's perfect for making remavable connections or strapping. It also exists connectors that fits on wirewrap pins to make connections outside the board.
Tubes in place verifying filament function.
Now i have applied B+ from an external powersupply. No fire not even smoke !
Starting with riaa stage. Some bugs sorted out :
- 240k instead of 240 ohm in R12 and R112
- one white led was only 2.44 Volt, tested several variants but 2 RED LED in series seemed best, then gave 4.04 Volt
- R12 and E112 changed to 300 ohm to reduce current in E88CC Dist now 0.06% at 1Volt out ( app 10mV in @1khz ). This THD includes HUM from the workbench.
Work in progress, as the object is flat on a wooden table hum is present everywhere.
Honor the board source at tubes4hifi.com
Feel trapped ?