Update:
I have replaced R49 with a 2.7 ohm 1/2 W fusible resistor. I managed to order some online :)
Still experiencing the same symptoms: powering on for approximately 60 - 90 seconds for the first time each day.
Here some more information I posted on the VSE forum:
The input of the voltage regulator (IC1) is giving a reading of 2.4 V DC. Both the output of the voltage regulator (IC1) and the anode side of D2 are giving a reading of 245 mV DC.
I have the original wall wart power supply (negative tip) 12volt 200ma which is giving a reading of 17.8 volt without load, so I'm assuming this is working correctly.
I have already replaced the power jack on my 707 because the connection was originally loose, however unfortunately it wasn't that simple to get the 707 running properly again.
From studying the schematic I believe I should be getting a reading of -10v at the anode of D2 and +5v at the output of IC1, however I'm getting a +2.6v at both these points
Furthermore if I take a measurement of the voltage directly from the power input jack. When the device is switched off it gives a reading of 17.8 volts, which is the same as the reading from the tip of the wallwart psu. However when I switch the 707 on, the voltage drops to around 5.5v.
One last bit of information that might help you identify what going on is, the TR 707 has temporarily turned on for approximately 60-90 seconds on a couple of separate occasions and then it just switches off. Today I managed to monitor the voltage whilst it was temporarily on, the voltage dropped from 17.8v when switch off, to 11.7v for 60 seconds when the device was on, then to 5.5v where it stays and the device is obviously off. This appears to only happen the first time I turn on the device each day for further testing.
Apologies if this is a double post, still working out how this forum works.
Cheers,
Jay