Hi all. Recently got a Enertec/Schlumberger 5224 oscilloscope on ebay, listed as not working but I liked the look of the scope 
The problem is in the HV circuit, schematic attached. junction of R31/R32 feeds the cathode on the CRT, it should be -1215Vdc but I'm getting -776Vdc. Adjusting R26 makes no difference, the output voltage is so far out of range it does nothing, output of U4 is going high to compensate and saturating Q9, making the whole regulator circuit draw 350mA when it is should be drawing far less (it's on a 160mA fused circuit)
Q9 has been replaced before very badly. Original part was a BD241C, I've put in a TIP31C which seems to be close enough spec wise. I've checked every component and all seems well. The only thing I'm not sure of is the transformer. The Q9 oscillator circuit is oscillating , a square wave of 15v pk-pk is on the collector, but the output of the transformer is far too low, pin 7 of the transformer should be about 570v but I'm only getting 350v.
I don't know what the original fault was before this was repaired previously, I'm thinking some turns are shorted on the primary of that transformer. Anyone got any other ideas before I unwind that bastard and get counting!?
measured inductance/resistance pin 1 to 2 - 146uH 0.4R, 3 to 4 - 26uH 0.2R, 5 to 6 - 3.8mH 5.8R, 5 to 7 - 178.8mH 46.8R
The problem is in the HV circuit, schematic attached. junction of R31/R32 feeds the cathode on the CRT, it should be -1215Vdc but I'm getting -776Vdc. Adjusting R26 makes no difference, the output voltage is so far out of range it does nothing, output of U4 is going high to compensate and saturating Q9, making the whole regulator circuit draw 350mA when it is should be drawing far less (it's on a 160mA fused circuit)
Q9 has been replaced before very badly. Original part was a BD241C, I've put in a TIP31C which seems to be close enough spec wise. I've checked every component and all seems well. The only thing I'm not sure of is the transformer. The Q9 oscillator circuit is oscillating , a square wave of 15v pk-pk is on the collector, but the output of the transformer is far too low, pin 7 of the transformer should be about 570v but I'm only getting 350v.
I don't know what the original fault was before this was repaired previously, I'm thinking some turns are shorted on the primary of that transformer. Anyone got any other ideas before I unwind that bastard and get counting!?
measured inductance/resistance pin 1 to 2 - 146uH 0.4R, 3 to 4 - 26uH 0.2R, 5 to 6 - 3.8mH 5.8R, 5 to 7 - 178.8mH 46.8R
