19-06-2020, 07:20 PM
(This post was last modified: 19-06-2020, 07:21 PM by Mike Watterson.)
Yes 0V = chassis = ground.
Though the reading should be steady with the 100K from the join of the 2 x 1M resistors to HT temporarily disconnected from HT. You need to do that to check the reading.
Try amp without that 100K after verifying there is about 1.04M from either pin 2 or 7 to ground / chassis/ OV. It seems like the 33K from the join of the two resistors is disconnected.
I presume your circuit is that.
If the 33K, R7 is connected and even +50% high, you can't get a reading of 1.24M. That's the effect of the 100K to HT slowly charging up the electrolytic from the meter. 1M + 33K is 1.033, or at worst about 1.04M. With the 100K (R5) connected, the reading will vary as the capacitor charges but can't get MORE than 1.04 M approx, unless the C2 and C4 electrolytic caps are charged to HT volts, then the result is unpredictable.
So a reading of 1.24 that's changing means the 33K (R7) is disconnected. It might not be 33K (orange, orange, orange) as it has a *. But it certainly can't be over 200k (1.24 - 1M = 240K). The presence of the 100K (R5), if anything, would tend to lower the value even more as it and any HT rail load will be in parallel with the 33K.
With the 33K missing/badly earthed/OV/Chassis you'll get the ECC83 biased heavily on, higher than normal volts on the 47 K cathode resistor (R9? to pins 3 and 8? The schematic is hard to read). The V3 will also amplify any small amount of hum on HT rail as well as drawing too much current.
It's not a very good phase splitter, but let's fix errors before considering flaws.
Though the reading should be steady with the 100K from the join of the 2 x 1M resistors to HT temporarily disconnected from HT. You need to do that to check the reading.
Try amp without that 100K after verifying there is about 1.04M from either pin 2 or 7 to ground / chassis/ OV. It seems like the 33K from the join of the two resistors is disconnected.
I presume your circuit is that.
If the 33K, R7 is connected and even +50% high, you can't get a reading of 1.24M. That's the effect of the 100K to HT slowly charging up the electrolytic from the meter. 1M + 33K is 1.033, or at worst about 1.04M. With the 100K (R5) connected, the reading will vary as the capacitor charges but can't get MORE than 1.04 M approx, unless the C2 and C4 electrolytic caps are charged to HT volts, then the result is unpredictable.
So a reading of 1.24 that's changing means the 33K (R7) is disconnected. It might not be 33K (orange, orange, orange) as it has a *. But it certainly can't be over 200k (1.24 - 1M = 240K). The presence of the 100K (R5), if anything, would tend to lower the value even more as it and any HT rail load will be in parallel with the 33K.
With the 33K missing/badly earthed/OV/Chassis you'll get the ECC83 biased heavily on, higher than normal volts on the 47 K cathode resistor (R9? to pins 3 and 8? The schematic is hard to read). The V3 will also amplify any small amount of hum on HT rail as well as drawing too much current.
It's not a very good phase splitter, but let's fix errors before considering flaws.
