Awful mess here. Do not think about the 6AS7 tube if the input voltage is too low.
Check voltages under load on C624a and C644a separately as suggested before.
Tell us these caps are original or not. Then we can proceed.
Let us stick to the schematic, leaving away speculative posts.
We only know that you own a DMM - how did you check the caps ?
Good that you checked the resistors, same applies to the rectifiers (but unlikely defective I think).
Check voltages under load on C624a and C644a separately as suggested before.
Tell us these caps are original or not. Then we can proceed.
Let us stick to the schematic, leaving away speculative posts.
We only know that you own a DMM - how did you check the caps ?
Good that you checked the resistors, same applies to the rectifiers (but unlikely defective I think).
Ok so I do have a component tester aswell a cheap one that gives me esr readings and transistor specs. But I don't have actual tube measurement gear such as tube testers. I do have a power supply that goes from 0-30v but thats only enough to power a heater of course. And a big box of 1W metal film resistors.
I'm not sure if the capacitors are original or not this has been used by a university according to all the stickers of servicing on the inside and its been used in the Philips lab for measurements according to the previous owner.
They are sprague can capacitors and they do fit in the slots but like I said they are not the same value as the schematic states so that might be the issue.
I'm not sure if the capacitors are original or not this has been used by a university according to all the stickers of servicing on the inside and its been used in the Philips lab for measurements according to the previous owner.
They are sprague can capacitors and they do fit in the slots but like I said they are not the same value as the schematic states so that might be the issue.
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You do not need any tube tester.
You have received some serious advice here and my recommendation would be to follow this advice.
The pictures are OK, but not good enough, some requested dc voltage measurements are still missing.
You have received some serious advice here and my recommendation would be to follow this advice.
The pictures are OK, but not good enough, some requested dc voltage measurements are still missing.
The voltage drop is due to the series impedance of the power supply and the current that's being drawn. So the series impedance is too high, or the current is too high. Measure the voltage drop across the 10 Ohm resistor R644.
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You can determine the current from Ohm's law. Tek doesn't show the current (would vary with plug-ins), but over 100 mA is likely a problem.