|
|
|
#16
12-04-2021, 03:55 AM
|
||||
|
||||
|
My Heathkit IM-12 was sort of like that. It was a few bad capacitiors around the vertical horiziontal positioning controls. There would be a trace for a few minutes and the it would creep off the screen.
|
|
#17
12-04-2021, 06:34 PM
|
||||
|
||||
|
The neat thing is this scope has neon indicators telling you where the beam is so you can use the controls to locate it and center it. The problem is that often I can get all four directional indicator lights out and there is still no beam, but it is sweeping because I can enlarge the scale until it overscans and you can see the left-right indicators flash in sequence.
|
|
#20
12-14-2021, 10:37 PM
|
||||
|
||||
|
They test fine for capacitance and resistance out of circuit.
Now one thing I have not done is test voltages to the schematic. I was planning to do that after I cleaned the chassis but COVID got in the way. Hell now that I think about it I have not even cleaned the tubes yet. Edited: Oh well that might also do it. Pin 1 on the 12AU7 stayed in the socket when I pulled the tube out. Last edited by MIPS; 12-14-2021 at 11:10 PM.
|
| Audiokarma |
|
#22
12-15-2021, 02:14 PM
|
||||
|
||||
|
It would explain what is wrong with the beam sweep because with pin 1 completely missing you are missing a feedback loop for the HV oscillator.
I'll have to dig around and see where my spares went.
|
|
#23
12-16-2021, 11:49 PM
|
||||
|
||||
|
My used spare read weak emission but I have a 12AU7A that tests like new so I threw that in.
Well now I can see a sweep but it still cuts out. https://imgur.com/59uwUnp
|
 |
|
|
Linear Mode
