11-06-2017, 12:39 AM
I noticed the EABC80 has a 4.7 Meg resistor on the grid which is R28. I thought that was really a high value. Someone on a guitar amp site was discussing this value so I quote:
"The grid resistor is typically very high in value, yours has 4.7 meg grid resistors. And those .05 coupling caps to the input jacks block any DC, so the grid can climb to a nice negative volt and be happy."
One other point mentioned way back in this long thread is the ratio detector having the diodes reversed, unlike the Foster Seeley which had both diodes +. In the Saalburg C51 has the capacitor markings depicted. The cap is 5 microfarads. Initially that polarity had me puzzled a lot. It now makes sense. Many people will be more used to seeing a ratio detector with silicon diodes.
Amazingly, I am more or less through this schematic and set to repair the set when my boat work wraps up. It's been a lot of work for questionable gain.
"The grid resistor is typically very high in value, yours has 4.7 meg grid resistors. And those .05 coupling caps to the input jacks block any DC, so the grid can climb to a nice negative volt and be happy."
One other point mentioned way back in this long thread is the ratio detector having the diodes reversed, unlike the Foster Seeley which had both diodes +. In the Saalburg C51 has the capacitor markings depicted. The cap is 5 microfarads. Initially that polarity had me puzzled a lot. It now makes sense. Many people will be more used to seeing a ratio detector with silicon diodes.
Amazingly, I am more or less through this schematic and set to repair the set when my boat work wraps up. It's been a lot of work for questionable gain.
