Correct filtering for 1968 Super Bass

[VintageCharlie]

Hey everyone,

as there are some really knowleadgable vintage Marshall fans here, i hope you could help me with a best guess as to what might have been the most likely original filtering on this 1968 Super Bass. To me it looks like all 4 big filter cap cans for mains/screens have been replaced - 2 are 100uF Cornell Dubilier, one is without a foil and says 220uF 400v in handwriting, one is black without markings.
The 2 other cans appear to be original, the preamp one is 40+40uF RS and the one single right next to the mains transformer is 32+32uF RS. Serial is SB/A 103XX.

Do the two remaining original caps give any hint as to what the other ones might/should have been?

AS far as i understand, it could have been anything between 32+32 throughout / 50+50 throughout or 100uF throughout.
I have nos Erie 100uF@350v that might be an option, but i am wondering if this amp might have actually had lower filtering 32+32uF?
Also, in case 50+50 or 100uF were used throughout, which one would be the better pic? I assume 50+50uF due to lower ESR?

What would you guys do in this situation?

Thanks a bunch in advance!

 

[21fret]

Nice, an early '68 10 series.
Let's see the some more shots of the board and a few others! Nice amp!

 

[TAZIN]

Hey everyone,

as there are some really knowleadgable vintage Marshall fans here, i hope you could help me with a best guess as to what might have been the most likely original filtering on this 1968 Super Bass. To me it looks like all 4 big filter cap cans for mains/screens have been replaced - 2 are 100uF Cornell Dubilier, one is without a foil and says 220uF 400v in handwriting, one is black without markings.
The 2 other cans appear to be original, the preamp one is 40+40uF RS and the one single right next to the mains transformer is 32+32uF RS. Serial is SB/A 103XX.

Do the two remaining original caps give any hint as to what the other ones might/should have been?

AS far as i understand, it could have been anything between 32+32 throughout / 50+50 throughout or 100uF throughout.
I have nos Erie 100uF@350v that might be an option, but i am wondering if this amp might have actually had lower filtering 32+32uF?
Also, in case 50+50 or 100uF were used throughout, which one would be the better pic? I assume 50+50uF due to lower ESR?

What would you guys do in this situation?

Thanks a bunch in advance!

View attachment 130757

View attachment 130758

This amp would have had four Dubilier Drilitic 100uF/450v cans for the mains & screens filtering. The Phase Inverter would've been the RS 32-32uF/450v can and the preamp filter was the Marcon 40-40uF/450v cap. BTW, the amp is a '69.

 

[21fret]

Serial is SB/A 103XX.

BTW, the amp is a '69.

oh? okay was thinking that the 10 serial is before the 1968 12 serials.

 

[TAZIN]

oh? okay was thinking that the 10 serial is before the 1968 12 serials.

There's is a 10 series before & after the 12 series amps. The one before has the prefix 'SB/' and the one after has 'SB/A'.

 

[neikeel]

Those Erie 100s are the nearest you are going to get for the mains and screens - assuming that they test and reform 100%. Failing that you’re looking at all F&T 50/50s wired appropriately