matta
Well-known member
Hi Guys,
I'm restoring a '67 Fender Bassman I bought a year ago and have it recapped, retubed and biased, she is sounding great... esp. considering some of the ORGINAL MALLORY Filter caps were in there, 2 of them dead as doornails.
To the best of my knowledge/research the original output trafo on these amps, along with their BF/SF Bassman brethren want to see a 4 Ohm load, though my research says Fender OT's are great for impedance mismatching and are happy to push 100% of their rated output, quite comfortably driving an 8 Ohm load if needed.
But looking at the OT it didn't look original and so I thought it must be an after market unit... (more on that later).
So I decided to open up the Fender 2x12 cabinet to look at the speakers and imagine my surprise when firstly they are not only NOT the original speakers, but grossly mismatched in that they are both 8 Ohms, wired in SERIES, reflecting a 16 Ohm load!
Both speakers are also only rated at 25Watts, but I'm guessing that having them in series allows the 40W amp to drive them without blowing/burning something out, but being HALF as efficient at doing so.
That said I'm now trying to work out who made the aftermarket transformer and it's specs.
It has a logo on the side on it that looks like a black circle with a lightning bolt through it, with the following legending:
P-5417-1
7A18
549-6142
The primary side has a RED, BLACK and ORANGE wire and the SEC has BLACK & YELLOW+BLACK.
I measured the DC resistance across the primaries at 287R.
Given that info is there anyway to extrapolate who made this OT and/or what kind of load it wants to see (I'm wanting to replace the speakers and want to find a pair that match the amps output).
Thanks in advance!
Cheers
Matt
I'm restoring a '67 Fender Bassman I bought a year ago and have it recapped, retubed and biased, she is sounding great... esp. considering some of the ORGINAL MALLORY Filter caps were in there, 2 of them dead as doornails.
To the best of my knowledge/research the original output trafo on these amps, along with their BF/SF Bassman brethren want to see a 4 Ohm load, though my research says Fender OT's are great for impedance mismatching and are happy to push 100% of their rated output, quite comfortably driving an 8 Ohm load if needed.
But looking at the OT it didn't look original and so I thought it must be an after market unit... (more on that later).
So I decided to open up the Fender 2x12 cabinet to look at the speakers and imagine my surprise when firstly they are not only NOT the original speakers, but grossly mismatched in that they are both 8 Ohms, wired in SERIES, reflecting a 16 Ohm load!
Both speakers are also only rated at 25Watts, but I'm guessing that having them in series allows the 40W amp to drive them without blowing/burning something out, but being HALF as efficient at doing so.
That said I'm now trying to work out who made the aftermarket transformer and it's specs.
It has a logo on the side on it that looks like a black circle with a lightning bolt through it, with the following legending:
P-5417-1
7A18
549-6142
The primary side has a RED, BLACK and ORANGE wire and the SEC has BLACK & YELLOW+BLACK.
I measured the DC resistance across the primaries at 287R.
Given that info is there anyway to extrapolate who made this OT and/or what kind of load it wants to see (I'm wanting to replace the speakers and want to find a pair that match the amps output).
Thanks in advance!
Cheers
Matt