May Birthdays 
I had this vintage Accutronics 4EB2C1B pan laying around for wich I have absolutely no use.
I decided to try and rewind the input transducer and turn it into a 4AB pan so I can use it with my Surfy Bear. 
Here are some of my findings and questions.
DC resistance of the 4EB input was 58 Ohms (exactly as stated in the table Accutronics provides on their website. See below for table.)
DC resistance of the 4EB output was 199 Ohms (again, pretty much exactly as in the table)
So, I dismantled the input transducer and counted the winds while unwinding the old wire.
I counted 1080 winds which is very close to the 1100 winds stated in the table. It's very likely I miscounted a few times.
But then came the moment to choose new wire for the 124 turn, 8 Ohm input.
I only have new Accutronics pans to go by and after holding several of my wires next to some 4AB input transducers, the closest wire I had was 0.25mm (AWG 30). Although very hard to eyeball, my wire looks a very tiny bit thinner.
[Edit:
Since this post I have also tried 0.36mm (AWG 27) but that is too thick. After 124 turns the coil extends beyond the bobbin, so you can no longer slide the leg of the lamination through because the other leg hits the coil.
I had to unwind it a bit (10 turns or so) before I could shove it over the leg of the laminated core.
The DC resistance was too low, around 0.5 Ohm. It works but isn't ideal.
I think around 0.30mm or slightly below (AWG 28 or AWG 29) might be very close to what is on the original. I'll update when I get hold of such wire.]
After rewinding, taping, soldering and rebuilding the rest of the transducer it measures 1.9 Ohms.
My 4AB pans all measure 1.7 Ohms so it seems the wire wasn't so far off after all.
The pan works fine but it's a medium decay (which seems rather short compared to the long decay).
This is mostly a proof of concept for me to see how feasible this kind of operation is.
Vintage 4AB3C1B's easily cost over 100$ and not so easy to find.
Vintage 4(E or F)B3C1B"s cost 5-20$ and there are a lot of them.
So my plan is to build me some vintage 4AB pans out of 4EB or 4FB pans.
The main question is if anyone knows what gauge wire was used in the old 4AB pans for the input transducer?
By the way, the wire in the output transducer measured 0.1mm or AWG 38.
Another question is why modern pans all have higher DC readings for both input and output.
I've googled around a bit and most people measure around 1.9 Ohm for the A-input (vintage table says 0.8 Ohm)
Most people measure around 250-270 Ohm for the B-output (vintage table says 200)
My 4EB vintage pan measures exactly what the table says (E:58 Ohms, B:199Ohms)
Are they using more turns or thinner wire or both?
Last edited: Feb 10, 2020 17:44:05
