while I’m working on a tweed champ 5f1 replica with 10″ speaker, I recall they say the output transformers affect the tone.
and, I noticed I never saw the back side of champ chassis before. it’s where I start finding a vintage OT for my project
I got confused with the primary impedance of this OT. this data sheet on classictone.com has the right dimension of it. the primary impedance is 17K here. and it’s 5K on mojotone’s page
they probably have the different sources of the original transformers I guess. anyway, it’s the dimension. 1 3/4 width, and 1 7/16 height just like the classic tone’s spec. it’s 42.5mm x 35mm in metric on my double sided hoechstmass tape measure.
tdpri forum and the members helped a lot since I got this champ. then again this time.
tweed princeton and champ are both 5w. and shared the transformers. mine has 106 and the member seems to be an expert with experience advices to try 107 which is larger than 110, 105, and 106.
maybe it’s the reason the replacement transformers have different primary impedance. but I still don’t get which one is correct for 5F1 or how the different ratio affects the tone on the same circuit.
this 1962 champ came with an OT marked 125A3A on it. and the size looks identical to Triad 106.
these two different 5F1’s sound quite different with the same tubes and the speaker. and I assume the yellow Astron and the blue Ajax are one of the minor differences. I thought the major difference came from the cabinet wood like the guitars. but, I’m not sure anymore.
I’ll dig more on the OT’s later.
didn’t have a luck for vintage Triad OT. but found these two from Stancor. A-3877 is 5K to 4ohm, and A-3878 is 7K to 4ohm. they both are 5 watts rated.
they are Heyboer PT and Classictone OT. both are slightly bigger than the original transformers. Classictone 40-18030 has two primary input tabs which are 5k and 8K. I tried them both but didn’t see a noticeable difference today. it was too late to turn up the volume enough to feel the difference. I simply went to 8k which is told hot and close to the vintage champ OT.
5k seems like the ideal spec. by the document and calculation. but 5F1 had 7k to 17k primary input from my research.