I have an old Silverface Dual Showman. Chassie stamped A 12712. Tube layout label marked AB763.
The transformer has been replaced and is marked W022756. How do i determine the OHMs on this amp. I would like to assume its 4 based on what it originally was manufactured as… but is there a way to test with an ohm meter? Do you test it with the speakers attached etc. Any help would be appreciated. I’m no technician so go easy guys…

Hello Claus, The 7355 power tube model of the Showman (and Twin) was a transitional model that was made from approximately September(?) 1963 until superseded no later than December ’63. One distinguishing characteristic of your amp should be the absence of the ‘middle’ knob on the 2nd channel (second channel will have volume ,treble, bass, speed, intensity knobs for a total of 5). If your amp still has the tube chart, there should be a two-letter ink stamp on it, first letter being ‘M’. The second letter is the month (‘A’ = January, ‘B’ = February, … ‘L’ = December). Also, on the top of the power transformer (black one on the far left as viewed from the rear of the amp), there should be some engraved codes; specifically “125P19A”, and “606327”.

Hallo, I have a Showman blond with the Factory No: A oo491. Could anybody tell me what was the production year. I bought the amp approx 1963- 64. It has the RCA 7355 Powertubes. After 50 years hidden it goes like new. I may have to replace one or two El-Condensers. thanks, Claus