No sound out of Sonic II/200s ext speaker port

[thanksgiving]

Hey everyone, just got my first Sunn head and took it to a respected local tech to get a full once over as it was all original, with the 2 prong plug. when plugging into the 4 ohm ext jack I get no sound. It's my understanding that with one cab the amp has a switch between 8 and 4 ohms between the main and ext jacks on the back. wanted to confirm this is true and not my own error before taking it back and making a stink... anything inside to look for or advice would be much appreciated. sunn forever 

ps... while ive got you- how much of a difference/what do you all prefer for guitar? k140 or the sunn transducers in a 200s cab? have the opportunity to buy either but not sure if its worth spending an extra $300 for the jbls.

[loudthud]

K140s are for bass. They are 3 or 4 dB louder than the Sunn transucers. For guitar, K130s are even louder.

The "4 Ohm" jack is an odd-ball part that does the 4 to 8 Ohm switching and it will be hard to find if you need a new one. There should be some sound if you just plug into only the 4 Ohm jack. At least one thread here has pictures of the internal wiring.

Link: https://forum.sunnstillshines.online/index.php?topic=4844.msg18880#msg18880

[Ryan Phelps]

Loudthud is correct. The 4 ohm jack is a Switchcraft 13A and is available from Antique Electronic Supply (AES). I bought a handful years ago for Sunn repair work.

[thanksgiving]

K140s are for bass. They are 3 or 4 dB louder than the Sunn transucers. For guitar, K130s are even louder.

The "4 Ohm" jack is an odd-ball part that does the 4 to 8 Ohm switching and it will be hard to find if you need a new one. There should be some sound if you just plug into only the 4 Ohm jack. At least one thread here has pictures of the internal wiring.

Link: https://forum.sunnstillshines.online/index.php?topic=4844.msg18880#msg18880

i understand that they are for bass, but would still be suitable for guitar no? would the sunn transducers sound better with a guitar?

the wiring in my sonic ii looks the same as the photo(minus the feedback wire), i suppose i will have to shoot the tech a message?
https://ibb.co/HYCj79c

[Isaac]

The JBL K140 has a top end of about 2000Hz. That's an octave or two too low for what most people want for a guitar sound. It will be a dark and midrangey sound, not bright. Imagine playing guitar through an amp with the treble turned all the way down. So, strictly for guitar use, I'd say that the Sunn Transducers will yield a better guitar sound. 130s - D, K or E - are a different matter. They are loud, clean, and low distortion. Not everyone's cup of tea for guitar, but some love them. I played with a guy who used a Sunn 1200S into two cabinets with two D130s each. What a sound! Loud and clean, and the differences between guitars and pedals were very clear.