Sound City 120

[CJ]

Sound City is a British amp, this one has 6 EL34's and some nice transformers,

here is a blub from Vintage Guitar Magazine>

https://www.vintageguitar.com/22338/sound-city-lb-120-mark-iv/

 

[CJ]

Z switch has been hard wired to the jacks which is a good move,

gonna fix the tie wrap pwr cord strain relief system,

transformers tweaked from impact, 

 

[CJ]

boiler plate

 

[CJ]

has a few mods, will ask customer if he wants it returned to stock,

nice chassis shape, more stable sitting on spk cak,

has had a cap job already.

 

[CJ]

OPT,

weird sq wave at 10 K,  buy one, get one free,

 

[CJ]

plenty of room in the OPT widow for a turns data bootleg operation, PRR method,

loading the ghost wind down with a resistor to get a good voltage read,

 

[CJ]

got the turns and core size,

leakage is about 220 mH which is usually what you get with this size core,  there seems to be a discrete number for each core as far as leakage inductance goes,


and note that the leakage value is sometimes close to the secondary inductance for a high ratio step down, (4 ohms etc)

 

[CJ]

break on the bobbin plate offers a guess as to the winding structure,

probably P-S-P-S-P-P-S-P-S-P with the 100 volt f/b wind thrown in somewhere,

probably 2 layers @ 120 = 240 and 4 layers @ 120 = 480 , 240 winds on outside and middle,

hard to read schematics can be found here>

http://soundcitysite.com/schems.shtml

 

[emrr]

Had one for awhile.  Only sounded great one way; dimed!  Shake a whole building through multiple walls.  EQ design makes for a noisy beast.