SUNN Beta-Lead // Resources

The schematics I was able to find online were scanned at a very low resolution … I tried my best to improve their legibility … what I have is posted here below, …

SUNN Beta-Lead front

SUNN Beta-Lead back

the amp had a few issues that turned out to be minor … leaky 2.2uF NP caps at the front end that made the guitar controls sound scratchy // every 2.2uF cap I could find and all the pots are highlighted here …

SUNN Beta-Lead pre amp schematic

SUNN-Beta-Lead-pre-amp-schematic

replacing these caps involves removing the preamp board from the chassis … while in there a 100k channel Master pot with broken shaft is replaced … I used a 24mm Alpha 100kLIN pot in lieu of the original // works fine …

SUNN Beta-Lead pre amp layout

SUNN-Beta-Lead-pre-amp-layout

the 470 ohm biasing resistors (pin 14 of the CD4069 chips) dropped voltage down to 8.4 volts on both IC104 and IC105, the CMOS chips that perform clipping duties …

SUNN Beta-Lead pre amp chip layout

Output stage was working fine and biased exactly as in the factory drawings …

SUNN Beta-Lead pwr amp schematic

SUNN-Beta-Lead-pwr-amp-schematic

SUNN Beta-Lead pwr amp layout

SUNN-Beta-Lead-pwr-amp-layout

I was able to get some great tones out of this thing … at high gain the preamp gets fairly noisy, but with the master turned up and the gain turned up not too high I was able to get some pretty sweet blues and rock tones … definitely a fine sounding SS amplifier



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