1972 Kustom K-250-1

Kustom was started in 1964 out of Chanute, Kansas by Charles A. “Bud” Ross and made both amplifiers and guitars. More famous for its amplifier line, Kustom was unusual for its time in that they built all analog solid-state amps using transistors and IC chips for guitar, bass, and PA uses - these were then covered in tuck-and-roll naugahyde inspired by the looks of hot-rodded cars. Not many amps made with all solid-state construction are collectible, valuable, or well built enough to justify full blown restorations by amp techs like myself. However there are models made by Kustom, Acoustic, and Roland (JC-120 only) that were made in the 1960’s through the 1980’s that are repairable and warrant the type of work normally reserved for tube amps. This is also true for hybrid amps from the same era, like anything made by MusicMan. This particular model claims 250 Watt RMS of power and has two individual preamp channels that are totally different in terms of schematic design - one uses discrete BJT transistors while the other utilizes an IC chip with an FET front end. This is rounded out by a Class AB power amp using discrete TO-3 style silicon power transistors. The sound of these older solid-state amps that were made with very high quality parts and thoughtful engineering is completely different from what we associate with solid-state design of today. Modern transistor amps are made for the lowest tier of the market cost-wise and therefore are rightfully maligned as sterile sounding and cheaply made electronics that are destined for the landfill, much like smart phones or laptops. Back in the 1970’s however many transistor audio designs were made with the same quality as tube amps and can sound great especially for bass or more commonly hi-fi where the low THD% and clean audio fidelity really shine. For guitar and bass though tube amps remain supreme, where their low-fi and character laden signal paths continue to beat out solid-state or DSP designs with ease. Notable players of Kustom amps include John Fogerty of CCR, Leon Russell, The Jackson 5, Sheryl Crow, and Herbie Hancock.

This amp came in to my shop having almost never been worked on before, with the exception of a replaced power switch. The amp had issues with hum and noise and was filled with 50 year old electrolytic capacitors in the filter section and the very unreliable tantalum type capacitors throughout the rest of the amp. This one needed a full restoration including a cap job for all electrolytics, replacement of all tantalum capacitors with low-ESR electrolytics, cleaning of all pots/switches, a new power switch, and re-soldering weak joints on the PCB’s.

The amp was given a full restoration. All the electrolytic can capacitors were replaced with upgraded voltage and temperature rated IC brand axial leaded electrolytics. Due to the fact that all production of capacitors in the correct ratings for this amp in their original physical format has ceased, a new custom made hand-wired circuit was devised using still available axial lead electrolytic capacitors and terminal strips. Already available holes were used for mounting this circuit so no new and non-original holes would need to be drilled in the vintage chassis. All tantalum capacitors were replaced with upgraded voltage and temperature rated Kemet/Nichicon/CE branded units. This was done for better noise floor and reliability. Vintage tantalum capacitors from the 1970's are notorious for shorting suddenly and going bad, so this was much needed for daily playing. A new Carling brand SPST power switch was installed to replace the broken one present.

All carbon composition resistors were tested to be within their 20% tolerance specification. Many had drifted upward in resistance which is common for this type of/age of resistor. All Power Transistors were tested for functioning and correct voltage readings - nothing was found to be amiss. All pots were cleaned and hardware tightened.