VintageKustom.com: Repairing Kustom Amps

Re: reverb issue [message #13259 is a reply to message #13234]

Thu, 25 March 2010 16:53

chicagobill
Messages: 2005
Registered: April 2003

Senior Member

There are many type of transistors and each one has been designed to perform a different function. Some are good for switching, some are good for radios, some are good for high voltage, etc.

The transistors in a Kustom amp (or any guitar amp) are general purpose type transistors. Unlike a radio they don't need to operate at high frequencies, only audio frequencies. They usually don't need to handle really high voltages and they don't really need to work in extreme temperature conditions.

So when picking a replacement transistor you only need to know a couple of things: how much voltage and how much gain. In a Kustom preamp, the voltage can at max be 16vdc, so any transistor rated at 25 volts or better will work fine. As for the gain spec I would suggest a high gain unit rated with an hfe of 200-300.

If you Google search the transistor numbers that you have available, you will find datasheets that contain the basic information that you need to know. They will list the voltage ratings and the dc current gain (hfe) ratings as well. And there will be a package outline drawing that will show you which lead is the base, emitter and collector.

I checked some of the numbers that you listed, and the 2N5088 would be the best choice as the replacement for the SE4002. It is rated at 30 volts, and has a minimum hfe rating of 300. When holding the transistor with the flat side facing you, the leads are EBC.

The original SE4002 transistors cases have a flat spot in the epoxy case that indicates the emitter lead.

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