Vox DA5 Battery Problem

[Carl]

I have a Vox DA5 with the battery power out of service. I thought it was just a bad connection but that does not seem to be true. I had a good amp tech look at it. He said that he thinks there is a transistor out. He can jump it so the battery works but then the on/off switch does not work. He needs a schematic to get any further.

Does anyone have any ideas?

Thanks,

Carl

[lemaroille]

hi,

here is the schematic of the supply part I get opening my amp.

hope it helps.

Can anyone tell me what is the aim of the KTC2026 transistor and the big 1 or 2W resistor ?

thx

[Roly]

Hi lemaroille, welcome!

Can anyone tell me what is the aim of the KTC2026 transistor and the big 1 or 2W resistor ?

It's a voltage regulator.

The "diode" connected to the 47 ohm and transistor Base will actually be a zener diode.  This provides a voltage reference for the transistor which does the actual voltage regulating, the Emitter being about half a volt lower than the zener voltage on the base.

HTH

[J M Fahey]

Agree.
The schematic shows 2 alternative power supplies.
The batteries provide straight 9V; the regulated one turns raw 12V (which in cheap wall adapters may be as high as 16 or 17V  :duh ) into stable 9V.
The Zener will be a 9.5V to 10V one.