teddy_pardo
Trade: Teddy Pardo
Here is a nice a simple mod that can be applied wherever a 317,337,1086 regulator is used.
The idea here is to insert a VBE before the 3-leg regulator. The VBE filters high frequencies noise (in fact almost all relevant frequencies) before they get to the regulator, and isolates the regulator from the power rail in a way that noise from one regulated circuit doesn't get back to the power rail (let's say less noise...). Doing that significantly boosts the performance of these simple regulators.
It looks like this (Carl, do you recognise your capacitors...):
Note that you have to cut the strip-board between the collector and the emitter of the transistor. Otherwise it will still work, but no benefit...
Isn't it lovely?
it's a pin-pin replacement with the original regulator, you can even reuse the original regulator. The original regulator circuit (resistors/capacitors) remains as is, no need to change anything. The VBE requires some dropout (about 1V), if you don't have it than simply replace the original 317 by a 1086 which is low dropout to compensate.
The circuit is based on the same VBE circuit used on the Flea (BC547c, 3.3uF film, 10K, and 10/22uF tant), but other combinations can be used. As is, it can only be used for low current circuits (few 10s of mA), for higher currents smaller resistors and larger capacitors at the transistor base should be used. I achieved excellent results with 22uF tantalums, and 10-56uF oscons.
I used this circuit to replace all the regulators in my CDX (there are about 20). I replaced each time 2-3 regulators, and each time the improvement was noticeable.
Highly recommended!
Ooops. I forgot to mention, a ground wire has to be connected from the circuit ground to the main PCB ground. I used a short wire connected to the ground leg of one of the main PCB tantalum (the Vout tantalum of the original regulator circuit).
Enjoy, Teddy
The idea here is to insert a VBE before the 3-leg regulator. The VBE filters high frequencies noise (in fact almost all relevant frequencies) before they get to the regulator, and isolates the regulator from the power rail in a way that noise from one regulated circuit doesn't get back to the power rail (let's say less noise...). Doing that significantly boosts the performance of these simple regulators.
It looks like this (Carl, do you recognise your capacitors...):
Note that you have to cut the strip-board between the collector and the emitter of the transistor. Otherwise it will still work, but no benefit...
Isn't it lovely?
it's a pin-pin replacement with the original regulator, you can even reuse the original regulator. The original regulator circuit (resistors/capacitors) remains as is, no need to change anything. The VBE requires some dropout (about 1V), if you don't have it than simply replace the original 317 by a 1086 which is low dropout to compensate.
The circuit is based on the same VBE circuit used on the Flea (BC547c, 3.3uF film, 10K, and 10/22uF tant), but other combinations can be used. As is, it can only be used for low current circuits (few 10s of mA), for higher currents smaller resistors and larger capacitors at the transistor base should be used. I achieved excellent results with 22uF tantalums, and 10-56uF oscons.
I used this circuit to replace all the regulators in my CDX (there are about 20). I replaced each time 2-3 regulators, and each time the improvement was noticeable.
Highly recommended!
Ooops. I forgot to mention, a ground wire has to be connected from the circuit ground to the main PCB ground. I used a short wire connected to the ground leg of one of the main PCB tantalum (the Vout tantalum of the original regulator circuit).
Enjoy, Teddy