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LF: DJ

To: [email protected]
Subject: LF: DJ
From: "hamilton mal" <[email protected]>
Date: Mon, 10 Jun 2002 19:59:31 +0100
Reply-to: [email protected]
Sender: <[email protected]>
Due to email received, mostly private about the DJ coil mods especially the ferrite approach, the required information follows.
Models using the BCB capacitor board, total series capacitance 24nf  need an inductance on the main ferrite core winding of 54 - 53 uH for 135 - 138 khz. Pick a ferrite or iron powder core about the same size as the amidon  T200 or larger and wind the reqd number of turns to get the above inductance value. My core needed 43 turns of 1mm enamelled wire. I use these cores for my LPF
capable of running several hundred watts RF output and they never get warm.
Pull out the capacitor board and connect the above coil in series to pin 5, also join the connectors labelled 7 and 8, connect a sig gen and scope in parallel to the input of coil and earth lead to pin 1 (as per original connections in cct diagram) for main coil. Tune the sig gen around 135 - 138 khz for min amplitude display, series resonant procedure, and adjust the inductor turns to the exact resonant freq rqd. If the C board value is as above then it will be easy to arrive at the desired resonant freq with the above inductor value. Two taps on the coil permits freq adjustment from 135.7 - 137.8 khz.
The beauty using the above procedure allows all adjustments to be made externally from the unit and when replaced it is spot on, no freq changes or going off resonance because of metal case proximity as happens with the air wound coils.
The ferrite/iron coil because of the small size can actually be mounted on the capacitor board, there is ample room at the top end, and convenient to adjust if necessary.
For the link winding follow the same procedure as above but only about 4uH is required, more details if required.
For the lower band models proceed as above but the C board BCA needs to be modified for a total series C of 24 nf.
 
 
Have fun de Mal/G3KEV   
 
 
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