Tunnel Diode Replacement and Modification: Difference between revisions

← Older edit

Tunnel Diode Replacement and Modification (view source)

Revision as of 09:20, 9 February 2022

14 bytes added , 9 February 2022

no edit summary

Peter

Bureaucrats, Interface administrators, Suppressors, Administrators

39,717

edits

@@ Line 1: / Line 1: @@
 == Sweep Trigger TD Substitution ==
@@ Line 14: / Line 13: @@
 Step by Step Modification Instructions:
 # Replace the bad 10 mA Tunnel Diode (D245) with a new 4.7 mA Tunnel Diode (e.g. [[1N3717]] or [[Russian tunnel diodes]]).
-# Replace transistors Q234 and Q244 with silicon transistors having Ft around 200 MHz and Beta around 100, such as 2N4248.
+# Replace transistors Q234 and Q244 with silicon transistors having f<sub>t</sub> around 200 MHz and Beta around 100, such as 2N4248.
-# Replace resistor R236 (30.1 kΩ) with a 47 kΩ 1Watt resistor.
+# Replace resistor R236 (30.1 kΩ) with a 47 kΩ, 1 W resistor.
-# Add new 30K 1 watt resistors in series with R247 and R248, which are each 15 kΩ 2 watts. (Total resistance is now 45 kΩ each).
+# Add new 30K 1 watt resistors in series with R247 and R248, which are each 15 kΩ, 2 W. (Total resistance is now 45 kΩ each).
-# Because the Tunnel Diode must be biased below its trigger point, there is less adjustment margin with a 4.7mA Diode than with the original 10 mA Diode. This means that the values of R247 and R248 can be quite picky. Because of the variations between individual tunnel diodes, it may be necessary to use slightly smaller or larger resistances.
+# Because the tunnel diode must be biased below its trigger point, there is less adjustment margin with a 4.7 mA Diode than with the original 10 mA Diode. This means that the values of R247 and R248 can be quite picky. Because of the variations between individual tunnel diodes, it may be necessary to use slightly smaller or larger resistances.
 Morris points out that the B Sweep Trigger circuit is identical to the A Sweep Trigger. This modification should therefore be equally applicable for that circuit.
-Dave Wise believes that for S/N 6740-up, you would modify R236, R233, and R246.  The goal is same node voltages with <4.7mA through the diode instead of <10mA.
+Dave Wise believes that for S/N 6740-up, you would modify R236, R233, and R246.  The goal is same node voltages with <4.7 mA through the diode instead of <10 mA.
 [[Category:Repair issues]]