SUPER EASY DIODE SUBBING

This method of subbing is especially set up for servicing TV's and VCR's, however
it will work for most other types of equipment using diodes rated at 5 amps or
less.  You don't even need the part no. of the diode! (in most cases). 

Use the 5 amp diode in any circuit needing a device rated at 2 to 5 amps. With 
diodes, higher voltage, amperage or faster switching speed is always o.k.  Please
note that when I list a (very low cost) substitute for a diode (“same as”), this
diode has exactly the same spec’s.   

Tiny glass diodes (1/8w resistor size) - if it's not a zener diode* use the ECG519.
Its extremely fast switching speed allows it to work in almost any circuit of any
device. 

1/8W  RESISTOR  SIZE  (not zener diodes*) 

ECG519    100V    200mA    4ns (trr)    (same as 1N4148**) 

Small plastic or ceramic diodes about the size of a 1/2w or 1/4w resistor - if it's
not used in a switch mode power supply (SMPS) or horizontal output / flyback
circuit. 

1/2W  RESISTOR  SIZE / NOT  FOR  SMPS  OR  FLYBACKS 

ECG125    1000V    2 . 5A    (same as RL257**) 

Smaller plastic diodes in the primary circuit of SMPS transformers (except for the
one on the ~160VDC winding), also for those in the secondary circuit of TV
flybacks. 

SMPS  PRIMARY / FLYBACK  SECONDARY
(1/2w resistor size)

ECG575    1000V    1A    70ns (trr)    (same as HER108**) 
(see ECG552 note at bottom of page) 

For the diode wired to the SMPS primary winding carrying  ~160VDC 

SMPS  160V  PRIMARY  WINDING 

ECG558    1500V    1A    250ns (trr) 
(no common generic found) 

SMPS OUTPUT  -  SMALLEST DIODES 
(1/2w resistor size) 

ECG575    1000V    1A    70ns (trr)    (same as HER108**) 
(see ECG552 note at bottom of page) 

SMPS  OUTPUT  -  LARGEST  DIODES 
(~1w resistor size) 

ECG577    1000V    5A    70ns (trr)    (same as HER508**) 

SMPS   Abbreviation for Switch Mode Power Supply
 
~  This is the scientific symbol for the word approximate 

* If there is a zener diode symbol on the board, read the diode and look it up
in the ECG guide (usually a two digit no. mixed with letters on the diode 
indicates the zener voltage).  Use the schematic, if necessary, to find the voltage rating.  Don't forget to contact the manufacturer or other techs if you need to.  
For some small bias diodes in the output circuit of audio amps, two 1N4148's may need to be wired in series to equal the 1.2 volt drop of the original diode 
(if it is that type of diode).

** These diodes available from Mouser Electronics in California (800 346 6873)
www.mouser.com and are much less expensive than ECG, many other types and sizes available.  You can use their catalog to select replacements for most ECG types.  I like to keep it simple and use just a few high rated diodes so I don't have to always look up the original part no.  With diodes, higher voltage, amperage or faster switching speed is always o.k. (except for zener diodes of 
course).

ECG552 (1N4937**) can be used for TV flyback secondaries and if you are sure
that the circuit is operating at 15KHz or less then use it in SMPS instead of the
ECG575 if you prefer.  It is rated at 600V 1A 200ns (slower than ECG575). For 
computor monitors use the 575.

         Copyright © 2000  Bil Green  All rights reserved

                    ECG is a registered trademark of Philips ECG, Inc.