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Help for test uc3845

Oldsnake00

Apr 15, 2015
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Apr 15, 2015
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Hi all
I want to test ic uc3845 form below circuit but I no have transformer. After finish circuit wiring I use osc. Measure signial from pin6. It no output.How to modify circuit for use osc. measure signalfrom pin6?
Screenshot_2016-03-20-13-05-27.png
 

Oldsnake00

Apr 15, 2015
33
Joined
Apr 15, 2015
Messages
33
To day I wiring circuit without transformer and feedback.and check signal at pin6 with osc. Why the uc3845 not send pulse from pin output(pin6)?
20160320_190059.jpg 20160320_190126.jpg
 

73's de Edd

Aug 21, 2015
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Sir Oldsnake00 . . . . . .



If I am reading between the lines and you are basically wanting to test a UC3845 of yours.
The simplest way I know is to refer to the old Unitrode Switchmode Design
Manual and breadboard up and try out the simplistic circuit of figure 28 on Page 3-64 of the info that I am providing you below.

( Hmmmmmmmm . . . . I now see that Tejas Instrumentations is now their big Sugar Daddy )

http://www.ti.com/lit/an/slua143/slua143.pdf

The USUAL failure mode on this family of devices is for one of the final totem pole driver transistors to fail.


73's de Edd

.
 
Last edited:

Oldsnake00

Apr 15, 2015
33
Joined
Apr 15, 2015
Messages
33
Thanks. All
I change cap. from 47pf to 1nf and res. 47k to 10k the uc3845 generate pulse about 80khz.
:D
 

73's de Edd

Aug 21, 2015
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Yep . . . . .that circuit was what I built up on a custom built board with an I.C. plug in socket for testing those devices
to evaluate one to see if it was basically good.
Seems like that family was introduced in the mid-late nineties.
A 100 ohm load resistor was used to present a challenging load for its capacitive doubler circuit .
Nowadays that chip still seems to be the principal building block for computer power supplys and others.

73's de Edd
 

Oldsnake00

Apr 15, 2015
33
Joined
Apr 15, 2015
Messages
33
.

Yep . . . . .that circuit was what I built up on a custom built board with an I.C. plug in socket for testing those devices
to evaluate one to see if it was basically good.
Seems like that family was introduced in the mid-late nineties.
A 100 ohm load resistor was used to present a challenging load for its capacitive doubler circuit .
Nowadays that chip still seems to be the principal building block for computer power supplys and others.

73's de Edd
Thank you.
This project build for caustom cdi to use on my old bike.
 
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