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Kendrick dew heater controller



 
 
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  #1  
Old January 25th 04, 11:47 PM
Dirk Lammerts
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Default Kendrick dew heater controller

Hi,
My Kendrick dew heater controller (model 4) blew up yesterday. The housing
of the TLC555 timer chip had literally blown up. Same thing happended after
I replaced the 555. The MOSFET and diodes look ok from what I can measure.
All other components look visually ok. BTW, what type of component are VR1
and J4?
Anyone who knows the circuit well enough to give me some guidance on which
components to check?
Thanks
Dirk


  #2  
Old January 26th 04, 01:46 AM
HAVRILIAK
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Posts: n/a
Default Kendrick dew heater controller

y Kendrick dew heater controller (model 4) blew up yesterday.

Sorry to hear that but how did it happen. I for one would like to avoid that
condition
  #3  
Old January 26th 04, 01:46 AM
HAVRILIAK
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

y Kendrick dew heater controller (model 4) blew up yesterday.

Sorry to hear that but how did it happen. I for one would like to avoid that
condition
  #4  
Old January 26th 04, 01:46 AM
HAVRILIAK
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

y Kendrick dew heater controller (model 4) blew up yesterday.

Sorry to hear that but how did it happen. I for one would like to avoid that
condition
  #5  
Old January 26th 04, 04:12 AM
Dirk
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

It happened when I connected the heater strip through an extension cord that
might have had a short circuit in the plug. Trust me, you don't want to have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition



  #6  
Old January 26th 04, 04:12 AM
Dirk
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

It happened when I connected the heater strip through an extension cord that
might have had a short circuit in the plug. Trust me, you don't want to have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition



  #7  
Old January 26th 04, 04:12 AM
Dirk
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

It happened when I connected the heater strip through an extension cord that
might have had a short circuit in the plug. Trust me, you don't want to have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition



  #8  
Old January 26th 04, 07:43 AM
Rex
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

Hi Dirk,

I havent opened up my Kendrick.....

Does the 555 drive the MOSFET directly??? or is there an opto device between
the two??

Sounds like the poor 555 is trying to sink to much current in "off" state.

How many 555's does the Kendrick use anyway???

R


"Dirk" wrote in message
om...
It happened when I connected the heater strip through an extension cord

that
might have had a short circuit in the plug. Trust me, you don't want to

have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but

it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of

the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is

causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition







-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
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  #9  
Old January 26th 04, 07:43 AM
Rex
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

Hi Dirk,

I havent opened up my Kendrick.....

Does the 555 drive the MOSFET directly??? or is there an opto device between
the two??

Sounds like the poor 555 is trying to sink to much current in "off" state.

How many 555's does the Kendrick use anyway???

R


"Dirk" wrote in message
om...
It happened when I connected the heater strip through an extension cord

that
might have had a short circuit in the plug. Trust me, you don't want to

have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but

it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of

the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is

causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition







-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----
  #10  
Old January 26th 04, 07:43 AM
Rex
external usenet poster
 
Posts: n/a
Default Kendrick dew heater controller

Hi Dirk,

I havent opened up my Kendrick.....

Does the 555 drive the MOSFET directly??? or is there an opto device between
the two??

Sounds like the poor 555 is trying to sink to much current in "off" state.

How many 555's does the Kendrick use anyway???

R


"Dirk" wrote in message
om...
It happened when I connected the heater strip through an extension cord

that
might have had a short circuit in the plug. Trust me, you don't want to

have
a short circuit in any of the outputs even for the shortest amount of time
if that was really the cause.

Here is more detailed protocol of the current state of the controller
(hoping that an electronic wiz out there can help me out):
1. Replaced the 555 timer and the MOSFET (did not have the exact one but

it
should be ok spec wise)
2. Turned on power without load (no heater strip) - everything looks fine,
circuit draws 100mA
3. Connected 11" heater strip (measuring 6.2 ohm) - circuit draws a little
over 2A (pretty much what I'd expect with 12V at 6 ohm), everything looks
(and smells) ok
4. After 4 secs (I read somewhere that this is exactly the cycle time of

the
Kendrick) current drops to 300-400 mA (I guess that means that the timer
flips and makes the MOSFET block) and 555 starts cooking (literally!).
I'd really appreciate any idea on what else could have blown that is

causing
this now. The only components I did not check are L1, VR1 (?), and J4 (?).
Thanks
Dirk

"HAVRILIAK" wrote in message
...
y Kendrick dew heater controller (model 4) blew up yesterday.


Sorry to hear that but how did it happen. I for one would like to avoid

that
condition







-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----
 




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