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JVC model:TU-4500U no 5v

 
 


Sidney
Unregistered User
nospam@spam.com

Oct 24, 2003, 11:50 AM

Post #1 of 2 (983 views)
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JVC model:TU-4500U no 5v Can't Post
JVC DV3 MPEG Dish Network receiver model:TU-4500U,year:1996,UL:87U3 during Hurricane Juan power was disrupted at the customer's house for 5 full days when the power came back the receiver did not turn on.
I found that the 5 volt rail on the main board not the power supply board has a short (8 ohms to gnd)so VR1 & VR2=LM3940IT-3.3=+ 3.3 volt regs obviously cannot provide a +3.3v output.I unsoldered both regs and two radial electrolytics next to it but the 5v rail short is still present,the main board has many smt IC's that are directly connected to this 5v rail along with many radial electrolytics I cannot unsolder those smt Siemen IC's and all of those electrolytics.
Does anyone know exactly which part is shorted?anyone have any common repair tips for this unit?.Thanks in advance.

Sidney
E-mail:sidneybek@yahoo.com
Dartmouth,Nova Scotia
Canada
http://www.herald.ns.ca/cgi-bin/home/displayphoto?2002/12/22+126.raw+1019+Business
http://www.herald.ns.ca/stories/2002/12/22/fBusiness126.raw.html



Sidney
Unregistered User
nospam@spam.com

Oct 24, 2003, 2:43 PM

Post #2 of 2 (968 views)
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Re: [Sidney] JVC model:TU-4500U no 5v [In reply to] Can't Post
I took one of my best friends:Fluke model 29 seies II DMM and placed it on low Ohms mode and calibrated the leads down to 0.03 Ohms and began to measure the resistance across all of the components (about 30) and found the one with the least resistance (7.8 ohms) being TNR1=the tuner module so I unsoldered that pin and voila the resistance increased to over 300 Ohms.
So the tuner is defective now I am going to unsolder the tuner from the main board and see if I can pin point the culprit if not I will have to buy a new tuner,I unsoldered the B+ (VCC) pin on LM324M (smt quad op amp) found inside the tuner and short is still there.

Sidney
E-mail:sidneybek@yahoo.com
Dartmouth,Nova Scotia
Canada
http://www.herald.ns.ca/cgi-bin/home/displayphoto?2002/12/22+126.raw+1019+Business
http://www.herald.ns.ca/stories/2002/12/22/fBusiness126.raw.html

 
 
 


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