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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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RCA TV model 20541, chassis CTC203J2 with Excessive Reg B+
Hi,
I have a 20" screen RCA TV model J20541, chassis CTC203J2 (mfg 10/00) in my service shop (no SM). TV tries to go on, but turns right off due to excessive HV. The regulated B+ measured +154V which is too high. I tested some parts in the voltage regulator circuit, but without a schematic, I am "handicapped". Did anyone fix a similar problem with this or similar chassis TV? Thanks in advance, Brad Before you type your password, credit card number, etc., be sure there is no active keystroke logger (spyware) in your PC. |
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RCA TV model 20541, chassis CTC203J2 with Excessive Reg B+
On Tue, 07 Oct 2008 14:11:55 GMT, (Brad) put
finger to keyboard and composed: Hi, I have a 20" screen RCA TV model J20541, chassis CTC203J2 (mfg 10/00) in my service shop (no SM). TV tries to go on, but turns right off due to excessive HV. The regulated B+ measured +154V which is too high. I tested some parts in the voltage regulator circuit, but without a schematic, I am "handicapped". Did anyone fix a similar problem with this or similar chassis TV? Thanks in advance, Brad There is this old thread in the Google Groups archives: http://groups.google.com/group/sci.e...1d1f36e403d846 It suggests that the fault may be in the feedback circuit on the secondary side. There is also the following manual at eserviceinfo.com. 148 page Thompson Consumer Electronics (RCA & GE) technical training manual for RCA ProScan color TV model # CTC203: http://www.eserviceinfo.com/download...CA_CTC203.html I don't know how relevant the above manual is to your chassis, but I notice that the manual does not specify a value for B+, which suggests to me that it may vary between versions. Anyway, it looks to me from the values of R14115 (143K), R14116 (2K), and R14126 (37.4K) that the B+ in standby mode should be about 190V. In run mode the B+ is about 5% less, ie 181V (= 2.5V x 145K/2K). Your chassis, if it is similar, may use different resistor values, and a different B+. If you are seeing a B+ voltage which is about 10V too high in run mode, then I'd check the +13Vr and +16Vs supply rails. Have you checked C14101 (2.2uF)? - Franc Zabkar -- Please remove one 'i' from my address when replying by email. |
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