[TechAssist] RCA Proscan PS36109 CTC197CH dead - flyback pn 237506 FYI
- From: "Leonard G. Caillouet" <lcaillo@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Mon, 4 Aug 2003 13:36:46 -0400
I thought this one was worth noting. Came in dead, flyback was the problem.
What is notable here is that the flyback tests between the new and old parts
were so similar and potentially confusing. I use a Sencore TVA92 and test
flybacks with the 25Vpp key pulse applied to the primary and look for the
appropriate DC voltage on the anode per the Sencore chart. This is usually
a very good test.
In this case, the old FBT tested with 430 VDC output, while the chart
suggested about 600VDC. There was also 160Vpp on the anode lead, a little
higher than I typically see. No problem, probably a leaky diode in the HV
rectifier stage, ordered a new one. The new one came in ad tested as
follows with the same input:
120Vpp & 504 VDC.
The set works fine with the new one. For those of you who use the Sencore
test, it is worth noting that the actual output of the FBT was quite a bit
lower than the chart suggests. I have found this with some Sony
transformers as well. It can lead to a misdiagnosis of a FBT problem. It
seems like a good idea to start testing new FBTs when we put them in and
posting any such results for others to refer to when troubleshooting.
Sorry I have been absent from the list a lot lately...overloaded with
lightning damage and sick kids...
Leonard G. Caillouet
Electronics World
Gainesville, FL
352-332-5608
352-332-5668 (fax)
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