[TechAssist] Re: Sony KV20VM30 FBT bad or OK ?
- From: "Leonard Caillouet" <lcaillo@xxxxxxxxxxxx>
- To: <techassist@xxxxxxxxxxxxx>
- Date: Tue, 25 Oct 2005 12:12:43 -0400
Hollis,
I have found many flybacks that ring test good but are bad. Ringing tests
may not show problems in the trippler stages. I identify quite a few bad
ones with the Sencore drive tests, using the TVA92 and the VA62A video
analyzers. Actually, I use the VA62A that I picked up used for $200 because
the TVA92 (newer unit, bought from Sencore) has been broken for a couple of
years and I have not been able to justify the cost to have it refurbed by
Sencore.
The drive test is simpl;y a horizontal key pulse applied at 25vpp to the
primary, measuring the DC output at the anode lead. For a 30Kv flyback, the
output should be over 600v on the test.
Seems like I have seen more Sony and Zenith FBTs that fail this way.
Leonard Caillouet
Electronics World
1261 NW 76 Blvd
Gainesville, FL 32606
352-332-5608
352-332-5668 fax
----- Original Message -----
From: <HSWAD@xxxxxxx>
To: <techassist@xxxxxxxxxxxxx>
Sent: Monday, October 24, 2005 5:51 PM
Subject: [TechAssist] Sony KV20VM30 FBT bad or OK ?
This TVCR shuts down instantly when powered up. regulated B+ is 121 volts,
which is the normal value. Collector waveform shows overload of flyback.
Ringing test of the FBT with no power applied is normal. Disconnecting
secondary
windings and then powering up still indicates a bad flyback. At a net of
approx $75 I hate to purchase one just to try it. Anyone cured this problem?
TIA
Hollis Bates , EE-retired, Lewiston, Maine, _HSWAD@xxxxxxxx
(mailto:HSWAD@xxxxxxx) , 207 784 8689
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