Sony trinitron weird distortion - Page 1
Forum section: electronics / repair

author: nate3012
author_rank: Newbie
timestamp: September 17, 2019, 02:52:42 pm
content: Sony trinitron 21" Model KV-HF21M80Initial problem leaked flyback transistor and a D2578 output transistor replacement. Unfortunately OEM Flyback transformer could not be installed. So, A chinese (Though it is marked as Malaysian made) Replacement was made. The technician who replaced the part sliced the high voltage ground wire and taped it together (Not the main HV+ one). After adjusting the tv was working fine until a few moments later it abruptly glitched and this distortion is present (No sound or any magic smoke)> Can anyone help me finding out the problem and what may cause this (I have the original leaked flyback transformer handy is there any way to fix that one?).Thank you

author: james_s
author_rank: Super Contributor
timestamp: September 17, 2019, 02:56:25 pm
content: Those are retrace lines. What happens if you turn down the sub brightness a bit? Odd that it happened abruptly though.

author: PKTKS
author_rank: Super Contributor
timestamp: September 17, 2019, 03:47:37 pm
content: All SONY more or less recent models usually share same PSU boardIn fact there are several known issues with those PSU modelsin particular those around the MCZ3001First thing to check is the voltages on the PSU board.Second pass if the voltages and regulators responsiblefor grid polarization are fineit the grid levels are wrong you would see the retraces...Voltage check following the service manual to the letter.Whatever happened to the transistor and fried the Flybackmay be fried other component tooPaul

author: shakalnokturn
author_rank: Super Contributor
timestamp: September 18, 2019, 11:50:24 am
content: It's a while since I've been in any of these, IIRC the MCZ3001 were often a problem but I don't see the link to a defective FBT.Your symptoms show a G2 voltage too high and a incorrect focus voltage too. (Maybe H-stat or V-stat as Sony's sometimes have both adjustments as well as focus.)If it was working correctly for some time on a reassembled FBT, the glitch and current symptoms don't look good for the FBT.

author: PKTKS
author_rank: Super Contributor
timestamp: September 19, 2019, 06:45:35 pm
content: Quote from: shakalnokturn on September 18, 2019, 11:50:24 amMCZ3001 based boards feed the Flyback which in turn generatesthe auxiliary volts for grid and focus.If the MCZ has gone wild.. probably the voltages are bad either** IF this psu is MCZ based...Paul

author: andy2000
author_rank: Frequent Contributor
timestamp: September 20, 2019, 03:10:11 pm
content: I have had mixed results with generic flyback replacements. Some work fine, but others didn't work properly. It's entirely possible it was fine at first, but then some internal insulation broke down. The only way to be sure would be to measure the output voltages (anode, focus, and screen voltages) and compare to the service manual.Also, you said the tech cut the HV wire and spliced it. If it was a poor splice job (it's nearly impossible to properly insulate such a splice with the materials most techs have on hand) it could have arced to something and caused damage.