Hi, I have an old 46" Magnavox TV model RH8520 AK08. The video just stopped working the other day. Audio still works fine. It turns on and off ok. Does anyone have any ideas what might be causing this? Maybe the light source?
Thanks John
-- jpgolf14
These sets have CRT's. Most likely the high voltage has quit, and there are numerous possible reasons. Bad flyback transformer, focus bleeder breakdown, cracked solder joints, protection circuit shutdown from over voltage, over current, loss of vertical scan...
You need a tech familiar with the set and armed with schematics. Learning curve is very steep for anyone not familiar.
Might get flamed, however...
I've got an RH8524 set with the same basic boardset (PTV300). I would check the screen/focus voltage as described in the troubleshooting section of the manual. My experience with this set is that if the HV fails, the whole set goes into shutdown which shuts down the audio as well. I suppose you could also have a bad HV splitter. I had this exact same situation occur on my set with a bad screen/focus connection at the flyback. Does the flyback HV exit from the top (gray flyback) or the side at a 45 degree angle (white)?
Send me your e-mail and I'll try to make some scans from the troubleshooting section of the service manual. I believe one of the tests is to remove the CRT board from each CRT and try it again. You have to remove the front speaker grill and drop the convergence board down to easily reach the CRT boards. I believe there is a release button on the right rear side that allows the trim piece above the grill to come loose. After that, simply remove the speaker grill, then the inner screws to drop the convergence board down. Many times, there is a wiring diagram on the back of the set.
Do not attempt to take voltage readings on this set while live even with an isolation transformer. I use jumpers to connect the meter where I want it AFTER unplugging the set. I know enough to know I don't know enough... There are a number of basic readings you can make on the power supply with it off to determine if the problem is there or on the deflection board. I'll look for the troubleshooting section of my manual.
Better safe than sorry... Sometimes you don't even get a first chance with line voltage!
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