Quote:
Originally Posted by Magnavox300
Hi, I am new member of this excellent forum, and this is my second post.
I just picked this nice Admiral up for $20.00.
Are these any good? I thought it was a great design, and in pretty good shape too. Only missing the antenna. Can't wait to clean it up, and recap it.
Since I am new to this hobby, (started my first TV just a few weeks ago),
I was wondering if there was any thing in particular I should be careful of, or watch out for when removing the chassis.
I just got it home today, and hooked up a RF modulator, there was clear sound, but there was also a constant loud buzz or humming. I couldn't get the picture still, and it seemed like the humming sound was possibly interfering with the picture.
Any help from the pro's would be welcomed!
Magnavox300
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Welcome to VK and to the wonderful world of vintage TV.
The humming sound you hear is likely 60-cycle AC hum. Your TV's picture is bending and will not stand still because the same 60-cycle hum is getting into the sweep circuits. These problems are almost always caused by defective filter capacitors in the set's main power supply. In a set as old as this one, it seems almost certain that the filters (and probably every other capacitor in the set) are weak or defective and must be replaced, as boobtubeman just mentioned. Once you do this, the picture should straighten up and the hum should disappear from the sound. There could be other reasons why your TV's picture is bending (incorrect setting of the AGC threshold control, defects in the AGC circuit itself, et al.), but I'd replace the filters and other caps first, just on general principles.
Your set is over 50 years old, so the filters must be replaced if the TV is to perform as the manufacturer intended. In fact, recapping, that is, replacement of defective capacitors, should always be the first step in restoring a vintage or antique television to past glory. Failure to do this, e. g. just plugging in the TV to the power line and turning it on without first recapping at least the power supply, may and probably will damage expensive and often NLA (no longer available) parts in the set.
Good luck. I've seen Admiral portable TVs like yours (I saw one in high school in the mid-'70s, in our basement electronics lab, when I was taking a basic electronics course), and they were good sets in their day. They can be as good as new or even better if the proper restoration procedures are followed. You will need an NTSC->ATSC converter box on your set to receive anything, as all full-power U. S. TV stations have transitioned to digital as of June 12, 2009; however, there may be some LPTV (low-power TV) or translator stations still operating in NTSC analog in your area, so you may get at least one channel with rabbit ears and without the box.
BTW, your set's picture bending could also be caused by incompatibility between your TV and your DVD player; I'd check into that if the picture still bends after replacing the filters. Modern DVDs and VCRs often do not work well with older televisions because of the set's sync circuits being unable to lock on to the RF modulator's own sync signals -- solidly or, in many cases, not at all. Older TVs were made with sync circuits designed to deal only with over-the-air TV signals, since today's advanced video technology (VCR, DVD, video on demand, et al.) did not exist when these sets were new. These sets may not operate properly with the non-standard (as the TV's sync circuits see it) sync signal from the modern RF modulator.