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#3
11-23-2005, 01:34 PM
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Jerry:
The primary cause of retrace lines in that TV is the absence of a blanking circuit. The CRT control grid returns directly to ground. It needs a 25 to 35 volt negative pulse to cut off the CRT during vertical retrace. When everything in that TV is working, there is little to spare so there's no place to get the negative vertical pulse without upsetting something else. The vertical output plate goes positive, the cathode is grounded, the B+ feed has nothing to spare so it leaves the oscillator plate. That's 60 v p/p, but at very high impedance so bleeding some off for blanking will reduce the vertical size and upset the oscillator timing. Look over some other GE portable designs of the era and you will see blanking schemes that could not be used on the 9" TV. I suspect the blanking circuit was the subject of a few engineering meetings with product planning. Finance eventually won out. It was a cost compromise and justified as a differentiator and a reason to step the customer up to the 14". That TV eventually cost GE a bundle. It sold for $99 and was quietly recalled to replace every 9QP4 CRT. Off-on-volume controls were another recurring problem. It would require a design effort using a transistor or two to isolate the CRT blanking network from the other circuitry. The chassis design and PC layout leave little heat-free room for additional components. In short, it is expected to have retrace lines as designed. Don 
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#4
11-23-2005, 04:40 PM
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Why were the CRTs recalled? I have seen that set and it looks like a direct competitor to the 8" RCA portable of the time. The RCA was the better set as it was hand wired and all metal. The GE/Hotpoint used PC boards and plastic front mask and trim if I remember correctly.
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#5
11-23-2005, 08:34 PM
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GE replaced the CRTs due to early failure rates. It was a new CRT design using a low wattage heater, light weight glass and a single ended connector. There is no separate anode connection. Within a few months of operation many experienced bad picture tubes and bad off-on switches. Many of the CRTs listed on ebay are the duds.
GE wasn't too particular about getting all the bad tubes back so some were stored around TV shops for years. New GE replacement tubes should have a blue monogram on the very end of the tube connector and a number-matching warranty card. The 8" RCA was a better basic design with a power transformer, conventional tubes and more B+. It had poor sensitivity and early vertical problems. Both had 2 video IFs, but RCA had 1 IF in the tuner and had to skimp on the tuner gain as well to keep it to two tubes. The 9" GE used a conventional Oak tuner. About the same time, Admiral made a rectangular 10' that was much better. Unfortunately, it suffered from bad tuner design. Don
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#6
11-23-2005, 10:39 PM
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Sensitivity is not great on the RCA. On a weak signal, the contrast drops off. It is still I think one of the best of the Fifties metal portables.
__________________
Just look at those channels whiz on by. - Fred Sanford
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#9
11-25-2005, 12:06 AM
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reduce you pic size to less than 200k (or less than 900x900) whichever is less. Then at the bottom of the thread where you normally post a reply, click "Go Advanced"
After you have done that, you will see a button labeled "Manage attachments" at the bottom of the page. Click it to bring up a window that will allow you to upload your file. When your done, click the "submit reply" Button. Alternately you can post the IMG code if you are hosting the picture on an image serivice (photobucket, imageshare, imageshack, etc...) Most of those sites have a code generator if you are unfamiliar with the syntax.
__________________
Jordan
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#11
11-25-2005, 08:25 PM
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Jerry:
That looks like video trouble or a defective CRT. Does the brightness or contrast affect the picture? Are you able to get a watchable picture with a good antenna? Don
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#12
11-25-2005, 09:46 PM
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If the brightness control has no effect, then the picture tube likely has a heater to cathode short which might be cleared with a rejuvenator.
__________________
Just look at those channels whiz on by. - Fred Sanford
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#13
11-26-2005, 01:38 AM
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You can also use a crt filament isolation transformer (looks like a "booster" but is for isolation only) if you have an h-k short.
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#15
11-26-2005, 08:59 PM
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Quote:
The set should produce a good pic with few/no retrace lines in under most conditions. It definitely needs a strong signal, i checked one of my sets and as soon as the signal drops off the retrace lines pop up, the switch next to the antenna terminals is a local/distant switch, it should be set to distant if you're in a weak signal area. Also the brightness needs to be kept low. You didn't mention if you've done any work to these sets? Usually replacing the capacitors is the minimum they will need to work right, also the horiz afc double diode is always bad on these (it's Selenium but can be replaced with two ordinary Silicone diodes) Wonder if GE will still honor the CRT recall and replace my CRT?  This set is using a rejuvenated tube. (The pic looks better than the actual picture on the set!) Eric
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