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1960s vintage 9" GE B & W Portable TV has no Picture
Hello Everyone today I had received from a friend of mine from church a 1960s vintage General Electric 9" Portable Black and White Television Set that when I got it home to test it out I got perfect audio but no picture, and from what I could see through the vent holes on the side of the unit most of the tubes that were visible through the vents were glowing like they were supposed to be, and from what I saw online on some YouTube videos about vintage television repair that if the video amp or the vertical or horizontal amp tubes are blown there isn't going to be a picture so I wonder if it might be a bad video amp tube or a bad vertical or horizontal amp tube inside the TV, or could the TV tube perhaps be blown? Although I thought that if a picture tube blew that there would be black sooty looking spots on the inside of the screen which there aren't any to be seen on the screen.
Any suggestions as to go about restoring this wonderful piece of history? Pics are coming later when I have access to my camera. |
#2
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There are many things that can cause a dark screen/no picture condition. The first thing I'd do is check for the presence of HV at the anode connector of the CRT. Be careful because there are many thousands of volts here and the CRT can hold a charge. A quick and dirty method to determine if HV is present is to draw an arc with a screwdriver. For a more accurate test, you meed a high voltage probe that will tell you exactly how much HV is getting to the CRT.
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http://www.youtube.com/user/radiotvphononut |
#3
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#4
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Many ways to go depending on equipment & knowledge.
Its not a vert problem. That shrinks the pix top to bottom sometimes so there is only a line going L-R. Most video problems on old B&W sets leave you with a lit screen so probably not that. No HV will kill the pix. If audio good most likely its the HV rectifier tube. IIRC its a 1X2 the tube the anode wire goes to. On GE's the sockets used to corrode, check for green crap on the tube pins & socket. You can usually detect HV by putting the back of your hand near the SCREEN, you will feel the static pulling on your hairs. BTW the socket can give you a shock when off. The cap on the other end is safe when off. A bad CRT is also possable. Run the set for a while in a room with NO light. If you see a very dark image its probably a bad CRT. Beyond that post the model # ( stamped on back). Chassis # ( look on tube chart) and maybe a screen shot of the chassis & a lot of us will try to help. 73 Zeno 73 Zeno |
#5
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Chassis number unsure as the tube chart is inside the cabinet and I had a heck of a time getting the cabinet apart the first time around, and I forgot to look for the chassis number when I did have it apart. When I powered it on when I got home from church to see how it worked the audio was perfect minus a little buzzing noise that would come on when you turned the volume control but then would disappear when you jiggled the volume control slightly (more than likely a dirty pot), but as for the picture it was completely blank not even a slight hint of a picture (which you said if the picture tube was bad there would of been a slight picture still and mine has no picture at all which is why I think its not a bad picture tube but something else associated with the video circuit e.g. bad video amp tube.) |
Audiokarma |
#6
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Update: I did some research and actually found out that my TV was from 1957 so actually my initial post title is inaccurate because I just assumed that the TV set was from the 1960s because of the TV having the built in 14-83 UHF tuner on it because I just assumed that all TVs from the 1950s just had VHF only because of what I had seen on most 1950s vintage TV sets I've seen at flea markets and antique malls and garage sales but now I know that apparently 14-83 UHF had been around as early as the mid 1950s at least (seeing as I had also seen an old Philco Predicta Television at the antique mall recently for sale that also had a 14-83 UHF tuner on it and the Predictas were only made in the 1950s from what I had heard and read so apparently what I had once known about 1950s TVs has changed...
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#7
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This set is OLDER than 1960 It is in sams 359-7, which makes it about 1957 or so. I was thihnking it was that little set they sold in about 1963 or so...with the wrap-around chassis...but it is a LOT older. GE"s answer to the 8" 8PT-7030 style RCA SET.
You need to know if the FILAMENT Of the CRT is lit. I think this is a hot chassis set so it VERY likely has to be lit for the other tubes to be on. I agree....it sounds as if you have lost HV. It is POSSIBLE...that you have a low B+ problem. Low B+ MIGHT give you enough powert for the SOUND to work...but NOT the deflection and HV. it is ALSO possible....that you have lost BOOST voltage. This is a voltage that is produced by yoke action and it is then ADDED to the main B+ voltage. Sort of hard to explain...but it helps to run the H-out and V out ckts AND voltages for the CRT. if it is LOW or GONE.. you will NOT get HV or very LOW hV and no raster. Like others have said...do the 'static test" on the front of the tube and see if you get any "static cling" from the tube. Good static from it meant likely good HV. |
#8
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Dumb question but, have you adjusted both the brightness and contrast controls? If it has an AGC I have also seen cases where misadjusting that can kill the raster.
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Bryan |
#9
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And Yes you are right, this is an "AA5" Series Strung set which tells me that like you said if I was seeing tubes glowing in this set that means that the Picture tube's filaments were glowing but apparently my H-V is probably low enough that its giving me sound but no picture/raster, so I will try the "static check" on the picture tube face when I power it up again and see if it has any H-V or not, and if no H-V then I guess I'll have to check the H-V Rectifier tube to see if its weak and or check the electrolytics to see if they may need replacement. |
#10
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Just REMEMBER...the HV rect tube will NOT really show a visible filamanet....so you need to REPLACE it with as known-good one--to rule it out.
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Audiokarma |
#11
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Anyways I hope I can get this TV up and running because I would love to use this TV in my office/workshop with a converter box just as a cool piece of functioning television history. |
#12
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The set will need recapped to work properly but before doing that I would try to get the CRT tested, the 9QP4 used in those sets was notoriously bad. |
#13
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#14
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The high voltage rectifier is a 1V2. All the tubes in that TV are single ended, including the CRT.
Check the ion trap position. It could have been moved. The CRT is certainly defective if it is the original and likely very dim, if a replacement. |
#15
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The person I got the TV from told me that the TV was used very little before it was put into storage for 40+ years which with that in mind would lead me to think that the picture tube should still be good, and the TV when I had it opened didn't look like it had any repairs made to the set from what I could see, plus the unit had PCBs in it for all of the circuitry and tube sockets which the PCBs showed hardly any heat damage which seemed to confirm my friend's story about it having low hours on the set. |
Audiokarma |
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