Home Forums For Sale / Wanted New Challenge (A Transistor One)

Viewing 11 posts - 1 through 11 (of 11 total)
  • Author
    Posts
  • #19080
    Ralph Spracklin
    Forum Participant

    New Challenge, (a Transistor one)

    Just picked up, at value Village, a Sears, Model 13924, Radio/TV Combo, for the price of a Big Mac Combo at McDonalds. This thing looks like it just came off the assembly line. AM/FM radio works 100%. AS it is analog by design I tried it using an old VCR, and TV also works OK, except for a slight vertical hold problem. This unit was made in Taiwan in 1981, and is identical to another re-brand name, Cariole, model Number 4287030010. Seems that I will need some help in finding a Schematic for this thing, being that it is of transistor design, which is outside my comfort zone. Guess I will have to research other such transistor units to discover a solution to the problem.

    Regards
    Ralph

    #19082
    Ralph Spracklin
    Forum Participant

    Here is an exact example of what is going on and what I am thinking is some sort of vertical problem, or vertical colapse problem????

    Ralph

    Attachments:
    #19086
    Doug Parker
    CVRS Member

    Ralph:
    Can you send me a few pictures of the television chassis. Usually they will have a remote board just for the radio portion. What I am looking for on the chassis is whether they used 1 or 2 “T220” styled veritical output transistors or did they use just 1 integrated circuit to drive the vertical circuit of the tv (both the transistors or the chip will be mounted on a heatsink to absorb the heat.. Sometimes there will be a potentiometer near that area or they will have the pot on an outside edge of the board for access through the combo case.

    Send me the pictures via my email please.

    #19087
    Ralph Spracklin
    Forum Participant

    Hello Doug

    Just came up from my workshop for the day. Tomorrow I will remove the cover and try to get some High Defination pictures. Taking good pictures could be hard to do as things, component wise, are tight. I gotta say, the quality of the build is real good. I am not getting any rolling or diagonal slicing. At first I had hoped it was a VCR problem, so I threw a tape in the VCR and it played real good on the TV I have here in my office. I Know very little about TV circuits, let alone those using transistors. Could it be a Raster problem?? The Vertical Hold and the Horizental Hold are rock solid steady. So I really don’t know for certain if it is indeed a Vertical problem?? Any help I can get will be apreciated. THanks for responding to my query.

    Regards

    Ralph

    #19090
    Ralph Spracklin
    Forum Participant

    Hello Again Doug
    I had a problem sending the pics to you by private message. So will send them here on the Forum.

    Ralph

    #19094
    Ralph Spracklin
    Forum Participant

    I keep trying to send extra pics but it won’t let me. I will try to send less pics at one time and see if tthat works.

    Ralph

    #19098
    Ralph Spracklin
    Forum Participant

    OK That worked. Here is three more

    #19102
    Doug Parker
    CVRS Member

    Ralph:
    Apon looking at the images that you had posted I do believe that since you have a full screen from top to bottom (Vertically) and you have 4 partial images that are across the screen from left to right that you have a horizontal oscillator problem. Looking at your chassis pictures there are numerous low quality electrolytics. Usually they are to blame for a majority of failures on a transistorized unit. Also any caps that are within close proximity of heatsinks are prone to fail due because the caps are usually rated at 85 degree Celcius. When swapping them out always use 105 degree.
    Small 1 ufd to 10 ufd caps are frequently used in oscillator circuits.

    Potentiometer VR704 is near two heatsinked T220 styled transistors. Since you have the tv out of the case hook it up to your vcr that you are using for signal and give that pot a tweak either way to see what changes on your picture. That will give you a clue if it is on the vertical circuit or the horizontal circuit. Just make sure that you put it back to where you started if there is no change.

    Give me a telephone call and we can discuss it easier than the written word.

    #19103
    Ralph Spracklin
    Forum Participant

    Hey Doug

    I will take you up on your offer by phone. However for the sake of those who may be following this post of mine, I would also like to continue the line of thought in solving this problem on line. Maybe it will attract some of the TV hobyiests out there to this our Vintage Radio Site. They both go hand in hand and maybe, also it could boost our Membership. I myself am also, already expanding my own knowledge of Vintage Electronics. This Sears TV is a Black and White set, And already I would like to pick up one of these Portable Sets in Color. That would look good on my work bench.

    I have also noticed from one of my posted pics, that the Pot VR704 looks very dirty. Maybe I will try cleaning it up, and I hope that cleaning it could solve the problem???

    Again thanks for your input. You seem to have a good take on these Portable TV sets. Also to others, there are plenty of such Portable TVs out there, for litle or no cost. Get your feet wet!

    Regards
    Ralph

    #19109
    Ralph Spracklin
    Forum Participant

    I made a post earlier this AM, Addressed to Doug, and of course for all. It registered as post # 10. but has now dissappeared . Could anyone explain as to why it would dissappear. It must stil be lurking there somewhere onthe WWW ?????? Later I will compose it again and post it to the site.

    Ralph

    #19110
    Ralph Spracklin
    Forum Participant

    Whle this post is for Doug, it is, of course for all.

    Doug, I have tried tweeking VR704, near those two heatsinks, but I have not achieved any positive results, as a matter of fact very little negative results either .How do I determine,on this main board, what components are the oscillator part of the circuit?? I am going to inventory all electroloytics used in this set, and replace them one at a time to see what results I can get. . Also I’ve checked all those caps for bulged tops, and they al look OK. My multimeter has a capacitor check function, but I am not certain how reliable it is but I will give that a try also. Actually there are only about a dozen plus Electrolytic Cans on this board. Because I do not have a big inventory of Low Voltage/Low Value Electrolytics, I will place an order with ‘Just Radio’ for those I need and then some.
    While I am researching on those TV sets and learning fast, I cannot yet find online anything related to those multible images on screen.
    I have also found a third identical Brand of TV, It s an Orion, Model 7152. I would guess that there are still other retailers/outtfits etc. out there who have the same sets branded as ther own. Maybe I will get lucky and come up with a Schematic fo one of these brands.

    Regards

    Ralph

Viewing 11 posts - 1 through 11 (of 11 total)
  • You must be logged in to reply to this topic.