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#1 ELzekio

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Posted 10 October 2017 - 09:25 PM

Hello every one!

I recently won a very rare JVC TV boombox a JVC CX 710 for cheap in an auction. The seller claimed that the cassette player worked while the tv and radio did not.

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After receiving it, I did some base line tests to determine where the issue was. By using the composite video and audio input, i can verify that the Radio amplifier and TV CRT work fine. The problem with the radio and tv is that they are doing a very poor job picking up stations.

I made a video linked below which gives a demonstration of how the unit behaves when tuning in stations. When trying to tune fm it seems that when i get the signal at its strongest, the music is loud, but sometimes distorted. When ever i get the "tuned" light to light up (signifying that the signal SHOULD be its best and clearest), all i can here is very faint audio with a hum. When i adjust the dial so the tuned light goes out, the signal comes in stronger, but sometimes the music is still poor sounding and distorted.

As for tuning in television, i have in the video a vcr connected to the coax input of the boombox. When i tune in channel 3 or 4 for the coax input, the audio may come in very faintly and the video signal just doesn't want to come threw.

If the unit was working properly, then when i got the dial even close to channel 3 the signal should easily lock in and i should be getting clear picture and audio, but with this unit, the best thing i can do is get the dial set in the perfect position and get very poor audio and a picture that is so week a d unstable you can Barley make out that there is a signal at all.

The picture i was able to tune in on the video linked was by far the best and most stable.
Usually the best it can get is much less stable,

Here is a link to the video

You may not see in the video, but there is two signal lights that light up. A "tuned" light and "FM stereo light", the light turning on is the "tuned" light, the fm stereo light right under it never turns on though it could be because the LED is burned out, or some other simple reason i can figure out when i open it up.

I have been busy so i wont be able to open the unit up for a bit, but i just wanted to see of anyone had any thoughts or suggestions they may be willing to share before i get started with it.

Ive got the service manual and schlematic that i can scan if necessary.

#2 Superduper

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Posted 10 October 2017 - 10:51 PM

Well, I guess it’s why you got it for cheap. Your tuner is out of alignment. Follow instructions in your SM to align the tuner to adjust. However, you may need to spend $$$$$$$$$$$$$$$$$$ to get the equipments to perform the adjustments & some serious learning.

#3 hopey

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Posted 11 October 2017 - 06:19 AM

The picture looks ok. There will be a connection on exterior of the crt which I think is ground. This can be cleaned up and will improve the picture. Try working the vertical and horizontal hold back and forth as well as the brightness adjustments. Have you tried the rca video in that would be the best input.

#4 ELzekio

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Posted 11 October 2017 - 07:39 AM

The unit does have rca video and audio composite inputs.

When i inputed a signal threw them i was getting a perfect picture threw the crt and perfect audio. No issues at all.

Just seems it has issues big problems tuning in vhf signal. As shown in the video i tried a connecting vcr directly threw a coax, but i also tried broadcasting a signal threw my blonder tongue agile modulator and i was not getting any better results.

Suppose i could try broadcasting a uhf signal to see if that changes anything.