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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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80's TV UHF tuner
Hi All,
I have an older TV set with the UHF tuner going up to channel 83. The tuner is a mechnical type. The output of the tuner goes back into the VHF tuner and you select the U on the VHF tuner to operate the UHF channels. In down conversion of the UHF band, what is the IF frequency of the UHF tuner? The set is an old RCA. pdrunen |
#2
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44 MHz, same as the VHF tuner, the VHF tuner is configured as an
amplifer when in UHF mode. Mark |
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#4
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wrote in message oups.com... Hi All, I have an older TV set with the UHF tuner going up to channel 83. The tuner is a mechnical type. The output of the tuner goes back into the VHF tuner and you select the U on the VHF tuner to operate the UHF channels. In down conversion of the UHF band, what is the IF frequency of the UHF tuner? The set is an old RCA. pdrunen What country are you in? |
#5
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What is the problem you are trying to solve, or were you just curious
about how it worked? Bob Hofmann Barney wrote: wrote in message oups.com... Hi All, I have an older TV set with the UHF tuner going up to channel 83. The tuner is a mechnical type. The output of the tuner goes back into the VHF tuner and you select the U on the VHF tuner to operate the UHF channels. In down conversion of the UHF band, what is the IF frequency of the UHF tuner? The set is an old RCA. pdrunen What country are you in? |
#6
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Thanks All,
No problem with the set, just trying to play around with the UHF tuner. It appears to have an input for 18VDC and line for the AFT. The TV had some other problems and I removed the tuner to see if I could do anything with it. I don't see anything on the O'scope out of it but will try a scanner at 44 MHz to see if I can hear any stations. Guess I will need a wideband FM scanner. |
#7
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) writes: Thanks All, No problem with the set, just trying to play around with the UHF tuner. It appears to have an input for 18VDC and line for the AFT. The TV had some other problems and I removed the tuner to see if I could do anything with it. I don't see anything on the O'scope out of it but will try a scanner at 44 MHz to see if I can hear any stations. Guess I will need a wideband FM scanner. If you're talking about putting the scope at the output of the UHF tuner, that's not likely to show anything. As someone pointed out, those tuners used a diode mixer, so you not only see no gain, but there is a loss between the input and the output. The signal is going to be very weak with that sort of tuner. I'm not sure when active tuners kicked in, but even those won't have too much of an output. Better to make sure the oscillator is oscillating. Use the scanner to tune in the tuner's oscillator signal. After that, either the diode is good, or it's not. Beyond that, if there's a problem it's not an active component, because you've just accounted for them all. Michael |
#8
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yep, the uhf tuner outpout will be too weak to se eon a scope but you may be able to use a scanner tuned to 41 to 47 MHz. The UHF tuner ocsillator will be very unstable compared to the narrowband signals in a scanner. The drift is not a problem for 6 MHz wide TV signal but might be a problem for narrow 30 kHz signals etc. If you work at it, you mat be able to generate an AFT signal from the scanner to stablize the tuner. Have fun Also, most cell phone signals are digital these days so you won't be able to use this method to hear them. Mark |
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