Motorola ts907 low hv

[timmy]

So if I never get this IF strip right to produce good video is there another way to get an RF signal from a cable line to put it into another device to produce the RF to put on test point B for video and just bypass the IF itself. Like if a flat panel tv had a separate IF board wire that in with its own power source don’t know if this is possible but it’s a thought. Or perhaps one of those mini pocket tvs using the output to test point B.

[Yamamaya42]

Any cheap used VCR you can find will work, preferably with remote, it really does not have to play tapes, but you will be hard pressed finding ones to don't , what is important is the tuning section of it.
Just one example of many.. https://tinyurl.com/348uu9p5


It can be used to tune into what ever station needed, and output A/V to the TV, however the video will have to be boosted a bit to 5v with a simple amp like.

https://www.electronicsforu.com/elec...ideo-amplifier

which works on 5v and can be adjusted by setting the resistor networks.

[timmy]

I would only need a channel 3 and I could change the channel by using the cable box. What about a b&w pocket tv like the Sony fd20 I have 2 of these. Here is the schematic for the tv I have if I cut number 4 from the rest of the circuit and place it on test point B it should give me video sound I would get later note the 4.5 volts at v3 IF.

[zeno]

Timmy
At this point I really think you need to invest in a MODERN analyst such
as the Sencore VA48 or VA62. That will give you a stable known source
that was built for your sets era. A scope is nice but an analyst
helps with other projects & do more than trace & show freq.

This is long distance servicing. VERY hard to do. A lot of us that
spent time in the biz fixin 10's of thousands of TV's could spend a
few mns looking , twisting & observing a set & know where to go.
You have stuck it out well & the next one will be easy.

BTW vid det diodes are usually in a can. Often the can has two parts
& if you pull the top half off the diode is there. You can always nip one end
of the diode & hang a new one in on the bottom for test.

73 Zeno
LFOD !

[Electronic M]

Originally Posted by zeno

Timmy
At this point I really think you need to invest in a MODERN analyst such
as the Sencore VA48 or VA62. That will give you a stable known source
that was built for your sets era. A scope is nice but an analyst
helps with other projects & do more than trace & show freq.

This is long distance servicing. VERY hard to do. A lot of us that
spent time in the biz fixin 10's of thousands of TV's could spend a
few mns looking , twisting & observing a set & know where to go.
You have stuck it out well & the next one will be easy.

BTW vid det diodes are usually in a can. Often the can has two parts
& if you pull the top half off the diode is there. You can always nip one end
of the diode & hang a new one in on the bottom for test.

73 Zeno
LFOD !

+1 a Sencore analyst or B&K 1077 analyst and a scope are things to have if you own more than 2 vintage TVs that you plan to maintain.
A daily driven tube TV is going to fail every 12 months give or take 6...If you get tricky troubles every 3rd time, the time you save with good equipment will pay for that equipment and it's storage several times over.

[Yamamaya42]

A cheap used VCR is the best choice for setting it up for direct AV input, cause as mentioned, they are still very easy to find, and have good stable tuners and output composite A/V, that Sony portable would not be a good choice cause it would need major adapting to be used, the schematic shown does not list any signal levels, but only the DC voltages at those points.

It should be easy enough to find a VCR, build the video amp, and adapt to A/V input until a future point you have the equipment or can get someone to help repair the IF section.

[timmy]

Using that small tv it wouldn’t take that much adapting it would need to be grounded to the chassis probably a single wire to get the sound and another singly wire to test point B and wire in the power source to the switch and make sure it’s tuned to channel 3 and forget the rest. Mount it on a small board out of the way. The antenna input would be setup on the tv board. Again just another thought.

[Yamamaya42]

Too many unknown factors with that, what is the peak to peak output at that point on that video buffer chip? You need 5v, is it inverted or not inverted?

The Sony schematic gives no clues as what the video signal is, only hints of a 5v vertical blanking pulse at q402.

The idea of this seems much more trouble than it's worth over a VCR.

Cable boxes do sometimes have composite A/V output that can be used for this such a thing, but you also need to input test patterns for convergence, so a VCR'S tuner is more flexible.

[timmy]

Well I do have the complete schematic for this Sony. I figured if it were that easy to get video from a DVD player I thought I could use the IF from that little tv and just input the cable to it and get video and maybe work out any other things after.

[Yamamaya42]

DVD players & VCRs have composite level video output, (positive 1v ptp), however, what that Sony has at that buffer chip is an unknown factor.
By adding that simple video amp listed before to boost it to 5v it should give it what the TV needs.

[timmy]

Originally Posted by Yamamaya42

DVD players & VCRs have composite level video output, (positive 1v ptp), however, what that Sony has at that buffer chip is an unknown factor.
By adding that simple video amp listed before to boost it to 5v it should give it what the TV needs.

So are you saying that using the little amp to boost to 5v and putting the IF from the Sony into it would it work is that what your saying?

[Yamamaya42]

What is unknown about the Sony, is what the peak-to-peak voltage of the video signal out of the buffer chip is, and if it is positive or inverted, chances are that one is positive, one is inverted (11,12) but w/o an oscilloscope to look and see what they are, this is a risk factor that it may or may not work due to the unknown factors of not really knowing what is being put out of the IC, for example, if you knew that it was putting out .5v positive peak-to-peak, then you could build an amp with enough gain to boost it to 5v.

On the other hand, a DVD/VCR always has an output of 1v peak-to-peak, thus you make a amp with a gain of +5, more or less.

[timmy]

Originally Posted by Yamamaya42

What is unknown about the Sony, is what the peak-to-peak voltage of the video signal out of the buffer chip is, and if it is positive or inverted, chances are that one is positive, one is inverted (11,12) but w/o an oscilloscope to look and see what they are, this is a risk factor that it may or may not work due to the unknown factors of not really knowing what is being put out of the IC, for example, if you knew that it was putting out .5v positive peak-to-peak, then you could build an amp with enough gain to boost it to 5v.

On the other hand, a DVD/VCR always has an output of 1v peak-to-peak, thus you make a amp with a gain of +5, more or less.

Ok but I’m looking for the cable input I don’t need vcr or dvd I just want to be able to watch regular tv and I would use the cable box remote change the channel. So in the end I could always try it there’s nothing I have to do to the set to try except try one of those wires or just take it from the 3rd IF and see what happens.

[Electronic M]

I'd just build the little 5V video amp and feed it with an RCA composite cable. That way I could plug a VCR in or any other device I want. If you find a good line level output point on the Sony later if there's an RCA composite video cable coming out of the moto you can plug it into the Sony later.

[timmy]

Here’s the full schematic notice after going along to 2 transistors it shows 5v p-p well it’s not clear enough