Motorola ts907 low hv

[timmy]

Originally Posted by old_coot88

Is it possible the video detector diode has gotten reversed? (I haven't read thru this whole tome, so this might have already been asked.)

I did have it out and put another in but it was worse and put the original back in making sure it was right

[Yamamaya42]

It should be easy to check if X6 is backwards or not via a DVM on diode check at L6 pins 2 -4, as others have said, it;s looking like it is almost.

Unless, ans I'm not sure this is possible, but could the IF be SO out of phase that it causes a negative video?

[timmy]

Originally Posted by Yamamaya42

It should be easy to check if X6 is backwards or not via a DVM on diode check at L6 pins 2 -4, as others have said, it;s looking like it is almost.

Unless, ans I'm not sure this is possible, but could the IF be SO out of phase that it causes a negative video?

If the IF is so sensitive then if it were out so bad I would think nothing would find it’s way to the output. As for the diode I know it’s in the correct way but it does check good but what would video look like if it were leaking as they say about these germanium diodes known for leaking. Can the video detect diode be mounted outside the coil housing rather then taking out the coil every time to try different diodes.

[Yamamaya42]

there is no reason why you can't unhook the line from pin 4 L6, hook a new 1n60 germanium up to pin 2 with the removed wire on it's anode for a temporary test run.

[timmy]

Originally Posted by Yamamaya42

there is no reason why you can't unhook the line from pin 4 L6, hook a new 1n60 germanium up to pin 2 with the removed wire on it's anode for a temporary test run.

The diode is in the coil can attached inside can’t get to remove one side. Correction I can try that.

[jr_tech]

Originally Posted by timmy

Yes the video looks like a negative but the pic I posted back a few pages was done with the subber on pin 2 of v2 but since changing the 22ohm resistors in v1 and v2 I am not able to get that back again not sure why

Did you ever figure out why? Perhaps wrong value resistors? Perhaps installed wrong? Cold solder joint or solder blobs? Many things can go wrong in what seems like a simple part replacement.

Recheck your work.

jr

[timmy]

Originally Posted by jr_tech

Did you ever figure out why? Perhaps wrong value resistors? Perhaps installed wrong? Cold solder joint or solder blobs? Many things can go wrong in what seems like a simple part replacement.

Recheck your work.

jr

Right resistors in the right place

[Username1]

Good Morning & Happy Tofu Turkey & Gluten Free Dinner Rolls Day to Everyone!

Timmy, I think for the first order of business, you should turn that detector diode around
& see if it makes a difference, It's just a signal diode, no 2 amps of current
running through it so you can't explode anything. If there ain't no improvement,
then just put it back....

Also back onto the look of the picture, I think you should also check the color killer
knob & with a so called picture on the tv, you should turn that control back & forth
& see what you get.... Turn the color knob up to about 1/3 & let it sit there....
You know what the color killer does, on a off channel with snow on the screen
a working color killer will make the snow B&W, Color Killer set wrong will
leave it with color snow.... It will also Not let the color circuits run on
B&W tv shows, so there might be odd color effects mixed in with a
picture that should be B&W. Your current Negative looking picture
looks to me like an open delay line, resulting in only color signal
being displayed on the screen, only here it's not color....
So with just turning the color killer knob lets see
if there is any effect there.... If no effect at all
then turn it fully counter clock wise & let it
sit there, so it's off, or set it to where it
was originally if you think no one ever
turned it and let it sit there....

Also I asked about the coils in that area, and you said that the IF Coils were already
checked, but that is not the coils I'm interested in....

I'm wondering about everything in the signal path of the Detector on-to the video
amp & output. L7 - L14, You don't have to take them out because they are all
low ohm, just test each series run of 3, you can see it amounts to about 6
ohms for each run of 3. Check R59 - L16, L17, R65, follow the signal
path through the delay line, (Check it too) & follow the signal path
to V5, are the voltages there close to what they should be? Does
the Brightness & Contrast knobs work properly? When you
have that negative looking picture on the screen,
does the Bright & Contrast have normal looking
effects on the screen?


.

[timmy]

Originally Posted by Username1

Good Morning & Happy Tofu Turkey & Gluten Free Dinner Rolls Day to Everyone!

Timmy, I think for the first order of business, you should turn that detector diode around
& see if it makes a difference, It's just a signal diode, no 2 amps of current
running through it so you can't explode anything. If there ain't no improvement,
then just put it back....

Also back onto the look of the picture, I think you should also check the color killer
knob & with a so called picture on the tv, you should turn that control back & forth
& see what you get.... Turn the color knob up to about 1/3 & let it sit there....
You know what the color killer does, on a off channel with snow on the screen
a working color killer will make the snow B&W, Color Killer set wrong will
leave it with color snow.... It will also Not let the color circuits run on
B&W tv shows, so there might be odd color effects mixed in with a
picture that should be B&W. Your current Negative looking picture
looks to me like an open delay line, resulting in only color signal
being displayed on the screen, only here it's not color....
So with just turning the color killer knob lets see
if there is any effect there.... If no effect at all
then turn it fully counter clock wise & let it
sit there, so it's off, or set it to where it
was originally if you think no one ever
turned it and let it sit there....

Also I asked about the coils in that area, and you said that the IF Coils were already
checked, but that is not the coils I'm interested in....

I'm wondering about everything in the signal path of the Detector on-to the video
amp & output. L7 - L14, You don't have to take them out because they are all
low ohm, just test each series run of 3, you can see it amounts to about 6
ohms for each run of 3. Check R59 - L16, L17, R65, follow the signal
path through the delay line, (Check it too) & follow the signal path
to V5, are the voltages there close to what they should be? Does
the Brightness & Contrast knobs work properly? When you
have that negative looking picture on the screen,
does the Bright & Contrast have normal looking
effects on the screen?


.

As for the color killer pot it works and the negative picture get color snow on the edges when turned up and brightness works as it should and the contrast does make some difference with the video as it is. The detector diode when I first removed it and tried another I marked the cathode end and made sure I put it back right and tried another yesterday and made no difference. I know what you mean about color snow I had that in the beginning but no more and really don’t know why. I have snow noise in audio and minimal snow on screen but no color snow like it once had. I did inject video again at point B and gave it some color and that worked out good. I listed the video amp and output on a previous page. This is injected video at test point B and just a quick addition of color so would this rule out any problems with the resistors and coils and delay line.

[Yamamaya42]

Once again, it’s pretty clear that there is a serious IF issue in your set, which is causing most of your video problems, and without the equipment and knowledge to adjust and debug it, the chances of getting it working is bleak, so unless you can find someone local to help you with it, your best way forward is to build a small video amp to boost the composite level to the 5v that the set expects at test point B, and rig for direct A/V input until some future point that you can find someone who can help you get the front end IF/ tuner input working the way is should.

[Username1]

That picture attachment of injected video at TP B is really nice & looks better than
the earlier pics.... I don't see any problems with the circuit components from
that point on. I guess it's still forward of that point. That leaves IF &
Detector, anything before TP B. This tv & it's problems sure are
illusive.... The negative looking picture bugs me. I think a number
of years ago someone on here had a 21xx55, I forget now the
full chassis, it was the first 21" with the chassis from the
15GP22, and if I recall correctly that person had a
negative or very faint picture, & he was thinking
it was a problem around the detector diode.
Anyway I don't recall it all that well, & Can't
find it. You may just have to go through
each little nook & cranny of the IF
strip & recheck everything you
already did..... I don't have a
good idea on where to go now.

I never had to do a full alignment on a TV IF, so you might just
have to invest in a scope & alignment marker generator to
figure this one out..... The thing is, how cold it have got
so far off to look like it does now?

.

[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 !