Motorola ts907 low hv - Page 80 - Videokarma.org TV - Video

timmy · #**1186** 12-06-2022, 09:20 AM

Would it hurt anything if I jumped the thermistor being it’s connected to line voltage anyway just to rule out this low voltage v3 pin 7-8 should be 210v but it’s only 162 v and r54 is new 4.7k 5 watt. V1-2 pins 7-8 should be 210v 100v but it’s 198v and 96v the 275v is only 256v 19v difference

Yamamaya42 · #**1187** 12-06-2022, 09:55 AM

Doing that won't likely get you anywhere, those voltages are close enough for things to be working.

If the thermistor was a problem, you would see large voltage drop across it after it was heated up, and sweep problems.
What you should see across it, is a large spike in voltage as it comes on when cold, that then lowers to a few volts when it warms.

If you really feel the need to try it out, try carefully jumping it after the set has been on for a little bit, but it's pretty much certain at this point, doing so will make no difference in the tuning problem that you have.

timmy · #**1188** 12-06-2022, 10:15 AM

Ok I jumped it and voltages did come up and stayed up it wasn’t much but I find the images I get on screen get more vivid and more contrast when I parallel another resistor to r54 in an attempt to raise the voltage on 7-8 of v3 clearly the voltage is to low there it should be 210v it makes no sense new resistor by itself voltage is to low.

timmy · #**1189** 12-06-2022, 10:43 AM

I know things are not working right but v1-2 the voltages are right now I got 210v on v3 pin 7-8 but pin 2 should be zero but I’m getting .9 -1.4 -2.0 fluctuating and pin 3 should be 2.5 I’m getting 4.5.

Yamamaya42 · #**1190** 12-06-2022, 11:07 AM

As it has been said many times, do not take the voltages shown on SAMS as an absolute, variances of 10-15% or even more are normal, also these were taken with a VTVM on a working well aligned set, yours is out of alignment, and you have a digital meter, all of these will alter voltage readings to a wide degree.

timmy · #**1191** 12-06-2022, 02:01 PM

This picture is from the sets own tuner so if the IF was out I would not get this and how I got this is rather odd and it may narrow down where a problem could be but I don’t know yet. A jumper between pin 1 v3 to what looks like L9 with a .01 in between.

timmy · #**1192** 12-06-2022, 02:48 PM

Being the jumper is on pin 1 of v3 is not exactly bypassing v3 itself otherwise if I put the jumper on pin 2 then I think that would be bypassing v3 maybe a cap at v3 ? No color or vertical is setup at all.

Yamamaya42 · #**1193** 12-06-2022, 03:04 PM

Bypassing things like a Christmas tree won't really help much with the underlying issue that the IF needs alignment to get the video clearly from the tuner to the 1st video amp.

evident that it's blocking color.

timmy · #**1194** 12-06-2022, 03:08 PM

Quote:

Originally Posted by Yamamaya42

Bypassing things like a Christmas tree won't really help much with the underlying issue that the IF needs alignment to get the video clearly from the tuner to the 1st video amp.

evident that it's blocking color.

The color is turned down along with the hue and no color controls are set and obviously the video is coming from v1 and v2 and somewhat v3 this is all coming from the tuner no subber.

timmy · #**1195** 12-07-2022, 10:12 AM

Why is it that when the color intensity knob is turned up alittle it then looks like it needs to be fine tuned.

Yamamaya42 · #**1196** 12-07-2022, 10:46 AM

Herringbone pattern in video.
Which is what I tried to point out yesterday.
http://www.videokarma.org/attachment...3&d=1670356881

All color is essentially being blocked in the tuner/ IF because the response curve is so far off.

Turn up the color, and the patterns show up, turn it down, they vanish, but put in video at test point B, and you see color, meaning that chroma bandpass is OK, and the corruption is in the IF, as been very evident for some time now.

Do review this thread, and how carefully and methodically he has been aligning the CT-100.
http://www.videokarma.org/showthread...=274959&page=9

There is just no getting around that sometimes it has to be done on these sets.

timmy · #**1197** 12-07-2022, 07:39 PM

Even though this set has problems v3 pins 7-8 should have 210v but only has 160v this voltage is not going to gain 50v simply by having this set working there’s more going on here.

Yamamaya42 · #**1198** 12-07-2022, 09:55 PM

I'll try to explain this again the best way I can, of all the tube circuits in the TV, the IF is the MOST sensitive and hardest to deal with, and unlike most other areas, you can NOT measure voltages in the area with a normal digital meter, because as soon as you hook it up, it will alter the circuit and change what you are trying to read. You MUST use a VTVM, or a FET VOM, otherwise you will get false readings due to the added load from the meter in the circuit.

timmy · #**1199** 12-08-2022, 04:49 AM

The voltages im referring to is the 210v that should be present at pin 8 v3 that comes right off of the 275v tap with a 4.7k resistor to drop it. Pin 8 is 50v short of what it should be.

Yamamaya42 · #**1200** 12-08-2022, 05:32 AM

Quote:

Originally Posted by timmy

The voltages im referring to is the 210v that should be present at pin 8 v3 that comes right off of the 275v tap with a 4.7k resistor to drop it. Pin 8 is 50v short of what it should be.

That still does not change that a digital meter will give inaccurate readings in this situation with a active RF circuit, you must use a use a VTVM, or a FET VOM, to get correct readings.