Motorola ts907 low hv

[timmy]

Oh I never rely on sams there’s always been mistakes so I do look at what’s in the chassis as I already found that there are parts not listed in the sams and yes I did look at the resistor and I knew it was 560k

[timmy]

Back to the same thing before sound is scratchy distorted and the -45 is jumping all over -39 -41 -30 and so on I can help but think maybe this new flyback is bad oh and no video.

[jr_tech]

Originally Posted by timmy

Back to the same thing before sound is scratchy distorted and the -45 is jumping all over -39 -41 -30 and so on I can help but think maybe this new flyback is bad oh and no video.

What does the 190 volt supply measure when the set is “working” ? Is it still somewhat low?

jr

[Yamamaya42]

So, you are saying you have gotten HV back and have a raster again and now back to the point of not able to tune in video?


So it's suggested again that you try a longevity run with video input at test point B, like you had it hooked up there before, ( removing 3rd IF V3), and work on sound and tuning after.

And as it says on the schematic, all voltages and waves are taken with test pattern input, w/o such input, it's understandable that voltages and waveforms will fluctuate as there is nothing to lock them into “normal” ranges.

[timmy]

So the -45v can fluctuate without anything to lock on to so is the horizontal oscillator and agc used with video input at test point b and the IF tubes out ?

[Yamamaya42]

Originally Posted by timmy

So the -45v can fluctuate without anything to lock on to so is the horizontal oscillator and agc used with video input at test point b and the IF tubes out ?

you can leave the other IF tubes in, and remove the 3rd, as it could interfere with the input.

As for AGC, the set has a combo tube, AGC SYNC SEP, , the latter being needed for video lock.

so all that's needed to be pulled is V3, the rest can stay, they will just have nothing to do with no input if they are in the RF/IF stages.

[timmy]

Ok here’s what it looks like and the -45 came back.

[Yamamaya42]

Unfortunately, tuning/IF problems are some of the hardest ones to debug, even with something like a B&K 1077b television analyst or the like, no easy task at all.

You might want to start with a voltage check at the tuner plug, working back through the IF stages 1-2-3. looking at grid, plate & cathode voltages, that may tell you something.

But if tuning / IF is out of alignment, there is little to do other then hope to find someone with a sweep marker generator setup, and who knows how to use it.

[timmy]

What gets me is at the beginning I had clear sound and it slowly went to static distorted sound.

[timmy]

It could also be the tuner it looks like at one time the cover was removed and maybe putting it back maybe cut a wire inside. But still I had sound and if I had sound that would usually mean the tuner is good so if the IF is out I should still have sound.

[Yamamaya42]

sounds almost like an AGC/noise gate issue, advancing those controls CW has no effect?

[timmy]

Neither one makes a difference at all and I thought it was odd that if I touch the antenna to the uhf terminals I get the same thing as if it were on the vhf terminal. I even tried the old tuner tubes. Well the tuner is not immune from drifting resistor’s.

[Yamamaya42]

If the tuner is out, there is very little, if anything that can be done about it, cause there is nobody around who works on them anymore.

They are very hard to work on as you end up doing more harm than good unless you really know what you are doing.

And as stated before, they have these to find out if it really IS the tuner that is faulty.
https://www.ebay.com/itm/16563422078...Bk9SR_DcmuTsYA

[timmy]

Well I have worked on watches very tedious work so if I have to I would attempt it and the unit on eBay how is that hooked up.

[Yamamaya42]

Originally Posted by timmy

Well I have worked on watches very tedious work so if I have to I would attempt it and the unit on eBay how is that hooked up.

I have one just like it, except mine has the AC option, that is battery only, (2 9-volts ), it simply acts as a substitute for the tuner you are testing, you unplug the RCA type cable from the tuner in the TV and plug it into the sub tuner, then feed the RF into it, set to whatever channel, adjust tuning and gain, see what happens, it's easy to use.