Motorola ts907 low hv

[zeno]

Does set still have 2 hoz out tubes ?
It would be interesting to see if they are drawing the same cathode current.
OK on discs. Almost all I changed were burning or cracking open or dead
shorted. BUT ?? If you try them I would nip one end then hang in.
Maybe someone still sells an assortment, I would go with 1KV ones.
BTW its getting long so what is the voltage on the G-1's of the
hoz outs ?

Zeno

[timmy]

Ok here’s the kicker the voltages we’re pretty close after checking yet more resistors still finding not a thing wrong switching tubes checking hv pot 6bk4 cap off still lousy hv until I have a light above the chassis I turned off to make sure the heaters were all lit and what do I find but one of the HO tubes top glowing blue lucky I had a good used one put it in reg tube cap off and a massive hiss and lots of corona and I did plug in the yoke on the bench. These 2 tubes were brand new but yet one was bad so I’m sure it’s going to be ok now I’ll find out Monday when I get 2 6eh7 tubes for the IF again new but we’re bad.

[zeno]

Originally Posted by timmy

Ok here’s the kicker the voltages we’re pretty close after checking yet more resistors still finding not a thing wrong switching tubes checking hv pot 6bk4 cap off still lousy hv until I have a light above the chassis I turned off to make sure the heaters were all lit and what do I find but one of the HO tubes top glowing blue lucky I had a good used one put it in reg tube cap off and a massive hiss and lots of corona and I did plug in the yoke on the bench. These 2 tubes were brand new but yet one was bad so I’m sure it’s going to be ok now I’ll find out Monday when I get 2 6eh7 tubes for the IF again new but we’re bad.

When you get NOS tubes beware that many came off a shops shelf
& may be damaged ESPECIALLY hoz outs & big audio outs.
Best to stick with RCA, GE, & Sylvania. Tubes from set mfrs like
Zenith Moto, Maggy etc are a safe bet, most are made by the big 3.
Lots to NOT by, Lyndal & IEC are two junker tube lines.
Well done, progress made !

Zeno

[Electronic M]

One thing to check for is that your CRT G2/screens aren't set too high...I have an industrial Setchell Carlson monitor that for more than a year I couldn't figure out why focus was terrible and HV was very low, but it was fairly bright....The CRT was good and strong and someone had one of the G2s set near max and it was literally making the gun conduct so HEAVILY that the CRT was literally overloading and lugging down the HV. I turned down the G2 and suddenly it was working really good and HV and focus were where they should be...It's not a common issue but it's something to be aware of.

[timmy]

Yes Tom early on I lowered the drives and the g2 pots.

[timmy]

Well at it again got perfect hv now but now I have good sound but no picture no video just a blank screen little fuzz checked tubes again even the tuner tubes. There is the 1n60 diode I don’t know if that affects video and sound or just video other then that any ideas from here maybe something obvious that again I’m missing.

[Yamamaya42]

Again, this is a situation where having an oscilloscope would be extremely helpful.
If sound is good, then tuner & IF up to #3 are most likely OK, as the sound is taken off the 3rd video IF V3. So the problem should be after that in L6 and after, the video detector may be faulty, or any one of those peaking coils between L6 & V4 P7.
If you did have a oscilloscope, the method would be to check for the 5v PTP video, starting from the anode of x6, and trace it down to V4 P7 to check it has a clear path.

But w/o one, it's much harder, check everything starting with x6 → V4 P7.

[timmy]

Can a 1n34 be used in place of the 1n60. P7 ?

[Yamamaya42]

Originally Posted by timmy

Can a 1n34 be used in place of the 1n60. P7 ?

As far as I can tell, the 1n34 is also a Germanium that's often used for TV video detectors, and as far as I know, they really are not that picky as long as you stick with the general type of diode.

[timmy]

Thanks but what’s the p7 you refer to

[Yamamaya42]

Originally Posted by timmy

Thanks but what’s the p7 you refer to

I'm looking at the SAMS for the set, P7 = pin7 of V4 video amp 6AW8A, should have a 5v PtP video there.

[timmy]

The voltages are somewhat low because the chassis is out and no tuner plugged in. I had picked up lindal tubes and they say they are no good so I have 2 more coming so maybe these tubes are no good since I had 2 others that didn’t move the needle on the tester and yet I had sound. X6 is almost impossible to reach but I did a test these Germanium diodes are so sensitive that testing each end causes the numbers on the meter to jump back and forth and that’s what the diode in the set did exactly with the diode I have in hand did the same so I’m assuming it’s good and from one end of the diode to pin 7 has continuity. Voltages on 6w8a are there but 7 I think was not 5 volts more like 12 volts but no tuner plugged in.the other part to this is channel 3 may be way off as far as tuned don’t know the history so took out the tuner and the slug for channel 3 was all the way in I don’t know if it’s usually in or out more then in so I ran it out and sprayed the gears the grease gummed up wasn’t really working now it is so I’ll find out tomorrow what happens.

[Electronic M]

One thing you can do as a diagnostic is to inject composite video at the output of the video detector if you get video on screen then the problem is between the tuner and detector, if not then the problem is in the video amp...This is a good way of eliminating half the video path from suspicion.

If you have tuner/IF issues and you another set with a modern 44MHz IF or a Blonder Tongue AM series agile modulator with an IF out port you could connect either of those in place of the sets original tuner and check if you get picture...If you do then troubleshoot the tuner in the set, if you don't troubleshoot the IF and AGC systems.

[timmy]

Well I’m putting my hopes on the tuner channel 3 is way out of where it should be to get a picture I do have sound but it was fading in and out.

[Yamamaya42]

if you are getting sound trough, you should be seeing SOMETHING on the screen, some kind of noise pattern, herringbone pattern, something getting through, as mentioned, the signal is getting as far as 3rd IF, even if it's distorted, you should se something on the screen.

and Electronic M has a valid idea, but be sure to put it through a isolation cap, like a .01 or something like that, so you don't fry your video source.

it needs 5v PtP, but you should see a faint image with standard composite 1v