Motorola ts907 low hv

[bandersen]

Pardon my ignorance, but what is the "focus coil" on the schematic? This set uses electrostatic focus.
Ah, nevermind - L49 - focus coil.

[timmy]

I still have pin 8 of v1 that the chart says 3.2k but I’m still getting 6.2k after changing the resistors so that’s a problem unless the chart has a typo. I have a Motorola book for different chassis and there is a 907-B I don’t know if mine is a B but if I take the 8.2 off ground then pin 8 shows the correct resistance maybe the 907-B is updated it’s from 1969.

[timmy]

I have to look into the video detect diode the one I put in may not have been good so can I mount this diode on the outside run 2 small wires to an opening on the chassis and mount it to a small tie strip for easy access to try different diodes. Maybe this diode has excessive leakage and it’s tough to reach it every time.

[Yamamaya42]

Originally Posted by timmy

I have to look into the video detect diode the one I put in may not have been good so can I mount this diode on the outside run 2 small wires to an opening on the chassis and mount it to a small tie strip for easy access to try different diodes. Maybe this diode has excessive leakage and it’s tough to reach it every time.

Altering the detector like that may result in unwanted undesired results.

[timmy]

How does one know if the diode has excessive leakage. Like many other things that test good but really is bad like tube testers.

[Yamamaya42]

The diode test with any DVM is good enough in this situation to detect any faulty diodes.
The detector is not under any high power load or voltage extremes.

[timmy]

Originally Posted by Yamamaya42

The diode test with any DVM is good enough in this situation to detect any faulty diodes.
The detector is not under any high power load or voltage extremes.

Well it does check good but at this point I’ll check anything to rule out.

[timmy]

Still didn’t come up with the reason why pin 8 v1 is at around 6.3k when it’s supposed to be 3.2k. I’m letting everything else go for now and have to focus on this discrepancy with pin 8 v1. I don’t even know if sams is wrong because pin 8 v2 is 6.4k and matches sams.

[Yamamaya42]

More likely than not, the data on the SAMs is in error, and 6.3k is correct.
You should really look into what Squirrel Boy mentioned, and try injecting IF signals into the string at the various stages via the grids of the tubes, (pin 2), using a decoupling capacitor to protect the tuner subber from any voltage that may be on the grid.

Since you can't place the chassis in service position for this, or have a tube test socket, you will have to get something like some 30 Gauge Wire Wrap Wire, and wrap a few turns around P2 of the tube of the stage under test, as this has to be done with it hooked up fully to the CRT to see if you get a picture.

[Electronic M]

Originally Posted by Yamamaya42

More likely than not, the data on the SAMs is in error, and 6.3k is correct.
You should really look into what Squirrel Boy mentioned, and try injecting IF signals into the string at the various stages via the grids of the tubes, (pin 2), using a decoupling capacitor to protect the tuner subber from any voltage that may be on the grid.

Since you can't place the chassis in service position for this, or have a tube test socket, you will have to get something like some 30 Gauge Wire Wrap Wire, and wrap a few turns around P2 of the tube of the stage under test, as this has to be done with it hooked up fully to the CRT to see if you get a picture.

+1 basically your using your tuner subber like a B&K analyst's IF output....Only I'm not sure why you bought the subber instead of an analyst in the first place....I never use my tuner subber, but I use my analyst more than my scope (it's probably second to my DMM interms of use).

[timmy]

Originally Posted by Yamamaya42

More likely than not, the data on the SAMs is in error, and 6.3k is correct.
You should really look into what Squirrel Boy mentioned, and try injecting IF signals into the string at the various stages via the grids of the tubes, (pin 2), using a decoupling capacitor to protect the tuner subber from any voltage that may be on the grid.

Since you can't place the chassis in service position for this, or have a tube test socket, you will have to get something like some 30 Gauge Wire Wrap Wire, and wrap a few turns around P2 of the tube of the stage under test, as this has to be done with it hooked up fully to the CRT to see if you get a picture.

So your saying inject signals from the subber to pin 2 of the first 2 IF tubes. Ok well that’s next. .01 cap or .1 I’ll leave the rf plug from the tuner out while trying each tube.

[timmy]

Ok v1 same v2 was impressive v3 nothing so either L4 was turned or something right there at v1 is the problem or just befor it I don’t know. The picture is from v2.

[Yamamaya42]

This is a 1st IF problem, something between L3 and L4.

First replace
R36,R37,R38,R42,R43,R44,R45 with all new carbon film parts, do not rely on any meter to tell you the old parts are OK, at this point, you want all new resistors in there, of coarse, paying close attention to lead dress and placement when put in, making it look as close to original as you can, then go on from there.

This obviously means all is good from the 2nd IF onward, including the detector diode!

[timmy]

Well this somewhat proves it don’t need a full blown alignment.

[Yamamaya42]

there is a problem in the first half.