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-   -   Motorola ts907 low hv (http://www.videokarma.org/showthread.php?t=275174)

Yamamaya42 10-01-2022 06:31 PM
Quote:
Originally Posted by zeno (Post 3245261)
Not sure where we are now but.......
To measure H Out current you need to open the cathode pin from GND
and put a ampmeter in series with it. Depending on the meter you should
decouple the cathode with a cap to smooth it out. It goes in // with the
meter.
SAMS has instructions on value of cap & procedure.
Adjusting the H. osc ( hold) will effect the G-1 negative voltage.
Keep in mind the whole thing by design needs to be in resonance
to be happy. If the G-1 is in spec you are good till that point.
A freq counter or scope can show you if its at 15,750.

AGC as a rule goes to the RF amp & IF # 1 & 2.
SAMS will show AGC voltages either with or without a strong signal
or both ways. AGC problems are VERY rare, I cant really remember
many in 40 yrs & tens of thousands of sets.

73 Zeno:smoke:
LFOD !

As mentioned above, this set does not have a horizontal efficiency/linearity coil to adjust, so where the cathode current can be measured, there is no way to adjust it on this.

and yes AGC problems are rare, they do happen, bit in this case, it's more likely the IF alignment is messed up.

timmy 10-01-2022 06:50 PM
Tomorrow I’m going to check resistances on the 6hs8 according to sams. when I had this running the agc control on the rear turning both ways made no difference at all but the noise gate did I do get video but it is distorted but can see images so since making k1 will see what this does. There is a .4 v rf source to agc if that’s missing from the tuner I don’t know what the consequence is if that’s not there.

timmy 10-02-2022 10:47 AM
Checked resistances on 6hs8 they are all wrong even with the couplet I made up tried it anyway and it seemed to make it worse. I don’t know if the couplet all together would have to be potted I did incapsulated it in heavy heat shrink.

jr_tech 10-02-2022 01:04 PM
Quote:
Originally Posted by timmy (Post 3245269)
Checked resistances on 6hs8 they are all wrong even with the couplet I made up tried it anyway and it seemed to make it worse. I don’t know if the couplet all together would have to be potted I did incapsulated it in heavy heat shrink.
How far off were the resistances? Perhaps you could list the measurements by pin number, so we might be able to figure out what’s going on here.

I don’t think that the potting is important.

jr

timmy 10-02-2022 02:14 PM
My mistake I had to measure from x2 not x1 and it turns out they are all good. But the voltages are not right at all 6hs8 pins 6-145v 114 7-200 119 3-2.5 8.3 8-230 143 9-140 31 2- 275 1-190

jr_tech 10-03-2022 05:47 PM
Quote:
Originally Posted by timmy (Post 3245274)
My mistake I had to measure from x2 not x1 and it turns out they are all good. But the voltages are not right at all 6hs8 pins 6-145v 114 7-200 119 3-2.5 8.3 8-230 143 9-140 31 2- 275 1-190
Am I reading this right: “pin 9 140 volts expected, 31 volts measured” ?

jr

timmy 10-03-2022 06:24 PM
Yup

jr_tech 10-03-2022 10:45 PM
What is the input impedance of your dmm? Most dmms are 10 megohms, but some are only 1 megohm. SAMS specifies use of a VTVM (11 megohms) but a 10 megohm is usually good enough!

jr

Yamamaya42 10-04-2022 07:40 AM
Quote:
Originally Posted by jr_tech (Post 3245295)
What is the input impedance of your dmm? Most dmms are 10 megohms, but some are only 1 megohm. SAMS specifies use of a VTVM (11 megohms) but a 10 megohm is usually good enough!

jr
It's very doubtful that his meter is 10m, because he has an electrician's (clamp) meter, and not a full function DVM, this has been brought up several times before by quite a few, including myself that he invest in a better one that has a dedicated 10a scale, and was made for the electronics field rather than an electrician, because it is very likely it's giving inaccurate readings in some cases.

He has this.
http://www.instrumart.com/assets/uei...nix-manual.pdf


Again, a better meter is suggested before believing any voltage readings, one that is known to be 10m, as the one on hand may be loading the circuit down.

timmy 10-04-2022 11:21 AM
Is it possible for a video detect diode to check good but be bad from leakage ? Has anyone ever seen this

jr_tech 10-04-2022 01:41 PM
Quote:
Originally Posted by Yamamaya42 (Post 3245298)
It's very doubtful that his meter is 10m, because he has an electrician's (clamp) meter, and not a full function DVM, this has been brought up several times before by quite a few, including myself that he invest in a better one that has a dedicated 10a scale, and was made for the electronics field rather than an electrician, because it is very likely it's giving inaccurate readings in some cases.

He has this.
http://www.instrumart.com/assets/uei...nix-manual.pdf


Again, a better meter is suggested before believing any voltage readings, one that is known to be 10m, as the one on hand may be loading the circuit down.
While not necessarily “better “ from a quality standpoint, this inexpensive dmm would be more suited to the task at hand.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

10 megohm input impedance (I have measured mine).
10 amp DC range.
No auto range (no confusion).
Inexpensive @ $12.50 (no tears if you break it).

not affiliated,
jr

Yamamaya42 10-04-2022 01:45 PM
Quote:
Originally Posted by jr_tech (Post 3245303)
While not necessarily “better “ from a quality standpoint, this inexpensive dmm would be more suited to the task at hand.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

10 megohm input impedance (I have measured mine).
10 amp DC range.
No auto range (no confusion).
Inexpensive @ $12.50 (no tears if you break it).

not affiliated,
jr
I have that exact one! :D

plus 2 other "disposable" types of the same price range.:yes:

timmy 10-04-2022 05:43 PM
Sounds like you guys won’t be happy until I buy a cheapy dvm or something from the early 60s. This dvm repaired many tvs. And the cap checker is priceless. I used to use a fluke 77 series and this I use now is better then that.

Yamamaya42 10-04-2022 06:28 PM
Quote:
Originally Posted by timmy (Post 3245308)
Sounds like you guys won’t be happy until I buy a cheapy dvm or something from the early 60s. This dvm repaired many tvs. And the cap checker is priceless. I used to use a fluke 77 series and this I use now is better then that.
funny you mention the fluke 77 series .

http://suzaku.live-evil.org/1004221812.jpg

what I and many other are saying is that the clamp meter you have is not 10m impedance, and that is quite important when it comes to tube stuff, there is a 90% chance that your voltage measurements are being skewed because of this.

$12.50 is a good investment to double check that you are being told correct voltage info with a meter KNOWN to be 10m, that both I and jr_tech have used, and I can say for a fact it gives readings on par with the Fluke.

timmy 10-04-2022 07:12 PM
Maybe this helps about this dvm


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