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  #1  
Old 07-19-2017, 11:50 AM
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Motorola ts4j

Ok so I have yet another one of these Motorola sets its been recapped power supply and all the wax caps got a great picture and sound but the vert hold works but won't lock, I can get the pic to stop but it won't lock at all. Checked the resistors on the hold and size pots and are good I subbed the 1000 pf and both the 100 and the 250 pf Micas and made no difference. I have the 2 tubular caps in the verticle and are the correct ones .0047 but I have 2 .002 10 kv ceramics in the horizontal I know there should be the correct tubular caps in there but the horiz is stable and ok. Checked other resistors around the 6sl7 and all are within range. Any ideas how to get this to stop rolling and lock.
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Old 07-19-2017, 12:53 PM
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Sounds like your vertical oscillator and output are working ok... I would check back farther, around the clipper/sync amp (v-11) and the integrator network for bad or miss-wired parts.

jr
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Old 07-19-2017, 01:05 PM
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If it can roll both directions, and especially if you can get it to stop, then your V osc. is probably fine. Lack of lock is usually lack of sync in that case. Since you have H sync the sync sep is probably somewhat functional.

My first step would be to change out all the parts that couple the sync sep to the V osc. and verify the values of what is in there now against the schematic while doing so. If your set matches the below schematic R-44,45 and C-47,48, 140
http://earlytelevision.org/images/mo..._VT71_TS4J.jpg

I don't see how the osc could run and at the same time cause the sync issues so if those parts are not the problem look for weak sync sep output next.
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Old 07-19-2017, 01:58 PM
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Ok, r44 and r45 check good and c47 and 47 are .01 caps and are new I replaced and I did check all the caps when I got them so as I didn't introduce any other problems to follow with defective caps and c140 is a 250 pf and this is one I subbed already with a 251 pf mica and no change. All the tubes are fine but maybe I should try other 12sn7 tubes. Other resistors like the 2 1 meg resistors are good also.

Last edited by timmy; 07-19-2017 at 04:34 PM.
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Old 07-19-2017, 04:42 PM
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I don't know but could the .002 ceramic caps in the horizontal be interfering with the verticle sync ? The correct caps that should be in the horiz is .001 but tubular type . Although the horiz is fine and stable. I can't find anything else wrong here and tried several different 12sn7 tubes and 6sl7 tubes also .
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Old 07-19-2017, 05:19 PM
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Best tool to find the fault will be a scope, with a isolation transformer to plug the set into. We do not want to do harm to any gear, tv, or tinkerer for that matter. Without the scope you are just making wild guesses as to what the fault is. All the best,Tom.J
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Old 07-19-2017, 09:14 PM
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Quote:
Originally Posted by timmy View Post
I don't know but could the .002 ceramic caps in the horizontal be interfering with the verticle sync ? The correct caps that should be in the horiz is .001 but tubular type . Although the horiz is fine and stable. I can't find anything else wrong here and tried several different 12sn7 tubes and 6sl7 tubes also .
Not likely... I would recheck the wiring between the sync clipper and the vertical oscillator tube... it appears that the vertical sync pulses are not reaching the vertical oscillator. Perhaps a side by side comparison to your VT-73 would reveal an error or wrong part.
Of course, a scope would tell you in seconds if the vertical sync pulses are wrong or missing.

jr
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Old 07-20-2017, 08:16 AM
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Quote:
Originally Posted by tom.j.fla View Post
Best tool to find the fault will be a scope, with a isolation transformer to plug the set into. We do not want to do harm to any gear, tv, or tinkerer for that matter. Without the scope you are just making wild guesses as to what the fault is. All the best,Tom.J
Quote:
Originally Posted by jr_tech View Post
Not likely... I would recheck the wiring between the sync clipper and the vertical oscillator tube... it appears that the vertical sync pulses are not reaching the vertical oscillator. Perhaps a side by side comparison to your VT-73 would reveal an error or wrong part.
Of course, a scope would tell you in seconds if the vertical sync pulses are wrong or missing.

jr
Exactly. [starts chanting] Scope!.. Scope!.. Scope!...

One other thing you may be able to do is try injecting V sync from the VT-73 (or a B&K analyst or test pattern gen) into the VT-71. Make sure the hot chassis polarity matches before applying power or bad things could happen.
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Old 07-20-2017, 09:18 AM
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The high voltage caps coupling the circuits won't work right, either, if they are ceramic disc..
Those were originally .005 10 KV for vertical, and, .002 10 KV.
I may have my caps mixed up, but, I'm pretty sure on voltages on both. The cap on h. v. rectifier should be either .001, or, .005 at 10,000 volts.


I think they actually work at seven thousand volts.
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Old 07-20-2017, 09:42 AM
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Quote:
Originally Posted by Bill Cahill View Post
The high voltage caps coupling the circuits won't work right, either, if they are ceramic disc..
Those were originally .005 10 KV for vertical, and, .002 10 KV.
I may have my caps mixed up, but, I'm pretty sure on voltages on both. The cap on h. v. rectifier should be either .001, or, .005 at 10,000 volts.


I think they actually work at seven thousand volts.
Wrong. Every unrestored Moto VT-71 / VT-73 I've seen has 6KV rated HV caps, and the schematic linked above shows .001 on the H deflection plate couplings.

The HV coupling caps don't work well if ceramic (unless you increase the capacitance), but the only HV ceramics he says are in there are in the working Horizontal section....Add to that that it is a NO sync issue in the vertical (and not a sweep size/linearity issue, which is what HV cap issues would cause) and the HV caps should basically be irrelevant to the problem described.
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Old 07-20-2017, 10:41 AM
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  #12  
Old 07-20-2017, 11:52 AM
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There is a .004 mfd paper cap from the vert oscillator to ground. It is the only .004 mfd cap in the set, and that cap is definitely leaky. Change it, with an exact .004 mfd cap, and that should solve the problem. A .0047 cap will not replace the .004 mfd cap.
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Old 07-20-2017, 03:07 PM
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Originally Posted by broadcaster View Post
There is a .004 mfd paper cap from the vert oscillator to ground. It is the only .004 mfd cap in the set, and that cap is definitely leaky. Change it, with an exact .004 mfd cap, and that should solve the problem. A .0047 cap will not replace the .004 mfd cap.
Ok I now have vert sync lock, and the .004 I did change I know that one is important. I'll post what the problem was shortly.
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Old 07-20-2017, 04:43 PM
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Well with this set upon looking it over for the first time I found a .001 tacked in place of a 250 pf but the 250 pf was not where it normally is, tucked under a tie strap and hard to see because a 1000 pf mica normally sits in front of the 250. So I mistook that 250 for another one nearby and after seeing the Motorola schematic for the ts4j that I have I was thinking that 250 pf was a possible production change because it was not there along with the 22 ohm resistor within the ballast is not wired for this set. No old solder, nothing it don't have it but the schematic shows the ballast has it but yet could not find it on the schematic. So some was my overlooking thinking changes were made back in the day. So I put the 250 in which was infact c140 and that fixed the problem. Thanks for the help guys.

Last edited by timmy; 07-20-2017 at 06:54 PM.
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Old 07-25-2017, 12:32 PM
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Ok while I have verticle lock now I can get the pic to stop rolling but when it's stable it gets Alittle jitter then starts rolling again every minute or so. Could this be from the IF maybe channel 3 is not tuned perfect, although the picture is good.
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