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  #16  
Old 07-14-2018, 11:04 AM
dieseljeep dieseljeep is offline
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Originally Posted by Zsuttle View Post
If that isn't the case, if anything at all had shorted, then the ballast should be blown right?

What should the voltage coming off of pin 4 and pin 3 be?
Almost full line voltage because of no load.
That set's a little trickier to troubleshoot because it uses a floating B- line instead of a hot chassis.
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  #17  
Old 07-14-2018, 11:42 AM
dieseljeep dieseljeep is offline
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Originally Posted by timmy View Post
I don't find a c79 power supply cap on the ts4j schematic.
I think he meant C97.
I just spent a half hour trying to find the B+ source. It seems it's sourced from the cathode of the 12SN7, 2nd clipper.
Slightly harder schematic to understand! Even the Sams isn't much better.
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  #18  
Old 07-14-2018, 12:24 PM
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Quote:
Originally Posted by dieseljeep View Post
I think he meant C97.
I just spent a half hour trying to find the B+ source. It seems it's sourced from the cathode of the 12SN7, 2nd clipper.
Slightly harder schematic to understand! Even the Sams isn't much better.
The TS-4 family created the B+ rail by using several stages between B++ and B- as a voltage divider. You know how some makes used the audio output as a voltage dropper instead of a resistor...Moto took it a step farther by using several tubes in series-parallel to make a voltage divider. Crazy but it worked.
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  #19  
Old 07-14-2018, 01:10 PM
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Quote:
Originally Posted by Electronic M View Post
The TS-4 family created the B+ rail by using several stages between B++ and B- as a voltage divider. You know how some makes used the audio output as a voltage dropper instead of a resistor...Moto took it a step farther by using several tubes in series-parallel to make a voltage divider. Crazy but it worked.
And later with the ts18 they used half of the I think it was the audio amp for the verticle oscillator, well they had there ways back in the day.
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  #20  
Old 07-14-2018, 01:35 PM
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Quote:
Originally Posted by dieseljeep View Post
I think he meant C97.
I just spent a half hour trying to find the B+ source. It seems it's sourced from the cathode of the 12SN7, 2nd clipper.
Slightly harder schematic to understand! Even the Sams isn't much better.
I was referring to C79 on the SAMs schematic(TS-4J Late). It's a little rf bypass connected to pin 3 on the ballast though it's located right behind the tuner.
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  #21  
Old 07-14-2018, 10:00 PM
dieseljeep dieseljeep is offline
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Originally Posted by Electronic M View Post
The TS-4 family created the B+ rail by using several stages between B++ and B- as a voltage divider. You know how some makes used the audio output as a voltage dropper instead of a resistor...Moto took it a step farther by using several tubes in series-parallel to make a voltage divider. Crazy but it worked.
It only seemed to be the 12SN7 feed and I didn't explore the rest of the circuit to determine the rest of the voltage divider circuit.
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  #22  
Old 07-15-2018, 10:58 PM
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So, does anyone have any good tips to keep troubleshooting? I've gone through the schematics up through the power supply, but haven't really checked much else.
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  #23  
Old 07-16-2018, 07:06 AM
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What exactly is wrong tubes won't light, caps won't charge to proper voltage ?
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  #24  
Old 07-16-2018, 09:41 AM
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Tubes light for about 30 sec and then they sorta flicker on and off and there's still something causing my caps to fry as well. The filament circuit problem is just caused by the faulty electrolytic caps, but I can't figure out what causes my electrolytics to fail in the first place. Some of the caps that were around 10-20uF are now testing in the hundreds range.
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  #25  
Old 07-16-2018, 10:28 AM
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The filament circuit should not be affected for the caps. There are two series filament strings that connect directly to the AC line through a ballast resistor.

Sounds like there is a problem in the voltage double B++ supply that is shorting out the AC line.

Note that none of the negative leads of the electrolytics connect to the chassis. The chassis is floating in this set - it is not common. Also make sure your diodes are not installed backwards.

Also I'm wondering about the values of the caps you're using. There should be a 140, 120 and 100 uF cap in the B++ supply circuit - nothing in the 10-20 range.
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  #26  
Old 07-16-2018, 02:29 PM
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There are 2 smaller caps in the circuit not the power supply so if they are going bad then it almost sounds like ac is getting into the DC circuit. I would stop and go over the schematic with a fine tooth comb and start at the diodes as bandersen noted that the b- does not go to the chassis at all. If the diodes were backwards you may get nothing but if one is backwards then you would have a problem, sort of maybe having DC on one side and ac on the other which should not be. The filiment string should not be dependant on an electrolytic cap the ac would distroy the cap . If it were then as soon as the cap takes a dump so does the filiment string, goes out.
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  #27  
Old 07-17-2018, 02:13 AM
EdKozk2 EdKozk2 is offline
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I noticed that C-45 in the Sams schematic you posted does not match the Motorola factory issued schematic for a TS-4J late model. The ground end of C-45 should be connected to the floating B- line, not chassis ground. Also if you are using an original metal can ballast, make sure that it does not have any internal shorts. Remove the ballast if you have to, and check the pins for proper continuity and resistance. Your set is supposed to use the latter ballast, as shown in the schematic you posted. A ballast with internal shorts will cause all kinds of problems.
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  #28  
Old 07-17-2018, 09:59 AM
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C-45 in the Sams is going to B-. B- is represented by the taper horizontal line symbol. Chassis is represented by the symbol with diagonal lines I circled at the top.

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  #29  
Old 07-17-2018, 10:19 AM
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Quote:
Originally Posted by bandersen View Post
Also I'm wondering about the values of the caps you're using. There should be a 140, 120 and 100 uF cap in the B++ supply circuit - nothing in the 10-20 range.
Yes, I recognise that the B++ power supply doesn't use any, however upstream in the audio circuit, the electrolytics are getting blown because they connect to the B++

Quote:
Originally Posted by EdKozk2 View Post
I noticed that C-45 in the Sams schematic you posted does not match the Motorola factory issued schematic for a TS-4J late model. The ground end of C-45 should be connected to the floating B- line, not chassis ground. Also if you are using an original metal can ballast, make sure that it does not have any internal shorts. Remove the ballast if you have to, and check the pins for proper continuity and resistance. Your set is supposed to use the latter ballast, as shown in the schematic you posted. A ballast with internal shorts will cause all kinds of problems.
Ed
I'm using a glass ballast resistor that came with the spare chassis. It matches the pinouts of what I need. Which schematic would be the correct? I saw there was one on the ETF website that I think is more correct.

I can't check it today, (Adding a new rack to the workbench) but I'm almost positive I connected the output of the capacitors directly to the chassis. This whole floating chassis thing is a real pain in the neck.
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  #30  
Old 07-17-2018, 10:35 AM
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Definitely do not connect anything to the chassis.

Quote:
Originally Posted by Zsuttle View Post
Yes, I recognise that the B++ power supply doesn't use any, however upstream in the audio circuit, the electrolytics are getting blown because they connect to the B++

Ah, that's weird. What caps do you mean exactly? There are two electrolytics in the audio circuit and neither goes to B++.

If you mean the 20uF cathode bypass on the audio output tube, it should only have about 9 volts across it. Perhaps that 25L6 has a short or is miss wired ?

The other is a 10uF in the FM ratio detector that should only have a few volts across it as well.
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