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Old 03-23-2018, 12:24 PM
albanks albanks is offline
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Attempting first project - Some questions if I may

Disclaimer: This is going to be some dumb/newbie questions, so if you're not patient this is not a good thread for you, lol.

OK so after two years of acquiring sets I finally am getting around to recapping and retubing my first set. A Zenith b/w table top. I've been reading here, watching videos from shango and Doug, read the antique radio guides, etc.

These are my questions (based on the pictures below).

1.) There are two electrolytic cans that have three terminal leads each with different values. After scouring the net I am guessing these types of twist lock style cans are no longer produced. I have two NOS exact part # Zenith replacement cans. I understand the point is that it is not a matter of used/unused it is a matter of time drying out the electrolytes. But really, if I use these, will it be the same result as not even replacing the old ones?

2.) In the photos that show under the current can already installed, I noticed the electrolytic capacitor only has wires going to two terminals leaving one unconnected. The schematic shows all three having connections. I have had this set on before and it worked as is. So what is up with this? I am not good at reading schematics but it shows that particular empty terminal supposed to be going to near the horizontal hold. So confused.

3.) Do these old cans just twist off? It looks like I will have to break the old one somewhat to get it out.

4.) The picture with the tape on the tube with a grounded wire to the chassis. What is that? I discovered that when I removed the plastic backing and it looks like someone rigged something up there.

5.) On the electrolytic marked "2407031", I have a nice new electrolytic for this one but I noticed on the right side it looks like there are two wires going to the + side. When I solder in the new one it is an axial style. Should I just make sure both of them are making contact to the new lead?

6.) Lastly, please look at my paper/film capacitor assortment. Are these the right type? All the values are matching the old ones I just didn't know if they are acceptable types. They are going to replace the old wax/paper ones.

OK, if anyone is bored/feeling charitable please feel free to answer these questions.

PS, anything to help me not get shocked before I begin? Nothing is too obvious for a beginner. The set has been unplugged for over a year.

Thanks!!!!!!
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  #2  
Old 03-23-2018, 01:33 PM
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(6) - Yes, suitable types. The only caution would be if the voltage ratings were lower than the original (they are most likely OK).

(5) yes, just connect both wires to the plus side of the new one.

(4) The conductive coating ("dag") on the outside of the tube MUST be grounded. This way the tube itself acts as a capacitor to filter the high voltage supply. If it's not grounded, the dag can charge up and arc to other things. It looks like someone fixed a loose or broken ground this way.

(3) and (2): Someone else more familiar should answer

(1) both time and temperature affect the degradation of electrolytic capacitors. So, the NOS might be better but still not good. Safest thing is to replace with new, especially if you have no way of testing them. It takes an old-fashioned tester that applies sufficient voltage to see if they are leaky. A modern low-voltage capacitance meter will not detect this.

PS: after a year disconnected, your only risk of shock is static from scuffing your shoes on the carpet. However, once you do fire it up, it's good to discharge both the lytics and the high voltage after you shut it off and before you go poking around.

Of course, don't do any work while it's plugged in. It's a good idea to UNPLUG the set (not just turn off a power strip) in case it is a hot chassis set (no power transformer) or is a transformer set that happens to have a short somewhere.
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Old 03-23-2018, 02:00 PM
albanks albanks is offline
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Quote:
Originally Posted by old_tv_nut View Post
(6) - Yes, suitable types. The only caution would be if the voltage ratings were lower than the original (they are most likely OK).

(5) yes, just connect both wires to the plus side of the new one.

(4) The conductive coating ("dag") on the outside of the tube MUST be grounded. This way the tube itself acts as a capacitor to filter the high voltage supply. If it's not grounded, the dag can charge up and arc to other things. It looks like someone fixed a loose or broken ground this way.

(3) and (2): Someone else more familiar should answer

(1) both time and temperature affect the degradation of electrolytic capacitors. So, the NOS might be better but still not good. Safest thing is to replace with new, especially if you have no way of testing them. It takes an old-fashioned tester that applies sufficient voltage to see if they are leaky. A modern low-voltage capacitance meter will not detect this.

PS: after a year disconnected, your only risk of shock is static from scuffing your shoes on the carpet. However, once you do fire it up, it's good to discharge both the lytics and the high voltage after you shut it off and before you go poking around.

Of course, don't do any work while it's plugged in. It's a good idea to UNPLUG the set (not just turn off a power strip) in case it is a hot chassis set (no power transformer) or is a transformer set that happens to have a short somewhere.
I appreciate your reply. I will re-read it when I get home. Just quickly though with regard to the "DAG", now that I understand what it is, the coating is worn off in several blotches of the tube. Would it be prudent that I re-coat these areas (if that is even possible)?
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Old 03-23-2018, 02:28 PM
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Quote:
Originally Posted by albanks View Post
I appreciate your reply. I will re-read it when I get home. Just quickly though with regard to the "DAG", now that I understand what it is, the coating is worn off in several blotches of the tube. Would it be prudent that I re-coat these areas (if that is even possible)?
Are you sure it's worn off, or could it be deliberately not applied in those areas? It should not be applied too close to the high voltage connector because of the possibility of arcing. (Of course, what is there should be contiguous so it's all grounded.) In any case, it's OK to wait until you have the set running to see if there is any problem. Aquadag (the full name) can be purchased and applied easily, but I wouldn't bother until you're sure you need it.
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Old 03-23-2018, 05:16 PM
zeno zeno is offline
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First thing is change the caps ONE AT A TIME ! Then recheck the
set & see if anything changed.

1) those NOS cans are OLD ! By the 70's they packaged them in just
plastic, not boxes. Since the set is running you may want to do them
last in this case.
2) it may be a subbed cap & there is another one hung in under there somewhere.
3) most Zeniths twisted 2 of the lugs & soldered the other 2 so breaking
off the twisted ones it will come out easy. You may need a very hot
iron such as the old classic Weller gun.
4) The CRT wasnt grounding good. Someone moused it to get by.
The GND is made either with a set of finger or a coil spring on the bottom.
Some use a very long, small spring across the DAG. If the DAG is chipping
off it can be replaced. Symptom are diagonal dots in pix, bad sync, sometimes hissing, sparkles & ozone smell. Can also radiate & bother other TV's radios etc.
5) not sure what you mean here.

Safety ! The most dangerous place is where the AC comes in. I never
heard of a tech dying from a TV HV shock. I got them once a week for
40 yrs. The filter cans in most sets will bleed off fast. The HV will stay
charged a LONG time with a tube rectifier. Avoid the base of the HV
rect tube & anode lead. If you discharge it it can build back up to a
lower level so discharge several times over a few minutes.

BTW Put up a few under chassis & chassis pixs & chassis ##

73 Zeno
LFOD !
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Old 03-23-2018, 07:38 PM
albanks albanks is offline
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Quote:
Originally Posted by old_tv_nut View Post
Are you sure it's worn off, or could it be deliberately not applied in those areas? It should not be applied too close to the high voltage connector because of the possibility of arcing. (Of course, what is there should be contiguous so it's all grounded.) In any case, it's OK to wait until you have the set running to see if there is any problem. Aquadag (the full name) can be purchased and applied easily, but I wouldn't bother until you're sure you need it.
Well I did notice it is not applied near the high voltage connector but I was thinking it was worn off due to the unevenness of it all. Toward the top it's chipping and peeling. After I recap it then perhaps I will see where I am with this aspect.
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Old 03-23-2018, 07:40 PM
albanks albanks is offline
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Quote:
Originally Posted by zeno View Post
First thing is change the caps ONE AT A TIME ! Then recheck the
set & see if anything changed.

1) those NOS cans are OLD ! By the 70's they packaged them in just
plastic, not boxes. Since the set is running you may want to do them
last in this case.
2) it may be a subbed cap & there is another one hung in under there somewhere.
3) most Zeniths twisted 2 of the lugs & soldered the other 2 so breaking
off the twisted ones it will come out easy. You may need a very hot
iron such as the old classic Weller gun.
4) The CRT wasnt grounding good. Someone moused it to get by.
The GND is made either with a set of finger or a coil spring on the bottom.
Some use a very long, small spring across the DAG. If the DAG is chipping
off it can be replaced. Symptom are diagonal dots in pix, bad sync, sometimes hissing, sparkles & ozone smell. Can also radiate & bother other TV's radios etc.
5) not sure what you mean here.

Safety ! The most dangerous place is where the AC comes in. I never
heard of a tech dying from a TV HV shock. I got them once a week for
40 yrs. The filter cans in most sets will bleed off fast. The HV will stay
charged a LONG time with a tube rectifier. Avoid the base of the HV
rect tube & anode lead. If you discharge it it can build back up to a
lower level so discharge several times over a few minutes.

BTW Put up a few under chassis & chassis pixs & chassis ##

73 Zeno
LFOD !
Thank you for the help. I am working on setting up a work area in the cellar then I can take more pics as I go. I don't want to open the set up again in my apartment as it is generally very dirty and crud always falls over the place.
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Old 03-23-2018, 08:16 PM
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Electronic M Electronic M is offline
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No need to remove the FP cans from the chassis....Just disconnect the positive terminal leads from the can and it will remain electrically dormant and preserve the original above chassis appearance.
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Old 03-23-2018, 08:39 PM
albanks albanks is offline
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Quote:
Originally Posted by Electronic M View Post
No need to remove the FP cans from the chassis....Just disconnect the positive terminal leads from the can and it will remain electrically dormant and preserve the original above chassis appearance.
I think I understand what you're saying. Leave it alone, disconnect it from beneath and put the new capacitor underneath. Neat idea. I have also read about rebuilding them and stuffing the new ones inside.

PS...If I forget the NOS Zenith stuff in the picture I will need the following:

1) 150uf-350v, 100uf-350v, 200uf-25v

2) 4uf-350v, 10uf-400v, 20uf-25v

I have been looking at all the major sites they don't seem to have capacitors with these three values each in 1 can. I was looking at that thread where the can went through the roof so I may want to avoid using the old and dried out NOS stuff after all.
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Old 03-23-2018, 08:57 PM
albanks albanks is offline
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Quote:
Originally Posted by zeno View Post
You may need a very hot
iron such as the old classic Weller gun.
I'm finding that out now. I will have to pick up something more heavy duty for desoldering. For the normal soldering of the paper caps will a 30 watt soldering iron from Harbor Freight work? I seem to remember reading somewhere 40watt is the normal minimum.
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Old 03-23-2018, 09:55 PM
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Electronic M Electronic M is offline
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Quote:
Originally Posted by albanks View Post
I think I understand what you're saying. Leave it alone, disconnect it from beneath and put the new capacitor underneath. Neat idea. I have also read about rebuilding them and stuffing the new ones inside.

PS...If I forget the NOS Zenith stuff in the picture I will need the following:

1) 150uf-350v, 100uf-350v, 200uf-25v

2) 4uf-350v, 10uf-400v, 20uf-25v

I have been looking at all the major sites they don't seem to have capacitors with these three values each in 1 can. I was looking at that thread where the can went through the roof so I may want to avoid using the old and dried out NOS stuff after all.
For the most part, having 3+ sections in 1 can is something that died with FP twist lock style cans...It is fine/normal practice to use 3 individual caps to replace one 3 section twist lock. Most twist locks have the can as the common negative to each section. Some capacitance values like multiples of 2,3,4,5 are not made anymore and have been supplanted with 2.2,3.3,4.7,etc. You can fudge the capacitance values a decent bit and be fine. The original parts often had +100%/-50% capacitance tolerance so anything close in value capacitance wise will be fine.

Voltage you can only fudge upwards...The voltage rating of a cap is the max input voltage it can take without going bang(!)...If you replace a 150V with a 200V part the 200V can take more abuse before going bang. If you replace a 150V with a 50V the 50 will probably have ~100V on it and go bang quickly.
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Old 03-24-2018, 09:41 AM
zeno zeno is offline
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For the caps use
1) 100mfd & a 47mfd in parallal 450V
100mfd 450 V
220mfd 50V

2) 4.7MFD 450V
10mfd 450V
22mfd 50V

Thats all using modern values & a little extra on the voltage. Best
way to change is leave the old can in, Cut off wires & use a terminal strip.
Mount the new stuff close to the old ! Here is the style strip.

https://www.radioshack.com/products/...terminal-strip

73 Zeno
LFOD !
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Old 03-24-2018, 08:54 PM
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Not too long ago I discovered that Mouser carries solder lug terminal strips by Keystone. I was surprised to see a vintage type of part there.
They have many versions with different number of lugs and in different arrangements. I've also gotten them from Radio Daze.
https://www.mouser.com/ProductDetail...HpkXpfvzp08%3d

A little hard to find on Mouser, search under "Keystone", terminals, lug terminals, terminal strips, solder type.
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Old 03-24-2018, 09:10 PM
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Quote:
Originally Posted by albanks View Post
Thank you for the help. I am working on setting up a work area in the cellar then I can take more pics as I go. I don't want to open the set up again in my apartment as it is generally very dirty and crud always falls over the place.
One of the first things you should do is clean the chassis. Some of that dirt may be conductive and lead to problems. You can use compressed air if you are careful. Don't hit the speaker or the DAG with high pressure air for instance.
Another way is using a vacuum cleaner and a soft brush (paint brush). Don't suck the Dag off the CRT.
A limited amount of window cleaner can be used but don't go near the tube numbers. The tube numbers can sometimes come off if you touch them.
It would be better if you worked on some radios first to get the hang of things.
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Old 03-24-2018, 09:20 PM
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Quote:
Originally Posted by albanks View Post
I'm finding that out now. I will have to pick up something more heavy duty for desoldering. For the normal soldering of the paper caps will a 30 watt soldering iron from Harbor Freight work? I seem to remember reading somewhere 40watt is the normal minimum.
30-40 W will do for most things. Things soldered to the chassis may take more, maybe 60W, but you don't have to remove the metal cased caps anyway most of the time. Also if a component lead is soldered to the chassis you can clip the lead near the old part and splice the new component lead to the old lead, no need for a big iron.
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