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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 05, 2019 8:24 am 
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The Case of the Mysterious Extra Electrolytic...

(While I was typing this out and continuing to review the schematic and specs, I actually figured out a lot more than I thought I was going to when I started! I now see that this extra electrolytic appears to be an existing SUBSTITUTE for Canned C2-C AND I had erroneously posted the routings for C2-B as if it were C2-C which confused everything even further... Below are my original ramblings and thoughts as I was writing.)

On the subject of mismatched wiring, I decided to do a proper analysis of the completely extra electrolytic that exists on the back of the chassis. This one is visible in some of the early photos I shared here. It is a 20UF 450V electrolytic, which does not match the specs of any capacitor beyond C2-C (20/50) and C1-C ▲ (20/200). I did replace this one with a new 22UF 450V some time back as well as all the other paper/plastic caps.

Attachment:
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Attachment:
extra-ec2.jpg
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The POSITIVE (+) end of this cap has a direct connection via terminal strip to:

  • V13 (6S4) Tube = Vertical Output - Pin 2
  • R5 = Vertical Linearity Control - Pin 2
  • C4 NEGATIVE (-) = Electrolytic 10UF 475V

The NEGATIVE (-) end of this cap terminates to ground.

...and now that I've compared to the schematic, I see exactly! These connections all align perfectly with C2-C of the canned electrolytic I tried replacing to much confusion and failure.

Attachment:
C2-C.jpg
C2-C.jpg [ 236.2 KiB | Viewed 501 times ]


QUESTION: Aren't all electrolytics in a can supposed to be tied to each other at negatives (to share a common ground) or can each of them route to whatever ground is in reach? This 'replacement' that correlates to the original C2-C connections in schematic only routes to C4 (standalone electrolytic) negative from its positive, not to C2-A or C2-B.

EDIT: And... Turns out I screwed up the symbols/info when I originally posted the C2 routing here. For whatever reason I thought C2-C was the SQUARE but it is really the BLANK one on the can, which makes perfect since considering this is the one that had NO wiring coming from it in the original can that I questioned previously (it had already been rerouted to this added capacitor).

So the proper schematic routing is:

  • C2-A ▲ (5/200) branches to R38 (8.2K) and V6 (Video Output Tube).
  • C2-B ■ (60/200) branches to C3(-) (40µ elec), C58 (.0047µ cap) and V11 (Audio Output Tube)
  • C2-C (20/50) branches to R5 (3K - Vertical Linearity Control), C4(-) (10µ elec) and V13 (Vert Multi Vert Output Tube). [Replaced with the substitute electrolytic at some point in history.]

This clears up everything, I think. I had confused C2-B with C2-C and everything seemed completely misrouted because of that and the replacement one that already existed but I didn't review.

Tomorrow I will go over which electrolytics I used as replacements for what as with all of this confusion and misidentification (which I still can't believe I would've err'd on) I easily may have done something wrong.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 05, 2019 1:47 pm 
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"Most" of the time, the negatives are tied together within the electrolytic can and often do go to ground. But the key words "Most" and "Often" need scrutiny. For example I have seen (rarely) capacitors that have two connections and one is + whilst the other is -. In other words, totally isolated from the can. Let's just say that the negative (-) is connected to the negative part of the circuit in which it is being used which may or may not be ground. It may be connected to the center tap of a power transformer that may not be connected to the chassis. Confused enough yet? Read the next paragraph.

Another place that has a strange electrolytic capacitor is the bias circuit of some tube amplifiers. Notably, HH Scott used a common positive electrolytic capacitor for its negative voltage bias circuit (and preamplifier filament circuit). That capacitor was often a four section 75-75-75-75 µFD common positive capacitor in a can. The can was clearly marked as such.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 05, 2019 3:01 pm 
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On common negative cans where the negative is connected directly to chassis I have been known (especially in cases where there isn't much room near the original can) to delete the positive wire going from a remote tube socket (or terminal strip)to the can positive and connect a new lytic between the tube socket and nearest chassis ground.... This won't work if the original can connects to a floating negative rail that is not chassis ground (though sometimes the rail has a convenient point near the positive of the section you are replacing which makes relocating the replacement practical).

This is what I'd call advanced technique... don't try it till you are comfortable changing lytics and don't get confused / make mistakes....if you get confused while making a significant change in lead dress finding your mistake becomes a good bit harder.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 3:37 am 
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Few Updates...

Variac - When powered through a variac at approximately 117 volts, Kill-A-Watt reads an average of 1.63A / 182 Watts. This is within 0.1 amps of the ratings spec in PhotoFact.

Canned Electrolytic - I redid the three electrolytics from the can that caused the failure previously. Still not a permanent arrangement (floating) but now that I better understand the routing and how one had been replaced previously it is better; I may end up cutting the base of the original can and using that for the mount point as I've seen done before since there really is no good spot under the chassis to mount a terminal strip.

Paper Caps - I replaced the three remaining paper caps on the sound board. However, I notice a loud buzzing from the speaker when turned on even with volume all the way down. Audio still sounds fine though during playback but I don't remember the buzzing being this loud or the volume control this sensitive. All of the replacement caps were to spec and 630V.

Power - The TV powers back on and is again at the state that it was in one of the prior updates. I am using the original damper vacuum tube which tested acceptable on a basic tester. There are still vertical linearity issues and even if set well it drifts and begins scrolling again within moments.

Potentiometers - On that note, I believe the pots could at least be partially at fault for the vertical scroll touchiness, such as an overly sensitive vertical linearity / vertical hold or debris that causes fluctuation. I have ordered the trio of CAIG DeoxIt (Fader/F5, D5, D100S) to attempt simple cleaning of them; I'll stick with F5 designed for pots although I've read using D100 first and then F5 can be helpful). The measurements I test using an ohm meter are often off compared to specs. The Vertical Linearity range seems to only be about 2K instead of 3K as listed. It also is quite stubborn to turn. So I will try spraying each of them when I receive the DeoxIt. Might some of these controls simply be bad and can be swapped out for a similar spec'd NOS replacement?

Dim Bulb Tester - Finally, I built a dim bulb tester but currently only have a 100W or less bulb to test in it. I have read seemingly clashing explanations with some suggesting to use a bulb only slightly higher wattage than the device draw, and others saying to use as high wattage as possible (e.g., 250W+). The 100W lights up and remains lit (but not full bright) when I try running the TV through it, but again the TV draws 182W so I believe this is expected and not indicative of a short (edit - well even after leaving the TV on several minutes only a couple of the tubes started glowing dimly, the light bulb remains quite lit hmm). The tubes never lit up while running it through the dim bulb but I also did not let it run for more than 30 seconds in this manner.

Next Steps - I have one final canned electrolytic to redo. All of the standard paper/plastic caps should be replaced at this point. I also replaced a resistor or two but have just began testing most of them; a few of the 2W ones I don't yet have replacements for but everything else I do so can replace as needed. I'll be cleaning the pots and plan to also clean the tube contacts which I did not do previously. I can also start checking resistance etc. of various controls and points to see if they are within spec, which should be easier now that I can operate it at 117V precisely through variac.


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Last edited by MattPilz on Sep Tue 10, 2019 4:17 am, edited 2 times in total.
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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 3:54 am 
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MattPilz wrote:
I have ordered the trio of CAIG DeoxIt (Fader/F5, D5, D100S) to attempt simple cleaning of them; I'll stick with F5 designed for pots although I've read using D100 first and then F5 can be helpful). The measurements I test using an ohm meter are often off compared to specs. The Vertical Linearity range seems to only be about 2K instead of 3K as listed. It also is quite stubborn to turn. So I will try spraying each of them when I receive the DeoxIt.

When I was reading through the CAIG web site, I came to the conclusion that Fader/F5 was designed for wire wound pots. And that D5 was to be used on carbon pots such as would be used for the Vertical controls. If Fader/F5 contains an abrasive or contains a thick lubricant than you should not use it on carbon pots.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 3:09 pm 
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Don't get hung up on the power draw of the set. Those numbers are more of a guide for the amount of things someone could expect to power from one outlet, extension cord, house breaker, etc.

You can use a meter (analog would be best) to look at the way the resistance varies as you move the pots.
As you turn the shaft an analog meter's pointer will move smoothly. If the pointer jumps around then the pot is dirty or bad. If cleaning the pot does not fix a pot in most instances a replacement can be found. They are getting a bit harder to find however.

You are kind of way past using a Dim-Bulb on this set. Dim-Bulbs are a gross check for problems. If you use a bulb wattage roughly equal to the set's normal wattage the set will see only about half its normal input voltage and so won't be able to work. The brightness of the bulb is a rough indicator of the set's current draw. If the bulb is at full brightness then something major is wrong with the set, but that is about all you can determine.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 3:16 pm 
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Only computer GUIs scroll... TV vertical circuits roll, and horizontal rolls, tears or is off frequency depending on how bad it is out of sync.

Vertical roll is one of 2 things vertical stage or sync separator stage. If all caps and resistors in the vertical are new and the transformer (s) and tube(s) test good then it is probably in the sync. You know it is in the sync if the horizontal rolls or the horizontal locking range is too small. Regard all components linking the vertical to the sync separator that aren't shared by the horizontal sync link as part of the vertical...

One other thing that can mess up sync is miss adjusted AGC. AGC stands for automatic gain control...it measures the detected video level (either as an average over several frames, or in the case of keyed AGC every horizontal sync pulse) and adjusts the amplification factor of the tuner and IF to hold detected video peak amplitude constant... An AGC control will have a range from no signal , increasing to a weak possibly unsynchronized signal, to a range of seemingly normal picture to a range where contrast is rediculously excessive and both deflection axes roll. Proper setting is to crank it till it hits the overcontrast roll point and back it down from there till the picture normalizes, and go a bit past that into the normal zone.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 4:29 pm 
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Tom Schulz wrote:
When I was reading through the CAIG web site, I came to the conclusion that Fader/F5 was designed for wire wound pots. And that D5 was to be used on carbon pots such as would be used for the Vertical controls. If Fader/F5 contains an abrasive or contains a thick lubricant than you should not use it on carbon pots.


I'm pretty sure you have that backwards. D5 is for cleaning metal contacts like in switches. It can eat up the carbon tracks in pots.

F5 is for potentiometers and other sliding contact controls.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 5:18 pm 
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bandersen wrote:
Tom Schulz wrote:
When I was reading through the CAIG web site, I came to the conclusion that Fader/F5 was designed for wire wound pots. And that D5 was to be used on carbon pots such as would be used for the Vertical controls. If Fader/F5 contains an abrasive or contains a thick lubricant than you should not use it on carbon pots.


I'm pretty sure you have that backwards. D5 is for cleaning metal contacts like in switches. It can eat up the carbon tracks in pots.

F5 is for potentiometers and other sliding contact controls.

I don't think that I have it backwards. A discussion about this came up awhile back and I went through Caig's web site quite carefully. I have been using D5 on carbon pots for quite awhile and have had no damage. Perhaps MattPilz can spray some F5 on some metal or plastic surface and tell me if it is abrasive or thick.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Tue 10, 2019 6:53 pm 
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I have both and can do as you ask tonight. I've had the solvents in D5 dissolve the carbon right off vintage TV controls.

Here's info on the D series: "Contact cleaner dissolves oxides and sulfides that form on metal surfaces" - https://caig.com/deoxit-d-series/

Here's info on the F series: "Formulated for Conductive Plastics & Carbon-Based Controls" - https://caig.com/fader-f-series/


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Wed 11, 2019 7:14 am 
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Here are the full specs and comparisons of DeoxIT F5 (and F6). It does mention several times that F5 is to be used for carbon controls/faders. My understanding is that since D5 contains 20% active cleaning solution and is meant for removing oxidation especially from metal contacts, that it can be more corrosive.

Tonight I tracked down the reasoning behind an extra resistor that was on the back of the sync board but not in the schematic. It was a 15MΩ and was running parallel to an identical one on the opposite side, where originally an 8.2MΩ was meant to be. It seems at one point the 8.2M went bad and was substituted with two 15MΩ which yielded close to the needed value but still a bit lower. I also replaced one of the three remaining electrolytics in the second can.

Quote:
the old crt is pretty much dead so you could try the rejuvinate function on your crt tester on the old crt. you dont have much to loose. this could improve it for awhile or kill it outright.


One of those two possibilities indeed occurred :lol:. I attempted this last night, iteratively going through all three rejuvenation steps as described in the manual. Each time the gauge would only budge millimeters up from the extreme end of "bad". Tonight I hooked the chassis back up and the CRT neck lit up brighter than ever instantly but before any image appeared it burned out entirely. So... Really the tube seemed very bad from the beginning. I guess my next process will be swapping it with the new one and hoping for the best from here on out. After I swap it I'll just have to be extra careful... Alternatively could look for one of the miniature test tubes to continue my tests that way.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Wed 11, 2019 4:02 pm 
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That seems a bit odd. The usual mode of failure is that the cathode material becomes exhausted or comes loose.
Rejuvenation processes often use a higher heater voltage to attempt to bring fresh material to the cathode surface. They also apply higher than normal voltages to the gun elements. The danger with this is that there could be no better material left. I suppose the higher heater voltage could have damaged the heater, maybe creating a short, so when you put it back in the set the heater blew.
Double check the heater voltage at the CRT socket before you connect it to the new tube. Maybe something caused the heater voltage to be too high in the set.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Wed 11, 2019 4:28 pm 
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To check heater voltage do I simply probe the two heater pins of CRT plug? E.g., pins 1 and 12 in this schematic.

I had been wanting to check voltage from anode lead but understand there may be dangers with that without using a high voltage probe.

Wish I had tested immediately after the rejuvenation process to verify but if it was something else that caused it at least I know that it is only one of two things I altered since.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Wed 11, 2019 6:17 pm 
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MattPilz wrote:
To check heater voltage do I simply probe the two heater pins of CRT plug? E.g., pins 1 and 12 in this schematic.
e.

Yup.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 1:06 am 
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Tube Specs:

Heater Voltage: 6.3
Heater Amps: 0.6

Measured Specs:

Heater Voltage: 6.33
Heater Amps: 0.72

Assuming there is room for this tiny difference, I think the readings are well within normal range. I have ordered a high voltage test probe so when/if I need to verify voltage from the anode/flyback I should be able to soon.

I've now read elsewhere on these forums some more of the risks of using rejuvenators especially on sets that were already using brighteners for a long time. I guess trying to heat it at the higher volts as part of that process may have sent it over the top when connected. It really was in rough shape so I was fine trying it out as a last ditch effort to improve anything (knowing I have a NOS tube still waiting).

Now that I have a better assortment of multimeter/testing equipment I will also be reviewing the new flyback for proper readings as well as the different tubes compared to the spec, and may also redo the solder points by flyback to ensure they are smooth to help eliminate any arcing.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 2:13 am 
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Since the old CRT heater seemed to burn out before your eyes I just wanted you to be sure it wasn't because of a problem that developed in the set.
The set seems to be functioning fairly well, I don't think there is anything major wrong at this point. If you are getting a recognizable picture, most of the TV systems are functional.
I really think you should finish the re-cap and go from there. There are probably some resistors that have drifted and I see some networks (couplates) in the sync path. Sometimes the couplates cause problems. There is also a "Noise Gate Control" that can effect the sync. I can't tell from the parts list whether there are any mica caps in the sweep sections, but it sometimes happens that they fail.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 3:29 am 
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MattPilz wrote:
Measured Specs:

Heater Voltage: 6.33
Heater Amps: 0.72

If the current is about right, can the heater really be burnt out?

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 3:37 am 
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MattPilz wrote:
Here are the full specs and comparisons of DeoxIT F5 (and F6). It does mention several times that F5 is to be used for carbon controls/faders. My understanding is that since D5 contains 20% active cleaning solution and is meant for removing oxidation especially from metal contacts, that it can be more corrosive.

Well, a pot has metal contacts. And when a pot is acting erratic, I have always thought that it was the metal contacts that are the problem. From that web page it looks like F5 has no cleaning action and that Caig is saying to first clean the pot with D5 and then lubricate with F5.
I will have to get some F5 and try that on the volume pot on my Stereo that I have had to clean every year for the last 20 years.

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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 8:54 am 
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I managed to swap picture tubes tonight but won't be hooking up the chassis until I first do so in a test tube (en route). I made a glaring oversight when I ordered the replacement...

The original schematic-referenced picture tube for this chassis was 21ALP4A (Spec Sheet)... This was the basis I compared the replacement to without carefully reviewing dimensions or other properties. The replacement is a 21ATP4 (Spec Sheet) Both of these measure 20 3/8" long and have a 7 11/16" neck.

However, the CRT that was actually in it was a 21CBP4A - which lists as a replacement for the others. But the 21CBP4A, including neck, is two inches shorter. So the new tube ends up sticking a couple inches out beyond the back of the cabinet which seems certainly risky. Assuming all works on it I will consider building a custom back for it. But I guess I should had better reviewed data sheets before ordering albeit the options these days are scant regardless.

I did run CRT tester emissions on it and it tested good again but was oddly much lower than the first time I ran it. Perhaps I did not have it running long enough or the tester itself is being odd so I probably will refrain from using it again until I check further into it. In any case the new CRT is installed into the cabinet but has not been hooked to the chassis, I will try that in a week or two after finishing the capacitors and resistor checks as well as tested on another CRT.


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 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Thu 12, 2019 4:01 pm 
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Tom Schulz wrote:
MattPilz wrote:
Measured Specs:

Heater Voltage: 6.33
Heater Amps: 0.72

If the current is about right, can the heater really be burnt out?

I wondered about the current reading. I was more interested in the voltage of course.
Strange, I don't know how the current was measured. I don't think he has a clip on current probe.

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