Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Aug Wed 12, 2020 4:11 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 312 posts ]  Go to page Previous  1 ... 7, 8, 9, 10, 11, 12, 13 ... 16  Next
Author Message
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sat 21, 2019 2:19 am 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
MattPilz wrote:
The 2077B is definitely going to need some work. I tried turning it on last night and there is one resistor, I believe, that almost immediately lit up orange from overheating and billows of smoke came out. After unplugging, it could still be heard sizzling for some time.

It also has a lot of electrolytics in it, more than the admiral itself. I have the part list and schematic so will review it this evening and should be able to replace some of them over the weekend but others I dont have on hand. I can use it as a time to experiment with my capacitor tester too.

I realize the one tool still lacking from my arsenal is a vacuum tube checker. This becomes annoying especially when I get new tube based devices and have no way of checking the tubes at home. So I may start looking for one although they do get costly on ebay often especially one that tests more than just good or bad.

Another project. I usually expect anything older than 1980 to require new electrolytics for a start.
Ebay is my last resort. Check out Craig's list or the classified area here.
You do not need a Hickok. B&K, Heathkit, EICO, Jackson, Superior are all good. You should be able to find something for less than $ 100. Be aware that some testers use tubes themselves and some require special things like specially tested tubes to calibrate the tester.

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sat 21, 2019 2:55 am 
Member

Joined: Jun Thu 25, 2015 3:21 am
Posts: 1352
matt pilz i have an extra hickok 532 mutual conductance tube tester if you want it it's yours for the cost of shipping. it does need a bit of work. there is a bad cap and possibly a bad resistor for the line adjust circuit. if your interested when i have time i will check the schematic so i can tell you which one it is.

your teleohmike wont need much work. change any paper caps with percision caps of the same value. this is percision instrument dont change values of the caps. i believe the replacements should have 1 percent tollerance. not sure if they use electrolytic caps in that or not. i dont think my teleohmike to3 does but it has been a long time since i took it apart. indeed checking caps in your television analyst will be a good way to get your feet wet using ur cap tester. as a general rule i check all new caps i buy before putting them in the circuit. maybe not likely but you can find a bad cap new from the factory on occasion.

if you are interested i have a b&k vtvm i was going to fix before i got my hickok 209A. you can have it for the cost of shipping. it does work somewhat but should be checked out and calabrated before being put into service. the 209A has a larger meater so it is much better for me with my vision problems these days so i will never fix the B&K for myself.

once you get it working right you will find your television analyst to be invaluable in troubleshooting televisions quickly and efficiently. an overheating resistor sounds to me like something that resistor is connected to is drawing to much current. check the components in the circuit that resistor is in and change the resistor. overheating can cause the value of the resistor to change. do not power it up till you locate and change the faulty component or components.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sat 21, 2019 9:12 am 
Member

Joined: Sep Thu 20, 2018 8:53 pm
Posts: 111
@Thomas that all sounds great! I will send you a PM, I appreciate your generosity in helping as I continue to get my feet wet in this hobby (honestly up to my knees by this point :lol:).

For reference the TO-5 has the following capacitor styles, mostly a lot of molded paper bumble bee style but there are a couple electrolytics as well. I have an alright collection of 400V and 630V capacitors but will have to verify tolerance and specs to see if I have exact matches. The electrolytics can be more of a pain to find but I will order the necessary ones this weekend.

  • 4x - Molded Paper .02uF ±10% 600V (C1, C2, C5, C11)
  • 1x - Molded Paper .02uF ±2% 600V (C8)
  • 1x - Molded Paper 2uF ±2% 400V (C9) [manual note: Two matched in parallel to value]
  • 1x - Molded Paper .005uF ±20% 400V (C12)
  • 2x - Dry Electrolytic 12uF 450V (C3, C4)
  • 1x - Silver Mica 180pF ±5% 500V (C6)
  • 2x - Adjustable Ceramic Trimmer 4-30pF (C7, C10)


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sun 22, 2019 12:38 am 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
EDIT: Do not forget that if you want to post about fixing the test equipment that those should be in separate threads.

_________________
Tim
It's not the Destination, It's the Journey.


Last edited by Notimetolooz on Sep Sun 29, 2019 5:36 pm, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sun 29, 2019 4:41 am 
Member

Joined: Sep Thu 20, 2018 8:53 pm
Posts: 111
Updates...

B&K 1077B Television Analyst - I replaced the electrolytics that I had on hand which included those surrounding the burned up resistor circuit (which I replaced as well). To my surprise this appears to have fixed the 1077B nicely! The picture tube is fully operational and everything seems to be functioning as expected at least when testing RF output, I've put 1-2 hours of testing into it but still haven't gone beyond the simple RF test. I also have not yet adjusted the B&K picture itself, centering etc.

Attachment:
1077b.jpg
1077b.jpg [ 221.99 KiB | Viewed 1192 times ]


Tektronix 475 Oscilliscope - I also tested the oscilliscope and verified it is functional but haven't done anything beyond the internal test probe signal. I'm not very clear on actually using this to troubleshoot the Admiral yet; I find good introductory videos but not really pertaining to electronic troubleshooting and most videos rely on signal generators that I do not have a need for.

Sylvania 8XP4 Test Tube - This is still working great. I now extended the speaker wiring from the Admiral cabinet so that I can reach the chassis without having to lug the entire cabinet over each time. This makes it a cleaner and safer environment especially now that the new picture tube is mounted into the cabinet. (The original removal instructions said the speaker was mounted by just two screws, but mine instead has four nails that appear driven in from the front of the cabinet undernath the front grill and I really don't know how I'd get it out without damaging the cabinet so this works just as well.)

Vertical Chop-Off - The vertical cut-off issue still persists on the test tube as well. If I move the yoke away from the tube slightly to see the more circular projection boundaries, the bottom part is still always cut. Still feels like a centering issue where if the entire vertical could be shifted down it could resolve this (but I also have the slow scroll issue, yet). I can try to post a picture of how this looks later, but here is how it looks with the yoke flush against the tube as intended. If I adjust vertical hold, vertical linearity, vertical height I can increase or decrease this bottom chunk to an extent but it never goes away.

Attachment:
1569726627638.JPEG
1569726627638.JPEG [ 203.46 KiB | Viewed 1192 times ]


Centering Ring - I still have that cardboard centering ring but am unsure if I'm supposed to be using it with the test tube or precisely how significant it is to use at all. I am seeking more information about the uses and optimal configuration of this, assuming the one I have is good yet.

Tube Socket Readings - I haven't yet had a chance to compare tube pin readings to the schematic. However, I did quickly try checking the Video Output Sync Phase Inverter and at least three of the pins were drastically off. Pin 3 was clocked in at 70K+ (spec: 10K), pin 8 only read 55 (spec: 27.6K) and pin 9 was 2M (spec: 24.3K)... There's a chance I was not testing correctly but the other pins on it were close to spec. I was testing by having one probe on ground and one on the pin.

---

EDIT - More Progress

After I posted, I hooked the 1077B up to the Admiral for the first time. I found that having the test pattern really helped me to understand the relation and affects of adjusting linearity/height and other controls in real-time. I also was able to more easily experiment with the centering behind the yoke and with that was able to shift the vertical center downward which helped eliminate the cut-off issue. Also I have found that since replacing the caps and such that cut-off area does not increase with time, and this may well be purely a centering issue at this point and one easily obscured when in the real tube and cabinet.

Further, I have found that the vertical roll is impacted when adjusting the brightness and/or contrast controls. I can cause the scroll to slowly go upwards or downwards by simply increasing or decreasing the contrast. Does that make much sense? If I crank up the brightness all the way then the scrolling pretty well stops outright and by adjusting contrast/brightness I can manage to get a stable image at least on the 1077. When I hook it to a DVD player or game system, the same observation is true in that contrast/brightness can affect the vertical roll but it seems these other devices always have a slight drift/bobble to them but perhaps this is something that just needs more fine-tuning and experimentation.

There is still the buzz coming from the speaker even at 0 volume but this is something barely audible when volume is set to a normal level. I will go over the audio board again to review the changes I made and see if anything stands out as being incorrect. I feel like this buzzing noise occurred after I had made some changes but it is entirely possible it always existed as I did not have it on much prior to that.

QUESTION: On the sound board there is a "Ratio Detector Secondary" and in the servicing guide it is noted: "To eliminate 'Sound IF Detector Buzz' adjust the ratio detector secondary (L21) located on rear of chassis." Is this supposed to have an adjustment screw like the horiz. osc.? It appears very similar to that with Ferrite (?) inside the tube but I cannot access it and see no other means of adjusting.

Attachment:
1569744753923 (Custom).JPEG
1569744753923 (Custom).JPEG [ 135.26 KiB | Viewed 1181 times ]


All-in-all, I think the repair is very nearing completion! I was never aiming for perfection but was just hoping to get some sort of picture out of this which I admit seemed like a long-shot when I first started given all the issues and problems. And now with some adjusting here are images just taken from the test tube (1077B, SNES, DVD).

Attachment:
File comment: 1077B
1 (Custom).JPEG
1 (Custom).JPEG [ 164.4 KiB | Viewed 1181 times ]


Attachment:
File comment: SNES
2 (Custom).JPEG
2 (Custom).JPEG [ 178.02 KiB | Viewed 1181 times ]


Attachment:
File comment: DVD 1
3 (Custom).JPEG
3 (Custom).JPEG [ 153.34 KiB | Viewed 1181 times ]


Attachment:
File comment: DVD 2
4 (Custom).JPEG
4 (Custom).JPEG [ 182.75 KiB | Viewed 1181 times ]


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sun 29, 2019 5:55 pm 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
Good news about the 1077. However there may be some other small issues to correct, later.

The GE set show something that is very typical for a lot of sets. The image shows "overscan", meaning you are missing some of the picture around the edges. It was common for manufactures to adjust TVs this way. The picture size can change when the supply voltage changes, because the power supplies are not well regulated,
so by adjusting it to overscan you don't see a black edge around the picture when the voltage goes low. People would think that they are missing part of the picture if they see black around the image when in reality they are missing the edges of the image normally. (Pet peeve of mine.) Now with flat digital screens there is no overscan
.
Scope, in effect you now have a signal generator with the 1077. To make it more usable with the scope you could make a slide with regular vertical stripes or similar.

Don't forget the 8XP4 is a "test" CRT, it has some differences from the normal CRT.

You need to get a non-metalic tuning wand, (dittle stick, tweeker, etc,), with a hex end to adjust many coils.
DO NOT use a metal allen wrench. Also do not twist too hard, the ferrite core is brittle, sometimes it is stuck with wax.

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Sep Sun 29, 2019 11:28 pm 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
MattPilz wrote:
Updates...
SNIP

Further, I have found that the vertical roll is impacted when adjusting the brightness and/or contrast controls. I can cause the scroll to slowly go upwards or downwards by simply increasing or decreasing the contrast. Does that make much sense? If I crank up the brightness all the way then the scrolling pretty well stops outright and by adjusting contrast/brightness I can manage to get a stable image at least on the 1077. When I hook it to a DVD player or game system, the same observation is true in that contrast/brightness can affect the vertical roll but it seems these other devices always have a slight drift/bobble to them but perhaps this is something that just needs more fine-tuning and experimentation.

There is still the buzz coming from the speaker even at 0 volume but this is something barely audible when volume is set to a normal level. I will go over the audio board again to review the changes I made and see if anything stands out as being incorrect. I feel like this buzzing noise occurred after I had made some changes but it is entirely possible it always existed as I did not have it on much prior to that.

QUESTION: On the sound board there is a "Ratio Detector Secondary" and in the servicing guide it is noted: "To eliminate 'Sound IF Detector Buzz' adjust the ratio detector secondary (L21) located on rear of chassis." Is this supposed to have an adjustment screw like the horiz. osc.? It appears very similar to that with Ferrite (?) inside the tube but I cannot access it and see no other means of adjusting.

Attachment:
1569744753923 (Custom).JPEG


On some sets the sync signal is taken after the contrast control, so changing the contrast varies the sync amplitude, however a properly working sync circuit would tolerate this. I'll check the schematic and see if this is the case. Another possibility is that the varying video amplitude (as you change the contrast) is varying the load on the local power supply and effecting the sync circuit.
If the hum is there when you turn the volume down all the way, (and you can carve this in stone), the hum is getting into the audio circuit between the volume control and the speaker. This applies to radios also. The hum might come from the power supply that feeds the audio. The buzz that the audio detector adjustment may vary is the buzz from the 60 Hz vertical sync pulses. But the detector is before the volume control so that is not the source of the problem in this case.
Getting an alignment tool with a hex end is a good idea anyway. Tool #8606 in this list of this link is what you would need. https://www.tubesandmore.com/products/a ... tronics-cb

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 8:10 am 
Member

Joined: Sep Thu 20, 2018 8:53 pm
Posts: 111
Tube Socket Cleaning and Resistance Checks

I removed all of the tubes and cleaned every socket pin hole using a small amount of D5 on dental floss brushes, and brushed the tube leads as well. I let this dry for a day before messing too much with it. I also cleaned around everything with air. I didn't notice any visual changes but at least I know the contacts have been cleaned.

I also got around to testing the resistance of each pin according to what SAMs lists. The vast majority of them tested within the ballpark of their intended amount. My earlier concerns were due to an oversight in that some of the pins I had tested needed to be done at other pins instead of ground.

However, there were six tubes that had 1-2 pins completely out of spec or not readable at all. These six include:

  • V1 RF Amplifier 6BC8 | Pin 6 = 223Ω (SPEC: 3.3KΩ) | Pin 7 = 404K (SPEC: 350K)
  • V11 Audio Output 6BF5 | Pin 7 = INF/NC (SPEC: 850K)
  • V13 Vert. Mult. - Vert. Output 6S4A | Pin 3 = INF/NC (SPEC: 1.5MΩ) | Pin 9 = 4KΩ (SPEC: 10KΩ)
  • V17 Damper 6AU4GTA | Pin 3 = INF/NC (SPEC: 400KΩ)
  • V19 LV Rectifier 5U4GB | Pin 4 = INF/NC (SPEC: 23Ω) | Pin 6 = INF/NC (SPEC: 25Ω)
  • V20 Cathode-Ray Tube 21ALP4A | Pin 4 = 2.93K (SPEC: 9K) | PIN 11 = 210K (SPEC: 170K)

I am hoping some of these differences are superficial. For instance, V11 Pin 7 actually does not connect to anything on the back--no wiring or trace solder--so I would entirely expect it to not read any resistance. Admittedly I have not studied the schematics as I just got the readings done tonight but I also am not well-versed at deciphering the tube part of schematics yet.

Attached are cropped sections of the schematic for each of the above six tubes. Also a full high resolution schematic with these tube areas highlight can be found at this link. I have not done a lot with actual resistor checking yet, and only replaced a single resistor that I recall.

QUESTION: Do any of these stand out as substantial? Again the video does render fine now (see below) except for the strange vertical sync issue and audio buzzing notable if at low or no volume.

---

Video Demonstration of Vertical Scroll

In my last update I noted the correlation between vertical and contrast/brightness settings. Well here is a clear video demonstration of its oddities. You can see a stable image but, depending on the contents ON the screen (not adjusting any controls), the rolling begins or ends. This is playing Super Mario Bros. but note when I go down the pipe which darkens the screen and a transition happens, suddenly it starts rolling. This is using a new 75 to 300 ohm transformer. You can see the artifacts on the screen as this occurs, even more at end of level and into level 2.

https://youtu.be/hzKTGBbYuQw

After seeing this video are there any clearer guesses as to the problem? I know that on other vintage sets I've used from the 60s-70s you can see when the vertical hold 'snaps' into place, but on this one it is a matter of meticulous adjusting to get it steady.

---

B+ Voltage?

It seems like B+ voltage is mentioned in many threads relating to vintage TV repair. I see many videos on YouTube of checking this on arcade CRTs and so on. I've watched and read some guides that try to explain this, but can't figure out how I would check this on the Admiral. Does the schematic contain the test points for it and I just overlooked it? My original naive interpretation was that the B+ voltage meant the anode lead but obviously that seems incorrect.


Attachments:
File comment: V1
V1 (Custom).jpg
V1 (Custom).jpg [ 166.56 KiB | Viewed 1136 times ]
File comment: V11
V11 (Custom).jpg
V11 (Custom).jpg [ 130.81 KiB | Viewed 1136 times ]
File comment: V13
V13 (Custom).jpg
V13 (Custom).jpg [ 209.79 KiB | Viewed 1136 times ]
File comment: V17
V17 (Custom).jpg
V17 (Custom).jpg [ 164.91 KiB | Viewed 1136 times ]
File comment: V19
V19 (Custom).jpg
V19 (Custom).jpg [ 126.31 KiB | Viewed 1136 times ]
File comment: V20
V20 (Custom).jpg
V20 (Custom).jpg [ 161.3 KiB | Viewed 1136 times ]
File comment: Resistance Measurement Original Specs
Specs (Custom).JPG
Specs (Custom).JPG [ 344.54 KiB | Viewed 1136 times ]
File comment: Tube Placement
Tubes (Custom).JPG
Tubes (Custom).JPG [ 126.28 KiB | Viewed 1136 times ]
Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 3:34 pm 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
Never rains but it pours!
Much of the differences are probably due to simple things.
V11 and V13 pin 3 are probably because they involve internal connections inside the tubes to other pins, I'm guessing you took these reading without the tubes plugged in. On the other hand some brands (or versions) of tubes did not make these internal connections.
V19 is because your chassis probably grounds the power transformer through the yoke, I'm guessing the yoke isn't plugged in.
V20 pin 11 is off because the setting of the brightness effects the reading.
V1 readings may indicate something wrong, like leaky caps.
V13 and V17 I don't see enough of the schematic, I'll take a look at the whole schematic later.
V20 pin 4 isn't shown to be connected to anything on the schematic, I wouldn't think there was even a wire up to it.
You have to plug everything including the tubes when you take these resistance readings.

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 3:49 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 265
Location: Arlington, TX, USA
I can't see it in the schematic pictures, but many tube sets power the vertical oscillator from a boosted B+ supply derived from the horizontal output circuit and if it has lot of variation with HV current (and picture brightness) it could throw the oscillator off frequency. Just one more thing to check for.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 3:50 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 1309
Location: Pewaukee, WI
See the 265V source on L23 off the power rectifier that is a 265V B+ source. There may be other voltage B+ sources derrived from the audio output cathode and or flyback.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 6:32 pm 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
I looked at the video and noticed a few things. The brightness is too high. The black bars separating the image frames visible when the picture rolls should be completely black. Remember the old TV screens were not as bright as the modern ones.
The normal CRT may look different and require different contrast and brightness settings.
The sharp edges on video games of this type look like pulse edges to the TV circuits and it is easy for the circuits to confuse these with the sync pulses. The sync separator and similar circuits have to be working well so the image content does not interfere. Also the sync pulses from the game may not have the pulse shape that is standard on the normal vintage analog TV signal, it would work well with the TVs made at the time however.
Does the SAMS include info on adjusting the "Noise Gate Control"? It may effect the sync stability.
Also there are several "couplates" in this set that may need to be replaced with discrete components.
C59,R68 area and M7.

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Tue 01, 2019 6:49 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 265
Location: Arlington, TX, USA
Video looks like it's AC coupled and no DC restoration, so black level is going to vary with picture content. Unfortunately this is common on tube era B&W sets. The brightness control may or may not be too high in this case, there really is no objective way to set it without a solid DC video level.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 6:13 am 
Member

Joined: Jun Thu 25, 2015 3:21 am
Posts: 1352
without studying the schematic i have a few thoughts on these results. if memory serves the damper tube is also involved in the boost voltage for the vertical section. if the boost voltage is low that can be a problem.

open circuit to the pin on the vertical tube also is bad.

if i was you i would start checking individual components connected to the pin on the vertical tube and the damper tube. lift one leg of each component in that circuit and test it. once this is corrected then i bet your vertical problems will be gone.

to measure b+ in your particular set put the negative lead on the chassis the positive lead on the positive lead of the cap. the section of the schematic you posted says it should be 260 volts.

some equiptment has the b- isolated from chassis ground so you would have to put the negative lead on the b- bus.

also in your set b+ can be tested from the plate or screen of each tube to chasis ground or to the b- bus if b- is isolated from the chassis. your set isnt isolating b- from the chassis. one quick way to tell is if b- was isolated from the chassis the origional cans would have a cardboard cover over them and the body of the can would be insulated from the chassis.

when making resistance readings or voltage readings the tube must be plugged in to the set and readings taken from the bottom terminals. alternatively you can plug in a tube test socket and plug the tube into that. a test socket has contacts on it connected to the different tube pins so readings can be taken from the top of the chassis.

personally i consider pc boards to be the devil. point to point wiring is much easier to troubleshoot. just my opinion dont take it as gospel.

pick one problem you want to solve and get that fixed then move on to the other. i would start with your vertical issue since that is most noticable. then move on to the audio buzz. if indeed the boost voltage is low to the vertical section or the b+ is low fixing that may go a long way to fixing the vertical issue.

there was one make of tv that were known to have buzz in the audio ratio detector circuit. i believe it was zenith if memory serves. they went so far as to include a buzz control in the audio circuit. i wonder if your audio buzz is something like that. just the way that tv is. that being said i didnt hear any buzz in your video on you tube. i am not at all familliar with what the video game should look like so i wont comment.

one thing i did notice is your picture seems centered correctly. the yoke should be all the way forward on the crt neck and fill out the screen if it doesnt and cant be adjusted with the correct controls there is a problem in your case with the vertical circuit


Last edited by thomas13202 on Oct Wed 02, 2019 7:32 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 7:13 am 
Member

Joined: May Sun 07, 2017 11:35 am
Posts: 970
Location: Belrose, NSW, Australia
Squash at the bottom of the raster was common with Admirals of that vintage. Back in the day, after changing out the paper caps, we'd simply bridge C2 (cathode of the vertical output tube) with 100uF 63v. Always fixed it. I suspect the ESR of the 20uF can was too high. Plus, our vertical freq was 50Hz, not 60Hz, so the effect was worse.

_________________
Wax, paper, bitumen, cotton, high voltages - what could possibly go wrong?


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 3:07 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 265
Location: Arlington, TX, USA
The audio detector isn't shown above, but I see a 6AV6 audio amplifier which leads me to believe this set uses a ratio detector. The gated beam detectors used by Zenith (and others, usually a 6BN6) gave a signal high enough to drive the audio output tube directly. If the audio detector (either type) isn't aligned for best AM rejection then buzz is going to be a problem, and can still come through even with perfect alignment.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 4:47 pm 
Member
User avatar

Joined: Nov Thu 11, 2010 6:03 pm
Posts: 1309
Location: Pewaukee, WI
Erich Loepke wrote:
The audio detector isn't shown above, but I see a 6AV6 audio amplifier which leads me to believe this set uses a ratio detector. The gated beam detectors used by Zenith (and others, usually a 6BN6) gave a signal high enough to drive the audio output tube directly. If the audio detector (either type) isn't aligned for best AM rejection then buzz is going to be a problem, and can still come through even with perfect alignment.

When it buzz goes through a properly aligned set it is usually caused by a cheap RF modulator.... usually the same carrier gets both FM and AM modulated for audio and video respectively. If the AM video carrier overmodulates it inverts the polarity of the carrier or more precisely shifts (modulates) it's phase 180 degrees. Phase modulation (PM) and Frequency modulation (FM) are basically the same effect (each one causes the other...the defining factor is which one carried the information directly). PM and FM transmitters and recievers can easily send and detect each other's signals and all one needs to do is apply a mathematical derrivitave or integral function to the modulation info at the transmitter or reciever....to change the transmission mode or effective reciever mode.
Since the AM overmodulation generates video derrived PM noise in the carrier and video has a 60Hz vertical rate you will get video dependent buzz.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 5:28 pm 
Member

Joined: May Thu 14, 2015 4:15 pm
Posts: 2348
Location: Dallas, TX
I think some contributors here have missed a few points.
He said that the hum was there with the volume turned down, that means it is originating the the audio output stage. "Buzz" isn't the problem really.
The TV plays. However he got an an infinite resistance measuring some pins to ground. These include the plates of the LV Rectifier and Damper cathode. The set wouldn't work with those problems. He is getting infinite resistance on some pins on the Vertical Output and Audio Output. Those pins have connections to other pins through internal tube connections. If you put the clues together it is pretty obvious that he made the measurements with the yoke and tubes unplugged.
The problem with the bottom of the image cutoff, vertical roll and maybe audio hum remain. Vintage equipment frequently has more hum than modern solid state items.

_________________
Tim
It's not the Destination, It's the Journey.


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Wed 02, 2019 10:54 pm 
Member
User avatar

Joined: Aug Thu 12, 2010 6:25 pm
Posts: 382
Location: Durham, NC
I noticed that the vertical roll (loss of sync) occurs with signals of low APL (Average Picture Level). Low APL occurs when the picture is predominantly dark, as when Mario goes down the tube, or between scenes. The sync separator in many sets is quite simple and prone to being affected by APL when bias is incorrect (often the grid resistor has changed in value) or plate voltage is wrong.

_________________
Mark Nelson
A collector of TV signal boosters and UHF converters -- God help me!
tv-boxes.com


Top
 Profile  
 
 Post subject: Re: 1956 Admiral Console - Some general technical questions
PostPosted: Oct Thu 03, 2019 5:41 am 
Member

Joined: Sep Thu 20, 2018 8:53 pm
Posts: 111
Thank you all for the many suggestions, it is a lot to review. A few updates and clarifications...

@Notimetolooz was correct, when I did the initial resistance checks I had the tubes out. I rechecked the most obviously flawed readings and it cleared up some of them. The Vertical Output tube (V13) still only gets a 4K instead of 10K reading on the 9th pin and I still wasn't able to get a good reading on the damper 3rd pin. The CRT socket (pin 10--not pin 4) still also reads 30% what it should.

I tried swapping some of the tubes with the originals including V13 just to verify they all are working equally. When I remove V11 all audio output ceases including the buzzing. The audio issue is really not of concern but I will still go over the components off of V11 and see if anything is really abnormal. I did replace all the caps on the audio board so will double check their specs (I have a vintage capacitor checker but it needs help and I haven't gotten to that yet).

Also the cut-off at bottom seems to have resolved itself when checking on the test tube with the centering on and better collaborated.

So really the only major problem with the set yet is the vertical syncing. I will attempt to trace and review the adjacent components to V13 (and possibly V6/V7 as well as these three pertain to vertical sync). If I learn more about the 1077 and how to perform its tests I can perhaps use that as well to help diagnose.

Quote:
I noticed that the vertical roll (loss of sync) occurs with signals of low APL (Average Picture Level).

Most definitely. Whenever the on-screen image gets dark the scrolling and issues become really apparent and alters the image.


Top
 Profile  
 
Post New Topic Post Reply  [ 312 posts ]  Moderators: 7jp4-guy, Mr. Detrola Go to page Previous  1 ... 7, 8, 9, 10, 11, 12, 13 ... 16  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 6 guests



Search for:
Jump to:  


































-->


Privacy Policy :: Powered by phpBB