Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Early Color Television

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #31  
Old 09-09-2018, 11:07 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,587
Over the years I've had a recurring bad dream where I come close to damaging the neck on the 21AXP22 in my CTC-5. Hopefully I won't have twice as many dreams now!

I was out of town for a few days but spent this rainy afternoon finishing the electolytics then started going section by section through the BB's. I've completed most of the LV, HV & horizontal. I did a brief filament-only power up with the LV rectifiers removed, just to check for any drama (there was none). I may allow myself a full-power up soon. I did goof one thing up today: while moving the chassis around on the bench I put too much pressure on one of the IF cans and bent it right over, snapping a couple wires inside. I couldn't find one end of one of them at all. The good news: it's a common part and a quick check of my big old coil box turned up 3 or 4 exact replacements in a few minutes. Hopefully the pain of having to deal with touching up the alignment will keep me from being so clumsy next time! It is HEAVY and rather awkward.
__________________
Bryan
Reply With Quote
  #32  
Old 09-11-2018, 01:48 PM
Robert Grant's Avatar
Robert Grant Robert Grant is offline
VideoKarma Member
 
Join Date: Feb 2008
Location: Monroe County, MI
Posts: 474
I notice that the fourth photo shows a tag on the chassis: ".75 AMP 250V".

This would be a rarity indeed - a 250V power supply when the only country with a color TV infrastructure was entirely 120V.

Was this built as a demonstration or test set to be used abroad?
Reply With Quote
  #33  
Old 09-11-2018, 02:18 PM
jr_tech's Avatar
jr_tech jr_tech is offline
VideoKarma Member
 
Join Date: Sep 2009
Posts: 3,820
Or perhaps this is just the spec of a fuse in the set?

jr

edit add: Sams shows a 3/4A 250V fuse as "M3", in the 240 Volt supply.

Last edited by jr_tech; 09-11-2018 at 03:51 PM. Reason: add info
Reply With Quote
  #34  
Old 09-11-2018, 03:25 PM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 10,095
Quote:
Originally Posted by Robert Grant View Post
I notice that the fourth photo shows a tag on the chassis: ".75 AMP 250V".

This would be a rarity indeed - a 250V power supply when the only country with a color TV infrastructure was entirely 120V.

Was this built as a demonstration or test set to be used abroad?
Probably a 120V set with a 250V spec fuse. That could be the B+ voltage for a fused B+ line...Or it could be that Philco recognized the voltage spec of a fuse if of little consequence and it is the current rating of the fuse that matters.
__________________
Tom C.

What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4

Reading between the scan lines since the mid 2000's.
Reply With Quote
  #35  
Old 09-11-2018, 11:02 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,587
Funny that fuses would get mentioned-get a load of this:
I tested the fuses and they were all fine, which was encouraging. I did power the set up briefly only to find a light show inside the 5U4-whoops! While studying the schematic I was trying to figure out why no fuses blew. Well...somebody long, long ago (they were covered with a thick layer of dust) replaced 2 of the three with 2 amp fuses and the third with 1.5 amp! Yep, well, think of the cold, hard cash they saved on all those fuses they once had to buy!

I have a handy dandy Sencore "Fuse Safe" circuit tester which clips in place of a fuse & has a meter to test current draw. It's the HV circuit that's causing issues. It took me some digging to figure out which circuit due to some confusion: Sams has the diagram mislabeled on their drawing as to which is which, plus there seem to have been some running changes as to what Philco specified for each one. I'm not the best diagnostician but I'll pluck away at it...if I keep disconnecting stuff I'm bound to figure it out! Oh, one more thing-when I powered up I let a nice puff of smoke (and a sharp bang) out of something. I was quite concerned, but less so after I spotted the culprit. It seems that yours truly, in a boneheaded move, picked up a 10v capacitor and wired it in where a 50v (IIRC) was called for. Poor little thing didn't stand a chance!
__________________
Bryan
Reply With Quote
Audiokarma
  #36  
Old 09-12-2018, 01:20 AM
Penthode's Avatar
Penthode Penthode is offline
VideoKarma Member
 
Join Date: Jun 2009
Location: Kitchener/Waterloo Ontario Canada
Posts: 693
Quote:
Originally Posted by Robert Grant View Post
I notice that the fourth photo shows a tag on the chassis: ".75 AMP 250V".

This would be a rarity indeed - a 250V power supply when the only country with a color TV infrastructure was entirely 120V.

Was this built as a demonstration or test set to be used abroad?
.75 amp 250v fuses are generally used for the horizontal sweep B supply. I do not think it has any reference to the a.c. input.
Reply With Quote
  #37  
Old 09-12-2018, 11:34 AM
dieseljeep dieseljeep is offline
VideoKarma Member
 
Join Date: Jul 2010
Posts: 6,366
Quote:
Originally Posted by Robert Grant View Post
I notice that the fourth photo shows a tag on the chassis: ".75 AMP 250V".

This would be a rarity indeed - a 250V power supply when the only country with a color TV infrastructure was entirely 120V.

Was this built as a demonstration or test set to be used abroad?
First of all: The set draws a lot a lot more primary current than .75 amp. At the time all low current fuses were rated at 250volts.
Fuses were designed for fault current as well as overcurrent protection. The line fuse, if used is somewhere around 8 amp, 125 volts, 125% of run current.
Fuses have changed drastically over the last 20 or 30 years regarding fault current. All fuses 10 amp and higher in the 3AG size are either porcelain tube or sand filled.
Reply With Quote
  #38  
Old 09-18-2018, 02:10 PM
benman94's Avatar
benman94 benman94 is offline
Resident Lunatic
 
Join Date: Jun 2011
Location: Detroit, MI
Posts: 1,126
The thread has been cleaned up. Let's try to keep the discussion limited to Bryan's Philco restoration going forward. The set was sold, the buyer and seller both seem to be happy with the sale, it's done.
Reply With Quote
  #39  
Old 09-27-2018, 10:24 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,587
Time for another update: there were some delays as I was out of town for a week on vacation, but I've been trying to tinker on the set for an hour or so each night. I've been scratching my head a lot, trying to figure out what was causing this large current draw in the horiz.limiting/damper circuit. I knew that, like all problems, the root cause was something simple. Finally, tonight, I stumbled upon it. I mentioned earlier that someone long ago had re-wired the set to use a 6AU4 damper rather than the oddball 6M3. I wired it back to original. I noticed that the filament wasn't lit and that's when I realized there was no ground to pin 2, an easy fix. For some reason it didn't occur to me to look closer-yep, they had simply moved the wire to pin 7 (correct for the 6AU4) and I totally ignored it. Internally in the 6M3 that's connected to pins 3 & 5...and the plate. So, yeah, I guess grounding the plate would cause that draw! The weird thing is that I'm certain I had yanked the tube and it didn't alleviate the problem-I don't understand how it couldn't. The good news is that the draw is gone.

I decided to do another quick and dirty power up with everything connected. While it would have been great to see "first light", what I did find were a few more things to troubleshoot: there is a 400mfd/50v cap (positive to ground) in the -25v circuit that blew. The purity circuit taps into this, among other things. I haven't replaced all the Black Beauties in that circuit so it could be as simple as that. And then, I briefly had some HV (I could hear it, smell the ozone, and there was a little snap-crackle-pop action going on) but then I lost it. No red plating of the horiz output; no raster, either. I'm not too concerned about it yet. All part of the "fun"!
__________________
Bryan
Reply With Quote
  #40  
Old 10-14-2018, 10:52 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,587
Another little update, and a question. I'm down to just a handful of Black Beauties to replace. In between that I've been trying to troubleshoot the HV issue. Right now I'm only getting about 5kv, and that's with the HO being driven with a substitution box. I need to figure the disconnect between horiz osc and horiz output. Tonight after replacing an out-of-spec 5w resistor I powered it up and noticed one of the 3A2's was faintly glowing red pointing to a bad doorknob cap which I know others have had trouble with. (the set has 4 of 'em) That particular one is 1000mmf at 15kv. The closest I had on hand was 500mmf so I threw it in there and was rewarded with the sound of some sharp crackles but no red plate...and no change in HV. I'll keep digging, and learning (which is a lot of what this is all about). My questions: how close in capacitance rating do I need to be for this application, percentage wise? And, I've seen some 1000uf 15kv disc caps that were a lot less expensive. Would they work in this application?
__________________
Bryan
Reply With Quote
Audiokarma
  #41  
Old 10-15-2018, 12:16 AM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 10,095
The set uses a doubler circuit in the HV so the doorknob caps need to be replaced with other doorknobs of the same rated capacitance and same or higher voltage. If the capacitance is not the same the HV may drop or increase. The original part probably has a tolerance rating. The only way you can use a part of another value is if that part is within tolerance of the original and the replacement has a tighter tolerance whose bounds do not fall outside the bounds of the original. most doorknobs were made in the time around when these sets were in use so closer tolerance parts that fit in bounds are probably harder to find than the right part.
__________________
Tom C.

What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4

Reading between the scan lines since the mid 2000's.
Reply With Quote
  #42  
Old 10-15-2018, 01:47 PM
benman94's Avatar
benman94 benman94 is offline
Resident Lunatic
 
Join Date: Jun 2011
Location: Detroit, MI
Posts: 1,126
Doorknob style capacitors rated between 40 kV and 175 kV or so are still available for use in medical equipment. They can be found on Mouser, etc. 40 kV, the lowest commonly available size, is overkill for all but the largest theater projection sets.

They're usually in the values we need (500-1500 pF) and the tolerances are no worse than the OEM part would have had when new.

They're rather pricey, running between $30 on the absolute low end and $100+ on the high end, depending on brand, voltage rating, and capacitance. Still, I'd rather spend $400 replacing leaky doorknobs than have a dark set with a bad flyback from the additional load placed on it.
Reply With Quote
  #43  
Old 10-25-2018, 10:46 PM
bgadow's Avatar
bgadow bgadow is offline
VideoKarma Member
 
Join Date: Oct 2003
Location: Federalsburg, MD
Posts: 5,587
Well, I know that thousands of followers are waiting on the edge of their seats for an update...

Buying doorknob caps can be confusing. I started with our friends at Moyers. They have some NOS 500pf but not the others (which were never a common need in TV repair circles). I checked out ebay, some Chinese suppliers, Fair Radio, Surplus Sales of Nebraska & numerous sites that cater to the Tesla coil crowd. I didn't really want to go used (I already HAVE used!) and that's mostly what they offer, and not in the exact values I wanted. The Chinese outlets were tempting with the expected low prices but I just didn't trust them. I ended up printing off pages from Vishay-Sprague & MuRata catalogs and trying to find what I needed in stock & benman94 steered me right. It wasn't real easy to find them without part numbers in hand. I ended up with a pair of MuRata 1000pf 20kv & a 2000pf 40kv. (For now I'm letting the 500pf be as I actually have a handful of them used, and can always grab one from Moyers-the only way I could find one from Mouser was at about the 40kv level, at a hefty price.)

The 1000's can be had with "inch" threads; the originals had studs made on them. I just cut down some screws with the proper threads and used them. They fit just fine (the new ones are a little taller but it all worked out). The 2000 is only available with metric threads but that wasn't too bad as the original mounted with screws so I just had to switch to metric. It probably took me an hour to switch the 3 over.

So, time to bench test. I had pulled the yoke and connected it but left the HV unhooked for now. I had a meter connected for cathode current. I flipped the switch. Current came up fine and rested in a good place. There were no unusual noises; I figured, well, that didn't fix it because I expected some sort of drama. I grabbed the HV probe. 24kv!

So, I did a quick re-install of the yoke & lugged the chassis over to the cabinet. Gentlemen, another one joins the living!

Yes, the yoke is crooked. I don't even have the convergence magnet assembly on the neck. I still have a half dozen caps to change in a "non-critical" circuits along with the reactance coil that I damaged earlier. Soon, though, I'll be able to start fine-tuning things. I'm very much looking forward to it!
Attached Images
File Type: jpg 20181025_192312.jpg (92.6 KB, 46 views)
File Type: jpg 20181025_192234.jpg (36.2 KB, 43 views)
__________________
Bryan
Reply With Quote
  #44  
Old 10-26-2018, 12:24 AM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 10,095
I'd like to know the tricks to finding those new door knobs. I've got a TM-21 with a dead shorted doorknob, and I suspect the somewhat unstable regulated HV level and slightly higher (than I like) H out current/temp in my 21CT55 may have something to do with bad doorknob caps.
__________________
Tom C.

What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4

Reading between the scan lines since the mid 2000's.
Reply With Quote
  #45  
Old 10-26-2018, 12:50 PM
bigaudioal's Avatar
bigaudioal bigaudioal is offline
Hello, I must be going
 
Join Date: Mar 2012
Location: Montgomery Village, MD
Posts: 602
CONGRATS! Great to see this set coming back to life.
__________________
-Al
Reply With Quote
Audiokarma
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 04:59 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2018, Jelsoft Enterprises Ltd.
ęCopyright 2012 VideoKarma.org, All rights reserved.