Admiral 26R12 restoration p3o5

The set is working, but not quite as good as I'd like. Time for some tweaking and modifications.

Category:

Howto & Style

Tags:

• vintage
• antique
• television
• restoration
• repairs
• admiral
• 26r12

[OlegKostoglatov]

The animation on the low power station reminds me of an ant farm with those dots moving around. That filter assembly would have to be tuned to reject a certain bandwidth of frequencies so I don't know how you could throw one together by using a randum RF choke from a junk drawer. Your approach makes much more sense then trial and error, find out what you need to block, and then what parts you need. This is good practice, apparently the Predictas have similar problems to these Admirals.

[bandersentv]

@OlegKostoglatov LOL - I guess it does look like ants :) I was just re-reading the servicing tips and noticed a key sentence I missed before - "The filter must be placed inside the high voltage housing and NOT under the chassis." So I'll give that a try .

[pskittle488]

Great vid, also great hints for solving troublesome issues. I was kinda wondering though, have you ever had a set you were working on do something weird and just fail? What are the most common causes and how were you able to fix them? Just curious.

[bandersentv]

@pskittle488 Hmmm, just a few come to mind. I had weird issues with that 20X11 I restored recently that were due to a burned out focus coil. Once, I had an electrolytic blow because I installed it backwards. Those were pretty easy to troubleshoot with just a voltmeter because there wasn't power flowing to all the circuits.

[bandersentv]

@pskittle488 I'd say the worst was when I had a set completely restored and fired it up one last time before sending it back to it's owner. It used dual 5U4 rectifiers and one blew out in a shower of sparks. I figured the tube had just given out so I popped in a new one. This time both tubes blew :( Eventually, I used a DMM to fnd that I had directly shorted out the 5U4s to ground when I tightened down a screw! I ruined four tubes while tracking that down :(

[gbowne1]

@bandersentv That's an expensive diagnosis. Four 5U4's are not that cheap.

[MrRaddios]

i need to watch this several times very interesting topics and information super video thanks BOB

[RadioHamGuy]

Excellent troubleshooting!

[ac4552]

@ac4552

Hi again,

I should say that you would need to assume the screen was full of the bar pattern; you have only 3, but can imagine how many would fit in 1/15750 hz.

One example I remember of this was in SSTV; at a 250 ms horizontal rate; 4hz horizontal sweep.

A 60 hz interference always gave about 30 vertical bars as I remember.

Working backwards, the bar rate was then [1/((1/4)/30)] / 2

Best regards,

Allison

[HD7100]

Very nice work. I have worked on sets years ago but I am learning much from you. Thanks!

[ac4552]

Hi,

I believe that the frequency of the interferer can be calculated as ((1/15750)/Number vertical bars on screen)/2. It is /2 since there are 2 dark bars per cycle of the interference; one for positive swing, one for the negative.

Best regards,

Allison

[OlegKostoglatov]

It would make sense for them to do that, extra terminal strips cost money and there is no advantage to adding them when they aren't needed. I would rather that either the factory or a service man use disused tube pins as tie points rather then tying components together in mid air like I found in the Medco radio I was working on. Some British and European radios left the factory like that. I know that you did it for testing purposes of course.