High voltages on Admiral 19A11.

[bigaudioal]

After about 40 minutes, my power transformer does heat up. It does not get too hot to touch. It heats up so that if I put my entire hand on it, it is nice and toasty. I can keep my hand on it indefinitely without burning myself. Once it gets to this temp, it seems to stabilize there.

[Phil Nelson]

Not sure about this set in particular, but a hot tube next to a transformer can also warm it somewhat.

Phil Nelson

[N8NM]

99.999% of my experience is in radio vs tv, but I'd consider it normal for a transformer to run warm but nowhere near "ouch" warm. Also, and again this is based on my very limited TV experience, it seems odd that the DC out (pins 2 and 8) of the 5Y3 would equal the AC in; I'm used to seeing it a bit higher, more in line with what you're measuring.

I'd be curious to hear what the TV experts have to say about that. Am I all wet, or what?

[bigaudioal]

The 5Y3 tube is right next to the transformer. That tube runs very hot and I guess you are right, it could warm up the transformer some. My transformer never gets to "ouch" status.


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[Username1]

Don't forget when a lot of those manuals were written meters were resistive VOM's and possibly even VTVM's and not Digital meters, that are possibly reading peaks of the pulses coming through the rectifier, and possibly not the more lower average reading the older meters may have been indicating. Higher line voltage also a very valid factor....

[init4fun]

Originally Posted by Username1

Don't forget when a lot of those manuals were written meters were resistive VOM's and possibly even VTVM's and not Digital meters, that are possibly reading peaks of the pulses coming through the rectifier, and possibly not the more lower average reading the older meters may have been indicating. Higher line voltage also a very valid factor....

Yep , the voltage figures on the schematics were likely taken with a voltmeter with around 10K ohms per volt loading , wheras modern meters are much higher (Maybe 1 to 5 Meg per volt ?) . Since the new meter puts less load on the circuit the voltage reading is higher .

Solution = get a nice old VOM like my favorite , the old reliable Simpson 260

PS , Most voltage charts will have a caption somewhere saying "Voltages measured with 10K per volt meter" or something similar .....

[bigaudioal]

Again, great to know! Set seems to be working fine other than the linearity issue, which hopefully the tubular kV caps will fix. So guess that remains the best diagnostic tool of the set right now - working well.

Thanks.

[earlyfilm]

Originally Posted by bigaudioal

After about 40 minutes, my power transformer does heat up. It does not get too hot to touch. It heats up so that if I put my entire hand on it, it is nice and toasty. I can keep my hand on it indefinitely without burning myself. Once it gets to this temp, it seems to stabilize there.

This may be a wild goose chase . . . . . but it is worth a check.

Make the power transformer resistance check suggested at the bottom of Rider page 3-9 and continuing at the top of page 3-10 in the 19A1 Rider schematic downloadable at:

http://www.earlytelevision.org/tv_sc..._diagrams.html

Then make sure you are using the correct rectifier tube!

The 19A1 chassis was occasionally supplied with power transformers made for the 5U4G instead of the 5Y3. If the wrong rectifier tube is used, this usually produces lower DC voltage, but if a 5Y3 were used with the less common 5U4 transformer, the DC might be slightly higher. The wrong tube can also produce transformer overheating.

James

[N8NM]

Since it's fun to irresponsibly speculate (lol), I think it's more likely that we're just spoiled by the precision of the test equipment we have available. It's nothing to read a couple hundred volts with .1V resolutin on a DMM, but takes some effort to read the same thing to within 10% on a typical analog meter (I'm thinking a "modern" 260 on the 500V scale.)

Most old consumer stuff used 10-20% tolerance parts, so I try not to get too hung up on the numbers. Back when I was in electronics school, one of my instructors (a grouchy old fart) was fond of saying "close enough for government work." Now that I'm becoming a grouchy old fart, I appreciate the simple brilliance of that statement.

[bigaudioal]

I may make sure that the power transformer in there is the one for the 5Y3 rect. tube. I do recall seeing in the SAMS a production change note in the parts list next to the Power Transformer. That's what it must have been. Easy enough to track down info and switch to the 5U4 tube if need be. Thanks for that info.

[bigaudioal]

Just read the Rider. Glad they supplied the resistance check, b/c when I first got the set I cleaned it up and REPAINTED the power transformer. HA! So any red dot that may have been there is long gone. I did tape off the part number and that remains and it is the correct part number. So the resistance check should reveal which transformer I have. Right now, the rect. tube in there is a 5Y3.

[bandersen]

Always take lots of reference photos before doing any work Is there a tube chart inside the cabinet ?

[bigaudioal]

There is. I believe that says 5Y3 for rect. tube.

[old_coot88]

'Member that the 5Y3 has a 2A filament and the 5U4 is 3A.

[init4fun]

Originally Posted by old_coot88

'Member that the 5Y3 has a 2A filament and the 5U4 is 3A.

Yep , if you use a 5Y3 where a 5U4 is called for , you end up with a very HOT (overloaded) 5Y3

If you use a 5U4 where a 5Y3 is called for , you end up with a hot power transformer .....