Just picked up a 1930s Battery operated Coronado

[vortalexfan]

Originally Posted by dieseljeep

I've been following this thread from the very beginning. I would knock together a simple B+ supply using a silicon rectifier or bridge rectifier, two 20mfd electrolytics , 2200ohm, 1 watt resistor and 180 ohm, 1 watt before the rectifier.
Once you get all the problems straightened out, you can go back to using battery power.
I built one 65 years ago because of the high cost of "B" batteries.
Flashlite cells were only 15 to 25 cents at the time.

I think what caused the faulty 9V battery in my "B" Supply was that I had taken this Radio over to my parents house last week to demonstrate the radio to them, and when I went to load the radio back into my car the "B" supply battery pack fell out of the back of my radio and landed on the ground which was covered in snow and I think that caused the battery to "short out".

[Kevin Kuehn]

Just goes to show that snow makes it more difficult to do most anything, with the possible exception of skiing down a hill.

[vortalexfan]

Originally Posted by Kevin Kuehn

Just goes to show that snow makes it more difficult to do most anything, with the possible exception of skiing down a hill.

Yep, I'd say so, because since I replaced that faulty 9V battery the radio has been working flawlessly since.

[vortalexfan]

OK, so I have a question and a little update on this radio.

I was finally able to acquire a tube tester that can test the tubes that these old 1930s radios used, and I tested all of the tubes in this radio (except for two of them) and they all tested like brand new, and they are the original Coronado Branded tubes!

Now for my question and the two tubes I was unable to test.

My Tube tester I have is a Knight Model 600 Tube Tester from the 1950s, and it had listed in its tube chart a 1A4P tube, but this radio uses a 1A4 tube, which from what I can see looking through the tube data sheets online they are basically the same tube, but then there are some tube data sheets that state that they are completely different tubes.

My tube tester results seem to confirm the latter idea, because when I used the setup data from my tube tester that is for a 1A4P to try and test my 1A4 tubes they get a mediocre reading and I know that can't be the case, because the rest of my tubes in my radio test like brand new (100+) and those 1A4 tubes couldn't both be the the same amount of deadness (40) and the rest be like brand new, and then have the radio working as well it does.

Anybody have any ideas as to why Knight would only list one 1A4 tube in their tester setup chart (the 1A4P) and whether or not there really is a difference between the 1A4 and the 1A4P tube?

Thanks for your help.

[jr_tech]

The 1A4-P is a pentode version of the 1A4, which is a tetrode (sometimes designated 1A4-T). This means that the P version has an additional grid, (suppressor grid), close to the plate to prevent secondary electron emission from the plate from landing on the screen grid. This improves the stability of the tube.

Since the secondary elections are repelled by the suppressor grid, and returned to the plate, plate current could be higher in the P version of the tube, which may account for differences in tube checker readings.

The additional grid in the P version is internally connected to the heater/cathode, so the tube base connections are the same.

jr

[vortalexfan]

Originally Posted by jr_tech

The 1A4-P is a pentode version of the 1A4, which is a tetrode (sometimes designated 1A4-T). This means that the P version has an additional grid, (suppressor grid), close to the plate to prevent secondary electron emission from the plate from landing on the screen grid. This improves the stability of the tube.

Since the secondary elections are repelled by the suppressor grid, and returned to the plate, plate current could be higher in the P version of the tube, which may account for differences in tube checker readings.

The additional grid in the P version is internally connected to the heater/cathode, so the tube base connections are the same.

jr

Ok, thanks for the explanation, so the 1A4s in my radio is probably fine then, especially since my radio is receiving quite well.

[init4fun]

Originally Posted by vortalexfan

Ok, thanks for the explanation, so the 1A4s in my radio is probably fine then, especially since my radio is receiving quite well.

Back when I was first starting out in the hobby I had the same mentality; "The tube tester says it's bad so it's gotta be bad" even though it still worked fine in the radio. I eventually learned that it's how the tube performs in the radio, and not on the tube tester, that determines whether a tube is good or not. Tube testers sometimes lie, whereas a properly performing radio does not

[Jeffhs]

Originally Posted by init4fun

Back when I was first starting out in the hobby I had the same mentality; "The tube tester says it's bad so it's gotta be bad" even though it still worked fine in the radio. I eventually learned that it's how the tube performs in the radio, and not on the tube tester, that determines whether a tube is good or not. Tube testers sometimes lie, whereas a properly performing radio does not

You are correct. Tube testers, even mutual-conductance testers, do not test vacuum tubes in so-called "real world" conditions, so they cannot be relied upon to provide reliable results. Replacement of a weak or outright defective tube with one known to be good has always been the best way to deal with tube problems. Tube testers are good, but they are not infallible. It is for this reason, again, that the best way to deal with a tube which a tube tester tells you is defective is to replace that tube with one you know is good.

[vortalexfan]

OK, So I have a question about this radio:

Is it normal for a tube powered battery radio like this to drain the "B" Battery supply so that it goes from supplying 90VDC to the radio's B+ Circuit to a little over 50VDC to the B+ Circuit in the radio (which makes the radio barely operable) in less than 2 months?

I thought the "B" Battery supply was supposed to last almost two years with barely any use, and I'm using store brand 9V batteries like what was suggested by Radiotvphononut on one of his Youtube videos where repaired a similar radio to this and created a rigged up battery supply using modern 9V and "D" Cell Batteries.

Any Ideas as to what might cause this weird aforementioned issue?

[Electronic M]

Originally Posted by vortalexfan

OK, So I have a question about this radio:

Is it normal for a tube powered battery radio like this to drain the "B" Battery supply so that it goes from supplying 90VDC to the radio's B+ Circuit to a little over 50VDC to the B+ Circuit in the radio (which makes the radio barely operable) in less than 2 months?

I thought the "B" Battery supply was supposed to last almost two years with barely any use, and I'm using store brand 9V batteries like what was suggested by Radiotvphononut on one of his Youtube videos where repaired a similar radio to this and created a rigged up battery supply using modern 9V and "D" Cell Batteries.

Any Ideas as to what might cause this weird aforementioned issue?

Check your B+ current drain with the set on and off. If it draws current off something is wrong, if the on current is more than 20% higher than the sum of the max plate currents of the tubes data sheets then something is wrong....if the heaters are parallel wired you should be able to troubleshoot by pulling tubes one at a time and observing change in B+ current. The drop in current when a tube is pulled is what it's drawing, and if that exceeds what the data sheet says it should be then the circuit it's in is suspect. If all the tubes are out and its drawing substantial B+ current look for B+ shorts and resistive dividers off the B+.

[vortalexfan]

Originally Posted by Electronic M

Check your B+ current drain with the set on and off. If it draws current off something is wrong, if the on current is more than 20% higher than the sum of the max plate currents of the tubes data sheets then something is wrong....if the heaters are parallel wired you should be able to troubleshoot by pulling tubes one at a time and observing change in B+ current. The drop in current when a tube is pulled is what it's drawing, and if that exceeds what the data sheet says it should be then the circuit it's in is suspect. If all the tubes are out and its drawing substantial B+ current look for B+ shorts and resistive dividers off the B+.

Ok, well I know that this radio uses a 2 section power switch and I wonder if the switch section that switches the "B" supply could be stuck on and is causing B+ current draw when the radio power switch is switched off?

The radio was completely recapped so I know leaky caps aren't the cause.

I'll check the power switch and see if that's working correctly, although come to think of it this radio is almost always "instant-on" when I turn it on, which makes me wonder if the B+ isn't actually being switched off by the power switch like it's supposed to be.

[Electronic M]

Instant on in battery sets is typically a function of the extremely short warmup time of filament type battery tubes.

[vortalexfan]

Originally Posted by Electronic M

Instant on in battery sets is typically a function of the extremely short warmup time of filament type battery tubes.

Ok, so I'll just check a few other things then.

[dieseljeep]

Originally Posted by vortalexfan

Ok, so I'll just check a few other things then.

Just disconnect the battery when not using it!
Batteries are expensive and when though showing it and how well it works, It isn't that difficult and it will give you piece of mind.

[vortalexfan]

Originally Posted by dieseljeep

Just disconnect the battery when not using it!
Batteries are expensive and when though showing it and how well it works, It isn't that difficult and it will give you piece of mind.

Ok, well I didn't realize that the radio was still drawing current from the batteries even when its turned off, because I know modern transistor radios don't usually draw current from a battery when its turned off.