All American Five but with a filament transformer

2/18/2013 6:46:38 PMsteve sherman

I was planning on building an S-38-like radio, but I'd feel safer by avoiding the stack-up of filaments used on the S-38.
Is there a later-day version of the All American Five that uses commonly available tubes whose filaments are powered in parallel by a 6.3v transformer?
If so, what are the tube model numbers?
Can you suggest an online schematic for such a radio?

thanks,
steve sherman

2/18/2013 7:18:10 PMLewis

Steve:
If you use a 12 Volt transformer, and replace the 35Z5 with a diode, find a 12 Volt output tube (12V6?), you can just about build the radio as original, and the 12 Volt tubes are easier to find than the 6 Volt equivalents. The audio output transformer will have to be different than the 50L6 for impedance matching purposes.
Lewis
:

2/18/2013 8:11:07 PMTom McHenry

Every series-string-heater tube has a 6V heater equivalent. For example, the 6L6 has the same transfer characteristics as a 50L6. The only trick is generating B+. You could go "whole hog" and buy a transformer that has not only the 6V filament winding but also a HV B+ winding and a 5V dedicated winding to run the heater on a rectifier tube like a 5Y3 or 5U4. However, it would be simpler (not to mention less expensive) to use a silicon diode voltage doubler to generate the B+ and just use a 6V transformer to run the heaters.

2/18/2013 8:55:23 PMRich, W3HWJ

I wouldn't compare a 50L6 to a 6L6. Substantially different power capability and voltages.

Using a silicon diode doubler still leaves you with your power supply connected directly to the power line... no isolation.

Rich

:Every series-string-heater tube has a 6V heater equivalent. For example, the 6L6 has the same transfer characteristics as a 50L6. The only trick is generating B+. You could go "whole hog" and buy a transformer that has not only the 6V filament winding but also a HV B+ winding and a 5V dedicated winding to run the heater on a rectifier tube like a 5Y3 or 5U4. However, it would be simpler (not to mention less expensive) to use a silicon diode voltage doubler to generate the B+ and just use a 6V transformer to run the heaters.
:
:
:

2/18/2013 11:44:48 PMJohn K

Looking at the Hallicrafters S-38 Tube complement,
V1 12SA7GT Converter
V2 12SA7GT IF amplifier
V3 12SQ7GT Detector/AVC/AF
V4 12SQ7GT BFO/ANL
V5 35L6GT Audio output
V6 35Z5GT Rectifier

Rick is correct. A 6L6 wouldn't be happy in your radio. The best sub for the 35L6 would be a 50L6. The 25L6 heater draws double the current, so it would work but can't be used in series with any of these tubes. But with a 25 volt filament supply, you could pair up the other four and run the 25L6 in parallel with the two pairs of 12 volt tubes. Drop the rectifier tube, don't need it.
You could use a 6V6 for the output and all 6 volt tubes in your lineup.

A 12L6 looks like it would work fine on 120 vdc on the plate, but it draws a whopping 0.6 amps on the heater, so you will need a hefty transformer to supply it and the other 4 12 volt tubes.

To use the original tubes, you need a 12 volt and a 35 volt filament transformers, and a 110 to 200 volt B+ transformer. The 35L6 puts out 1.5 watts at 110 v, but that jumps to 3 watts with 200 volts on the plate.

I've had some good luck constructing isolation transformers by taking two transformers from old stereo tuners or tape machines and connecting them back to back (or front to front :>). Find two similar secondaries and hook them together. If there is a mismatch, you can step up the output, giving you a higher B+. Then you search for other windings coming out of the two transformer to supply the heaters. Replace the rectifier and you got it built. Good Luck. John

:I wouldn't compare a 50L6 to a 6L6. Substantially different power capability and voltages.
:
:Using a silicon diode doubler still leaves you with your power supply connected directly to the power line... no isolation.
:
:Rich::

2/19/2013 1:03:35 AMTom McHenry

Yes, my comparison of the 50L6 to a 6L6 was a hasty oversimplification made to illustrate a point. Both tubes are beam-power, octal-based audio output tubes with identical pinouts, but their respective designs have been tailored to specific target-application classes. If they were hand tools and not tubes, both types might be classified as hammers; although one is like a claw hammer and the other is like a sledgehammer.

My original point was that one doesn't have to look too far afield to find a 6.3V heater "analog" to one of the series-string tubes; although successfully using any tube in a circuit means fully understanding that tube's operating requirements and characteristics. As far as I can tell, there never was any committment by the tube industry to locking in performance parameters across a range of heater voltages/currents, although quite often it worked out that way.

2/19/2013 10:27:13 AMNorm Leal

Best 6.3 volt sub for 35L6 or 50L6 is 6W6. It will operate on low plate voltage. Suggest using 6.3 volt tubes which don't require rewiring except filaments. As others have mentioned, they are available.

For 35Z5 could use a 6W4. Slight wiring change but a good way to use up a damper diode.

Norm

: Yes, my comparison of the 50L6 to a 6L6 was a hasty oversimplification made to illustrate a point. Both tubes are beam-power, octal-based audio output tubes with identical pinouts, but their respective designs have been tailored to specific target-application classes. If they were hand tools and not tubes, both types might be classified as hammers; although one is like a claw hammer and the other is like a sledgehammer.
:
:My original point was that one doesn't have to look too far afield to find a 6.3V heater "analog" to one of the series-string tubes; although successfully using any tube in a circuit means fully understanding that tube's operating requirements and characteristics. As far as I can tell, there never was any committment by the tube industry to locking in performance parameters across a range of heater voltages/currents, although quite often it worked out that way.
:

2/21/2013 12:08:43 AMPeter G. Balazsy

Norm:
How about a 12L6 GT?
.. looks like that's a perfect fit, and cheap... no?

2/21/2013 12:13:44 AMPeter G. Balazsy

Also, keeping everything 12-volt..... how about a 12x4?

2/21/2013 12:33:16 AMNorm Leal

Peter

Initial post mentioned using 6.3 volt tubes but those will do the job if 12.6 volts is used for filaments.

12L6 is the 12 volt version of 6W6. 12X4 is 12 volt version of 6X4 & 6X5. Nothing wrong with using 12.6 volts if the filament transformer is available.

Could even use a 12AX4 damper diode for rectifier. There are a lot around and not much use.

Norm

:Also, keeping everything 12-volt..... how about a 12x4?
:
:

2/21/2013 4:08:28 PMsteve sherman

Gentlemen,
As suggested by The S-38 Guy, I'll use a polarized plug to avoid the possibility of making the chassis hot.
I'll stay with the original S-38 five tube lineup, since I've been able to find all five amongst the junk radios I've accumulated. In fact, I just bought 250 tubes very cheaply. I have only one of the 12SQ7, so can anyone suggest a replacement?
I guess I can still shock myself in that 100+ voltages exist within
the S-38 architecture.
With the series filament arrangement, will any five tubes play together?
Or might one tube in the string drop more voltage and somehow cause other tubes to be under-heated?
I'm not trying to do anything extraordinary. I'd simply like some exposure to tubes. Any other suggestions for a tube novice would be appreciated.

Thanks,
Steve Sherman
:Peter
:
: Initial post mentioned using 6.3 volt tubes but those will do the job if 12.6 volts is used for filaments.
:
: 12L6 is the 12 volt version of 6W6. 12X4 is 12 volt version of 6X4 & 6X5. Nothing wrong with using 12.6 volts if the filament transformer is available.
:
: Could even use a 12AX4 damper diode for rectifier. There are a lot around and not much use.
:
:Norm
:
::Also, keeping everything 12-volt..... how about a 12x4?
::
::
:
:

2/21/2013 4:59:15 PMPeter G. Balazsy

Steve:
Try to find a 12sq7 out there somewhere.

If you use the original tube line up (four 12v tubes and two 35v tubes) you'll notice that they all add up to 118v when in series. (close to today's 120-125v mains)
So each tube drops the voltage according to its number.

Now, if you decided to use a 12v filament transformer and connect all the tubes in parallel, then you can still use all the original 12v tubes but in place of the 35z5 you can use a 12x4 and in place of the 35L6 you can use a 12L6.
All the filament currents in parallel will require a combined total of about 1.5amps of current so a 12 volt 2-amp filament transformer will be fine.

2/21/2013 10:00:20 PMJohn K

Hello Steve. Now that we know your real quest - to learn more and not shock yourself - we can help you better. Forget filament transformer installations for now. Concentrate on re building the original radio, then making it safe to use.
The 12SQ7 is an octal Duo-Diode High-Mu Triode tube. 12SR7 and 12SW7 could be subbed in there, but they are Medium Mu, which means the amplification factor is much lower, so you will lose performance, output volume. As Peter says, find a 12SQ7. Visit a local radio club and offer trades, since you have boxes of tubes to trade.
With new capacitors installed and the radio ready to play, plug it into an isolation transformer for improved safety. I described how to build one in my earlier post.
Good luck. John

:Steve:
:Try to find a 12sq7 out there somewhere.
:
:If you use the original tube line up (four 12v tubes and two 35v tubes) you'll notice that they all add up to 118v when in series. (close to today's 120-125v mains)
:So each tube drops the voltage according to its number.
:
:Now, if you decided to use a 12v filament transformer and connect all the tubes in parallel, then you can still use all the original 12v tubes but in place of the 35z5 you can use a 12x4 and in place of the 35L6 you can use a 12L6.
:All the filament currents in parallel will require a combined total of about 1.5amps of current so a 12 volt 2-amp filament transformer will be fine.
:
:

2/22/2013 10:28:15 AMClifton

Perhaps one could use a transformer with dual 120 volt primaries and a 12 volt secondary. The other 120 volt primary could be used for the B+ voltage and the 12 volts could be used for the filaments. Hammond may make such a transformer.

Clifton

:Hello Steve. Now that we know your real quest - to learn more and not shock yourself - we can help you better. Forget filament transformer installations for now. Concentrate on re building the original radio, then making it safe to use.
:The 12SQ7 is an octal Duo-Diode High-Mu Triode tube. 12SR7 and 12SW7 could be subbed in there, but they are Medium Mu, which means the amplification factor is much lower, so you will lose performance, output volume. As Peter says, find a 12SQ7. Visit a local radio club and offer trades, since you have boxes of tubes to trade.
:With new capacitors installed and the radio ready to play, plug it into an isolation transformer for improved safety. I described how to build one in my earlier post.
:Good luck. John
:
::Steve:
::Try to find a 12sq7 out there somewhere.
::
::If you use the original tube line up (four 12v tubes and two 35v tubes) you'll notice that they all add up to 118v when in series. (close to today's 120-125v mains)
::So each tube drops the voltage according to its number.
::
::Now, if you decided to use a 12v filament transformer and connect all the tubes in parallel, then you can still use all the original 12v tubes but in place of the 35z5 you can use a 12x4 and in place of the 35L6 you can use a 12L6.
::All the filament currents in parallel will require a combined total of about 1.5amps of current so a 12 volt 2-amp filament transformer will be fine.
::
::
:
:

2/24/2013 10:01:50 AMsteve sherman

Gentlemen,
For the S-38 architecture, can I use a modern-day IF transformer?
On Mouser, I see a few XICOR transformers that are inexpensive.
Which would have the appropriate primary/secondary impedances?
Will it work in a 100v environment?

Thanks again,
Steve

:Perhaps one could use a transformer with dual 120 volt primaries and a 12 volt secondary. The other 120 volt primary could be used for the B+ voltage and the 12 volts could be used for the filaments. Hammond may make such a transformer.
:
:Clifton
:
:
::Hello Steve. Now that we know your real quest - to learn more and not shock yourself - we can help you better. Forget filament transformer installations for now. Concentrate on re building the original radio, then making it safe to use.
::The 12SQ7 is an octal Duo-Diode High-Mu Triode tube. 12SR7 and 12SW7 could be subbed in there, but they are Medium Mu, which means the amplification factor is much lower, so you will lose performance, output volume. As Peter says, find a 12SQ7. Visit a local radio club and offer trades, since you have boxes of tubes to trade.
::With new capacitors installed and the radio ready to play, plug it into an isolation transformer for improved safety. I described how to build one in my earlier post.
::Good luck. John
::
:::Steve:
:::Try to find a 12sq7 out there somewhere.
:::
:::If you use the original tube line up (four 12v tubes and two 35v tubes) you'll notice that they all add up to 118v when in series. (close to today's 120-125v mains)
:::So each tube drops the voltage according to its number.
:::
:::Now, if you decided to use a 12v filament transformer and connect all the tubes in parallel, then you can still use all the original 12v tubes but in place of the 35z5 you can use a 12x4 and in place of the 35L6 you can use a 12L6.
:::All the filament currents in parallel will require a combined total of about 1.5amps of current so a 12 volt 2-amp filament transformer will be fine.
:::
:::
::
::
:
:

2/24/2013 3:20:52 PMsteve sherman

:Gentlemen,
I've moved on from the discussion of a filament transformer.
Can I use a XICOR IF transformer?

Thanks,
steve sherman

Gentlemen,
:For the S-38 architecture, can I use a modern-day IF transformer?
:On Mouser, I see a few XICOR transformers that are inexpensive.
:Which would have the appropriate primary/secondary impedances?
:Will it work in a 100v environment?
:
: Thanks again,
: Steve
:
:
::Perhaps one could use a transformer with dual 120 volt primaries and a 12 volt secondary. The other 120 volt primary could be used for the B+ voltage and the 12 volts could be used for the filaments. Hammond may make such a transformer.
::
::Clifton
::
::
:::Hello Steve. Now that we know your real quest - to learn more and not shock yourself - we can help you better. Forget filament transformer installations for now. Concentrate on re building the original radio, then making it safe to use.
:::The 12SQ7 is an octal Duo-Diode High-Mu Triode tube. 12SR7 and 12SW7 could be subbed in there, but they are Medium Mu, which means the amplification factor is much lower, so you will lose performance, output volume. As Peter says, find a 12SQ7. Visit a local radio club and offer trades, since you have boxes of tubes to trade.
:::With new capacitors installed and the radio ready to play, plug it into an isolation transformer for improved safety. I described how to build one in my earlier post.
:::Good luck. John
:::
::::Steve:
::::Try to find a 12sq7 out there somewhere.
::::
::::If you use the original tube line up (four 12v tubes and two 35v tubes) you'll notice that they all add up to 118v when in series. (close to today's 120-125v mains)
::::So each tube drops the voltage according to its number.
::::
::::Now, if you decided to use a 12v filament transformer and connect all the tubes in parallel, then you can still use all the original 12v tubes but in place of the 35z5 you can use a 12x4 and in place of the 35L6 you can use a 12L6.
::::All the filament currents in parallel will require a combined total of about 1.5amps of current so a 12 volt 2-amp filament transformer will be fine.
::::
::::
:::
:::
::
::
:

2/24/2013 6:45:14 PMBill G.

Hi Steve,
I think not. Modern IF transformers are designed for use with transistors, which use lower voltages of course and are unlikely to insulate the 100+ volts necessary.
Transistors require a lower impedance, too, making thse unsuitable.

Sorry for the bad news, but I want to save you the time of an unecessary experiment.

All the Best,

Bill

2/25/2013 11:17:21 AMsteve sherman

Bill,
I don't have the S-38 schematic in front of me. But, its not clear to me that 100 volts of d.c. is actually dropped across the primary or secondary coils.I'll take a closer look tonight.

Thanks,
Steve
:Hi Steve,
: I think not. Modern IF transformers are designed for use with transistors, which use lower voltages of course and are unlikely to insulate the 100+ volts necessary.
: Transistors require a lower impedance, too, making thse unsuitable.
:
: Sorry for the bad news, but I want to save you the time of an unecessary experiment.
:
:All the Best,
:
:Bill
:

2/19/2013 9:50:02 AMWarren

If you need like a 12A6 I have plenty of those. And a lot of other 12 volt tube for radios. I also have an all-original S-38 with the metal bottom (early run). The radio is un-restored but working still excellent and in very good condition. If you would like to own this radio, contact me by E-Mail.
It just so happens I have a converted S-38A now transformer operated, full wave diode rectifier and in-line filter choke. An added 3rd I.F. stage that uses a 6AK5. There is an added gain control where the pitch control would have been like the S-38 The radio now has a 6BS7Y converter tube, and uses a 6V6 output tube. There is more modifications to list.
If you would like some pictures and descriptions of the radio, let me know. I can send you by E-Mail again. This radio is so sensitive and selective it rivals the SX models.

2/20/2013 9:40:07 PMJohn K

:If you need like a 12A6 I have plenty of those. And a lot of other 12 volt tube for radios. I also have an all-original S-38 with the metal bottom (early run). The radio is un-restored but working still excellent and in very good condition. If you would like to own this radio, contact me by E-Mail.
: It just so happens I have a converted S-38A now transformer operated, full wave diode rectifier and in-line filter choke. An added 3rd I.F. stage that uses a 6AK5. There is an added gain control where the pitch control would have been like the S-38 The radio now has a 6BS7Y converter tube, and uses a 6V6 output tube. There is more modifications to list.
: If you would like some pictures and descriptions of the radio, let me know. I can send you by E-Mail again. This radio is so sensitive and selective it rivals the SX models.
:
:

Warren, I am curious. Is your hotrod radio using a higher than original B+ for the 6V6 output tube?

2/21/2013 12:39:17 AMWarren

Yes, the plate voltage is around 350 VDC I could also use a 6F6 in place of the 6V6.

3/19/2013 9:57:31 PMRAYMOND

:I was planning on building an S-38-like radio, but I'd feel safer by avoiding the stack-up of filaments used on the S-38.
:Is there a later-day version of the All American Five that uses commonly available tubes whose filaments are powered in parallel by a 6.3v transformer?
:If so, what are the tube model numbers?
:Can you suggest an online schematic for such a radio?
:
: thanks,
: steve sherman
:Yes there is a set that uses that tube arrangment! Look under ZENITH Model M660, They use pretty much those same tubs, I have one of those & they are a FANTASTIC preformer. In the owners manual ZENITH describes this set as having an unuasualy HIGH degree of sensitivity & were they EVER RIGHT!!!! Up here in the north woods that set matches up with the 3000-1 & gives it one hell of a good run for it's money. Use the circuitry from sam's & NOT the hallicrafters THAT MATCHES UP TO IT. The HALLICRAFTERS match-up is the HALLICRAFTERS S-118.

3/19/2013 9:58:53 PMRAYMOND

::I was planning on building an S-38-like radio, but I'd feel safer by avoiding the stack-up of filaments used on the S-38.
::Is there a later-day version of the All American Five that uses commonly available tubes whose filaments are powered in parallel by a 6.3v transformer?
::If so, what are the tube model numbers?
::Can you suggest an online schematic for such a radio?
::
:: thanks,
:: steve sherman
::Yes there is a set that uses that tube arrangment! Look under ZENITH Model M660, They use pretty much those same tubes, I have one of those & they are a FANTASTIC preformer. In the owners manual ZENITH describes this set as having an unuasualy HIGH degree of sensitivity & were they EVER RIGHT!!!! Up here in the north woods that set matches up with the 3000-1 & gives it one hell of a good run for it's money. Use the circuitry from sam's & NOT the hallicrafters THAT MATCHES UP TO IT. The HALLICRAFTERS match-up is the HALLICRAFTERS S-118.
:
:

3/21/2013 9:05:53 PMRAYMOND