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Halicrafters SX17 transformer

 

A few months ago I acquired a Hallicrafters SX17 receiver intending to restore it as a winter project. Well the winter months have come and gone and I have finally gotten around to getting it on the bench (without injury to self I might add - it is a bit of a boat-anchor!) for a preliminary look. This is my first time on here, so just wanted to say hello to everyone and thank the moderator for accepting me into the group.

As might be expected for something from circa 1937, the radio is in a bit dirty and metal surfaces are oxidized. Some of the wiring (particularly the mains) looks a bit of a mess and will require re-wiring, but the immediate showstopper is the fact that the power transformer (T7) has an open primary. There seems to be no indication on the radio of the mains input voltage, however, I have read that these were made to be powered from a 110Vac line? Since the radio is located in the UK, it may have been previously assumed that it would run from UK mains which is at 230Vac, which might perhaps explain the open transformer....

Can anyone confirm whether these were ever made for the UK market and for 240Vac mains supply?

The next question is whether it is possible to source a replacement? The manual I have found does not indicate the transformer voltages so I wondered whether anyone has this information?

This looks like it is going to be a huge project but I think it would be interesting to restore this circa 90 year old receiver if possible.
 

¿ªÔÆÌåÓý

John ,? very often, there was a universal transformer option.? For many models it is listed only in the parts list after the normal transformer.

I looks on? BAMA?? ??

but don¡¯t see any transformation at all in the parts list. Others know more I¡¯m sure

don

?

?

From: [email protected] [mailto:[email protected]] On Behalf Of John via groups.io
Sent: Monday, May 27, 2024 1:04 PM
To: [email protected]
Subject: [HallicraftersRadios] Halicrafters SX17 transformer

?

A few months ago I acquired a Hallicrafters SX17 receiver intending to restore it as a winter project. Well the winter months have come and gone and I have finally gotten around to getting it on the bench (without injury to self I might add - it is a bit of a boat-anchor!) for a preliminary look. This is my first time on here, so just wanted to say hello to everyone and thank the moderator for accepting me into the group.

As might be expected for something from circa 1937, the radio is in a bit dirty and metal surfaces are oxidized. Some of the wiring (particularly the mains) looks a bit of a mess and will require re-wiring, but the immediate showstopper is the fact that the power transformer (T7) has an open primary. There seems to be no indication on the radio of the mains input voltage, however, I have read that these were made to be powered from a 110Vac line? Since the radio is located in the UK, it may have been previously assumed that it would run from UK mains which is at 230Vac, which might perhaps explain the open transformer....

Can anyone confirm whether these were ever made for the UK market and for 240Vac mains supply?

The next question is whether it is possible to source a replacement? The manual I have found does not indicate the transformer voltages so I wondered whether anyone has this information?

This looks like it is going to be a huge project but I think it would be interesting to restore this circa 90 year old receiver if possible.

_._,_._,_


--
don??? va3drl
 

John
The SX17 manual says that the measurements shown in the tube voltage chart were made at a line voltage of 115 VAC.? That does not mean that the SX-17 was designed for operation at 115 VAC, it just means that the voltages measured are most likely within +/- 10% of the values given in the chart at that line voltage.? Note too that the voltmeter was specified at 1000 ohms per volt.? Modern DVMs have a much higher input impedance so the voltages you measure will also be higher then those listed in the chart.

Restating the above with some background, the 1927 NEMA socket voltage convention is that the 115 VAC line will vary +/- 10% so one can expect a line voltage to vary from 104 VAC to 126 VAC.? The 1930 Rider's Perpetual Troubleshooters Manual lists the early battery eliminators which show a similar variation in line voltage.? Once the radio manufactures accepted the 115 VAC convention, they only listed the average 115? AC line voltage on schematics and parts lists.? When all is said and done, you want the vacuum tube (valve) heaters to be at a nominal 6.3 volts as measured at the tube socket.? Best tube life will be at a heater voltage of 6.0 volts or so. Plate voltage can vary +/- 10% and the radio will still operate satisfactorily.

About the power transformer rating.? You should be able to calculate the cathode current for most tubes in the SX-17.? The voltage given for the cathode is listed in the tube voltage chart, the cathode resistor value is given in the parts list.? Or one can just look in your favorite tube manual for plate and screen currents at the plate voltage given.? Same can be done for heater current for all tubes except for the power rectifier.? When all of this is done you should have a good idea of the requirements for the power transformer.

The show stopper may be the foot print of the power transformer.? How tall the replacement transformer is should not be that important as long as the replacement transformer is taller.? More iron is better, especially at 50 cycles.? You might as well look for a dual primary transformer so that you can operate at either 115 or 230 volt line.? Let us know what you figure out and what you used for your calculations.??

I may have a suitable power transformer here in Arkansas for the cost of postage.
Regards,
Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy


On Monday, May 27, 2024 at 12:55:23 PM CDT, John via groups.io <siloam@...> wrote:


A few months ago I acquired a Hallicrafters SX17 receiver intending to restore it as a winter project. Well the winter months have come and gone and I have finally gotten around to getting it on the bench (without injury to self I might add - it is a bit of a boat-anchor!) for a preliminary look. This is my first time on here, so just wanted to say hello to everyone and thank the moderator for accepting me into the group.

As might be expected for something from circa 1937, the radio is in a bit dirty and metal surfaces are oxidized. Some of the wiring (particularly the mains) looks a bit of a mess and will require re-wiring, but the immediate showstopper is the fact that the power transformer (T7) has an open primary. There seems to be no indication on the radio of the mains input voltage, however, I have read that these were made to be powered from a 110Vac line? Since the radio is located in the UK, it may have been previously assumed that it would run from UK mains which is at 230Vac, which might perhaps explain the open transformer....

Can anyone confirm whether these were ever made for the UK market and for 240Vac mains supply?

The next question is whether it is possible to source a replacement? The manual I have found does not indicate the transformer voltages so I wondered whether anyone has this information?

This looks like it is going to be a huge project but I think it would be interesting to restore this circa 90 year old receiver if possible.

 

On Mon, May 27, 2024 at 11:23 PM, don Root wrote:

I looks on? BAMA?? ??

but don¡¯t see any transformation at all in the parts list. Others know more I¡¯m sure

don

Thank you for the reference to BAMA. I was not aware of that resource.
 

On Tue, May 28, 2024 at 06:37 AM, Jim Whartenby wrote:
John
The SX17 manual says that the measurements shown in the tube voltage chart were made at a line voltage of 115 VAC.? That does not mean that the SX-17 was designed for operation at 115 VAC, it just means that the voltages measured are most likely within +/- 10% of the values given in the chart at that line voltage.? Note too that the voltmeter was specified at 1000 ohms per volt.? Modern DVMs have a much higher input impedance so the voltages you measure will also be higher then those listed in the chart.
Thanks. I got my information from a couple of online articles which mentioned 110V as well as 117V, but I appreciate that mains voltages vary and measurements vary depending on the instrument used. I am using a DMM, but do occasionally check with an AVO 8 for comparison.
?
?
About the power transformer rating.? You should be able to calculate the cathode current for most tubes in the SX-17.? The voltage given for the cathode is listed in the tube voltage chart, the cathode resistor value is given in the parts list.? Or one can just look in your favorite tube manual for plate and screen currents at the plate voltage given.? Same can be done for heater current for all tubes except for the power rectifier.? When all of this is done you should have a good idea of the requirements for the power transformer.
?
I thought about that? myself and will try and do some calculations. I am curious about your exclusion of the rectifier from the heater current calculation. It is obviously heated so must draw some current?

?
I may have a suitable power transformer here in Arkansas for the cost of postage.
Regards,
Jim
That's a kind offer. I will do the calculations first and see what is needed.
 

I think your AVO 8 is a 20Kohm/Volt meter. Most modern DVM or
electronic voltmeters are about 10 megohm fixed input resistance. Very
old VOM's are often 1000 ohms/Volt. The reading you get depends on the
impedance or source resistance of the circuit. The input resistance of
passive voltmeters depends on the sensitivity of the meter and the
resistance of the divider. Ohms/Volt means ohms times the full scale
voltage of the particular range. For instance, I have a military meter
with a 20K ohm/volt divider and a 1000 volt maximum range. That is
20Megohms! Will not load some high impedance circuits like AVC busses
but also is not good for measuring very low voltages where you might
want such a high resistance load.
If you know the source resistance you can calculate the reading you
will get under load but the source resistance is often not known for
many radio circuits.
Good luck with finding a replacement transformer. Some recent
correspondence in a couple of these mailing lists suggests that there
are not many people left who will rewind old transformers.


On 5/28/2024 9:41 AM, John via groups.io wrote:
On Tue, May 28, 2024 at 06:37 AM, Jim Whartenby wrote:

John
The SX17 manual says that the measurements shown in the tube voltage
chart were made at a line voltage of 115 VAC.? That does not mean
that the SX-17 was designed for operation at 115 VAC, it just means
that the voltages measured are most likely within +/- 10% of the
values given in the chart at that line voltage.? Note too that the
voltmeter was specified at 1000 ohms per volt.? Modern DVMs have a
much higher input impedance so the voltages you measure will also be
higher then those listed in the chart.

Thanks. I got my information from a couple of online articles which
mentioned 110V as well as 117V, but I appreciate that mains voltages
vary and measurements vary depending on the instrument used. I am using
a DMM, but do occasionally check with an AVO 8 for comparison.

About the power transformer rating.? You should be able to calculate
the cathode current for most tubes in the SX-17.? The voltage given
for the cathode is listed in the tube voltage chart, the cathode
resistor value is given in the parts list.? Or one can just look in
your favorite tube manual for plate and screen currents at the plate
voltage given.? Same can be done for heater current for all tubes
except for the power rectifier.? When all of this is done you should
have a good idea of the requirements for the power transformer.

I thought about that? myself and will try and do some calculations. I am
curious about your exclusion of the rectifier from the heater current
calculation. It is obviously heated so must draw some current?

I may have a suitable power transformer here in Arkansas for the
cost of postage.
Regards,
Jim

That's a kind offer. I will do the calculations first and see what is
needed.
_._,_._,_
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
 

Comments in RED

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy


On Tuesday, May 28, 2024 at 11:41:30 AM CDT, John via groups.io <siloam@...> wrote:


On Tue, May 28, 2024 at 06:37 AM, Jim Whartenby wrote:
John
The SX17 manual says that the measurements shown in the tube voltage chart were made at a line voltage of 115 VAC.? That does not mean that the SX-17 was designed for operation at 115 VAC, it just means that the voltages measured are most likely within +/- 10% of the values given in the chart at that line voltage.? Note too that the voltmeter was specified at 1000 ohms per volt.? Modern DVMs have a much higher input impedance so the voltages you measure will also be higher then those listed in the chart.
Thanks. I got my information from a couple of online articles which mentioned 110V as well as 117V, but I appreciate that mains voltages vary and measurements vary depending on the instrument used. I am using a DMM, but do occasionally check with an AVO 8 for comparison.
I had to look up the AVO 8 meter specs, it is a 20k ohms per volt meter movement.? It will still read a bit high because it will load the circuit less then a 1k ohms per volt meter will.? This is not really a problem as long as you are aware of this issue.? This higher voltage measurement adds to the myth about high line voltages over time.??BTW, 110 volts is the ancient Edison DC specification, funny how things get mixed up.?
About the power transformer rating.? You should be able to calculate the cathode current for most tubes in the SX-17.? The voltage given for the cathode is listed in the tube voltage chart, the cathode resistor value is given in the parts list.? Or one can just look in your favorite tube manual for plate and screen currents at the plate voltage given.? Same can be done for heater current for all tubes except for the power rectifier.? When all of this is done you should have a good idea of the requirements for the power transformer.
?
I thought about that? myself and will try and do some calculations. I am curious about your exclusion of the rectifier from the heater current calculation. It is obviously heated so must draw some current?
The heater for the rectifier is a separate winding on the power transformer since it is at B+ potential so it's requirements are already accounted for in the power transformer, about 5 volts @ 3 amps .? ?The other tube heaters are in parallel so their current requirements are additive.??
?
I may have a suitable power transformer here in Arkansas for the cost of postage.
Regards,
Jim
That's a kind offer. I will do the calculations first and see what is needed.?
No problem, I have saved more components then I have a need for.? I am not aware of what books and aids that are available on your side of the pond but I recommend that you download a pdf of the "Radiotron Designers Handbook," 4th edition.? It is a great resource and it has the answers to many questions that come up in tube equipment.? Take what you read online with a grain of salt.? If it contradicts RDH4 then it is misinformation, IMHO.? Your replacement power transformer that meets the heater winding current spec will most likely have a B+ winding that is a bit high.? It is not a problem to just live with the higher voltage since any resistance you add will affect voltage regulation with the change in B+ current as the radio plays and the audio sections draws power.? Some resistance in the rectifier plate circuit is OK to limit the current seen by the rectifier tube cathode.? See page 99 of the RDH4 for more information on this point.
Regards,
Jim?
 

John,

If you need any good images inside or outside of the SX-17 I have one in excellent condition and long time ago, I dumped all my images of my SX-17 in the photos section here: /g/HallicraftersRadios/album?id=95319

Good luck with the project.

K2WH
 
Edited

John, I expect you know this, but the transformer you need for your 230 v,50Hz won¡¯t be a ¡°replacement¡± ?of the

?

original [oops? I meant the original US transformer]? ; it will need more iron for the 50hz, ??and then the primary will need twice the turns to get to 230v

?

There is good reason to believe that most halli¡¯s were sold? in England ?and ?likely with the proper??? transformer for the area.? See this and other issues of

but it is not clear about the 50Hz and 230 volts?

?

--
don??? va3drl
 

Nice photos!

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy


On Tuesday, May 28, 2024 at 02:50:50 PM CDT, Bill (Group Owner) <k2wh@...> wrote:


John,

If you need any good images inside or outside of the SX-17 I have one in excellent condition and long time ago, I dumped all my images of my SX-17 in the photos section here: /g/HallicraftersRadios/album?id=95319

Good luck with the project.

K2WH
 

Thank you for sharing the images.?

I have been looking at the table in the manual and diagram as well as valve data sheets to determine the spec of the transformer. The rectifier is connected to its own heater winding and its heater operates at 5vac. The remaining heaters operate at 6.3vac. Finally, the anode voltage at the 6V6 is stated as 300Vdc. Most of the remaining valve anodes are driven via limiting resistors at 260V which is curious given that the datasheet states the maximum operating voltage is 250V, although there is a 10% leeway. In any case.

The three secondaries must therefore be rated at 5Vac, 6.3Vac and 300Vac RMS.

I also looked at the maximum permitted anode current of each valve and added them all up together. It comes to 144mA. The rectifier is rated at 225mA, so that would seem to be well within its capability, assuming all valves were driven at their full current potential, which I dare say, they are probably not.

Rounding up a little for simplicity, 300V x 0.150A = 45W. One also has to allow a bit for lamps etc.

I am not sure how the cathode voltage factors into the calculation of the current each valve is drawing, and have been looking at some valve reference books to understand, but so far have failed to understand. perhaps someone could kindly enlighten me, then I might be a able to arrive at a more accurate calculation.

Thank you for all the feedback and comments so far. They have been very helpful.
 

John
Cathode current flows through the cathode resistor developing the cathode voltage.? Knowing any two one can calculate the third using Ohm's Law.

Using the maximum plate / screen grid currents from the tube manual I find the same 120mA that you report.

Using the cathode voltage and cathode resistor combinations I calculate about 100mA.? This might be a bit high since I substituted tube manual plate current for those tubes that have a grounded cathode.? So the actual plate current is most likely between these two limits.

Summing all of the heater currents, I calculate 3.9 amps.? Need a 4 amp rating or better for the heater winding.

Using 300 volts @ 120 mA for the plate winding, I found three power transformers in the various catalogs.? Using the lower plate current should allow a few more candidates.??

Still need to know the hole spacing for mounting the power transformer to the chassis.
Regards,
Jim



Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy


On Wednesday, May 29, 2024 at 01:25:02 PM CDT, John via groups.io <siloam@...> wrote:


Thank you for sharing the images.?

I have been looking at the table in the manual and diagram as well as valve data sheets to determine the spec of the transformer. The rectifier is connected to its own heater winding and its heater operates at 5vac. The remaining heaters operate at 6.3vac. Finally, the anode voltage at the 6V6 is stated as 300Vdc. Most of the remaining valve anodes are driven via limiting resistors at 260V which is curious given that the datasheet states the maximum operating voltage is 250V, although there is a 10% leeway. In any case.

The three secondaries must therefore be rated at 5Vac, 6.3Vac and 300Vac RMS.

I also looked at the maximum permitted anode current of each valve and added them all up together. It comes to 144mA. The rectifier is rated at 225mA, so that would seem to be well within its capability, assuming all valves were driven at their full current potential, which I dare say, they are probably not.

Rounding up a little for simplicity, 300V x 0.150A = 45W. One also has to allow a bit for lamps etc.

I am not sure how the cathode voltage factors into the calculation of the current each valve is drawing, and have been looking at some valve reference books to understand, but so far have failed to understand. perhaps someone could kindly enlighten me, then I might be a able to arrive at a more accurate calculation.

Thank you for all the feedback and comments so far. They have been very helpful.
 

I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?
 

John
There are various catalogs from replacement transformer manufacturers, I looked at STANCOR and THORDARSON, for example.? There are others.? I have not looked at my junque box so there are still other possibilities.
?
STANCOR? model PC8420 / PM8420 (same transformer, different mounting) has the following specs:
2 1/2 inch by 2 9/16 mounting hole spacing
325 - 0 - 325 volts @ 150mA
5 volts @ 3 amps
6.3 volts @ 5 amps

THORDARSON? model 22R05
2 1/2 inch by 3 1/8 inch mounting hole spacing
300 - 0 - 300 volts @ 120 mA
5 volts @ 3 amps
6,3 volts @ 5 amps

Another transformer of interest is the one found in the Hewlett-Packard 200CD audio oscillator.? This might be available either locally to you or on eBay?? It has 115 - 230 volt split primary windings which is a plus.
PAECO model 910-94
2,5 inch by 2.34 inch mounting hole spacing
315 - 0 - 315 volts @ 125 mA
5 volts @ 2 amps
6.3 volts @ 3.55 amps.? It should do 4 amps with no trouble.
This is an over designed power transformer with very conservative ratings so it should fit the bill but it's mounting is upright not horizontal like that in the SX-17.? It also contains a 8H @ 125 mA filter choke.? The manual is available on-line, with photos.? I have a history with this transformer.

Regards,
Jim


Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy


On Thursday, May 30, 2024 at 05:28:29 AM CDT, John via groups.io <siloam@...> wrote:


I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?
 

¿ªÔÆÌåÓý

Jim, are these 50 cycle ?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Thursday, May 30, 2024 11:18 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

John

There are various catalogs from replacement transformer manufacturers, I looked at STANCOR and THORDARSON, for example.? There are others.? I have not looked at my junque box so there are still other possibilities.

?

STANCOR? model PC8420 / PM8420 (same transformer, different mounting) has the following specs:

2 1/2 inch by 2 9/16 mounting hole spacing

325 - 0 - 325 volts @ 150mA

5 volts @ 3 amps

6.3 volts @ 5 amps

?

THORDARSON? model 22R05

2 1/2 inch by 3 1/8 inch mounting hole spacing

300 - 0 - 300 volts @ 120 mA

5 volts @ 3 amps

6,3 volts @ 5 amps

?

Another transformer of interest is the one found in the Hewlett-Packard 200CD audio oscillator.? This might be available either locally to you or on eBay?? It has 115 - 230 volt split primary windings which is a plus.

PAECO model 910-94

2,5 inch by 2.34 inch mounting hole spacing

315 - 0 - 315 volts @ 125 mA

5 volts @ 2 amps

6.3 volts @ 3.55 amps.? It should do 4 amps with no trouble.

This is an over designed power transformer with very conservative ratings so it should fit the bill but it's mounting is upright not horizontal like that in the SX-17.? It also contains a 8H @ 125 mA filter choke.? The manual is available on-line, with photos.? I have a history with this transformer.

?

Regards,

Jim

?

?

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

?

?

On Thursday, May 30, 2024 at 05:28:29 AM CDT, John via groups.io <siloam@...> wrote:

?

?

I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?

_._,_._,_


--
don??? va3drl
 

¿ªÔÆÌåÓý

Another possible replacement is a Hammond 372DX.

See attached.

?

73, Jacques, VE2JFE in Montreal

?

De?: [email protected] <[email protected]> De la part de don Root
·¡²Ô±¹´Ç²â¨¦?: 30 mai 2024 13:08
??: [email protected]
Objet?: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Jim, are these 50 cycle ?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Thursday, May 30, 2024 11:18 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

John

There are various catalogs from replacement transformer manufacturers, I looked at STANCOR and THORDARSON, for example.? There are others.? I have not looked at my junque box so there are still other possibilities.

?

STANCOR? model PC8420 / PM8420 (same transformer, different mounting) has the following specs:

2 1/2 inch by 2 9/16 mounting hole spacing

325 - 0 - 325 volts @ 150mA

5 volts @ 3 amps

6.3 volts @ 5 amps

?

THORDARSON? model 22R05

2 1/2 inch by 3 1/8 inch mounting hole spacing

300 - 0 - 300 volts @ 120 mA

5 volts @ 3 amps

6,3 volts @ 5 amps

?

Another transformer of interest is the one found in the Hewlett-Packard 200CD audio oscillator.? This might be available either locally to you or on eBay?? It has 115 - 230 volt split primary windings which is a plus.

PAECO model 910-94

2,5 inch by 2.34 inch mounting hole spacing

315 - 0 - 315 volts @ 125 mA

5 volts @ 2 amps

6.3 volts @ 3.55 amps.? It should do 4 amps with no trouble.

This is an over designed power transformer with very conservative ratings so it should fit the bill but it's mounting is upright not horizontal like that in the SX-17.? It also contains a 8H @ 125 mA filter choke.? The manual is available on-line, with photos.? I have a history with this transformer.

?

Regards,

Jim

?

?

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

?

?

On Thursday, May 30, 2024 at 05:28:29 AM CDT, John via groups.io <siloam@...> wrote:

?

?

I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?

372DX.pdf
372DX.pdf

 

¿ªÔÆÌåÓý

Jacques, as I read it this is a 60 Hz , nota ?50 Hz ?unit

Don

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Thursday, May 30, 2024 1:59 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Another possible replacement is a Hammond 372DX.

See attached.

?

73, Jacques, VE2JFE in Montreal

?

De?: [email protected] <[email protected]> De la part de don Root
·¡²Ô±¹´Ç²â¨¦?: 30 mai 2024 13:08
??: [email protected]
Objet?: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Jim, are these 50 cycle ?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Thursday, May 30, 2024 11:18 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

John

There are various catalogs from replacement transformer manufacturers, I looked at STANCOR and THORDARSON, for example.? There are others.? I have not looked at my junque box so there are still other possibilities.

?

STANCOR? model PC8420 / PM8420 (same transformer, different mounting) has the following specs:

2 1/2 inch by 2 9/16 mounting hole spacing

325 - 0 - 325 volts @ 150mA

5 volts @ 3 amps

6.3 volts @ 5 amps

?

THORDARSON? model 22R05

2 1/2 inch by 3 1/8 inch mounting hole spacing

300 - 0 - 300 volts @ 120 mA

5 volts @ 3 amps

6,3 volts @ 5 amps

?

Another transformer of interest is the one found in the Hewlett-Packard 200CD audio oscillator.? This might be available either locally to you or on eBay?? It has 115 - 230 volt split primary windings which is a plus.

PAECO model 910-94

2,5 inch by 2.34 inch mounting hole spacing

315 - 0 - 315 volts @ 125 mA

5 volts @ 2 amps

6.3 volts @ 3.55 amps.? It should do 4 amps with no trouble.

This is an over designed power transformer with very conservative ratings so it should fit the bill but it's mounting is upright not horizontal like that in the SX-17.? It also contains a 8H @ 125 mA filter choke.? The manual is available on-line, with photos.? I have a history with this transformer.

?

Regards,

Jim

?

?

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

?

?

On Thursday, May 30, 2024 at 05:28:29 AM CDT, John via groups.io <siloam@...> wrote:

?

?

I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?


--
don??? va3drl
 

Since the radio is in the UK, it would need to operate on 50Hz mains. Looking at the data, the Stancor appears to be for operation on 60Hz, whereas the Thordarson catalog states that the 22R05 operates on both 50 and 60Hz.

I am also going to post on a vintage radio forum which is predominantly UK based so see whether there is a UK based outlet or whether anyone here in the UK might have a suitable salvaged spare, and now that I know what I m looking for, also check eBay. I am happy to ship from the USA if need be and options are limited, but obviously shipping to the UK is not cheap so I do appreciate Jim¡¯s kind offer.
 

¿ªÔÆÌåÓý

Don, please read the .pdf more attentively.

Just at the right of the GRY ¨C ELECTROSTATIC SHIELD, what do you see ??

?

73, Jacques, VE2JFE in Montreal

?

De?: [email protected] <[email protected]> De la part de don Root
·¡²Ô±¹´Ç²â¨¦?: 30 mai 2024 14:39
??: [email protected]
Objet?: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Jacques, as I read it this is a 60 Hz , nota ?50 Hz ?unit

Don

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jacques_VE2JFE
Sent: Thursday, May 30, 2024 1:59 PM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Another possible replacement is a Hammond 372DX.

See attached.

?

73, Jacques, VE2JFE in Montreal

?

De?: [email protected] <[email protected]> De la part de don Root
·¡²Ô±¹´Ç²â¨¦?: 30 mai 2024 13:08
??: [email protected]
Objet?: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

Jim, are these 50 cycle ?

?

From: [email protected] [mailto:[email protected]] On Behalf Of Jim Whartenby via groups.io
Sent: Thursday, May 30, 2024 11:18 AM
To: [email protected]
Subject: Re: [HallicraftersRadios] Halicrafters SX17 transformer

?

John

There are various catalogs from replacement transformer manufacturers, I looked at STANCOR and THORDARSON, for example.? There are others.? I have not looked at my junque box so there are still other possibilities.

?

STANCOR? model PC8420 / PM8420 (same transformer, different mounting) has the following specs:

2 1/2 inch by 2 9/16 mounting hole spacing

325 - 0 - 325 volts @ 150mA

5 volts @ 3 amps

6.3 volts @ 5 amps

?

THORDARSON? model 22R05

2 1/2 inch by 3 1/8 inch mounting hole spacing

300 - 0 - 300 volts @ 120 mA

5 volts @ 3 amps

6,3 volts @ 5 amps

?

Another transformer of interest is the one found in the Hewlett-Packard 200CD audio oscillator.? This might be available either locally to you or on eBay?? It has 115 - 230 volt split primary windings which is a plus.

PAECO model 910-94

2,5 inch by 2.34 inch mounting hole spacing

315 - 0 - 315 volts @ 125 mA

5 volts @ 2 amps

6.3 volts @ 3.55 amps.? It should do 4 amps with no trouble.

This is an over designed power transformer with very conservative ratings so it should fit the bill but it's mounting is upright not horizontal like that in the SX-17.? It also contains a 8H @ 125 mA filter choke.? The manual is available on-line, with photos.? I have a history with this transformer.

?

Regards,

Jim

?

?

Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy

?

?

On Thursday, May 30, 2024 at 05:28:29 AM CDT, John via groups.io <siloam@...> wrote:

?

?

I completely forgot about noting the current on the low voltage windings! I added up the heater currents and arrived at the same 3.9A that you did. In addition to this, according to the data-sheet, the heater for the rectifier on the 5V winding takes 3A.

For the exercise, I also tried calculating the valve currents according to the cathode voltage and the cathode resistor. I did struggle to understand how to apply that for the 6R7 and the 6J5, but was able to do calculations for some of the other valves. The meter amplifier valve also puzzled me since the 95ohm resistor and 10V cathode voltage would suggest 100mA or thereabouts, but the data-sheet states that the maximum running current for the 6J7G is 2mA, so that didn¡¯t make sense. For those that I was unsure of, I just used the value from data-sheet and arrived at somewhere around 150mA which is in a similar ball-park, although in all probability there are errors in my calculations. The values for first two 6K7¡¯s were also curious as they come to approximately 12mA (8/700) which is more than the 10mA shown on the data-sheet. There is, of course, R1, the RF gain control in series, but one would presumably have to assume the highest case at minimum setting? It would seem that the valves can be pushed pretty hard at that setting.

I struggled a bit with the transformer screw positions but they seem to be placed 100mm (4 inches) apart on the long side and 77mm (3 inches) apart on the short side. Removing the transformer would allow me to make more precise measurements, but that will have to wait for another day or two until I am feeling well enough. I came down with some kind of bug a coulple of days ago.

Anyway, thank you for your help and for taking the time and trouble to confirm the calculations.

As a matter of curiosity, what catalog are you looking at please?

?


--
don??? va3drl

 

It seems to me that most 60Hz power transformers will perform OK on
50Hz although they may run hot.


On 5/30/2024 12:34 PM, John via groups.io wrote:
Since the radio is in the UK, it would need to operate on 50Hz mains.
Looking at the data, the Stancor appears to be for operation on 60Hz,
whereas the Thordarson catalog states that the 22R05 operates on both 50
and 60Hz.

I am also going to post on a vintage radio forum which is predominantly
UK based so see whether there is a UK based outlet or whether anyone
here in the UK might have a suitable salvaged spare, and now that I know
what I m looking for, also check eBay. I am happy to ship from the USA
if need be and options are limited, but obviously shipping to the UK is
not cheap so I do appreciate Jim¡¯s kind offer.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998

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