Bruce Tell us about yourself.? What is your electronics skill level?? What test equipment is available?? Hand tools, soldering iron, tube tester, test meter and such.? Have you mastered the skill of soldering?? Can you read a schematic?? I am sure that we as a group can guide you through the repair process even if you are a beginner.
I personally would not apply power until I have had a look under the hood, so to speak.? All filter, coupling and bypass capacitors are suspect and should be considered bad and in need of replacement.? As Richard said, if the resistors checked are within 20% then I would think that they are good enough.? There is an octal socket on the rear apron.? There should be a plug installed with two jumpers, is that there?
About the switch problems.? I have found that the dollar store can of penetrating oil spray will do wonders on switches and volume controls.? Just spray and operate the control a few dozen times to work the fluid into the switch / pot.? You can verify operation with your VOM. Regards, Jim
Logic: Method used to arrive at the wrong conclusion, with confidence.? Murphy
On Tuesday, April 16, 2024 at 08:36:45 AM CDT, Richard Knoppow <1oldlens1@...> wrote:
You will definitely have to remove the bottom cover. Simple, a few
screws. The S20R is a straight forward receiver and not difficult to
work on. When restored they are quite good performers and worth the
trouble.
What instruments do you have? To start out you must have a VOM
(Volt-Ohm-Milliamp) meter. Even a very simple one will do. Perfectly
adequate meters are available at places like Harbor Tools for around
$15.00. Without one you can't do very much.
I also suggest looking at tubebooks.org at books on trouble shooting.
A couple of first suggestions: look at the rec/send switch to see if
its working. Use the ohm meter first. Secondly, check the switch in the
headphone jack. If its not connecting the speaker you won't hear
anything. Plugging into the jack a few times may clear the contact. Note
that the headphones are connected to the audio driver stage so the
phones must be high impedance to hear anything there. Old fashioned
magnetic phones, of the sort used for crystal radios, are required.
Do measure the resistance of the tube filaments. That will at least
eliminate any complete duds but burned out filaments are actually quite
rare.
Once you have a VOM do the socket resistance checks. A variation of
20% is normal. It is helpful to follow the schematic when doing the
measurements so you know what you are measuring. In some places there
may be capacitors involved so that the measurements will change with
time and perhaps polarity without indicating anything wrong.
Then do the socket voltage checks. This requires removing the bottom
cover. If you are not used to vacuum tube gear watch your fingers, you
can get quite painful shocks.
For general trouble shooting always begin with the power supply. If
the power supply is not working nothing else will work.
Again, in general, begin at one end and work toward the other, from
input to output, or sometimes the other way. Do ONE thing at a time so
you know what has changed.
Thoroughly clean all the switches before you begin. Evidently the
power switch gave up since it appears to have been bypassed. This is on
the tone control switch and is an add-on type switch. I had to replace
the switch on my S-40A, which is almost identical to the S-20R. It may
be the Send/receive switch is also kaput, look at its terminals with the
ohm meter to see if its working. This is a plain Jane toggle switch so
will be relatively easy to replace.
All the tubes in the S-20R were originally metal except for the
rectifier. There are glass (GT) versions of all of them but the metal
ones provide some additional shielding. If your tubes turn out to be
good just leave them.
All the paper and electrolytic caps will have to be replaced. An
original can type filter cap is available from Hayseed Hamfest. He may
also have a kit of other caps. Modern plastic caps will much improve the
performance of the receiver. There is one low inductance cap in the RF
section, has a woven lead at one end. Just replace it with a modern
plastic cap, they have much lower parasitic reactance than the original
paper caps.
You will have to go over the resistors. Carbon composition
resistors invariably increase in value with time. You will probably find
that all resistors with values of 50K and above are way out of
tolerance. Modern carbon film resistors are better than the old ones
when new and will last forever. Probably any resistor with value within
20% can be left in place.
Since most S-20R receivers were built in war time or shortly
afterward you may find some "bult up" resistors consisting of paralleled
resistors where the right value was not available.
Note that the original speaker is electrodynamic, that is, the
magnet is an electromagnet and acts as a choke for the power supply.
Mostly they are still good. If the speaker does have to be replaced for
some reason a permanent magnet speaker can be used with the field coil
replaced with a 1000 ohm about 5 Watt wire wound resistor. See the
S-40A, which is nearly identical, to see how this is done.
In my S-20R I replaced the detector and noise limiter with the
circuit from the S-40A but the original works OK.
If you have questions I will try to answer them plus you will get a
lot of help from others on this list.
There is an old book "Modern Radio Servicing" by Girardi (not sure
of the spelling) which is helpful, I think its at tubebooks.org
Good luck, neat receivers.
On 4/16/2024 4:39 AM, Bruce KX4AZ wrote: On Sat, Mar 30, 2024 at 09:19 AM, Bruce KX4AZ wrote:
....decided to take a chance on an Ebay sale of an "as is" unit.
The cosmetic appearance didn't look too bad, and the fact that it
powers on with at least /a /hiss?in the speaker, /and/ that it was
part of a ham estate,? gave me just enough hope to make an offer
that was accepted.? But once I have it in hand I will need to lean
heavily on the S20R experts here, since I have limited skills
(truthfully, ZERO) with regard to troubleshooting and/or restoring
tube radios of this type.
An update on this, I received the S20R boat anchor last week, and I was
encouraged by the above average cosmetic appearance of the cabinet, and
the fact that the power cord had previously been replaced.? The unit
powers on as soon as plugged in (power switch bypassed?), with dial
lights and tube filaments illuminated....at least the tubes with a glass
enclosure.? But there is absolutely nothing detectable from the speaker,
not even a hiss of any kind.? I have the schematic and service manuals
in hand...but I am pondering what the next most logical steps might be.
I am thinking that would be to open the chassis cover to see if any of
the caps etc have already been replaced.? Would checking for the
presence of B+ voltage be another key step? And I suppose checking the
filaments on the non-glass tubes would make sense too.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
You will definitely have to remove the bottom cover. Simple, a few
screws. The S20R is a straight forward receiver and not difficult to
work on. When restored they are quite good performers and worth the
trouble.
What instruments do you have? To start out you must have a VOM
(Volt-Ohm-Milliamp) meter. Even a very simple one will do. Perfectly
adequate meters are available at places like Harbor Tools for around
$15.00. Without one you can't do very much.
I also suggest looking at tubebooks.org at books on trouble shooting.
A couple of first suggestions: look at the rec/send switch to see if
its working. Use the ohm meter first. Secondly, check the switch in the
headphone jack. If its not connecting the speaker you won't hear
anything. Plugging into the jack a few times may clear the contact. Note
that the headphones are connected to the audio driver stage so the
phones must be high impedance to hear anything there. Old fashioned
magnetic phones, of the sort used for crystal radios, are required.
Do measure the resistance of the tube filaments. That will at least
eliminate any complete duds but burned out filaments are actually quite
rare.
Once you have a VOM do the socket resistance checks. A variation of
20% is normal. It is helpful to follow the schematic when doing the
measurements so you know what you are measuring. In some places there
may be capacitors involved so that the measurements will change with
time and perhaps polarity without indicating anything wrong.
Then do the socket voltage checks. This requires removing the bottom
cover. If you are not used to vacuum tube gear watch your fingers, you
can get quite painful shocks.
For general trouble shooting always begin with the power supply. If
the power supply is not working nothing else will work.
Again, in general, begin at one end and work toward the other, from
input to output, or sometimes the other way. Do ONE thing at a time so
you know what has changed.
Thoroughly clean all the switches before you begin. Evidently the
power switch gave up since it appears to have been bypassed. This is on
the tone control switch and is an add-on type switch. I had to replace
the switch on my S-40A, which is almost identical to the S-20R. It may
be the Send/receive switch is also kaput, look at its terminals with the
ohm meter to see if its working. This is a plain Jane toggle switch so
will be relatively easy to replace.
All the tubes in the S-20R were originally metal except for the
rectifier. There are glass (GT) versions of all of them but the metal
ones provide some additional shielding. If your tubes turn out to be
good just leave them.
All the paper and electrolytic caps will have to be replaced. An
original can type filter cap is available from Hayseed Hamfest. He may
also have a kit of other caps. Modern plastic caps will much improve the
performance of the receiver. There is one low inductance cap in the RF
section, has a woven lead at one end. Just replace it with a modern
plastic cap, they have much lower parasitic reactance than the original
paper caps.
You will have to go over the resistors. Carbon composition
resistors invariably increase in value with time. You will probably find
that all resistors with values of 50K and above are way out of
tolerance. Modern carbon film resistors are better than the old ones
when new and will last forever. Probably any resistor with value within
20% can be left in place.
Since most S-20R receivers were built in war time or shortly
afterward you may find some "bult up" resistors consisting of paralleled
resistors where the right value was not available.
Note that the original speaker is electrodynamic, that is, the
magnet is an electromagnet and acts as a choke for the power supply.
Mostly they are still good. If the speaker does have to be replaced for
some reason a permanent magnet speaker can be used with the field coil
replaced with a 1000 ohm about 5 Watt wire wound resistor. See the
S-40A, which is nearly identical, to see how this is done.
In my S-20R I replaced the detector and noise limiter with the
circuit from the S-40A but the original works OK.
If you have questions I will try to answer them plus you will get a
lot of help from others on this list.
There is an old book "Modern Radio Servicing" by Girardi (not sure
of the spelling) which is helpful, I think its at tubebooks.org
Good luck, neat receivers.
toggle quoted message
Show quoted text
On 4/16/2024 4:39 AM, Bruce KX4AZ wrote: On Sat, Mar 30, 2024 at 09:19 AM, Bruce KX4AZ wrote:
....decided to take a chance on an Ebay sale of an "as is" unit.
The cosmetic appearance didn't look too bad, and the fact that it
powers on with at least /a /hiss?in the speaker, /and/ that it was
part of a ham estate,? gave me just enough hope to make an offer
that was accepted.? But once I have it in hand I will need to lean
heavily on the S20R experts here, since I have limited skills
(truthfully, ZERO) with regard to troubleshooting and/or restoring
tube radios of this type.
An update on this, I received the S20R boat anchor last week, and I was
encouraged by the above average cosmetic appearance of the cabinet, and
the fact that the power cord had previously been replaced.? The unit
powers on as soon as plugged in (power switch bypassed?), with dial
lights and tube filaments illuminated....at least the tubes with a glass
enclosure.? But there is absolutely nothing detectable from the speaker,
not even a hiss of any kind.? I have the schematic and service manuals
in hand...but I am pondering what the next most logical steps might be.
I am thinking that would be to open the chassis cover to see if any of
the caps etc have already been replaced.? Would checking for the
presence of B+ voltage be another key step? And I suppose checking the
filaments on the non-glass tubes would make sense too.
--
Richard Knoppow
Los Angeles
WB6KBL
SKCC 19998
|
I picked up my two HT-9s from the Claremore, OK hamfest this past weekend. They were as advertised and even the second one was in great shape despite a few somewhat reversible modifications. The seller was able to locate a number of tank coils for this rig which will save me some time in this restoration. What I¡¯m still missing are the tuning units. I recently purchased a tuning unit for 20m but this is a tuning unit that is used in the doubling circuit and requires another tuning unit to double the crystal frequency on anything above 10 mhz.
I would like to use my ¡°parts¡± box to fabricate a plugin tuning unit for 80m. Hallicrafters provides the circuit for the tuning units in their manual but doesn¡¯t provide any component details. Hallicrafters only changes the part number for the TU assembly. The variable, the inductor and the fixed mica cap that is shown on the schematic for all the under 10mhz tuning units isn¡¯t addressed.
My focus right now would be for a 80m tuning unit to allow me to put this fine old transmitter on the air. Is there anyone out there that can give me a head start on values of the components that would be used for a 80m TU?
BTW, the Claremore hamfest was great (a great venue in their expo center with plenty of free parking and friendly people). The town provides easy access to motels and ?restaurants. There is also a great museum in town that is a must visit for anyone interested in firearms (and a lot of other items not firearm related). The JM Davis Museum displays the largest firearms collection in the world with over 14,000 firearms beautifully displayed and organized along with many other items such as beer steins, saddles, clocks etc. all this is organized by subject. A $5 admission allows you to spend several hours to view if you don¡¯t slow down to read the data on each item or the history behind it. You could easily spend a day looking in more detail.
Any help on the 80m tuning would be greatly appreciated.
Tom N5AMA
|
On Sat, Mar 30, 2024 at 09:19 AM, Bruce KX4AZ wrote:
....decided to take a chance on an Ebay sale of an "as is" unit.? The cosmetic appearance didn't look too bad, and the fact that it powers on with at least a hiss?in the speaker, and that it was part of a ham estate,? gave me just enough hope to make an offer that was accepted.? But once I have it in hand I will need to lean heavily on the S20R experts here, since I have limited skills (truthfully, ZERO) with regard to troubleshooting and/or restoring tube radios of this type.
An update on this, I received the S20R boat anchor last week, and I was encouraged by the above average cosmetic appearance of the cabinet, and the fact that the power cord had previously been replaced.? The unit powers on as soon as plugged in (power switch bypassed?), with dial lights and tube filaments illuminated....at least the tubes with a glass enclosure.? But there is absolutely nothing detectable from the speaker, not even a hiss of any kind.? I have the schematic and service manuals in hand...but I am pondering what the next most logical steps might be.? I am thinking that would be to open the chassis cover to see if any of the caps etc have already been replaced.? Would checking for the presence of B+ voltage be another key step? And I suppose checking the filaments on the non-glass tubes would make sense too.
|
Re: SX-140 Audio transformer
Thank you very much for that info. I will look into that for sure. I have one coming hopefully later this week. Thanks again,Tony?
toggle quoted message
Show quoted text
On Apr 14, 2024, at 6:45?PM, Leon Robinson via groups.io <leon-robinson@...> wrote:
? Tony, A few years ago I had a National NC-109 with an open audio transformer.? I didn't have any audio transformers but I did have a 6.3 Volt filament transformer, I did some calculations and found that the Impedance ratio were almost exactly the same. I installed it and it worked perfectly.
Leon Robinson ?? K5JLR
Political Correctness is a Political Disease.
Politicians and Diapers should be changed
often and for the same reasons.
On Friday, April 12, 2024 at 05:21:39 AM CDT, Tony Lunsford <tony@...> wrote:
Hello everyone, I¡¯m in the process of getting a SX-140 back on the air. If anyone has an audio output transformer (T4) that you would like to sell, I would really appreciate it. Thanks. ?Tony N5DIM?
--
Tony Lunsford?
|
Re: SX-140 Audio transformer
Tony, A few years ago I had a National NC-109 with an open audio transformer.? I didn't have any audio transformers but I did have a 6.3 Volt filament transformer, I did some calculations and found that the Impedance ratio were almost exactly the same. I installed it and it worked perfectly.
Leon Robinson ?? K5JLR
Political Correctness is a Political Disease.
Politicians and Diapers should be changed
often and for the same reasons.
On Friday, April 12, 2024 at 05:21:39 AM CDT, Tony Lunsford <tony@...> wrote:
Hello everyone, I¡¯m in the process of getting a SX-140 back on the air. If anyone has an audio output transformer (T4) that you would like to sell, I would really appreciate it. Thanks. ?Tony N5DIM?
|
|
|
Update.? I got a cap installed.? This one is brand new from tubesandmore.com.? it does not fit.? I had to make it fit.? I used a cut off D shaft and a Millen Flex coupler.? I have not tested on air yet.? Will load it up tomorrow.? The cap is rated at 600v and has slightly less capacitance. Fingers crossed.
|
|
|
Re: SR2000 RF drive level
|
Hello everyone, I¡¯m in the process of getting a SX-140 back on the air. If anyone has an audio output transformer (T4) that you would like to sell, I would really appreciate it. Thanks. ?Tony N5DIM?
|
I'll take one.? TNX
wa3gin
On Tue, Apr 9, 2024 at 9:22?PM W7WRX < clark@...> wrote: I have only one Masonite back panel for my PS 2000.? ?I dropped it off to a print shop and contracted them to reproduce these.? If anyone wants one, please let me know.? I have no idea what they will cost.? I dont care. Once I find out I will post it.?
C?
|
I¡¯ll take one.
73, Jim N9WW
|
Re: SR-150 Injection Voltage
OK, good luck with it. 73
Walt Cates, WD0GOF
?
A majority of acceptance is not proof of correctness.
toggle quoted message
Show quoted text
?
Thanks, Walt. Will go back and verify what I am measuring and it looks like this stage is working properly. Next on to the mixer xtals, etc..
|
I have only one Masonite back panel for my PS 2000.? ?I dropped it off to a print shop and contracted them to reproduce these.? If anyone wants one, please let me know.? I have no idea what they will cost.? I dont care. Once I find out I will post it.?
C?
|
Re: SR-150 Injection Voltage
Thanks, Walt. Will go back and verify what I am measuring and it looks like this stage is working properly. Next on to the mixer xtals, etc..
Right now the radio is mute but have not started any tracing. It was rescued from a house fire where it did not get damaged directly but was in a fume environment apparently so probably needs detailed contact cleaning.. Looks deceptively clean but we know how that can go.
73 ... Ed
On Tuesday, April 9, 2024 at 05:57:47 PM CDT, waltcates <cateswa@...> wrote:
See red below
Walt Cates, WD0GOF
?
A majority of acceptance is not proof of correctness.
?
This question mainly for Walt. Finally starting on the first of two radios here and question the voltage reading for V6. The original manual only calls for 7 volts but in your instructions, Walt, you call for peaking T4 for a 30V
level. The 7v in the manual is rms that equals 19.8vpp
The initial reading on this rig was about 11-12 volts with my Boonton rf meter and frequencies were both dead on. So far so good. Next tested peaking T4 and could indeed get to 30V easily with a slight roll off to the correct side.?Here
again the Boonton is measuring rms. 11vrms = 30.8vpp
Now wondering which is the level I need? Been a long time since I studied product detector theory and don't remember if the higher oscillator injection voltage was required. Can you clarify for me?
TNX es 73 ... Ed, WA9GQK
|
Re: SR-150 Injection Voltage
See red below
Walt Cates, WD0GOF
?
A majority of acceptance is not proof of correctness.
toggle quoted message
Show quoted text
?
This question mainly for Walt. Finally starting on the first of two radios here and question the voltage reading for V6. The original manual only calls for 7 volts but in your instructions, Walt, you call for peaking T4 for a 30V
level. The 7v in the manual is rms that equals 19.8vpp
The initial reading on this rig was about 11-12 volts with my Boonton rf meter and frequencies were both dead on. So far so good. Next tested peaking T4 and could indeed get to 30V easily with a slight roll off to the correct side.?Here
again the Boonton is measuring rms. 11vrms = 30.8vpp
Now wondering which is the level I need? Been a long time since I studied product detector theory and don't remember if the higher oscillator injection voltage was required. Can you clarify for me?
TNX es 73 ... Ed, WA9GQK
|
This question mainly for Walt. Finally starting on the first of two radios here and question the voltage reading for V6. The original manual only calls for 7 volts but in your instructions, Walt, you call for peaking T4 for a 30V level.
The initial reading on this rig was about 11-12 volts with my Boonton rf meter and frequencies were both dead on. So far so good. Next tested peaking T4 and could indeed get to 30V easily with a slight roll off to the correct side.
Now wondering which is the level I need? Been a long time since I studied product detector theory and don't remember if the higher oscillator injection voltage was required. Can you clarify for me?
TNX es 73 ... Ed, WA9GQK
|
Hallicrafters R274 parts wanted
I am looking for a Hallicrafters R274? parts radio, or individual parts, im looking for the entire tuning gear assembly, including the main dial showing the frequencies,,, let me know what you might have...Thanks...WV8KU
|
LOL, a early and a late HT-9 would be good but even better would be having coils and tuning units to put one of the two on the air.
73,
Tom N5AMA
|
Jim Whartenby
Dave Jordan
waltcates