Re: Old Heathkit Ham Linear Tube Amplifiers .... Mods, Repairs, best Refurbishment practices ?
Gren,
One of the best online amplifier reference website is found at:
73,
Ray, W4BYG
On 1/19/2024 21:57, gren wrote:
Hoping to stimulate some discussion on Old Ham Tube Linear Amps:
? Are there any experienced with the various Tube Amp issues,
???? ... such as Arcing and Band SW,? coil,? capacitor & tube
and HV Xfrmr destruction in these amplifiers ?
I am beginning to refurbish two old Heathkit Linear Amps:
?? the SB-1000? ( similar to the AL-80)?
& the SB-200.
? Scouring the Web looking for information on refurbishing issues
and modifying old Heathkit Ham Linear Tube amplifiers
quick summary:
PS Cap board
Metering board /Bias
Soft-Key
Soft-Start
Parasitic's
Glitch resistor
HEC HV Caps
Self-biasing of relays
"Corona Washer "
QSK
new tubes ...
poor solder joints (expected)
Band Sw issues,
etc.
There are plenty of Ham Blogs on the SB-200? & SB-220,? ...?
but fewer on the SB-1000 & HL-2200.
?Articles by Richard Measures, and others, some with theory,
discussion, diagrams, photos ,
??? and, as with anything,? some miss-information and some
corrections.
There are a lot of YouTube videos,? and ? AmpRepairGuy.com?? has
some videos of his repairs.
? Likely others , all requiring sifting the information and
reasoning.
Harbach Co.? & CTR Engineering? Kits,? parts for? Mods
(depending on the Amp Model):
? Having good instruction,? kits, ? PCB's ?? and downloadable
pdf's at both of these? two? web sites:
Possibly the Richard Measures (SK) Amp Forum, has some priceless,?
sometimes buried help:
The "search" bar? { below }? can still dial in the query:
example:
And,
? ....? there seem to be some PCB's? from?? W7RY , although I have
not been successful getting adequate answers or actually
purchasing the PCB's
thanks,
--
"If you want to build a strong house, I'll give you my engineer's number.
If you want to build a strong life, I'll introduce you to my carpenter."
Lebron and Heather Lackey
|
Re: Old Heathkit Ham Linear Tube Amplifiers .... Mods, Repairs, best Refurbishment practices ?
I have *no* experience in this domain, so I am unable to offer advice. However, I have a Yaesu FT-101E and a Kenwood TS-520 in queue for functional restoration for sentimental reasons both of which are hybrids with tube finals. So I shall be paying close attention to the discussion.
The *only* contribution I might be able to make is generic WW II era parts that my Dad left me. If, for example, someone finds an HRO in need of a tuning capacitor I have several NOS HW-4s. Those were $30 list in 1942 per the handbook catalog. That was a week's wages for the people who made them. As those are about as pure unobtainium as it gets I shall be very picky about whom I sell them to, and it will probably be more than $30. Price based solely on my assessment of the buyer. Free to "RF Gods". but it will take a strong publication record in QST to rate that status. To the best of my knowledge, those are the finest air variables *ever* made on a production basis.
Have Fun!
Reg
On Friday, January 19, 2024 at 08:57:27 PM CST, gren <hrgerson@...> wrote:
Hoping to stimulate some discussion on Old Ham Tube Linear Amps:
? Are there any experienced with the various Tube Amp issues,
???? ... such as Arcing and Band SW,? coil,? capacitor & tube and HV Xfrmr destruction in these amplifiers ?
I am beginning to refurbish two old Heathkit Linear Amps:
?? the SB-1000? ( similar to the AL-80)?
& the SB-200.
? Scouring the Web looking for information on refurbishing issues and modifying old Heathkit Ham Linear Tube amplifiers
quick summary:
PS Cap board
Metering board /Bias
Soft-Key
Soft-Start
Parasitic's
Glitch resistor
HEC HV Caps
Self-biasing of relays
"Corona Washer "
QSK
new tubes ...
poor solder joints (expected)
Band Sw issues,
etc.
There are plenty of Ham Blogs on the SB-200? & SB-220,? ...? but fewer on the SB-1000 & HL-2200.
?Articles by Richard Measures, and others, some with theory, discussion, diagrams, photos ,
??? and, as with anything,? some miss-information and some corrections.
There are a lot of YouTube videos,? and ? AmpRepairGuy.com?? has some videos of his repairs.
? Likely others , all requiring sifting the information and reasoning.
Harbach Co.? & CTR Engineering? Kits,? parts for? Mods (depending on the Amp Model):
? Having good instruction,? kits, ? PCB's ?? and downloadable .pdf's at both of these? two? web sites:
Possibly the Richard Measures (SK) Amp Forum, has some priceless,? sometimes buried help:
The "search" bar? { below }? can still dial in the query:
example:
And,
? ....? there seem to be some PCB's? from?? W7RY , although I have not been successful getting adequate answers or actually purchasing the PCB's
thanks,
|
Re: Old Heathkit Ham Linear Tube Amplifiers .... Mods, Repairs, best Refurbishment practices ?
Watch out for failed dropping resistors for the metering circuit for the high voltage. IIRC they are 4.7meg. Replace them with metal oxide 3W in place of the 2W ones there. I would do that anyway even if those old carbon comp resistors measure okay. Needless to say the HV supply can kill you quite easily!
Sam Reaves
ARS W3OHM
Owner / Moderator of: LeCroy Owners Group on Groups.io
Sencore Owners Group on Groups.io Sprint Layout Group on Groups.io?? Pulsonix EDA Group on Groups.io
LPKF Owners Group on Groups.io
Electronics and Mechanical Hardware Design Engineering Manager
Staff Scientist Andritz Rolls Global Research Center (RETIRED)
Hoping to stimulate some discussion on Old Ham Tube Linear Amps:
? Are there any experienced with the various Tube Amp issues,
???? ... such as Arcing and Band SW,? coil,? capacitor & tube and HV Xfrmr destruction in these amplifiers ?
I am beginning to refurbish two old Heathkit Linear Amps:
?? the SB-1000? ( similar to the AL-80)?
& the SB-200.
? Scouring the Web looking for information on refurbishing issues and modifying old Heathkit Ham Linear Tube amplifiers
quick summary:
PS Cap board
Metering board /Bias
Soft-Key
Soft-Start
Parasitic's
Glitch resistor
HEC HV Caps
Self-biasing of relays
"Corona Washer "
QSK
new tubes ...
poor solder joints (expected)
Band Sw issues,
etc.
There are plenty of Ham Blogs on the SB-200? & SB-220,? ...? but fewer on the SB-1000 & HL-2200.
?Articles by Richard Measures, and others, some with theory, discussion, diagrams, photos ,
??? and, as with anything,? some miss-information and some corrections.
There are a lot of YouTube videos,? and ? AmpRepairGuy.com?? has some videos of his repairs.
? Likely others , all requiring sifting the information and reasoning.
Harbach Co.? & CTR Engineering? Kits,? parts for? Mods (depending on the Amp Model):
? Having good instruction,? kits, ? PCB's ?? and downloadable .pdf's at both of these? two? web sites:
Possibly the Richard Measures (SK) Amp Forum, has some priceless,? sometimes buried help:
The "search" bar? { below }? can still dial in the query:
example:
And,
? ....? there seem to be some PCB's? from?? W7RY , although I have not been successful getting adequate answers or actually purchasing the PCB's
thanks,
|
Old Heathkit Ham Linear Tube Amplifiers .... Mods, Repairs, best Refurbishment practices ?
Hoping to stimulate some discussion on Old Ham Tube Linear Amps:
? Are there any experienced with the various Tube Amp issues,
???? ... such as Arcing and Band SW,? coil,? capacitor & tube and HV Xfrmr destruction in these amplifiers ?
I am beginning to refurbish two old Heathkit Linear Amps:
?? the SB-1000? ( similar to the AL-80)?
& the SB-200.
? Scouring the Web looking for information on refurbishing issues and modifying old Heathkit Ham Linear Tube amplifiers
quick summary:
PS Cap board
Metering board /Bias
Soft-Key
Soft-Start
Parasitic's
Glitch resistor
HEC HV Caps
Self-biasing of relays
"Corona Washer "
QSK
new tubes ...
poor solder joints (expected)
Band Sw issues,
etc.
There are plenty of Ham Blogs on the SB-200? & SB-220,? ...? but fewer on the SB-1000 & HL-2200.
?Articles by Richard Measures, and others, some with theory, discussion, diagrams, photos ,
??? and, as with anything,? some miss-information and some corrections.
There are a lot of YouTube videos,? and ? AmpRepairGuy.com?? has some videos of his repairs.
? Likely others , all requiring sifting the information and reasoning.
Harbach Co.? & CTR Engineering? Kits,? parts for? Mods (depending on the Amp Model):
? Having good instruction,? kits, ? PCB's ?? and downloadable .pdf's at both of these? two? web sites:
Possibly the Richard Measures (SK) Amp Forum, has some priceless,? sometimes buried help:
The "search" bar? { below }? can still dial in the query:
example:
And,
? ....? there seem to be some PCB's? from?? W7RY , although I have not been successful getting adequate answers or actually purchasing the PCB's
thanks,
|
Re: A third hand system that actually works!
Nice idea!
--
With best regards
Tam HANNA
Enjoy electronics? Join 21k4 other followers by visiting the Crazy Electronics Lab at
|
A third hand system that actually works!
FYI I thought this would be of sufficient interest to justify crossposting a link.
!/msg5248170/#msg5248170
Let's just say I bare the scars of the magnifying glass and alligator clip devices.
These magnetic bases are really weak. Stronger ones will let you use a sheet of galvanized steel under the ESD mat which adds a lot of friction if you happen to push on one.
But for ~$20 this such an improvement it's hard to describe. You can also just attach the arms to a flat steel plate with rubber feet and no magnets. Even stiffer and ~$6 cheaper.
Have Fun!
Reg
|
Re: Class-E Amplifier Woes
Just a moment for a few memories of my old friend Nathan..
I .Often Visited Nat at Design Automation in 1980s
He was a brilliant engineer, and teacher, with a wide range of interests, especially power electronics topology.
Nat collaborated with other engineers in East Europe and Asia.
He created a CAD program for class E design and wrote the book on class E.
Nat recieved an IEEE award for his class E invention.
As ¨¤ consultant, Nathan Sokal was my mentor.
RIP Nathan, old friend...
from Jon in Paris
|
Re: Super low noise PSU for the OXCOs
I'm finally getting around to setting up an instrument I've had for a year or two and you suggest another instrument? Get real. For my use case there is no benefit.
On Thursday, October 12, 2023 at 08:03:05 PM CDT, David Kirkby <drkirkby@...> wrote:
You might consider looking for an HP 34970A. It¡¯s basically a 34401A 6.5 digit multimeter with plug in cards. But unlike the 3457A, the different cards do different things.
Digital I/O RF switching D to A Relay switches Voltage current, 2 and 4 wire resistance? Supports various thermocouple types with cold junction compensation?
It takes up to 3 cards. If you just want two wire measurements, you can probably measure in excess of 100 channels.?
The 34980A is similar but has USB and LAN rather than GPIB. These fetch more ????¡¯s
It¡¯s worth looking for the service notes on the 34970A and comparing them with the S/N of a model that you but. In later S/N the ventilation in the case was changed, the fan type changed. This was to improve thermocouple measurements.?
On Thu, 12 Oct 2023 at 23:02, Reginald Beardsley via <pulaskite= [email protected]> wrote: I've had a chance to work on this and am making a board with 3x LM317s to test along with 3x LM399s and 3x AD584JH modules.? The 10th channel of the 44492A will monitor the output of the LT3045.? For now I simply glued a thermal pad between the LT3045 eval board and? and the heatsink.? All the references will be in a gasketed aluminum box with batting to suppress convection currents.
I'd be very? grateful for links to examples of reading data from the 3457A in 7.5 digit mode using the 44492A.
I'm also looking for? low cost? temperature, humidity & barometric pressure loggers so? I can collect data in several points in the lab in case anyone has suggestions.
Have Fun!
Reg
|
Re: Super low noise PSU for the OXCOs
You might consider looking for an HP 34970A. It¡¯s basically a 34401A 6.5 digit multimeter with plug in cards. But unlike the 3457A, the different cards do different things.
Digital I/O RF switching D to A Relay switches Voltage current, 2 and 4 wire resistance? Supports various thermocouple types with cold junction compensation?
It takes up to 3 cards. If you just want two wire measurements, you can probably measure in excess of 100 channels.?
The 34980A is similar but has USB and LAN rather than GPIB. These fetch more ????¡¯s
It¡¯s worth looking for the service notes on the 34970A and comparing them with the S/N of a model that you but. In later S/N the ventilation in the case was changed, the fan type changed. This was to improve thermocouple measurements.?
On Thu, 12 Oct 2023 at 23:02, Reginald Beardsley via <pulaskite= [email protected]> wrote: I've had a chance to work on this and am making a board with 3x LM317s to test along with 3x LM399s and 3x AD584JH modules.? The 10th channel of the 44492A will monitor the output of the LT3045.? For now I simply glued a thermal pad between the LT3045 eval board and? and the heatsink.? All the references will be in a gasketed aluminum box with batting to suppress convection currents.
I'd be very? grateful for links to examples of reading data from the 3457A in 7.5 digit mode using the 44492A.
I'm also looking for? low cost? temperature, humidity & barometric pressure loggers so? I can collect data in several points in the lab in case anyone has suggestions.
Have Fun!
Reg
|
Re: Super low noise PSU for the OXCOs
Thanks for the tip.
BTW are there any parts which are hard for you to get? I'd like to see if I can help.
On Thursday, October 12, 2023 at 05:41:03 PM CDT, Daniel Ricardo Perez LW1ECP via groups.io <danyperez1@...> wrote:
Serendipity. I have just found this in my inbox:
https://www.analog.com/en/products/ltm8080.html
These are advertised as "Ultralow Noise, Ultrahigh PSRR" regulators, though they are SMPS.
Check the noise nanovolts versus f to decide if this fits your needs.
Daniel Perez LW1ECP
|
Re: Super low noise PSU for the OXCOs
Serendipity. I have just found this in my inbox:
https://www.analog.com/en/products/ltm8080.html
These are advertised as "Ultralow Noise, Ultrahigh PSRR" regulators, though they are SMPS.
Check the noise nanovolts versus f to decide if this fits your needs.
Daniel Perez LW1ECP
|
Re: Super low noise PSU for the OXCOs
I've had a chance to work on this and am making a board with 3x LM317s to test along with 3x LM399s and 3x AD584JH modules. The 10th channel of the 44492A will monitor the output of the LT3045. For now I simply glued a thermal pad between the LT3045 eval board and and the heatsink. All the references will be in a gasketed aluminum box with batting to suppress convection currents.
I'd be very grateful for links to examples of reading data from the 3457A in 7.5 digit mode using the 44492A.
I'm also looking for low cost temperature, humidity & barometric pressure loggers so I can collect data in several points in the lab in case anyone has suggestions.
Have Fun!
Reg
|
Re: CTI OSC5A2B02 OXCO module high precision frequency reference project
I have 20x bare OXCOs of which 10x have been tested to determine the voltage required to set to near (dF < 0.1 Hz) 10 MHz. Based on that result I bought 10x more.
The voltage varies quite a bit, but I only care if they oscillate at 10 MHz under voltage control.
The motivation for the project was a very basic error analysis using the CTI datasheet. Then I realized that the tuning rate and 0.05 ppb/s stability implied a 50 uVrms noise level on Vctl. That was not easy to do when these were made. The LM399 is guaranteed at <20 uVrms.
So I got to wondering. If I feed these really clean power in a clean environment what will they do?
More importantly, can I measure the 10 MHz voltage for a year and predict the voltage to within 1-2% for the next year? With length of valid prediction equal to length of observed behavior that becomes pretty powerful. 1-2-4-8-16-32 year cal intervals.
I've done a lot of numerical experiments solving the heat equation which has a similar mathematical form using basis pursuit and GLPK with arbitrary accuracy arithmetic.
I'm mostly considering the Peltier's as a means of doing tempco testing. However, I'd like to note that when John Strong's ruling engine was in operation at Johns Hopkins in the early '50s it was immersed in a massive quantity of temperature controlled oil. There was a visitor area that allowed visitors to view the machine in operation. But visitor number and duration was strictly limited to avoid overwhelming the oil bath (0.01 C IIRC) controller.
Have Fun!
Reg
On Monday, September 11, 2023 at 04:10:44 AM CDT, Gerhard_DK4XP via groups.io <dk4xp@...> wrote:
On 08.08.23 03:42, Reginald Beardsley via groups.io wrote:
> These?are?available?for?$3?each?on?ebay.??They?are?salvaged?from?old?cell?tower?GPSDOs.
> The?new?specs?are?very?good?and?they?are?well?aged?so?long?term?stability?should?be?excellent
> and?an?order?of?magnitude?or?more?better?than?a?new?OXCO.
> 10?year?aging?rate?is?specified?at?0.4?ppb/yr.
My experience with cheap Chinese crystal ovens that have spent their
useful live on a cell tower is: ? They have been removed from their
home with hammer and sickle (my explanation of the scars) and they drifted
towards the extremes of their tuning range, where they may cease to
oscillate
with some tuning voltages.
I have given up on that. Here are some pics from opening a failed Morion
MV89A
double oven oscillator that was such a case.
I could at least salvage the 5 MHz SC cut crystal.? These are hard to get.
<
? >
and the photos to the right.
If you use complete oscillators and do not construct them yourself, then
the last
voltage regulator (the one that counts) usually is already in the can,
where it can enjoy
the constant if elevated temperature.
And Peltiers are not the way to go. Nobody does that in oscillators.
They have
a very low thermal impedance, so temperature changes of the environment are
passed to the inside on the spot. The control loop then must make up for it.
All a Peltier can do is to produce a temperature offset.
Gerhard DK4XP
|
Re: CTI OSC5A2B02 OXCO module high precision frequency reference project
On 08.08.23 03:42, Reginald Beardsley via groups.io wrote: These?are?available?for?$3?each?on?ebay.??They?are?salvaged?from?old?cell?tower?GPSDOs. The?new?specs?are?very?good?and?they?are?well?aged?so?long?term?stability?should?be?excellent and?an?order?of?magnitude?or?more?better?than?a?new?OXCO. 10?year?aging?rate?is?specified?at?0.4?ppb/yr. My experience with cheap Chinese crystal ovens that have spent their useful live on a cell tower is: ? They have been removed from their home with hammer and sickle (my explanation of the scars) and they drifted towards the extremes of their tuning range, where they may cease to oscillate with some tuning voltages. I have given up on that. Here are some pics from opening a failed Morion MV89A double oven oscillator that was such a case. I could at least salvage the 5 MHz SC cut crystal.? These are hard to get. < ? > and the photos to the right. If you use complete oscillators and do not construct them yourself, then the last voltage regulator (the one that counts) usually is already in the can, where it can enjoy the constant if elevated temperature. And Peltiers are not the way to go. Nobody does that in oscillators. They have a very low thermal impedance, so temperature changes of the environment are passed to the inside on the spot. The control loop then must make up for it. All a Peltier can do is to produce a temperature offset. Gerhard DK4XP
|
Re: CTI OSC5A2B02 OXCO module high precision frequency reference project
A quality GPSDO is good to 1e-13. I'm seeing 1e-10 over several days in a very unstable temperature environment from a single OXCO with a lab supply and loads of EMI.
I plan 4 OXCOs which will be filtered to the fundamentals and fed to 6 mixers. Each mixer output will be the difference frequency of a pair of OXCOs. These low frequency signals will then be fed to zero crossing detectors and counters to measure the relative frequency differences.
As needed an MCU will update the DAC outputs controlling the OXCO frequencies based on measured environmental and aging history to attempt to maintain 1e-11. A factor of 10 better than current generic Chinese PCB version.
That doesn't seem that big a stretch. We'll just have to see.
Have Fun!
Reg
On Sunday, September 10, 2023 at 05:12:34 PM CDT, David Kirkby <drkirkby@...> wrote:
On Tue, 8 Aug 2023 at 02:42, Reginald Beardsley via <pulaskite= [email protected]> wrote: After?some?study,?I've?concluded?that?the?main?limitation?on?the?stability?of?these?is?power?supply?noise?and?temperature?stability.??I'd?like?to?get?to?0.01?ppb/yr?just?to?see?if?I?can.??The?10x?rule?of?thumb?dictates?that?I?need?noise?and?voltage?drift?in?the?single?uV?range?which?will?not?be?easy?or?quick.
Reg
0.001 ppb/year sounds unrealistic to me - by a long way. Looking at the specifications of a high-end frequency counter from Keysight, with an optional ultra high stability oven, its 50 ppb/year
Keysight specs are pretty conservative, so we might assume they actually achieve 5 ppb/year, but what you would like to get is 5 000 times better than that.
The datasheet for the Stanford Research PRS10 rubidium oscillator gives (5 x 10^-11 / year), which is 50 times worst than you would like to get.
I know you laughed at my earlier suggestion of using an LTZ1000A, but even with that, you are not going to achieve anywhere near what you want.
|
Re: CTI OSC5A2B02 OXCO module high precision frequency reference project
On Tue, 8 Aug 2023 at 02:42, Reginald Beardsley via <pulaskite= [email protected]> wrote:
After?some?study,?I've?concluded?that?the?main?limitation?on?the?stability?of?these?is?power?supply?noise?and?temperature?stability.??I'd?like?to?get?to?0.01?ppb/yr?just?to?see?if?I?can.??The?10x?rule?of?thumb?dictates?that?I?need?noise?and?voltage?drift?in?the?single?uV?range?which?will?not?be?easy?or?quick.
Reg
0.001 ppb/year sounds unrealistic to me - by a long way. Looking at the specifications of a high-end frequency counter from Keysight, with an optional ultra high stability oven, its 50 ppb/year
Keysight specs are pretty conservative, so we might assume they actually achieve 5 ppb/year, but what you would like to get is 5 000 times better than that.
The datasheet for the Stanford Research PRS10 rubidium oscillator gives (5 x 10^-11 / year), which is 50 times worst than you would like to get.
I know you laughed at my earlier suggestion of using an LTZ1000A, but even with that, you are not going to achieve anywhere near what you want.
|
Re: Super low noise PSU for the OXCOs
As it happens I got an LT3045 module a few days ago, but had not yet opened the bag. I've been working on a leaky roof. And discovered I'm in *really* poor shape. 90 minutes and I'm beat.
I just calibrated a Mastech GPS-1850D 0-20 V 0-5 A linear supply so it reads to within 0.05%. Though manual, that should serve very well for testing the LT3045. I can put a Peltier device on the fins of the LT3045 module and then fins on the opposite side and measure temperature variation. Should be fun. I've got a pair of 34401As to measure the input and output voltages.
I couldn't find any information about long term aging in the LT3045 datasheet. Do you know of any?
I'm modifying a 3497A to multiplex 100 sources to a 3457A for long term monitoring. I'm going to buy 50 new ones and compare them side by side. Is there an improvement in stability with aging? What is the limit of stability? Can I predict it?
I'll have two loops of air flow on either side of a Peltier device so I can vary the ambient temperature in a voltage controlled fashion when I compare the new and used devices. Half on each side. I'll actually have to cut the number of devices because of the need to measure thermocouples interspersed with the LM317s. My expectation is I'll be able select pairs of LM317s such that the output voltage is especially stable over temperature and at the same time reduce the voltage from the transformer to the 20 V input limit of the LT3045.
I just checked the fit of a Peltier module on the LT3045 and I just need longer screws.
Have fun!
Reg
On Sunday, September 10, 2023 at 02:01:42 PM CDT, Gerhard_DK4XP via groups.io <dk4xp@...> wrote:
On 10.09.23 18:46, Reginald Beardsley via groups.io wrote:
> I'm familiar with the LM317 and happened to find used ones. They have
> a 1.25 V zener reference
> which should be very stable due to aging. I'm hoping that I'll be able
> to pair tempcos to be zero under normal lab conditions.
Ignoring the progress in electronics of the last 40 years does not help.
No, they have a band gap reference and it shows in the horrible noise
plots. Band gap references live on amplifying
the difference between tiny voltages generated by small currents and
different current densities. The LM317 / 350
is 40 dB worse in noise than LT3042 / 3045 or the negative LT3094.? The
file names of the trace files show the part
values used in their resp. standard data sheet circuits.
A 1.25V Zener would have next to no noise at all, but a very soft knee.
If the LT* are too weak, an external power transistor can take the heat.
The noise behavior stays essentially the same.
(data sheet of 3043/45 page 17 or so)
I have described that in 2022 Dubus, and soon on my web site, when I
have re-established ftp access to the
maintainer interface.
I wonder how LT designed the reference current source. With 0.5% Susumu
thin film ref resistors, the output
voltage is usually on spot within a milliVolt. Thick film resistors can
have worse 1/f noise than carbon composition
when there is a DC voltage across them.
The noise plots have been made with averaging over 10 * 2 ADA-4898 op
amps. The preamp in front of the
Agilent 89441A FFT analyzer features a noise density of 220 pV/rt Hz. At
very low frequencies, it shows that
the input capacitor is too small (noise rise steeper then 1/f ).
There are noise plots of Zeners, LEDs abused as voltage reference and
other things on my Flickr account
<
?? >
73, Gerhard?? DK4XP
|
Re: Super low noise PSU for the OXCOs
On 10.09.23 18:46, Reginald Beardsley via groups.io wrote: I'm familiar with the LM317 and happened to find used ones. They have a 1.25 V zener reference
which should be very stable due to aging. I'm hoping that I'll be able to pair tempcos to be zero under normal lab conditions. Ignoring the progress in electronics of the last 40 years does not help. No, they have a band gap reference and it shows in the horrible noise plots. Band gap references live on amplifying the difference between tiny voltages generated by small currents and different current densities. The LM317 / 350 is 40 dB worse in noise than LT3042 / 3045 or the negative LT3094.? The file names of the trace files show the part values used in their resp. standard data sheet circuits. A 1.25V Zener would have next to no noise at all, but a very soft knee. If the LT* are too weak, an external power transistor can take the heat. The noise behavior stays essentially the same. (data sheet of 3043/45 page 17 or so) I have described that in 2022 Dubus, and soon on my web site, when I have re-established ftp access to the maintainer interface. I wonder how LT designed the reference current source. With 0.5% Susumu thin film ref resistors, the output voltage is usually on spot within a milliVolt. Thick film resistors can have worse 1/f noise than carbon composition when there is a DC voltage across them. The noise plots have been made with averaging over 10 * 2 ADA-4898 op amps. The preamp in front of the Agilent 89441A FFT analyzer features a noise density of 220 pV/rt Hz. At very low frequencies, it shows that the input capacitor is too small (noise rise steeper then 1/f ). There are noise plots of Zeners, LEDs abused as voltage reference and other things on my Flickr account < ?? > 73, Gerhard?? DK4XP
|
Re: Super low noise PSU for the OXCOs
I'm familiar with the LM317 and happened to find used ones. They have a 1.25 V zener reference
which should be very stable due to aging. I'm hoping that I'll be able to pair tempcos to be zero under normal lab conditions.
On Sunday, September 10, 2023 at 11:36:01 AM CDT, Jerry <jerry@...> wrote:
Why did you overlook the lt3045 ldo modules?? There are prebuilt modules having pins that plug in like an lm317.? I use the modules with batteries on my phase noise test system.
The LM317s arrived. Now I have to characterize them. The tabs are the outputs so I've ordered nylon threaded hex spacers to assist in mounting them. I have a nice 20 V 5 A linear lab supply to feed the parts and a precision voltage reference and op amp to drive the Vctl pins and the metering system. And a suitable means of controlling the environment. I've got 5x 44421/2A relay cards and a 3457A. Inclination is to use an ATMega to drive the relay cards via GPIB along with the 3457A. At NPLC 10 the 3457A will read each device twice a minute at 7.5 digits in MATH HI-RES mode. 15 mV seems a good choice of reference voltage as that will put the 3457A mid range on its lowest scale. I've been wrestling with the how to measure thermal stability. A circulating system with a set of Peltier devices and lots of thermal sensors and muffin fans seems a start. I just cut a pair of 83 mm squares of 0.200" aluminum which I'll glue with thermal cement to opposite sides of four 40 mm Peltier junctions which will in turn be attached to large heatsinks. The plates are because the heatsinks are only 70 mm wide. It should improve transfer from the Peltier device to the heatsinks. That will let me measure them heating and cooling just by reversing the Peltier polarity. A hot loop and a cold loop. Muffin fan apiece. There's no need for strength, so roof flashing will serve for ductwork. Foil face foam insulation mounted at the corners inside a large box with batting to suppress air currents. I built a triple stacked junction device with a CPU fan. It will hit freezing in seconds. That's part of a more elaborate version of this environmental test setup. The relevant question is what are the "ideal" parameters? I have no clue at this point other than simple stability over time and temperature. That may be it. Pick pairs which have best lab environment stability. Have Fun! Reg
|
Re: Super low noise PSU for the OXCOs
Why did you overlook the lt3045 ldo modules?? There are prebuilt modules having pins that plug in like an lm317.? I use the modules with batteries on my phase noise test system.
The LM317s arrived. Now I have to characterize them. The tabs are the outputs so I've ordered nylon threaded hex spacers to assist in mounting them. I have a nice 20 V 5 A linear lab supply to feed the parts and a precision voltage reference and op amp to drive the Vctl pins and the metering system. And a suitable means of controlling the environment. I've got 5x 44421/2A relay cards and a 3457A. Inclination is to use an ATMega to drive the relay cards via GPIB along with the 3457A. At NPLC 10 the 3457A will read each device twice a minute at 7.5 digits in MATH HI-RES mode. 15 mV seems a good choice of reference voltage as that will put the 3457A mid range on its lowest scale. I've been wrestling with the how to measure thermal stability. A circulating system with a set of Peltier devices and lots of thermal sensors and muffin fans seems a start. I just cut a pair of 83 mm squares of 0.200" aluminum which I'll glue with thermal cement to opposite sides of four 40 mm Peltier junctions which will in turn be attached to large heatsinks. The plates are because the heatsinks are only 70 mm wide. It should improve transfer from the Peltier device to the heatsinks. That will let me measure them heating and cooling just by reversing the Peltier polarity. A hot loop and a cold loop. Muffin fan apiece. There's no need for strength, so roof flashing will serve for ductwork. Foil face foam insulation mounted at the corners inside a large box with batting to suppress air currents. I built a triple stacked junction device with a CPU fan. It will hit freezing in seconds. That's part of a more elaborate version of this environmental test setup. The relevant question is what are the "ideal" parameters? I have no clue at this point other than simple stability over time and temperature. That may be it. Pick pairs which have best lab environment stability. Have Fun! Reg
|
Ray, W4BYG
Sam Reaves
Froggie the Gremlin
Daniel Ricardo Perez LW1ECP
