My Boonton 92 quit working.

[amdx]

I got a Boonton 92EA off Ebay and it worked fine, I left it on overnight
and now it doesn't work. I found the 15 volt regulator has no output.
The part is obsolete, I did find one cheap $4 but with a $25 minimum
order. The Regulator is a 4 pin 78MGCP. I want to replace it with a
plain old 7815.

I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?
Other than, physical differences.
Here's is a link to the 78MGCP datasheet pdf.
http://pdf1.alldatasheet.net/datasheet-pdf/view/129322/FAIRCHILD/UA78MGC.html

Here's the schematic and my proposed sub with the 7815.
http://s395.photobucket.com/user/Qmavam/media/Boonton15VRegulatorSub_zps0e61ff6d.png.html

Mikek

 

amdx <nojunk@knology.net> wrote:

I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?

"Art of Electronics" 2nd edition talks about four-terminal regulators.

This might take you to the relevant page:
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or
<http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false>
or even
http://is.gd/wBtiHz

If not, Google, in quotes, "Historically they were preceded by four-
terminal adjustable regulators" and that should take you to the AoE page
(345 in the 2nd edition).

In the pages around that one, Table 6.9 claims 1% typical line and load
regulation for the uA78GU1C , for up to half max current and a 30 V
supply (or, 150 mV load regulation). Table 6.8 claims 12 mV line
regulation and 4 mV load regulation for the LM7815CT, for max current
and a 30 V supply. So the 7815 has closer regulation on paper.

However, table 6.8 also claims that the LM7815CT has a 4% accuracy on
the output voltage, so the output can be anywhere from 14.4 to 15.6 V.
There is no accuracy spec for the adjustable regulator, presumably
because it can be adjusted to whatever you want. The rest of the
Boonton may or may not care about this much variation on the +15 V
line. You might also check the data sheet on your proposed 7815 to see
if they've gotten any better since 1989.

If you do go with the 7815, you could disconnect R1/R2 altogether to
save a milliamp. (Exercise: Will the electricity this saves over the
on-time of the Boonton be less or more than the electricity needed to
run the soldering iron for long enough to desolder them?)

Another idea would be to put in a LM317. Change R1 to 240 ohms and
select R2 to give you 15 V as accurately as you want at the output.
Table 6.9 again claims 0.1% typical line and 0.2% typical load
regulation for the LM317T (or, 30 mV load regulation) - better than
the four-terminal regulator.

Matt Roberds

 

[Phil Hobbs]

On 3/14/2014 10:49 PM, amdx wrote:

I got a Boonton 92EA off Ebay and it worked fine, I left it on overnight
and now it doesn't work. I found the 15 volt regulator has no output.
The part is obsolete, I did find one cheap $4 but with a $25 minimum
order. The Regulator is a 4 pin 78MGCP. I want to replace it with a
plain old 7815.

I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?
Other than, physical differences.
Here's is a link to the 78MGCP datasheet pdf.
http://pdf1.alldatasheet.net/datasheet-pdf/view/129322/FAIRCHILD/UA78MGC.html


Here's the schematic and my proposed sub with the 7815.
http://s395.photobucket.com/user/Qmavam/media/Boonton15VRegulatorSub_zps0e61ff6d.png.html


Mikek

There was nothing very special about the old 4-terminal regulators,
except that they split out the voltage sense lead from the ground return
for the internal circuitry, so that you could use a higher -impedance
voltage divider. The LM317/337 pretty much killed them off.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Michael Black]

On Sat, 15 Mar 2014, Phil Hobbs wrote:

On 3/14/2014 10:49 PM, amdx wrote:
I got a Boonton 92EA off Ebay and it worked fine, I left it on overnight
and now it doesn't work. I found the 15 volt regulator has no output.
The part is obsolete, I did find one cheap $4 but with a $25 minimum
order. The Regulator is a 4 pin 78MGCP. I want to replace it with a
plain old 7815.

I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?
Other than, physical differences.
Here's is a link to the 78MGCP datasheet pdf.
http://pdf1.alldatasheet.net/datasheet-pdf/view/129322/FAIRCHILD/UA78MGC.html


Here's the schematic and my proposed sub with the 7815.
http://s395.photobucket.com/user/Qmavam/media/Boonton15VRegulatorSub_zps0e61ff6d.png.html


Mikek

There was nothing very special about the old 4-terminal regulators, except
that they split out the voltage sense lead from the ground return for the
internal circuitry, so that you could use a higher -impedance voltage
divider. The LM317/337 pretty much killed them off.

So it's not something like the extra pin allows a place for a capacitor
that helps to improve the output?

It's been a long time since I looked at one of those four pin regulators,
I don't think I've ever seen one close up.

Michael

 

[Baron]

mroberds@att.net scribbled thus:

Another idea would be to put in a LM317. Change R1 to 240 ohms and
select R2 to give you 15 V as accurately as you want at the output.
Table 6.9 again claims 0.1% typical line and 0.2% typical load
regulation for the LM317T (or, 30 mV load regulation) - better than
the four-terminal regulator.

Matt Roberds

+1

This is the way I would go ! At least you can trim it to exactly 15V.

--
Best Regards:
Baron.

 

[amdx]

On 3/14/2014 10:50 PM, mroberds@att.net wrote:

amdx <nojunk@knology.net> wrote:
I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?

"Art of Electronics" 2nd edition talks about four-terminal regulators.

This might take you to the relevant page:
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or even
http://is.gd/wBtiHz

If not, Google, in quotes, "Historically they were preceded by four-
terminal adjustable regulators" and that should take you to the AoE page
(345 in the 2nd edition).

In the pages around that one, Table 6.9 claims 1% typical line and load
regulation for the uA78GU1C , for up to half max current and a 30 V
supply (or, 150 mV load regulation). Table 6.8 claims 12 mV line
regulation and 4 mV load regulation for the LM7815CT, for max current
and a 30 V supply. So the 7815 has closer regulation on paper.

However, table 6.8 also claims that the LM7815CT has a 4% accuracy on
the output voltage, so the output can be anywhere from 14.4 to 15.6 V.
There is no accuracy spec for the adjustable regulator, presumably
because it can be adjusted to whatever you want. The rest of the
Boonton may or may not care about this much variation on the +15 V
line. You might also check the data sheet on your proposed 7815 to see
if they've gotten any better since 1989.

If you do go with the 7815, you could disconnect R1/R2 altogether to
save a milliamp. (Exercise: Will the electricity this saves over the
on-time of the Boonton be less or more than the electricity needed to
run the soldering iron for long enough to desolder them?)

Another idea would be to put in a LM317.
Matt Roberds

Thank you, for the analysis.
I have found an LT1085CT that is adjustable and has 0.15% line and
0.1% load regulation.
I think I can just change the values of R1/R2 and use the LT1085CT.
Yes, I have made the sub to the LT1085CT, I had to insulate a it from
it's mount and swap two leads, but it's in. I changed R1/R2 to make the
regulator output 15 Volts which I missed it is 14.87 Volts Looks like
Boonton wasn't to precise either, the -15 is -15.18 Volts. I did put in
a temporary parallel resistor to bump the +15 up and it did not change
the reading on the 1mv scale so, I'm assuming (right or wrong) that the
measurement is not altered by slight power supply variations.
Here's a pdf of the LT1085CT.
http://cds.linear.com/docs/en/datasheet/108345fg.pdf

Thanks for the help, Mikek

Now back to HF probe development, I'd like to build a 100 to 1 adapter,
the 92EA only measures to 3 Volts.

 

[Phil Hobbs]

On 3/15/2014 11:59 AM, Michael Black wrote:

On Sat, 15 Mar 2014, Phil Hobbs wrote:

On 3/14/2014 10:49 PM, amdx wrote:
I got a Boonton 92EA off Ebay and it worked fine, I left it on overnight
and now it doesn't work. I found the 15 volt regulator has no output.
The part is obsolete, I did find one cheap $4 but with a $25 minimum
order. The Regulator is a 4 pin 78MGCP. I want to replace it with a
plain old 7815.

I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?
Other than, physical differences.
Here's is a link to the 78MGCP datasheet pdf.
http://pdf1.alldatasheet.net/datasheet-pdf/view/129322/FAIRCHILD/UA78MGC.html



Here's the schematic and my proposed sub with the 7815.
http://s395.photobucket.com/user/Qmavam/media/Boonton15VRegulatorSub_zps0e61ff6d.png.html



Mikek

There was nothing very special about the old 4-terminal regulators,
except that they split out the voltage sense lead from the ground
return for the internal circuitry, so that you could use a higher
-impedance voltage divider. The LM317/337 pretty much killed them off.

So it's not something like the extra pin allows a place for a capacitor
that helps to improve the output?

It's been a long time since I looked at one of those four pin
regulators, I don't think I've ever seen one close up.

Michael

Not primarily. Back in the day people used to use 7805s like 317s
sometimes, but the regulation is the pits because the bias current is
like 100 times higher. IIRC the 78G multiplied the reference up to 5
volts, so a 15V supply needed a 1k/2k voltage divider.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[John Fields]

On Sat, 15 Mar 2014 15:52:06 -0500, amdx <nojunk@knology.net> wrote:

On 3/14/2014 10:50 PM, mroberds@att.net wrote:
amdx <nojunk@knology.net> wrote:
I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?

"Art of Electronics" 2nd edition talks about four-terminal regulators.

This might take you to the relevant page:
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or even
http://is.gd/wBtiHz

If not, Google, in quotes, "Historically they were preceded by four-
terminal adjustable regulators" and that should take you to the AoE page
(345 in the 2nd edition).

In the pages around that one, Table 6.9 claims 1% typical line and load
regulation for the uA78GU1C , for up to half max current and a 30 V
supply (or, 150 mV load regulation). Table 6.8 claims 12 mV line
regulation and 4 mV load regulation for the LM7815CT, for max current
and a 30 V supply. So the 7815 has closer regulation on paper.

However, table 6.8 also claims that the LM7815CT has a 4% accuracy on
the output voltage, so the output can be anywhere from 14.4 to 15.6 V.
There is no accuracy spec for the adjustable regulator, presumably
because it can be adjusted to whatever you want. The rest of the
Boonton may or may not care about this much variation on the +15 V
line. You might also check the data sheet on your proposed 7815 to see
if they've gotten any better since 1989.

If you do go with the 7815, you could disconnect R1/R2 altogether to
save a milliamp. (Exercise: Will the electricity this saves over the
on-time of the Boonton be less or more than the electricity needed to
run the soldering iron for long enough to desolder them?)

Another idea would be to put in a LM317.
Matt Roberds

Thank you, for the analysis.
I have found an LT1085CT that is adjustable and has 0.15% line and
0.1% load regulation.
I think I can just change the values of R1/R2 and use the LT1085CT.
Yes, I have made the sub to the LT1085CT, I had to insulate a it from
it's mount and swap two leads, but it's in. I changed R1/R2 to make the
regulator output 15 Volts which I missed it is 14.87 Volts Looks like
Boonton wasn't to precise either, the -15 is -15.18 Volts. I did put in
a temporary parallel resistor to bump the +15 up and it did not change
the reading on the 1mv scale so, I'm assuming (right or wrong) that the
measurement is not altered by slight power supply variations.
Here's a pdf of the LT1085CT.
http://cds.linear.com/docs/en/datasheet/108345fg.pdf

Thanks for the help, Mikek

Now back to HF probe development, I'd like to build a 100 to 1 adapter,
the 92EA only measures to 3 Volts.

---
http://boonton.com/sales/request-information

 

[amdx]

On 3/16/2014 1:26 AM, John Fields wrote:

On Sat, 15 Mar 2014 15:52:06 -0500, amdx <nojunk@knology.net> wrote:

On 3/14/2014 10:50 PM, mroberds@att.net wrote:
amdx <nojunk@knology.net> wrote:
I don't see anything special about the 78MGCP that would prevent that.
Anyone see why I shouldn't make the sub?

"Art of Electronics" 2nd edition talks about four-terminal regulators.

This might take you to the relevant page:
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or
http://books.google.com/books?id=bkOMDgwFA28C&lpg=PA345&ots=F3hjXH91Tx&dq=%22historically%20they%20were%20preceded%20by%20four-terminal%20adjustable%20regulators%22&pg=PA345#v=onepage&q&f=false
or even
http://is.gd/wBtiHz

If not, Google, in quotes, "Historically they were preceded by four-
terminal adjustable regulators" and that should take you to the AoE page
(345 in the 2nd edition).

In the pages around that one, Table 6.9 claims 1% typical line and load
regulation for the uA78GU1C , for up to half max current and a 30 V
supply (or, 150 mV load regulation). Table 6.8 claims 12 mV line
regulation and 4 mV load regulation for the LM7815CT, for max current
and a 30 V supply. So the 7815 has closer regulation on paper.

However, table 6.8 also claims that the LM7815CT has a 4% accuracy on
the output voltage, so the output can be anywhere from 14.4 to 15.6 V.
There is no accuracy spec for the adjustable regulator, presumably
because it can be adjusted to whatever you want. The rest of the
Boonton may or may not care about this much variation on the +15 V
line. You might also check the data sheet on your proposed 7815 to see
if they've gotten any better since 1989.

If you do go with the 7815, you could disconnect R1/R2 altogether to
save a milliamp. (Exercise: Will the electricity this saves over the
on-time of the Boonton be less or more than the electricity needed to
run the soldering iron for long enough to desolder them?)

Another idea would be to put in a LM317.
Matt Roberds

Thank you, for the analysis.
I have found an LT1085CT that is adjustable and has 0.15% line and
0.1% load regulation.
I think I can just change the values of R1/R2 and use the LT1085CT.
Yes, I have made the sub to the LT1085CT, I had to insulate a it from
it's mount and swap two leads, but it's in. I changed R1/R2 to make the
regulator output 15 Volts which I missed it is 14.87 Volts Looks like
Boonton wasn't to precise either, the -15 is -15.18 Volts. I did put in
a temporary parallel resistor to bump the +15 up and it did not change
the reading on the 1mv scale so, I'm assuming (right or wrong) that the
measurement is not altered by slight power supply variations.
Here's a pdf of the LT1085CT.
http://cds.linear.com/docs/en/datasheet/108345fg.pdf

Thanks for the help, Mikek

Now back to HF probe development, I'd like to build a 100 to 1 adapter,
the 92EA only measures to 3 Volts.

---
http://boonton.com/sales/request-information

I'm a low budget tinkerer, I have about $9.00 into a probe they
charge at least $465 for. Only tested to 10Mhz cause that's all my
equipment will do. I hope to be able to get it characterize to 1.2GHz
and if it makes it that high.
Thanks, Mikek

 

[amdx]

On 3/16/2014 3:43 PM, Maynard A. Philbrook Jr. wrote:

In article <lg4q91$kkb$1@dont-email.me>, nojunk@knology.net says...

I'm a low budget tinkerer, I have about $9.00 into a probe they
charge at least $465 for. Only tested to 10Mhz cause that's all my
equipment will do. I hope to be able to get it characterize to 1.2GHz
and if it makes it that high.
Thanks, Mikek


That would mean you first need to acquire a signal generator and scope
or RF meter of sufficient range!

Unless there is a super deal, I'll try to find someone that has that
equipment

A few years ago I got a couple of HP 8640B units with all the extra
goodies in them from E-Bay.,..


Just looking, it seems they value of these units are still up there!

Jamie

Most are more than I want to pay since I have no on going use for them.
I just looked on Ebay for the 8640B, $300 to $950.
I see one guy wants $110 for economy shipping!
I see the max frequency range listed as 512 Mhz and 1024 MHz, are there
options for both on the B model?
Thanks,Mikek

 

[Maynard A. Philbrook Jr.]

In article <lg4q91$kkb$1@dont-email.me>, nojunk@knology.net says...

I'm a low budget tinkerer, I have about $9.00 into a probe they
charge at least $465 for. Only tested to 10Mhz cause that's all my
equipment will do. I hope to be able to get it characterize to 1.2GHz
and if it makes it that high.
Thanks, Mikek

That would mean you first need to acquire a signal generator and scope
or RF meter of sufficient range!

A few years ago I got a couple of HP 8640B units with all the extra
goodies in them from E-Bay.,..


Just looking, it seems they value of these units are still up there!

Jamie

 

[Maynard A. Philbrook Jr.]

In article <lg5042$73o$1@dont-email.me>, nojunk@knology.net says...

On 3/16/2014 3:43 PM, Maynard A. Philbrook Jr. wrote:
In article <lg4q91$kkb$1@dont-email.me>, nojunk@knology.net says...

I'm a low budget tinkerer, I have about $9.00 into a probe they
charge at least $465 for. Only tested to 10Mhz cause that's all my
equipment will do. I hope to be able to get it characterize to 1.2GHz
and if it makes it that high.
Thanks, Mikek


That would mean you first need to acquire a signal generator and scope
or RF meter of sufficient range!

Unless there is a super deal, I'll try to find someone that has that
equipment
A few years ago I got a couple of HP 8640B units with all the extra
goodies in them from E-Bay.,..


Just looking, it seems they value of these units are still up there!

Jamie



Most are more than I want to pay since I have no on going use for them.
I just looked on Ebay for the 8640B, $300 to $950.
I see one guy wants $110 for economy shipping!
I see the max frequency range listed as 512 Mhz and 1024 MHz, are there
options for both on the B model?
Thanks,Mikek

Not sure about the (B) on the model, but I made sure when I got them
they had options 1, 2 and 3 installed.

Option 1 is the audio generate which starts around 20 hz up to 600khz
option 2 is the frequency doubler so that we can get the 1 Ghz.
option 3 is a back feed protector of up to 50watts.

There is an option 4 for avionics, I don't have that and I don't think
I need it..

The unit sold for $12k new.

The manual for this unit is on the net. It's a well worth generator, I
have two, one of them is missing the little tin foil sticker on a knob
head, but otherwise works great.. Plus they come with AM, FM, etc
modulation and you can use the freq counter for external measurements,
too.

Jamie