I looked inside an old Astron RS10 power supply that I had bought at a flea
market. The power transformer (seen in these pictures), looked husky enough
to power a 100 watt ham transceiver so I decided to pull the guts out of the RS10
and transplant them into this FP757 HD supply box. The POWER TRANSFORMER
IS A SPECIFIC TYPE OF DESIGN ..which results in proper operation of the 723
voltage regulator chip.
market. The power transformer (seen in these pictures), looked husky enough
to power a 100 watt ham transceiver so I decided to pull the guts out of the RS10
and transplant them into this FP757 HD supply box. The POWER TRANSFORMER
IS A SPECIFIC TYPE OF DESIGN ..which results in proper operation of the 723
voltage regulator chip.
Above: the main circuit board from the RS10 mounted vertically against one of the side
panels inside the old Yaesu supply box. To the left..is the DIAC Overvoltage protection
circuit which I wired and placed on a green fiberglass mounting board. I cut the fiberglass
board from a piece of stock I had on hand. I have lots of parts around here and a huge
"junkbox". IT keeps things insuated from shorting to chasis and provides a good mounting
platform for parts and the old RS10 circuit board itself.
I sell parts and buy parts and I build stuff as well. THIS kind of gutting and rebuiding has
one advantage over completely scratch building a unit from the ground up. It means less
work trying to do chasis work. I dont have a machine shop and metal bending tools ect.
The Blue colored electrolytic capacitors are from my junk box. They have a 40 volt working
rating. The old capacitors from the yaesu supply were only rated at 25 volts so I didnt use
them.
panels inside the old Yaesu supply box. To the left..is the DIAC Overvoltage protection
circuit which I wired and placed on a green fiberglass mounting board. I cut the fiberglass
board from a piece of stock I had on hand. I have lots of parts around here and a huge
"junkbox". IT keeps things insuated from shorting to chasis and provides a good mounting
platform for parts and the old RS10 circuit board itself.
I sell parts and buy parts and I build stuff as well. THIS kind of gutting and rebuiding has
one advantage over completely scratch building a unit from the ground up. It means less
work trying to do chasis work. I dont have a machine shop and metal bending tools ect.
The Blue colored electrolytic capacitors are from my junk box. They have a 40 volt working
rating. The old capacitors from the yaesu supply were only rated at 25 volts so I didnt use
them.
Circuit Discussion AND SOME MEASUREMENTS
BELOW is the schematic I obtained on line from the web. Just google "Astron Power Supplies and manuals" and you will come up with the data.
Here you see the RS10 only uses one pass transistor. If you look at the RS20 design, it is very similar. R1 is 15 ohms in the 20 amp supply vs 27 ohms with the 10
amp supply. I changed R1 to 15 ohms in my homebrew supply.
I did not use 2 NPN pass transistors but I used a bank of 4 2n3055 pass transistors because I had them already wired up and on heat sinks and ready to go.
I felt that 4 NPN pass transistors vs. only 2 pass transistors would be more rugged as well. BOTTOM LINE..THE PROCEDURE HAS WORKED!
The UA723 and RCA29 (TIP29) drove the bank of 4 2n3055s quite nicely in my homebrew supply and it powers the FT301D at 100 watts perfectly.
The regulation of the output is adequet but I suspect not entirely as good as would be measured with an unmodified RS20 (at the higher current levels).
I did notice a bit of a voltage drop but it was within reason and the rig works well..so I am leaving well enough alone and going with it.
BELOW is the schematic I obtained on line from the web. Just google "Astron Power Supplies and manuals" and you will come up with the data.
Here you see the RS10 only uses one pass transistor. If you look at the RS20 design, it is very similar. R1 is 15 ohms in the 20 amp supply vs 27 ohms with the 10
amp supply. I changed R1 to 15 ohms in my homebrew supply.
I did not use 2 NPN pass transistors but I used a bank of 4 2n3055 pass transistors because I had them already wired up and on heat sinks and ready to go.
I felt that 4 NPN pass transistors vs. only 2 pass transistors would be more rugged as well. BOTTOM LINE..THE PROCEDURE HAS WORKED!
The UA723 and RCA29 (TIP29) drove the bank of 4 2n3055s quite nicely in my homebrew supply and it powers the FT301D at 100 watts perfectly.
The regulation of the output is adequet but I suspect not entirely as good as would be measured with an unmodified RS20 (at the higher current levels).
I did notice a bit of a voltage drop but it was within reason and the rig works well..so I am leaving well enough alone and going with it.
The Astron power supply schematics and tech info RS10, RS12, RS20 and RS35 are all
published on line and easy to find. Examining the schematics for both the RS10 and
RS20 ..I saw a great deal of similarity in the circuit. Almost identical. I did change one
resistor on the board and that was R1. It goes from the emmitter of the driver transistor
(RCA29) (TIP29) to the base of the pass transistor(s). I changed it from 27 ohms to 15
ohms. The power transformer looked pretty heavy duty in the RS10 supply and I was
sure it could put out 15 to 20 amps to power the typical 100watt ham radio rig. I would
venture to guess that the RS10 through RS20 all used the same transformer! for
simplicity sake and economy.
The original FP757 HD used 3 - 25000 volt filter capacitors rated at only 25 volts. Since
almost 24vdc appears on the filter capacitors..I felt this was cutting the safety margin
too thin. I used these blue colored capacitors , a 19,000 uf and a 10,000 uf at 40 wvdc. A
bit less capactance than maybe I should have used but it seems to work fine.
You can see the full wave bridge on a part of the original FP757hd heatsink. I actually
cut the heatsink with a dremel tool and I have insulated it from chasis ground. The
power supply ground is actually isolated from chasis ground. I dont think this was the
case with the RS10. The - (minus) line is somewhat like a ONE POINT GROUND. I seen in an
ARRL HANDBOOK power supply...a circuit like this where every ground point is tied to one single point
ground.
published on line and easy to find. Examining the schematics for both the RS10 and
RS20 ..I saw a great deal of similarity in the circuit. Almost identical. I did change one
resistor on the board and that was R1. It goes from the emmitter of the driver transistor
(RCA29) (TIP29) to the base of the pass transistor(s). I changed it from 27 ohms to 15
ohms. The power transformer looked pretty heavy duty in the RS10 supply and I was
sure it could put out 15 to 20 amps to power the typical 100watt ham radio rig. I would
venture to guess that the RS10 through RS20 all used the same transformer! for
simplicity sake and economy.
The original FP757 HD used 3 - 25000 volt filter capacitors rated at only 25 volts. Since
almost 24vdc appears on the filter capacitors..I felt this was cutting the safety margin
too thin. I used these blue colored capacitors , a 19,000 uf and a 10,000 uf at 40 wvdc. A
bit less capactance than maybe I should have used but it seems to work fine.
You can see the full wave bridge on a part of the original FP757hd heatsink. I actually
cut the heatsink with a dremel tool and I have insulated it from chasis ground. The
power supply ground is actually isolated from chasis ground. I dont think this was the
case with the RS10. The - (minus) line is somewhat like a ONE POINT GROUND. I seen in an
ARRL HANDBOOK power supply...a circuit like this where every ground point is tied to one single point
ground.
The Astron RS10 power supply circuit board. The ua723 voltage regulator chip is
in a socket. I damaged the original 723 when I was working on this project. I think
it was when I connected up the large filter capacitors and there was a spark. I
had plenty of spares and replaced the chip.
Just the other day, I did a few things with the power supply and when I turned it on no juice on the output.
Replaced the UA723 chip once again and it was up and running again. Watch you dont short out your supply
even if it is turned off..could damage the chip! Fortunately..the chips are cheap..easy to get and I have lots
of them around here.
With my power supply here, built in to the FP757 power supply chasis, I have the back fan on all the time as
well as a bright GREEN LED (through a 10K resistor) to the +13.8 vdc output ..and these two loads will drain
the filter capacitors when the supply is turned off.
There is a green sub mounting circuit board keeps the connections from the ASTRON power supply from
shorting to chasis and keeps the Astron circuit board mounted in place in the FP757 chasis. To the upper left
corner..you can see theprotective TRIAC 2N681. It is an over voltage protection. (photo below shows circuit
board from the RS10 with a
an addition of a circuit board to accommodate the TRIAC I used point to point
wiring to wire up this board. The voltage adjust potentiometer is the small black
one to the lower left of the circuit board. I did have to adjust it to get the power
supply to output about 13.8 volts.
in a socket. I damaged the original 723 when I was working on this project. I think
it was when I connected up the large filter capacitors and there was a spark. I
had plenty of spares and replaced the chip.
Just the other day, I did a few things with the power supply and when I turned it on no juice on the output.
Replaced the UA723 chip once again and it was up and running again. Watch you dont short out your supply
even if it is turned off..could damage the chip! Fortunately..the chips are cheap..easy to get and I have lots
of them around here.
With my power supply here, built in to the FP757 power supply chasis, I have the back fan on all the time as
well as a bright GREEN LED (through a 10K resistor) to the +13.8 vdc output ..and these two loads will drain
the filter capacitors when the supply is turned off.
There is a green sub mounting circuit board keeps the connections from the ASTRON power supply from
shorting to chasis and keeps the Astron circuit board mounted in place in the FP757 chasis. To the upper left
corner..you can see theprotective TRIAC 2N681. It is an over voltage protection. (photo below shows circuit
board from the RS10 with a
an addition of a circuit board to accommodate the TRIAC I used point to point
wiring to wire up this board. The voltage adjust potentiometer is the small black
one to the lower left of the circuit board. I did have to adjust it to get the power
supply to output about 13.8 volts.
The power supply I
built with the RS10
guts being modified
similar to the RS20
works.
I went in with my V.O.M.
and made a number of
key DC
measurements. The
base of the pass
transistor I measured
was always greater than
the voltage of the
emmitter of the
transistor. With no load
or very light load by .5
volt,
with a nominal load (my
FT301 on receive
drawing about 1 amp)
the base voltage was
about .7 volts higher.
With a heavy load ie
Ft301 on 100 watt
transmit..the base
voltage
was 1 volt higher.
I will use these real life
measurements when I
go to finish up a
design I made of a 13.8
volt 20 amp supply.
built with the RS10
guts being modified
similar to the RS20
works.
I went in with my V.O.M.
and made a number of
key DC
measurements. The
base of the pass
transistor I measured
was always greater than
the voltage of the
emmitter of the
transistor. With no load
or very light load by .5
volt,
with a nominal load (my
FT301 on receive
drawing about 1 amp)
the base voltage was
about .7 volts higher.
With a heavy load ie
Ft301 on 100 watt
transmit..the base
voltage
was 1 volt higher.
I will use these real life
measurements when I
go to finish up a
design I made of a 13.8
volt 20 amp supply.
C
B
E
ABOVE IS THE SCHEMATIC OF THE "ORIGINAL" RS 10 POWER SUPPLY. This is the circuit before I removed it from the chasis/box it was in and transplanted
it into the YAESU FP757HD power supply box/chasis.
I did some DC MEASUREMENTS that I am giving here in order for you (and me) to understand this supply, how it works under light load and heavy load
conditions.
* Light No load DC voltage
** Light Load DC voltage (ie load = my FT301D transceiver on receive (about 1 Amp or so being drawn)
**** HEAVY LOAD DC voltage (ie load= my FT301D transceiver putting out about 100 watts into a dummy load). -- approx 20 AMPs on peak being drawn
it into the YAESU FP757HD power supply box/chasis.
I did some DC MEASUREMENTS that I am giving here in order for you (and me) to understand this supply, how it works under light load and heavy load
conditions.
* Light No load DC voltage
** Light Load DC voltage (ie load = my FT301D transceiver on receive (about 1 Amp or so being drawn)
**** HEAVY LOAD DC voltage (ie load= my FT301D transceiver putting out about 100 watts into a dummy load). -- approx 20 AMPs on peak being drawn
POINT A -- THE rectified output from
the higher voltage tap on the
transformer
* 29.9 volt no load
** 29.2 Volt light load
the higher voltage tap on the
transformer
* 29.9 volt no load
** 29.2 Volt light load
POINT B -- THE Base of the pass
transistor
* 14.5 volt no load
** 14.7 Volt light load
*** 15.4 volt heavy load.
transistor
* 14.5 volt no load
** 14.7 Volt light load
*** 15.4 volt heavy load.
POINT C -- THE Collector of the
pass transistor (which is also the
voltage at the larger filter
capacitor C101
* 23.9 volt no load
** 23.1 Volt light load
*** 18.4 to 18.9 volt heavy load.
pass transistor (which is also the
voltage at the larger filter
capacitor C101
* 23.9 volt no load
** 23.1 Volt light load
*** 18.4 to 18.9 volt heavy load.
POINT E -- THE Emitter of the pass
transistor (which is also the
voltage at the larger filter
capacitor C101
* 23.9 volt no load
** 23.1 Volt light load
*** 18.4 to 18.9 volt heavy load.
transistor (which is also the
voltage at the larger filter
capacitor C101
* 23.9 volt no load
** 23.1 Volt light load
*** 18.4 to 18.9 volt heavy load.
| 4 pass transistors 3055s here (in parallel) in the place of Q101 |
| Additional NOTES and mods. Each 3055 pass transistor (and I used 4 of them in parallel) in this RS-10A (modified) circuit had a .1 ohm resistor in the emitter lead. R1 was changed from 27 ohms to 15 ohms. NOTE in the RS 35A (35 Amp) supply; R1 is a 15 ohm resistor but there is another resistor r1x shown in parallel. That would lower the resistance. D1 and D2 were beefed up by adding a second diode in parallel (piggy back on the circuit board . Not sure if it was all that necessary a thing to do but I i did it anyways and you can see it in the photos (near the heatsink) of the TO220 pass transistor. This series of ASTRON power supplies all use this "trick" of a higher voltage winding being rectified and passed on to the input of the ua723 regulators. NOT sure but this could be a type of proportional regulation that gives better regulation to the output. FOR THIS REASON..I CHOSE NOT TO USE THE ORIGINAL FP757 YEASU TRANSFORMER. ...I MIGHT EVEN SELL IT LATER. ITS A DANDY LOW PROFILE POWER TRANSFORMER but it does not have the extra secondary taps that the ASTRON LINEAR supplies use and I wanted to stick with the ASTRON DESIGN. |
Below is a snapshot I took of the RS20 supply. I (easily) googled these Astron Power supply schematics and manuals and found
them on line.
The RS10 and RS20 are almost the same. Certainly the components are about the same. It would not be too hard to add a
second pass transistor (and maybe a bit more filter capacitance) to an RS10 in order to make it into a good power supply for a
100 watt HF rig.
I have the schematics posted on a page I made concerning ASTRON POWER SUPPLIES..click here to visit this page
them on line.
The RS10 and RS20 are almost the same. Certainly the components are about the same. It would not be too hard to add a
second pass transistor (and maybe a bit more filter capacitance) to an RS10 in order to make it into a good power supply for a
100 watt HF rig.
I have the schematics posted on a page I made concerning ASTRON POWER SUPPLIES..click here to visit this page
A
C
| fuse |
hamelectronicsmagazine.com -- JUNE 2011
| Rebuilding a defective Yaesu FP-757 HD supply using the "innards" of an Astron RS-10 supply (modified for 20 ampere operation)... |
Above: the schematic of the Astron RS20 power supply. The main difference between the RS10 (10 amp supply) and RS20 (20 amp supply) is
the fact that 2 pass transistors are used instead of one. The base resistor R1 is a lower value 15 ohms vs. 27 ohms. I used a 15 ohm resistor
for R1 in my version of the power supply (mine has 4 pass transistors 2n3055) and it worked when powering my 100 watt transceiver.
I have been using this new modified supply now for about 10 months in my shack..not only to power my 100 watt transciever but also to
power my Ten Tec 10 watt transverter for 6 meters and my other 2 meter FM radio. IT IS WORKING FINE FOR ME.
It is working so fine, in fact, that I am just going to keep running it this way and to heck with trying to insert a switching supply inside the case.
the fact that 2 pass transistors are used instead of one. The base resistor R1 is a lower value 15 ohms vs. 27 ohms. I used a 15 ohm resistor
for R1 in my version of the power supply (mine has 4 pass transistors 2n3055) and it worked when powering my 100 watt transceiver.
I have been using this new modified supply now for about 10 months in my shack..not only to power my 100 watt transciever but also to
power my Ten Tec 10 watt transverter for 6 meters and my other 2 meter FM radio. IT IS WORKING FINE FOR ME.
It is working so fine, in fact, that I am just going to keep running it this way and to heck with trying to insert a switching supply inside the case.
THE VOLTAGE ADJUST POT
ON THE original RS10
board just half visible
lower right of circuit board
assembly.
Any RS10 or RS12 could be
reconfigured to 20 amp
service for a ssb/cw rig.
You should be able to fit
everything into the RS 10
cabinet as it is quite large.
I used the FP757HD
cabinet to match the
FT757GX rig I just bought.
ON THE original RS10
board just half visible
lower right of circuit board
assembly.
Any RS10 or RS12 could be
reconfigured to 20 amp
service for a ssb/cw rig.
You should be able to fit
everything into the RS 10
cabinet as it is quite large.
I used the FP757HD
cabinet to match the
FT757GX rig I just bought.
When building and fixing
this supply and
troubleshooting it (it
didnt work the first
time)..I managed to
damage 2 of the ua723
ICs.
The power supply twice
simply would not work.
NO OUTPUT. Replacing
the 723 chip solved the
problem both times.
I have quite a few spare
723 voltage regulator
chips.
One fellow (an engineer
I spoke to about power
supplies) told me the
company he worked for
stayed away from the 723
chips for the most part.
I seem to have had good
luck with them and the
power supply has been
working fine for about 6
months now.
this supply and
troubleshooting it (it
didnt work the first
time)..I managed to
damage 2 of the ua723
ICs.
The power supply twice
simply would not work.
NO OUTPUT. Replacing
the 723 chip solved the
problem both times.
I have quite a few spare
723 voltage regulator
chips.
One fellow (an engineer
I spoke to about power
supplies) told me the
company he worked for
stayed away from the 723
chips for the most part.
I seem to have had good
luck with them and the
power supply has been
working fine for about 6
months now.
The shiny aluminum bracket
provides the mounting fixture and
heatsink area for 3 of the 4
2n3055s NPN pass transistors.
THE OTHER 2N3055 is on the back
panel with a small heatsink ..see
picture and to the left of the green
square.
The cooling fan runs all the time
now. Before it was connected to a
thermostat on the FP757HD
heatsink. I run it at a lower
rpm..just to keep air moving in the
cabinet.
The full wave bridge is insulated
from chasis ground using rubber
sheet and yellow electrical tape. It
has its own small heatsink. I made
that buy sawing one of the original
Yeasu Pwr Supply heatsinks down
to fit in the cabinet.
I used blue colored computer
grade capacitors with a higher
voltage rating (but less
capacitance) than the original
FP757HD supply. The original
yaesu supply used filter capacitors
pretty close in voltage ratings to
the actual positive voltage
outputted from the full wave bridge
provides the mounting fixture and
heatsink area for 3 of the 4
2n3055s NPN pass transistors.
THE OTHER 2N3055 is on the back
panel with a small heatsink ..see
picture and to the left of the green
square.
The cooling fan runs all the time
now. Before it was connected to a
thermostat on the FP757HD
heatsink. I run it at a lower
rpm..just to keep air moving in the
cabinet.
The full wave bridge is insulated
from chasis ground using rubber
sheet and yellow electrical tape. It
has its own small heatsink. I made
that buy sawing one of the original
Yeasu Pwr Supply heatsinks down
to fit in the cabinet.
I used blue colored computer
grade capacitors with a higher
voltage rating (but less
capacitance) than the original
FP757HD supply. The original
yaesu supply used filter capacitors
pretty close in voltage ratings to
the actual positive voltage
outputted from the full wave bridge
NOTE: how the POWER TRANSFORMER..in the schematic above from the ASTRON RS10 schematic... has
multiple secondary taps. The higher voltage secondary tap is rectifed by diodes and a 1000 uf capacitor
and then passed on to the 723 regulator chip. The slightly lower voltage secondary taps are rectified
(by a larger set of diodes and a larger filter capacitance.
This arrangement can only have one purpose and that is to improve the regulation of the output of the
power supply. It is for this reason I chose to remove the original Yaesu FP757HD power transformer
and mount in the smaller but more suitable RS10 power transformer. NOTE; I still have the Yaesu Power
Transformer and will use it in another homebrew supply..or maybe sell it to a ham who needs to replace
his power transformer.. wanna buy it???
multiple secondary taps. The higher voltage secondary tap is rectifed by diodes and a 1000 uf capacitor
and then passed on to the 723 regulator chip. The slightly lower voltage secondary taps are rectified
(by a larger set of diodes and a larger filter capacitance.
This arrangement can only have one purpose and that is to improve the regulation of the output of the
power supply. It is for this reason I chose to remove the original Yaesu FP757HD power transformer
and mount in the smaller but more suitable RS10 power transformer. NOTE; I still have the Yaesu Power
Transformer and will use it in another homebrew supply..or maybe sell it to a ham who needs to replace
his power transformer.. wanna buy it???
Above: the "heart" of this supply..the regulator
circuitry. The 723 chip is below the
TIP 29 power transistor (Q2).
In the RS10 ..the TIP 29 pink square marks in above
picture..drives the base of a single NPN pass
transistor...in the RS10 supply. In my power supply..it
drives the bases of 4 npn pass transistors wired in
parallel.
In the RS20..the TIP 29 drives the base of two
NPN pass transistors. I decided to go with 4 2n3055
TO-3 metal can NPN pass transistors for an extra
margin of capability and because I had plenty of 3055s
in my junkbox.
In the RS 35 the same or very similar circuitry is used.
These are all LINEAR POWER SUPPLIES. You should
be able to google any of these astron supplies and
come up with complete schematics and manuals and
discussions.
Another option I could have taken and was thinking
of doing..was to gut the Yaesu Supply and insert a 23
amp switching supply in the cabinet. I could not find
an inexpensive enough switching supply to perform
the repair (in my budget) so I chose to stay LINEAR, at
least for now.
circuitry. The 723 chip is below the
TIP 29 power transistor (Q2).
In the RS10 ..the TIP 29 pink square marks in above
picture..drives the base of a single NPN pass
transistor...in the RS10 supply. In my power supply..it
drives the bases of 4 npn pass transistors wired in
parallel.
In the RS20..the TIP 29 drives the base of two
NPN pass transistors. I decided to go with 4 2n3055
TO-3 metal can NPN pass transistors for an extra
margin of capability and because I had plenty of 3055s
in my junkbox.
In the RS 35 the same or very similar circuitry is used.
These are all LINEAR POWER SUPPLIES. You should
be able to google any of these astron supplies and
come up with complete schematics and manuals and
discussions.
Another option I could have taken and was thinking
of doing..was to gut the Yaesu Supply and insert a 23
amp switching supply in the cabinet. I could not find
an inexpensive enough switching supply to perform
the repair (in my budget) so I chose to stay LINEAR, at
least for now.
| This article has been fixed up and editted January 10 2012. |
I have another page of pictures and information on this
homebrew supply. I'm still not quite finished it but you are
welcome to look it over...CLICK HERE TO GO PAGE 2
OF THIS ARTICLE
homebrew supply. I'm still not quite finished it but you are
welcome to look it over...CLICK HERE TO GO PAGE 2
OF THIS ARTICLE
| NAVIGATION LINKS: >>>> |
INFORMATION ON THE 4 PNP TRANSISTOR SUPPLY AND PICTURES OF THIS
"FAILURE POWER SUPPLY" ARE FOUND ON THIS PAGE CLICK HERE.
presented for the learning experience!!!
"FAILURE POWER SUPPLY" ARE FOUND ON THIS PAGE CLICK HERE.
presented for the learning experience!!!
PREVIOUS to using the Astron RS10
circuitry to "rebuild" the Yaesu 20 amp
supply..I had tried another circuit using PNP
transistors. It did not work well at all. Tons
of ripple and hum!! Very bad. I still have the
experimental circuit intact and I plan to try it
out again in the future. (( I have a suspicion
..that the PNP transistors are causing the
problems)..NOT SURE..but I will test one
of these suspect "pass" transistors in a
good working single pass transistor pnp
supply I built back in my college days..that
worked fine
INFORMATION ON THE 4 PNP
TRANSISTOR SUPPLY AND PICTURES
OF THIS
"FAILURE POWER SUPPLY" ARE
FOUND ON THIS PAGE CLICK HERE.
presented for the learning experience only.
!!!
circuitry to "rebuild" the Yaesu 20 amp
supply..I had tried another circuit using PNP
transistors. It did not work well at all. Tons
of ripple and hum!! Very bad. I still have the
experimental circuit intact and I plan to try it
out again in the future. (( I have a suspicion
..that the PNP transistors are causing the
problems)..NOT SURE..but I will test one
of these suspect "pass" transistors in a
good working single pass transistor pnp
supply I built back in my college days..that
worked fine
INFORMATION ON THE 4 PNP
TRANSISTOR SUPPLY AND PICTURES
OF THIS
"FAILURE POWER SUPPLY" ARE
FOUND ON THIS PAGE CLICK HERE.
presented for the learning experience only.
!!!
link to my home page www.hamelectronicsmagazine.com
schematics and information about ASTRON linear power supplies can
be found on this information page in my site (note: If you "google" the
words "ASTRON power supply and Schematics" you can get full
schematics and information from various web sources.
be found on this information page in my site (note: If you "google" the
words "ASTRON power supply and Schematics" you can get full
schematics and information from various web sources.
The original power supply below pictured. It had been modified when I
bought it. There was a different main power resistor installed and it was
just hanging on in the inside of the supply (flying leads).
The relay was wired up differently and the power supply was not
running the FT757GX properly. The rig was ok on receive but on
transmit the radio would not work much over 40 watts output because
the power supply regulation was not good enough.
I ended up gutting the entire supply because I figured the power supply
was closing in on being 25 years old. The main capacitors may be
getting a bit long on the tooth...and wires were falling off of the
soldered connections and it all made for a difficult to work on project.
I decided to use a working supply I had surplus to my needs..an ASTRON
10 AMP supply. I would use the Astron Power Transformer..which looked
good enough for 20 amp service (intermittent like cw/ssb) and I would
beef up the pass transistors from just one that the RS10 had to quantity
4 - 2N3055s.
bought it. There was a different main power resistor installed and it was
just hanging on in the inside of the supply (flying leads).
The relay was wired up differently and the power supply was not
running the FT757GX properly. The rig was ok on receive but on
transmit the radio would not work much over 40 watts output because
the power supply regulation was not good enough.
I ended up gutting the entire supply because I figured the power supply
was closing in on being 25 years old. The main capacitors may be
getting a bit long on the tooth...and wires were falling off of the
soldered connections and it all made for a difficult to work on project.
I decided to use a working supply I had surplus to my needs..an ASTRON
10 AMP supply. I would use the Astron Power Transformer..which looked
good enough for 20 amp service (intermittent like cw/ssb) and I would
beef up the pass transistors from just one that the RS10 had to quantity
4 - 2N3055s.
Above: the relay was sitting in the cabinet (loose) not strapped down as was this
power resistor. I dont know who had worked on this power supply but it was not
working..would not power the FT757GX.
power resistor. I dont know who had worked on this power supply but it was not
working..would not power the FT757GX.
A BETTER OPTION..would have been to gut the original Yeasu Power Supply (except for the
loudspeaker and power lines) and insert a modern small switching power supply. I still might in
fact do this. -- I will be looking around at ham radio flea markets or I may even go out and buy a
new switching supply of perhaps 25 amps. I would then gut this homebrew version but I would
mount all the old innards into a different cablinet entirely.
loudspeaker and power lines) and insert a modern small switching power supply. I still might in
fact do this. -- I will be looking around at ham radio flea markets or I may even go out and buy a
new switching supply of perhaps 25 amps. I would then gut this homebrew version but I would
mount all the old innards into a different cablinet entirely.