Jetstream JTPS35BCM Switching Power Supply Mods

Modifications to my Jetstream 35 Amp Power Supply

Adding Anderson Power Poles
Modifying Fan Circuitry

I purchased my Jetstream power supply at one of the local hamfests from Al’s Radio Service out of IL.
I had purchased a 14 amp supply with meters from him previously, and have been very happy with it, with the exception of the loud fan.

Jetstream JTPS35BCM Switching Power Supply

When I saw that Jetstream had a new power supply with a battery charger, and auto switch over circuitry I thought this would be a good upgrade to my Astron 35M in a lighter package. I wanted something that was lighter and more mobile for use in Field Day, and other radio activities that required me to move my equipment around. It has served me well in the shack, Running 24 hours at Field Day, and powered my TS-2000 at Ellis Elementary School for an International Space Station contact that our Radio Club set up.

I did have a problem with the power supply when I got it. The Amp meter did not return to zero, and was not reading accurately. A called Jetstream to see if there was an internal adjustment I could do, but was told no there was not. I could send the power supply in and they would take care of it. It tool about 1 1/2 weeks to get the power supply back, and all was well. The folks at Jetstream where very friendly and helpful and I was happy with the turn around. I also asked if a schematic for the power supply was available, but was told they did not offer one.

This power supply has the same noisy fan that my 14 amp power supply has. It does not come on as often, but when it does it is loud, The good thing is that it does not run very long. I use this power supply to run my Kenwood TS-2000 and my dual bander in the shack, as well as assorted accessories. The power coming out of the power supply is very clean when viewed on a scope, and I have not found any noise on the HF bands even when using my little QRP rigs.

The other thing that I did not like about the power supply was that all the power connections are on the front of the supply with the exception of the connection for the battery which is on the back. This would be fine for a work bench supply, but I like to keep my power supply for the radios were I can keep an eye on the meters. With this type of configuration you have the wires running from the front of the unit which just does not look professional.

Light Weight,
Adjustable Voltage
Lighted Meters
Clean Power
Battery Backup
Cigarette Lighter Socket on Front

All the power connections are on the front of the unit.
Silly speaker wire power connection on front.
Loud Fan

As with anything there is always room for improvement!

I use Anderson Power Poles on all my equipment, I like the interchangeability of using them. Most of our Radio Club has standardized on them as well, which makes it nice when we do something like Field Day. I have some breakout boxes that have Power Poles in them, but you always wind up with a rats nest of wires. I wanted to add Power Poles directly to the back of the power supply, and while I was at it I replaced the little speaker terminals on the front of the unit with some also. These will be handy for quick hookups of temporary equipment and such.

Standard Disclaimer!

There are very high voltages in side any power supply. Be sure to unplug the supply while working on it. The capacitors in the supply will also hold a charge even after it is unpluged. You should know what you are doing before attempting any thing like this. I take no responsibility for damage to your power supply, or harm to your self, your equipment, etc. These modifications will definitely void your warranty, and have the potential to cause you great harm if you are not careful.


Front panel of stock power supply.


Rear of stock power supply. The Binding posts are for connection to a 12 volt battery


These are the Anderson Power Pole chassis mounts that I had on hand.

These are actually designed for 2 sets of 3 plugs. They also sell them in 2 pair and 4 pair configurations also.
The metal pins could not be used as I used these for 3 pairs of two, instead of 2 sets of three.
To secure them I insearted my Power Poles with out wires, and glued them into the chassis mount to secure them.

These can be ordered from
Quick Silver Radio


Once you have the front panel removed this is the circuit board that the Binding Posts and Speaker Wire Type Connection is soldered to.
You need to remove the board to make room for our Power Poles, and we will have to cut part of the board off.
We will discard the Speaker Wire Type Connection and replace it with out power poles.
The hole is a little smaller than the Chassis mount we are using and you will have to make it larger to get it to fit.
I carefully opened the hole with an exacto knife and file.


Here we see the board cut in half, as well as my Power Poles after Glueing into the Chassis Mount


The 3 pair mount is a very good fit for this project, but I think you could get the 4 pair Chassis mount to fit with a little more cutting.
Note that the Binding posts have a threaded metal piece on the front of the panel. I did not remove them from the board, but instead unscrewed them from the front panel. You can see if the photo that only the binding post on the right has the round threaded nut attached.


Here is the back view after the chassis mount is in place. I soldered the wires to what was left of the circuit board that the binding posts are attached to.

This completes the modification to the front of the power supply!

On to the Back!


There is not much room on the back of the power supply to add my Power Poles.
On the right there is a switch to allow the operation of the power supply from 110 or 220 volts AC.
As I will most likely never use the power supply on 220 volts, I decided to remove the switch, and add my Power Poles there.


Here is the view of the 110/220 volt switch from inside the power supply. The switch is on for 110 operation and off for 220.
The switch connects to the circuit board by the two black wires.


Here the switch is removed, and a jumper soldered to the terminals on the circuit board to permanently strap it for 110 volts.


I used a sheet metal nibbler tool to open up the back of the chassis.
Radio Shack used to sell these, I have also seen them in tool catalogs, and on-line.
The nice thing about this tool is that it pulls the metal cutting out so you do not get pieces of metal inside the case while you are cutting.
I chose to leave the circuit board in the case while cutting the hole. Be sure you can account for all the metal you cut away.
You do not want metal pieces floating around in the power supply when you are done.
Do not use a Dremel or a file to cut the hole, the metal shavings will get in the power supply and ruin in.


Here is the hole after I opened it up. The edges do not have to be perfect.
The Chassis mount has a lip that will cover up the rough edges.
Be sure to leave enough room at the bottom for the Chassis Mount to fit.


Power Poles in place on power supply.
As you can see the nibbling tool left some scratches on the back of the case.
This could have been avoided by putting some masking tape on the case to protect the finish while I was cutting the hole.
Next time I will remember to do this.

The power supply has an extra set of lugs on the circuit board were the front panel gets its power from.
I simply connected the rear Power Poles to these with spade plugs, and a length of heavy wire.
You can see that in the photo 2 down from here.

Now on to fixing that annoying fan.


On the rear of the circuit board there are 3 connectors.
Left Connector goes to the lights on the meters
Upper Right is from the thermistor on the heat sink
Lower Right goes to the fan.

The circuitry to run the fan is very simple:
+12 volts goes to the fan at all times.
The ground lead to the fan is run through the thermistor, which acts as an on off switch.
Once the thermistor gets warm enough it turns on and connects the ground to the fan.
The fan comes on and pulls air over the heat sink until the thermistor gets cool enough to turn off.

I had a few options here on how to modify this and quite the fan down.
I could have replaced the fan with a quieter one.
Slowed the existing fan down so it was not too noisy.
Try to keep the power supply heat sink cooler so the fan does not come on as often.

I chose the later. The reason being is that if the power supply does indeed get hot enough I want the fan to run to cool it back down.
So how do we keep the heat-sink cooler? By running the fan at a low speed all the time.

To accomplish this we need to complete the circuit to the fan so that it has a small voltage to constantly turn is slowly.

To do this we are going to add a 220 Ohm resistor from ground to the ground side of the fan.
This value of resistor was chosen because it allowed the fan to run at a slow speed, but is almost silent.

I added the resistor to the bottom of the circuit board, but then I realized I could have just added it to the thermistor on the heat sink. This would have been simpler and not required removing the circuit board. Both ways accomplish the same thing.


If you choose to add it to the circuit board, there are only two screws that hold the circuit board in place.
They are located towards the front of the board at the end of each large heat-sink.
You do not have to remove the board, just slide if over a bit so you can solder to the bottom of it.


This is a view of the bottom of the circuit board.
We will be adding the 220 Ohm resistor from the square solder pads to the upper most right pad.


Here you can see the added resistor soldered in place.


Here is the thermistor on the heat sink.
If you do it this way just solder the 220 Ohm resistor, with one leg going to the black wire, and one leg going to the red wire.
Be sure that the legs of the resistor can not touch the heat sink!


Here is the completed power supply after it is put back together.


And from the rear!

73’s de KB9JJA/Dale