N5GIZ (1)

Below is a photo of Sam Morris, N5GIZ, the father of the QRP brothers.  Sadly, he became a silent key in 2009.  The photo was taken in 1985.  He started as a ham about 1983 with a Kenwood TS-420. He put a tri-band Yagi held by a wooden tower atop his house and spent his days running down DX. 

As the 80's passed he was quick to try every new technology that came along.  Commodore 64 computer with automatic demodulation of CW...  keyboard to CW, many other innovations. 

After he retired from ATT in early 90's he adopted Internet technology and started and opened up his own Internet business selling wooden gavels and and paper towel holders.  I was so proud that my kids had a high tech grandpa...

Craftsman 10" bandsaw 113.244513 (2): Workstand built

 I designed a stand for my Craftsman band saw in Fusion 360. The stand is made from 2 X 4 legs and 1 X 4 stringers. The top is 12 inches by 16 inches.  I picked up all the wood from KA5VZE's scrap pile.  

The photo below is the stand as built with the band saw mounted.  My garage floor is uneven, so I'm going to buy some leveling logs to put on the front legs.  Sooner or later I'll add wheels to it.   The way I built it was not really conducive to getting everything aligned well. 

Craftsman 10" bandsaw 113.244513 (1): Introduction

 I bought this bandsaw on August 31st, 2023, and puttered around cleaning and tuning it up.  I think I finally have it working reasonably well. 

The model number is 113.244513

Philmore PS123 Power Supply (11): 4th Unit -- Fan on LM2596 fail

 I previously reported that the LM2596 regulator goes into thermal limiting after about a minute at 3 amps load.  I ordered some small fans to try to cool the device.  Upon experimentation this fan did not supply enough air to cool the device and prevent thermal limiting. 

There are a couple of youtube videos that show using a sink sink on one of these units to prevent thermal limiting. For example here.  I am going to try mounting to a heat sink to try to duplicate their results.  After that it will be a problem of where and how to mount the unit with heat sink.

Philmore PS123 Power Supply (10): 4th Unit - Initial testing with LM2596 board installed.

 The photo below shows the PC board for the LM2596 unit installed in the 4th PS123 power supply.  I added a 3300 uF 35V capacitor, on the bottom of the board. It filters the output of the diode bridge for voltage ripple suppression at the input to the regulator.   The regulator is installed in the center of the board next to a PCB mounted fuse.  The screw terminals are input voltage on the left and regulated 13.8 volts output on the right. 

 

The photo below shows the LM2596 regulator unit before installation on the board.

The photo below shows the test setup for the 0 to 3 amp current load test.

The test results are shown below.  I tested and compared the performance of three regulator schemes.  Load current is on the X axis, load voltage is on the Y axis.  The first unit, blue curve, is the LM2596 unit, Unit 4. This unit output voltage declines 0.36 volt (2.8%) from no load at 3 amps load.  The second curve in red, shows the performance of the 2N3055 regulator, Unit 1, which declines 0.88 volt (6.2%) at 3 amps load compared to no load.   Finally, Unit 3, and original Philmore PS123, with a PNP 2SB410 pass transistor, shows a 0.34 volt decline (2.4%).   Looks like the original design has better load regulations than either of the modified versions. 

The LM2596 version has definite thermal issues at full 3A load.   The voltage drops out after about a minute of running.  

Bayite DC 6.5-100V 0-100A Voltmeter/Ammeter/Wattmeter

 For testing my DC power supplies, I have ordered a unit that can simultaneously measure voltage and current on a load.  The unit also calculates load power consumption.

I purchased the item off of Amazon.com for about $16.  It comes with a 75mV per 100 watt current shut, so it can be used for loads of up to 10,000W.  It's a 4 terminal measurement, one voltage measurement across the load, and one voltage measurement across the current shunt.

The unit is available from Amazon, Ebay, Aliexpress, under many different distributors, however, as far as I can tell the original manufacturer is Peacefair, in China, and the model number is PZEM-051

DC power supply dummy load

 In order to test my DC supplies I have built a DC dummy load.  Assuming the load voltage is 13.7 V then a 27 ohm resistor will draw about 0.5A and will dissipate about 7W.  My dummy load jig consists of six 27 ohm 10W resistors that can be individually switched into or out of the load.  

Aside from no switches on (zero load current) the load current can be varied from 0.5A to 3A in 0.5A increments. The schematic is shown below. 

I soldered the circuit together as shown in the photo.  At some later time I'll 3D print a cabinet for it. 

I bought 10 switches and 10 resistors off of Amazon for a cost of about $15.  I'll design and build an electronic load later. 

Portable, field day, sota, & pota operations readiness: preliminary planning. Part 2

 

30' Squid Pole with random wire and counterpoise

KA5VZE in operation 

Finally have a break in the weather and set up a QRP portable in my back yard in preparation for a POTA activation.  I picked up a pota stn N4XT, Mike from GA and had a nice 2XQRP chat with Carl, N1CUU from PA.  I'm ready for POTA activation for 2024.  Next stop is either WOTA  (Whales on the Air) in Catoosa, OK, (the famous rt 66 Blue Whale) or Keystone St. Park, Okla.  I've also pondered on setting up at the top of a parking garage and activate it as PGOTA. :-)  The gear is:

• You Kits HB1B at 4 W
• Kit built tuner from 4SQRP
• UNUN
• AMECO straight key (my novice key)
• Random wire with counter poise
• 30' Squid pole

Philmore PS123 Power Supply (9): 4th Unit - testing LM2596 regulator

 I received the LM2596 regulator units this evening.  I was able to adjust the output voltage to 13.8V when it was connected to my bench power supply. When connected to a 15 ohm resistor,  the module produced about 0.9 amps as expected. 

Tomorrow I will reinstall the diode bridge in the PS123 and test the how the LM2596 unit functions.

Philmore PS123 Power Supply (8): 4th Unit

 I now have four of these antique Philmore PS123 power supplies.  The first I got from KA5VZE as a basket case, back in May of 2023.  That is the unit covered by most of the posts in this blog.  I first attempted to redesign the unit with an LM338K.  That was a long saga where I wasted a lot of energy designing and building the LM338K unit, only to find I couldn't get the LM338K parts. I did get some LM338Ks, but they were counterfeit units that wouldn't handle over 1 amp... 

OK then...  I did a 2nd redesign, changing from a PNP pass transistor  to an NPN 2N3055.  This worked out ok, I modified the board I built for the previous LM338K circuit into the 2N3055 circuit.  On initial testing it appears to work ok but I haven tested it up to 3 amps yet.  See this link for info. 

In the process of this work I found  second and third PS123 units on Ebay.com.  The second was an unused unit in the box, see link. This was very nice since the original factory wiring and parts were intact and it included manufacturer's one page instructions contained a schematic.  This unit cost me \$10 plus \$20 shipping.

The third unit was ordered at the same time as the second and when it arrived it appeared to be operating well, and contained original parts and wiring, but with the 2SB411 PNP pass transistor replaced.  It cost \$15 plus \$15 shipping.

I found another PS123 unit on Ebay, it was described as "not working" for parts only.  I paid \$5 for the broken unit plus \$12 for shipping.  I figured the 18VAC 3 amp transformer in the unit is worth that much.  Here's a photo of the unit as it arrived. 

Upon inspection I found that 1) a wire from the transformer to the diode bridge had broken off,  2)  the base drive transistor heat sink was in contact with the transformer,  3) the emitter lead was in contact with the unit's case at the transistor.  

     I repaired these physical faults, plugged the unit it and turned it on, then observed a wisp of smoke.  I pulled the diode bridge out and tested it.  It was good.  I then pulled the pass transistor out and found it was shorted.  

The 2SB411 germanium transistor is obsolete of course and the cheapest replacement is in the \$15 range.  I could probably substitute a silicon transistor like the MJ2955 (PNP complement to the ubiquitous 2N3055).  But, I'd have to deal with avoiding counterfeit devices again. 

Instead, I ordered some LM2596 based buck converters from Amazon.  

The LM2596 uses a 150kHz switching regulator which should be able to take the 18 to 26V output of the diode bridge to supply 3 amps at 13.8 volts.  I'm looking forward to trying it out. 

Philmore PS123 Power Supply (7): 2N3055 version built and tested

After the experience of building a fix to my old Philmore PS123 power supply, only to find that the I couldn't get the obsolete LM338K regulators that I designed in, and worse still, ordering LM338Ks from China only to find that they were counterfeit devices that blew out when current went above 1 Amp,  I put away the project and worked on other things.  See this link for my post describing the experience with the counterfeit regulators in May 2023.

I finally redesigned the project using a 2N3055 pass transistor.  See the circuit below.

I was going to use a 2N2102 to drive the base of the 2N3055 but that device is apparently obsolete these days.  Browsing between Amazon.com and Digikey, I found a 60V 1.5 amp NPN device that should work well.  I bought an assortment of BD135 family devices from Amazon, 60 total for about $9.  The transistors should arrive next week, so in the mean time I used a BC337 50V 0.8 amp device I got from a TO-92 transistor assortment I bought last year from Amazon. This transistor will only handle about 635mW dissipation. Worst case dissipation is 2W if the 2N3055 has only current gain of 20 at 3 amps collector current.  The worst case assumes the 2N3055 is the datasheet minimum, but more likely the current gain will be 50 to 70, so it's hard to determine the exact dissipation for the base driver transistor. 

At any rate I made the modifications and the unit appears to work as expected. I tried three different currents to test the regulation: 

Load current    Output voltage

0.036 A            14.3V

1.390 A            13.9V

1.710 A            13.7V

This corresponds to 4.2% load regulation over about 2 amps, which is probably pretty good for this type of pass transistor regulator. 

Photo above shows front view of power supply with cover removed

Photo above shows side view of power supply without cover. Circuit board with filter and regulator appears vertically on the right side. 2N3055 heat sink is on the back of the unit.