Thursday, March 29, 2018

Norcal 40A 30A..that's "30" for tonight.. (Update)

Posting WB6JDH's 30 meter mods for the 40A. These are more comprehensive than W0CH's mods and will be the ones we pursue on our builds. Stay tuned.

30 Meter Mods Per WB6JDH
(1) Install 8 MHz crystals for X1-X6.
(2) Matched X1-X4.
(3) T1 is wound as follows:
    Pri 13T
    Sec 3T
(4) T2 is wound as follows:
    Pri 2T
    Sec 17T
(5) T3 is wound as follows:
    Pri 18T
    Sec 4T
(6) C6 is 22 pF NPO
(7) C9-C13 are 470 monos or 470 C0G or 470 NP0 if they fit
(8) C14 is 47 pF NP0
(9) C35 is around 151 pF (see notes below)
(10) C38 is 68 pF NP0
(11) C52 and C53 are 1500 Poly
(12) L4 is 10 uH
(13) L5 is 15 uH
(14) L6 is 24T
(15) L9 is 62T
(16) RFC1 = 15 uH
(17) R12 is 18-22 Ohms
(18) AGC Mute Circuit
    R4 is 4.7 MOhm
    R8 can be jumpered

Sanity Check Test Measurements
(1) U2 measurement:
    Pin 6 = 0.80 Vpp
(2) U4 measurements (on transmit):
    Pin 4 = 0.15 Vpp
    Pin 6 = 0.30 Vpp
(3) Q5 Measurements (on transmit):
    Source = 1.0 Vpp
(4) Q7 Measurements (on transmit):
    Base 2.5 Vpp
(5) Q8 Measurements:
    Source = 3.4 Vpp
    R23 on C7 side = 0.8 Vpp
    Rxvfo label = 0.8 Vpp
Regarding the oscillator circuit for U4, Dick was concerned because the drive to the base of Q7, the final transistor, was too low at 2.5 Vpp. At first, he thought it might be due to the crystal activity of X6 hanging off of pin 6. However, fishing through his stack of 8 MHz crystals and finding a substitution with more poop did not alter the drive that much.

Instead he proposed dropping the value of C35 hanging off of U4 pin 7 with something a little less than the 270 pF original. Dick tried a 150 pF NPO cap and reports that the power output for his 30m version was raised to just a shade under two watts. Recommend you try a temporary insertion until an optimum value is found. But be careful, however, as too low a value will swamp U4's oscillator.

Important Building Caveat
Q6 is the 2N222A driver and it requires a ferrite bead on the base. This is specified in the original NorCal 40A assembly manual as:

   FERRITE BEAD, 0.146" O.D., 0.138" long #64 material

The original assembly instructions tell you to "[after installing the ferrite bead on the base] push Q6 down onto the PC board so that its leads are as short as possible". Follow these instructions but be sure that the bead DOES NOT TOUCH the other two leads of Q6 or you will be in a world of hurt.

When I was doing the final tests on this, a mysterious 2.80 VDC voltage showed up on the collector of Q4 (the 8V TX keying circuit) and in the part of the circuit involving U4 (the transmit mixer) and Q5 (the buffer). This voltage turned on transmit and resulted in two tones (signal generator input and transmit side tone) and other general havoc. After trying to isolate Q4 from any other external influences like removing it (Q4), U4, and Q5, C29, and C30, the mysterious voltage still persisted.

Finally, I surmised that it must be Q6 and it was wicked out causing the voltage to disappear. After Q6 was correctly reinstalled with the ferrite bead insulated from the other two leads and all of the removed components were replaced things more or less returned to normal. Seems that some ferrite beads are made of materials that are conductive and caused a voltage to appear on the base of Q6 that leaked back into the transmit mixer circuit and played the hell described above.

..oh! And this note: Joe, W2KJ, sent me a PM and said correctly pointed out that the TO-18 (metal can) 2N2222A has a different pinout than the PN2222A. The former (looking at it with the metal tab on the left) is EBC left-to-right while the TO-92 PN2222A (looking at the flat side) is CBE left to right. But hey, PNP BJTs are kinda the same as MPF 109s or J310s, right?

Bottom line, I replaced Q6 with a PN2222A in lieu of the TO-18 2N2222A and that seems to work fine.

Tuesday, March 27, 2018

Marking time with a Pixie..

Noticed that John Clements, KC9ON, who produces the outstanding aftermarket boards capable of reaching back in time and bringing the Heathkit HW-7s and HW-8s back from the stone age, has come up with some interesting products for the low-end Chinese kit market. These are principally his Pixie Switch which turns the $5 Pixie kit into a little radio capable of four channels.

John also offers a kit package including the Pixie kit and his switch and three 40 meter crystals: 7030 Kc, 7055 Kc, and 7110 Kc. The intent is to use the 7023 Kc crystal in the Pixie to round out the four frequencies. Intrigued, I sent off for several copies of the Pixie plus switch package, a couple of extra switch boards and a crystal pack. In addition to that, I got a Chinese Frog Sounds QRP kit off of eBay that should arrive sometime in the next decade.

Anyway, I gave one Pixie plus switch to N6VCW to keep him busy and, since I had some spare time waiting for NorCal 40A parts to come, I put the other package together. Here are some pictures.

Now, I am not sure if the kit works correctly or not. It seems to be constantly on transmit so I have to go back and debug the circuit but, for as simple as it is, I followed the parts placement diagrams very carefully. I am guessing I will have to review the circuit and double check the details. But, suffice to say, it was good soldering practice and seems to emit a clean signal. It hears quite well on 40m -- at least from my signal generator -- and the front end is as wide as a barn door. There's also the added bonus of being able to listen to KFI out here in Southern California on 640 Kc.

So an Collins 75S-1 or a Hammarlund HQ-180 it ain't!

Sunday, March 25, 2018

NorCal 40A 30A build starts at last..

O.K., this is really it! I am starting the NorCal 40A build -- except that I am building it for 30 meters since I already have a 40A in hand that I scored at TRW from a seller for a decent price. I tuned that one up and adjusted its output to 995 milliwatts so it could rightly work QRPp. Quite a few Qs for the few times it was used, actually. One of my faves was the Maritime Station at Bolinas Beach, KPH. The ham station 700 miles from my QTH, K6KPH, was worked twice and represented an exhilarating accomplishment for me.

Since then, I ordered a NorCal 40A from Bob Dyer at Wilderness Radio before he retired. That kit still awaits the soldering iron. But, in addition to the 40A kit and the KPC1 keyer and frequency enunciator unit, I ordered an additional labeled blue face plate for the original 40A as shown above.

Some time later, in conjunction with K7QO's QRP-Tech 25th Anniversary GOTA project, I ordered the boards from China (surveyed here) and am, as we speak, beginning the 30m effort in order to document WB6JDH's effort. By the way, visit Chuck's website here for additional notes and links to his videos. He has even kept notes on his assembly work that bear looking into. And, finally, the site has links to the videos he produced. Also, I did a page on these for convenience.

A couple of months ago, I had gone up to Dick's house to do some preliminary recon work..

..but had not dug into the project until now. Starting out without anyone looking over my shoulder, I had to take the bull by the tail, as it were, and look the problem squarely in the face. At first, I was going to build and test sections at a time but, after reviewing K7QO's videos on this, I decided to proceed with stuffing the "generic" (i.e., non-band-determining) parts and then do Chuck's basic tests before Dick and I got together to make notes on just how to get the radio on 30 meters.

When that is done, it will be written up here and constitute a rough tutorial on how to build the 30 meter version for anyone who has built a 40A before. So stay tuned.

Along the way, some discoveries and assumptions have been made. Basically:
  • Wayne Burdick or Bob Dyer apparently had a barrel of 0.047 disk caps that he used liberally throughout the kit. Standard 0.1 caps can be used in lieu of these.
  • Q1 is specified as a 2N4124 NPN transistor but, according to Jim Kortge, K8IQY, a 2N3904 is an acceptable substitute. (Note that a 2N2222 is not acceptable.)
  • An MVAM 108 is an acceptable substitute for the called for MVAM 108.
Further bulletins as warranted.

At first, I thought about laying out all the parts on a Styrofoam board to inventory them. But since the project was behind the power curve, I just stuck them into the board figuring that was as good a way as any to see what went where and what was needed. Guess the results can be rightfully described as "the porcupine".

Here's a few shots of the work to date.

UPDATE: See the picture below.

Monday, March 19, 2018

Astron Supply back in the land of the living..almost.

After a couple of family emergencies and a small cold/flu attack, this project was finally buttoned up. I reinstalled the charging ports and the meter. as you will see in the pictures below. However, this time, I added a diode and a fuse to negate my reverse-biasing and blowing the pass transistors to high heaven. Here's the screamingly simple circuit; no challenge here - except to install in the supply. Not great wiring, but it'll do.

Try not to be overwhelmed by the complexity of this circuit!

..and here's the pics.

And, no, I did not cut out a hole in the front panel. The steel is pretty thick and doesn't nibble readily. If I need to convert the supply back to "sorta stock" there are fewer/smaller holes to plug. Also, don't get nervous about the meter showing 14.01 volts. It reads a little high. The adjustment pot on the regulator board was set to 13.9 VDC whuich is a good compromise for running test radios and topping off my gel cells., back to the NorCal 40A project.

Friday, March 16, 2018

Spare to my needs: Paddles..

I am a pack rat and have a habit of accumulating stuff to the point of redundancy. Lately, I am girding my loins for an April-May foray into rejuvenating my Morse code [questionable] talents by way of the infamous CW Academy. In casting about the shack/clubhouse/workbench, I noted that I was overflowing in the CW paddle category and sought to disburse these who are desirous of same.

Of course, these are offered at a fair price but are in decent condition. Herewith a description, comments, and pictures.

This came to me many moons ago via the TRW Swap Meet and was my main weapon of choice for many years. When my father (N6ABV) passed away in 1992, I inherited his Bencher BY-2 (the chrome base model) and was using that. My BY-1 was stored lovingly (i.e., not out back in the garden near the water spout or near the septic tank overflow nozzle), has been cleaned and adjusted and is ready to get back into the game. As I was cleaning it and testing it, I was surprised at how really good it was -- in my opinion, as good as the BY-2. If space were not a premium and since I only have one code fist..

This paddle poses the question: was there a Code Warrior Senior? (No, there was not.) Anyway, I picked this up after one or two waltzes with the NorCal Paddle Kit released in 1997. Remember?

Those were actually incredibly marvelous little items given the price and -- with a little care -- the resulting product. And, except for the plastic paddles, they were also pretty rugged. No Italian $500 shack queen here, they could be taken out to the woods, ridden hard, and put away wet. But you had to take along a set of drilled out guitar picks just in case!

When Vibroplex came up with these, I got a set and, true to form, the plastic paddles gave up the ghost. Instead of some famous rocker's signature guitar picks, I used a thin piece of copperclad PCB painted black. To my wonderment, they were better than the thick plexiglass originals.

Here's the pictures:

Hope these go to a good home.

Wednesday, March 14, 2018

Beyond Astron Revitalization: Protection..

So we got here because the genius that I am thought it would be cool to re-purpose an Astron supply to charge batteries as well as provide power for radios I was checking out. Sadly, when the mods were done, I zapped the PS and launched the series of posts below to restore it to normal. Still faced with the prospect of making my contemplated mods non-lethal, I sent the following email to my dear friend and trusted resource, Dick, WB6JDH:

I finally got this beast squared away -- as in back to normal before I modded and zapped it. But I have a question regarding my mods and how to prevent a re-occurrence on the problem; Here is the product I am using to display the battery charging aspect of the PS:
As you can see, it has a schematic on the back of the device. Also, it is shunted for 20A -- hence the circuit shown above. However, I am not putting this "in series" with the whole power supply in order to have it show current draw as I am downright nervous about running an actual 15-20 amps through this meter; I am not willing to push it.

I will be using the PS to do two things:

(1) Power 12VDC radios that I am testing -- which I will do on reduced power and well under 15 amps.

(2) Recharge my gel cell batteries -- which draw only about 2 amps max.

The gel cells will plug into the front of the PS as shown below. The normal back post terminals will power radios being tested and the meter will be switched out of the circuit by the front panel switch.
So here's the question: is it sufficient to put a diode on the positive line to the banana jack in front to prevent battery back washing and protect against reverse polarization and frying my pass transistors as I did before? Or should I also add a reverse polarization diode across the lines as well?

Some guys on the repeater builder's site have described putting a diode of sufficient size across the C-E junctions of the pass transistors but I felt that since the battery charging part of the circuit would be switched in when used, that might be overkill.
Your faithful servant, etc.
Anyway, in preparation for Dick weighing in on this, I did some research and came up to the realization that merely slamming a diode into line solves the problem by incurs a 0.7 VDC drop and, in the case of the charger, would force me to run the PS at about 14.5 VDC to effect gel cell charging. This would, of course, might not be so peachy for the 12 VDC radios I want to bench test. So, in studying alternatives, I came across this video:

Now, the first and third methods are flat out unworkable as I want to keep it simple. The diode across the power leads with the fuse in line appeals to me as being a direct solution. The downside, of course, is the prospect of mounting a fuse somewhere. If it is inside the PS then I'd have to unscrew the case every time I sinned, But, then again, that would teach me a lesson.

This video explains a more sophisticated solution and I might consider that:

..stay tuned, still pondering.

Sunday, March 11, 2018

Astron Revitalization (Part 3)

So it turns out that there was an outright rebellion of the posters on the Repeater Builders' Yahoo Group. The newcomers ALL said that the problem was the pass transistors. Jeff, WN3A, replied as follows:
> (1) Grief came to the DUT when the PS terminals were
> shorted/reversed polarized by a gel cell I was charging.
> (Long story; yes, I am aware of the caveats arising therefrom.)

Which was it - shorted or reversed? If reversed, then I would think the
first damage to occur would be to the pass transistors since the
base-emitter breakdown voltage is likely to have been exceeded.
> (c) Pass transistor voltages
> E=10.7
> B=23.3
> C=23.0

Sure looks like blown pass transistors to me...
--- Jeff WN3A
Heretofore, I was somewhat squeamish about pulling them and checking them but this sealed the deal and, to my surprise, it was quite simple to do as you just unscrew the little bastages. After pulling them, they were checked with an ohm meter. Now, I was never really clear on romping around a transistor and checking the junctions -- you know, the E-C, C-E, B-E, E-C, X-Y, Z-A and all that crap -- so I went out to YouTube and found a how-to that made it simple:

Following this method showed me that both pass transistors were as dead as last week's meatloaf. Not only that, it showed me that the ones I had in my junk box were not too terribly peachy as well. So I ordered two 2N3771s (the 2N3055's tougher brother) and, until they came, I scrounged a couple of good 2N3055s in my box, greased 'em up, and slammed 'em back in the holes.

Waddya know! The PS came back to life and I am a happy camper! Here are the good voltages:

So what's left to do on this project:

Astron Revitalization (Part 2)

Thinking that the gremlin dwelt on the rectifier board, I attacked it with savage fury!

The first thing that WA1MIK says is, in effect, that if all else seems O.K., swap the LM723 regulator chip. And this seems reasonable because it's (a) socketed and (b) it's cheap. (About 99 cents.) So I rocketed down to JK Electronics, got one, and rocketed back home breathlessly expecting everything to be rosy.

Sadly, It wasn't! So on with the analysis.

So, yet again, back to JK Electronics to purchase a TIP29A and back to the bench where..

.. I was met with the same disappointment!

Borne of frustration, I started swapping any and all parts on the regulator board I could (without going back to JK Electronics).

After scratching my head and re-reading and further cogitation, I returned to the Repeater Builder Yahoo Groups thread and was met with a pleasant surprise. Initially, I received only two replies from my pleas for help but, in the interim, a crapload more had appeared.

Tune in to see what the final episode holds for our hero!

Astron Revitalization (Part 1)

..don't let the title fool you. The revitalization was occasioned by stupidity on my part. I was trying to modify a perfectly fine Astron RS-20A to facilitate gel cell charging. I installed one of those nifty Chinese LCD Volt/Amp/Watt panel meters to monitor the charging process of gel cells. When they are down, I put 'em on and -- even in a severely discharged state -- they top right up by drawing about 500-600 mA at first and then the current dwindles as they reach a charged voltage of about 13.5 volts nominally. The important thing is they are not left on interminably to cook. They get yanked when the current gets consistently below 100 mA in about 6-8 hours.

Well, I had done the mods and was testing it with several batteries around the shack when tragedy struck! I reversed polarized one and zapped something because the PS terminal voltage dropped to about 9-10 volts. So, going into debug mode, I did some poking around and put together a description of the problem to be posted on the Repeater Builder Yahoo Group. Herewith is my initial plea. (Note that I turned these into images to preserve the spacing that the HTML interpreter kills.)

Before we go any further, the Repeater Builder site (not the Yahoo Group) has a wealth of articles on R&R of these beasts. If you are in the same hell I was in, click on the links and read further:

These aren't the only ones. There are many others that offer a treasure trove of knowledge. If you do as I have done, you will become pretty adroit at understanding and repairing these. Not an expert but good enough to spot a PS at a swap meet labeled "parts or repair", pick it up for $5, and have it running in no time with just a few inexpensive parts.

The main article was Repairing Astron 13.8V Linear Power Supplies by WA1MIK. It works its way from the wall socket to the binding posts and helps you trouble shoot by symptom. (Mine was "low voltage".) I reduced the main part of the article to a sort of checklist:

Going through the above, I thought that it drove me pretty convincingly to the regulator board as being the problem -- and that everything else was just dandy! Boy what a mistake that was!

Stay tuned..