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..

Saturday, March 10, 2018

Senility sets in: Reorganizing the clubhouse..

O.K., that's it! I started misplacing things and coming up with duplicate items because I did not know I had picked one at a precious sale or swap meet. So, I was determined to "re-org" the clubhouse, put things away, label the boxes..

..and, in the process, integrate my dust-collecting DR-235 220 radio into the shack. Here's the pics:

The old VHF radio (left) nest to the new 220 radio (right) alternative to ultra-running preening and fishing stories!

All the rigs..with the revived TS-180S!

"New" scanner just in from Yuma, other acquisitions, and standby rigs.

Got sick of dragging out a DMM on the bench, so I added one I scored at TRW to my SAMPO's

Latest project is reviving an Astron RS-20A.

All parts and projects organized and labelled. Anal retentiveness lives! (Don't tell the USPS!)

QRP Rigs and test equipment stowed out of the way.

Cables and connectors sorted and labeled.

Heathkit HW-7s and HW-8 and HW-9 station awaiting mods.

And note that they show a dissected Astron RS-20A on the bench. Well, that's my latest project and the subject of a near-future write-up. Stay tuned.