Saturday, September 28, 2013

Why Do My Projects Always Expand?

Whoo boy....I'll bet all of my friends out here know what I'm talking about!

About 8 months ago my radio club had a members-only auction to get rid of equipment we no longer use in the club station. I came home with an ICom R-71A shortwave receiver, and a Yaesu FT-726 VHF/UHF multimode transceiver.

The ICom works OK, so it went on the shelf, but the reason I got the Yaesu for $25 is that it allegedly had a problem with the UHF module, it's not suited very well for repeater (FM) use because it doesn't have a CTCSS "Tone Board", it has no "Comm Port" on it so you can't run it with a PC and it wasn't usable for satellite use, as it lacked the satellite module.



It's basically an FM/SSB, 10-Watt output radio that covers 2 Meters (144~148 MHz) and UHF (430~440MHz), and while it would be a very good radio for "rover" or home use with some external amplifiers, NOBODY wanted it, so I won it with the opening bid of $25.

I got it home, and it sat for awhile whilst I went through my "Medical Adventures". I finally started working on it a month or so ago.

I pulled the covers and knobs off to scrub them, and lo and behold, what's this?

It has the satellite module installed!

Some basic testing shows that it puts out 10 Watts on both bands, and the satellite unit works as per the manual, BUT, it's 8 kHz off in frequency on transmit on both bands.

What makes this radio unique, along with it's newer big brother the FT-736, is that the radio itself, without any of the modules, is a "10 MHz, I.F.", and the individual modules act as "transverters" to upconvert the 10 MHz to whatever, and then downconvert the whatever back to 10MHz.

So, since the frequency is off the same amount on two different bands, it points to a problem in the basic radio chassis, exclusive of the band modules.

ANYWAY.....I figured I should do a full alignment on it to ensure it works properly before I sell it, and that's when the fun started......

I got started doing the alignment, and then got to the step where I needed my RF Probe. Hmmm...where'd I put it? Can't find it, order a new one. While waiting for the new one to arrive, I use my frequency counter and DMM to adjust the things that I can, which goes fine.

New RF probe arrives, and I finish up the initial alignment steps. The SSB and CW portions of the basic radio are now operating per spec. Time to do the FM section....UH-OH....I need a Deviation Meter to adjust the FM deviation. Huh...never have owned one of those. Probably time to buy one, as I'm sure I'll need it after I retire and really start doing radio stuff!

OUCH.....SIX HUNDRED BUCKS?!  Oh, well....off to eBay where I find an old Lampkin Engineering one made in the 1950's for $30, FREE shipping!





It arrives in great shape for being as old as I am, and works *perfectly*. Super...time to set the FM deviation!

Uh-oh.....I need a calibrated source of 300Hz and 2800Hz. I have a two-tone generator for aligning HF SSB radios, but it operates at two different, fixed frequencies, and my service manual is very specific on why you must use 300 and 2800Hz.

Hmm....well, I have that ancient HP signal generator I'm slowly rebuilding as a memorial to my friend, but I'm waiting on some esoteric parts for it. I also have a newer HP solid-state signal generator, BUT that dirty old thing was the piece of equipment I was working on the night before I got the MRSA infection in my finger. Think before I handle that one again I'll put some gloves on, and scrub it down with bleach, and then hydrogen peroxide!

Off to eBay again, where I score a MINT Heathkit IG-18 audio generator for $70, FREE shipping!



While waiting for the generator to get here I start searching for a manual for it. Since my Google-Fu is strong, I find that with a few simple modifications, you decrease the Total Harmonic Distortion by a factor of TEN or more, and also make the frequency accuracy better by the same amount!

Wow....! These things are already pretty good, and for about $30 in parts I can make them an ORDER OF MAGNITUDE better?!?

GO FOR IT!

The generator gets here on time, and all the parts I either have, or picked up on the way home from work on Friday. I take the covers and knobs off the generator (why do I feel Deja Vu coming on?), scrub them and dry them, and start testing the generator to make sure it works before I modify it.

Note to others:  ALWAYS test the equipment before you modify it to make sure it works, or you can wind up chasing you tail thinking you screwed up the mods!

The generator tests out fine after I clean the switches and controls with some DeoxIT (amazing stuff!) to clear up some erratic operation.

Then BANG!!

My six-month old LED magnifying lamp goes casters up with a bang and cloud of smoke. I really liked this thing as the color temp of the LED's made it really nice to work with, the big 5" 3-diopter GLASS lens was clear with no distortion, it was light weight and easy to move around on the extension arm, and it didn't throw off enough heat to warm the shack in the winter time.



And I'm getting old enough to really need a nice illuminated magnifying lamp for close-in work.

Oh, well......hop in the car and drive to the closest office supply store, which happens to be an Office Max that I go to regularly. I shop what they have, and pick one with a circular fluorescent tube in it, mostly because the only LED lamps they have are either too small, or have crummy PLASTIC "lenses" in them for "magnifying" what your working on.

It's not as bright as the LED lamp, and even though it shouts that it's "FULL SPECTRUM!!" on the box, I still prefer the color temp of the LED light. I took the cover off the LED light, and sure enough, the 59-cent switching "power supply" they used has vaporized. I'm going to count the number of LED's in it, see how they're connected, and come up with some kind of external supply to run it with, I like it that much.

Get home, unpack the new lamp, set it up, and start using it to inspect the soldering job on the generator. It is, after all, a HeathKIT, and some builders were less competent than others.

Touch up about 1/3 of the solder connections, set my Tektronix 2465B on the bench for the first time (don't worry, it works fine!) so I can adjust the generator, and HEY....it's 11 PM already?

Sigh........

So, here I sit waiting for the soldering iron to warm up, small pile of parts at the ready, fingers crossed, and wood knocked, and hopefully I can have the generator modified and operating tonight.

13 comments:

  1. BTDT, and it's frustrating. I'm encouraged by how easily you're able to come up with what you need, though. But isn't that the way projects go? At least, MINE always do that...

    ReplyDelete
  2. Well, I guess it helps that I know what I'm doing.

    Several years ago I came *this close* to buying what's called a "Service Monitor", which is a fancy box with certain instruments in it built specifically for this kind of use, but I was out at-sea for work, and even though I told my "friend" to hold it for me, he sold it before I got back.

    The main thing we lose when we don't have what we need on-hand is time, and that's the really frustrating part.

    ReplyDelete
  3. Do you check the gsa auction site? The "Electrical and Electronic Equipment and Components" tab usually has some neat stuff that goes for decent prices. Got to know what the stuff is worth before bidding as I have seen some equipment go for more than some dealers will sell new stock . One bad thing about the gsa sales is that they do not ship, so you have to figure travel into your bid.

    ReplyDelete
    Replies
    1. If I was in the surplus equipment business, I'd be all over the GSA auctions.

      However, I'm not, so while I look at them once in a while, I have no intention of bidding.

      I can just see myself getting stuck with a pallet full of dead oscilloscopes, like a friend of mine did.

      He sure go a good price, though.....

      Delete
  4. Replies
    1. At 0330 the status is that I had to resolder ALL of the connections on the two small circuit boards in it.

      The point-to-point wiring and soldering is very nice, so I'm guessing whoever originally built this kit had some experience.

      Most of the solder connections on the board suffered from too much solder, and not enough heat. As I was removing a couple of components that get changed, I noticed some of the connections were loose on the foil side of the board! They had a pretty, shiny solder connection to the lead coming through the board, but the solder had not properly flowed out onto the foil, indicating a lack of heat to get the foil hot enough to allow the solder to flow on to it.

      I used solder wick to remove the solder, and then resoldered all the connections.

      The flux in the solder wick is pretty aggressive, so the new solder (Kester "44" 60/40) flowed out very nicely.

      All the components in the modification have been changed, and a couple of doubtful electrolytic capacitors were also swapped out. Now I'm adding the meter buffer circuit to it. It's a little board that mounts on the studs coming out of the meter, and provides a buffer between the sine wave generator circuit, and the rectifiers that provide the DC to drive the meter. Without the buffer, the rectifiers hanging on the meter act like mixer diodes, and generate spurs that ride along on the sine wave output to the front panel. Heathkit corrected most of the circuit defects over the years, but never did anything about this particular one.

      Delete
  5. So far I count $130 to get your $25 radio tweaked and in spec? Not including the RF probe and the ring light/magnifier?

    Sounds about right, really.

    ReplyDelete
    Replies
    1. HAH!

      The new lamp was about $60, and the RF probe was around $40, so tack on another hundred bucks, and you're close.

      BUT, I consider these tools, and they cost will be amortized out over all the other things I'll be working on.....;-)

      Delete
  6. My head just went, POP. You are too good. Wish I had a tenth of your tech knowledge.

    ReplyDelete
    Replies
    1. Stephen, I've been doing stuff like this since I was 10 years old, so in 50+ years of experience, you tend to pick up a lot of knowledge.

      Delete
  7. For the want of a nail the kingdom was lost?!?

    I'm sure glad you know what you're doing, because I'd be hiring it all out myself.....

    ReplyDelete
    Replies
    1. Typically, you'd pay about $75~$100 to have somebody go through a radio like this and do a cleaning and alignment.

      I don't think Yaesu services these anymore, so you'd have to find an independent repair shop (like me!) to do the work.

      If it were a Kenwood radio, I'd tell you to send it to Clif at AVVID in Texas. He does outstanding work @$50/hr.

      Delete

Keep it civil, please....