SA2CLC Fixes the Cavity Resonator on his HP8640 -- Not for the Faint of Heart!

 

https://sa2clc.blogspot.com/2025/01/hp8640-died-this-is-me-catching-up-on.html?m=1

Part 2: CuriousMarc Fixes an All-Discrete Counter -- "Like an IC, but in discrete form."

Marc nicely sums up this project with this line:  "It's an IC but in discrete form!"  On the same theme, he later says, "Who needs a logic analyzer when you can do a visual debug with neon bulbs?" 

Very cool.  Lots of troubleshooting and repair lessons in this video: 

-- Again we see the benefits of paper manuals.  (Todd K7TFC commented astutely on this under yesterday's post.)

-- 2N2222s to the rescue.  

-- A surprisingly large number of bad transistors (6?) found.  Why did they go bad? 

-- Marc repeatedly says, "Let me poke around."  Poking around is often important.  Mark fixes the reset line after poking around.  He is not sure HOW he has fixed it, but he has... by poking around.  Sometimes this happens.  Thank God for small favors. 

-- Marc has some fancy HP board extenders.  I am jealous.  

-- He also has a cool de-soldering tool.  More jealousy.  Want one. 

-- Marc's understanding of how the HP engineers had to put one of the flip-flops "on the edge of stability," and how his 'scope probe was capable of disturbing this stability. 

-- Remember that those Nixies are TUBES with enough voltage on them to really zap you.  So be careful in there.  This is an especially dangerous mix of transistor tech and tube tech.  With transistors you can work on them with the rig fired up.  With tubes, well, you have to be careful.

Part III tomorrow. 

My HP8640B Signal Generator Lives Again

I'd really come to like this old signal generator.  The construction is superb.  It was built to be repaired.  As you open it up you find all kinds of useful diagrams and pointers.  It is very solidly built - it looks like something that was built for the Apollo program.  And it was given to me by a friend:  Steve Silverman KB3SII gave it to me in 2017 -- he had it in his New York City shack.  Dave Bamford W2DAB picked it up for me just before Steve moved out of the city.  

I've already done one complex  repair on it -- one of the tines on one of the selection switches fell of and I had to replace the tine.  That was difficult, but it was a very satisfying repair.  

But lately, the HP8640B started acting up again.  It developed an intermittent problem that caused both the signal generator and the frequency counter to just shut down.  

I was thinking that this might be the end of the road for the HP8640B.  I even started looking for alternatives.  But they were all very unappealing.  They come in plastic boxes with names like Feeltech and Kooletron.  The boxes are filled with flaky wiring and boards hot glued to the plastic.  Yuck.  The contrast with the HP8640B could not be stronger.  

So I started to think about the problem.  This was the first part of the troubleshooting process.  I asked myself:  What would cause several different systems (counter, frequency generator, and display) to all shut down?   The power supply was a leading candidate.  

I started reading the power supply section of the HP8640B manual.  There was a line in there that caught my eye:  The power supply boards had on them LEDs that glowed if the board was functioning.  Thank you Hewlett Packard!  I opened the top of the signal generator and found the power supply boards. Sure enough, there were the LEDs.  I turned the generator on, and found that one of the lights was out. Bingo. (Trevor takes a look at the power supply boards in the video above.  I have it cued up to the 12:57 point at which he talks about and shows these boards.) 

Here was the other clue:  The problem was intermittent.  It kind of seemed like a loose connection.  So I just unseated the board and took it out.  I put some De-Oxit on the connector and popped it back in.  Boom:  The LED came on and the HP8640B came pack to life. 

There is a whole bunch of great info and videos on the HP8640B on the internet.  It is almost as if a cult has developed.  This signal generator is worthy of a cult following.  Count me in.  

I especially liked the video below.  Kevin really captures the admiration that many of us feel toward the way this piece of gear was built.  He also kind of hints at the way this sig gen could become a pirate transmitter on the FM broadcast band (at 8:44):  

I know that eventually the problematic plastic gears in this device might fall apart.  I am prepared for this:  I already have the metal replacement gears from India.   

Thanks again to Steve Silverman KB3SII and Dave Bamford W2DAB for bringing me into the HP8640B cult. 

Mr. Carlson Replaces Old Capacitors -- Bathtub Capacitors

I recently posted a video from CuriousMarc about whether or not to replace electrolytic capacitors in old pieces of gear.  This is a hot topic in restoration circles. 

This week Mr. Carlson put out a video (above) in which he got rid of a bunch of "bathtub" capacitors in an old receiver. 

One of the many interesting things in Mr. Carlson's video was how his test gear initially showed the old capacitors to be good, but on further examination with better test gear he found them to be BAD! 

Out with old, in with the new!  

To Re-Cap or Not to Re-Cap -- Curious Marc on the Electrolytic Controversy in Ham Radio

A while back I got some fairly acerbic feedback when I DARED to suggest that perhaps it would be a good idea to replace the old electrolytic capacitors in ham radio equipment.  It was as if I had attacked motherhood and apple pie!   

Yesterday I was looking at CuriousMarc's YouTube channel and I came across the above video.  While I had been in the preemptive replacement camp, Marc makes a good case for leaving some of the old caps in place.   The fact that the electrolytics usually are open when they fail, and that there are fuses in the power supply to protect the transformers,  are important points.  His admonition not to replace electrolytics with tantalum caps (which fail closed) was also very useful. 

OK, my flame-proof suit is on! 

CuriousMarc (AJ6JV) Goes to a Hamfest

Jean Shepherd once said that all of us at one point come to a cross-roads in our lives -- one road leads to success, the other to ham radio flea markets.  

As I watched this, I realized that CuriousMarc sounds like a ham.   Sure enough, some Googling revealed that his real name is Jean-Marc Verdiell and his ham radio callsign is AJ6JV. 

I knew Marc was one of us when, in the video, he opens up the teletype.  He says that the seller claimed that it still worked.  But Marc comments that he hopes that this is not true, so that they will be able to troubleshoot and fix the device.  FB.  That's the spirit.  

We are really lucky to have someone as successful and creative as Marc in the ranks of ham radio operators.  

Be careful with the high voltage Marc!  

R-390s, KWM-2s, Airplanes, and Magnetic Loops -- A Really Interesting Interview with Ted Robinson K1QAR

Eric Guth 4Z1UG has a really interesting interview with Ted Robinson K1QAR.  

I really enjoyed hearing Ted's inspiring story: 

https://www.youtube.com/watch?v=SUUzlKMMANg

https://www.qsotoday.com/podcasts/K1QAR

Listeners will like the discussion of the R-390 and the KWM-2.  And his talk about airplanes.  And the joy of repair.  

Here is Ted's QRZ.com page:  https://www.qrz.com/db/K1QAR

Thanks Eric!  Thanks Ted! 

Repairing the Sony ICF SW1 Receiver -- Used for Numbers Station Reception? Why no replacement for C-625?

Ten years ago, my friend John gave me this tiny Sony receiver.  It wasn't working.   I tried to fix it but quickly discovered that the tiny size of the device made repair difficult.  All you needed to do was to swap out some leaking electrolytics, but they are surface mount electrolytics -- replacing them is not for the faint of heart.  Kits are available, but again, this is not easy. 

In 2020 I got one of the kits, but didn't try to use it until yesterday.   It only supplied six of the electrolytics.  In the video above, they discuss replacing seven electrolytics, including the one that seems to be placed in the round black holder. C-625.  Why didn't my kit include a replacement for that one?  Could it be that this capacitor was not one of the leaky SMD caps?  

Replacing these caps really wasn't easy. At one point I inadvertently removed not just the bad cap, but also a nearby surface mount resistor.  Luckily the schematic showed it to be 0 ohms.  That was easily replaced.  I lifted one of the pads on one of the other caps -- I just slid it back into place and hoped for the best. 

BTW, I just today discovered that this little receiver may have been used late in the Cold War by those who needed to receive messages from the infamous Numbers Stations: 

 https://www.cryptomuseum.com/spy/sony/icfsw1/index.htm

WD-40: Not Quite the Pope's Pee

This is the second time that Todd K7TFC has sent in a comment that is so good that it gets elevated to the main blog page.  When I was typing yesterday's post about how WD-40 had restored life to the hard drive in my old Tandy 1000 computer, I knew that this would stir up anti-WD-40 sentiments.  I'm grateful that Todd weighed in with such a thoughtful response.  

What can I say?  I was young and foolish.  I thought WD-40 was the answer.  Now I know better.  I have can of DeOxit D5 on my shelf.  I only use the WD-40 on my bicycle.

Todd K7TFCApril 9, 2022 at 7:49 PM wrote: 

I think even the Pope would argue his pee has already served its only real purpose: to remove unwanted substances from the body. WD-40 is useful for that purpose as well--it's pretty good at dissolving and blasting away dirt and grease from tools, hardware, or small mechanisms. That's no doubt why it worked to get your hard-drive spinning again. As a lubricant, though, it is deeply flawed.

If you have nothing else at hand, it can also substitute as an penetrating rust buster. The purpose its developers intended is coded in the name itself: "WD" stands for water displacement, and its very good at doing that. It's not so good at many of the other uses to which it's commonly put.

A very-long time ago, I worked at a company that made its own PCBs, and they had some very-precise NC machinery (programmed with punched tape in those days) for drilling and routing the boards. After a series of baffling and costly shutdowns, the culprit was discovered and WD-40 was banned entirely from the plant. The plant-maintenance guy and janitors couldn't even have any.

It was found that once completely dry, the oils and waxes in it would slowly polymerize (as they were intended), leaving behind a sticky film that protected from moisture and rust just fine, but it gummed up precision machinery. The Chief Production engineer (my father) got the company brass to ban WD-40 entirely.

Why ban it from even plant-maintenance and janitorial work? Because you couldn't keep the PCB-production crew from resorting to it in a "crisis" if they could find any at all in the building. It meant they weren't careful enough to keep the proper lubricants in stock. You could either fire them for their shade-tree-mechanic mentality, or you could ban WD-40.

Needless to say, I've kept my congenital anti-WD-40 animus alive all these years, but I do have a can I use for cleaning and water-displacement purposes. When tempted to use it otherwise, though, the memory of my father sniffing the air suspiciously for its distinctive odor flashes in my head, and I reach for something else. --73, K7TFC  

WD-40, a Hard Drive, a Coat-Hanger Antenna, Dumpster Diving, and Amateur Radio Satellites from the Azores

 

Last month I was talking to Ira VP2EIH on my new 1712 SSB rig.  Ira is interested in satellites.  Talking to him caused me to dig up some old material about satellite operations.   Here is a 2003 QST article about working the satellites from the Azores: 

http://www.gadgeteer.us/AZORESSP.HTM

Regarding the usefulness of WD-40, during my time in the Azores John EI7BA once told me that WD-40 is, "the Pope's pee!"  Apparently that is high praise in Ireland.  It is indeed good stuff. 

Messias CU2BJ is a Silent Key.  I hope Ray CU3GC, WL7CDK is doing well.  

The Next Time You Hear Someone Complaining About Winding Toroids....

... send them this video. 

Lin is in Hong Kong. What a great job she does with very simple tools.  Notice how she casually mentions that for those parts that have been lost, she will make them herself.  Three cheers for Lin! 

This video reminded me of the people in Santo Domingo 25 years ago who rewound the transformers and RF chokes from my HT-37.  These parts still work.  

Chuck KF8TI recently told me that when he was a Peace Corps Volunteer in the Philippines (1965-1967) he visited a transformer re-winding shop there, seeing piles of insulation and wire on the floor.  Apparently business was good!  

Lin's YouTube channel: https://www.youtube.com/channel/UCpPt42tLH5FRk__ytvMsejw

Right to Repair Update

Allan WA9IRS sent me this article.  Thanks Allan.  

https://www.digitalengineering247.com/article/right-to-repair-movement-attracting-attention?oly_enc_id=4802E9408878H3Y 

The French "repairability index" is an interesting concept.  I wonder how modern ham radio "radios" would score. I think our homebrew rigs would max out the index. 

Pete has commented on manufacturing processes that do (or don't) factor in access for repair. 

One of the recent horror stories we've heard is about a certain manufacturer of mobile phones.  It seems that they have designed the phones so that if you dare to replace a broken screen, the new screen won't work unless you de-solder the associated chip, then re-solder in the SAME CHIP.  

Previous blog posts on this: 

https://soldersmoke.blogspot.com/2010/11/knackers-of-world-unite-you-have.html

https://soldersmoke.blogspot.com/2021/03/mending-vs-ending-fight-against-planned.html

No Longer On the "Shame Shelf" -- Pete Fixes His KWM-1

 

I think a good troubleshoot is almost as satisfying as a successful homebrew.  And we can sense that high level of satisfaction in Pete N6QW's description of his repair of a Collins KWM-1:   

http://n6qw.blogspot.com/2021/10/resurrection-of-kwm-1-sn-673.html

I liked Pete's troubleshoot/repair story, but -- as is often the case -- I struck by his turn of a phrase.  I think Pete has added something important to the SolderSmoke lexicon: 

THE SHAME SHELF 

Most of us have a shelf like this. I have an HW-101 on mine.  Pete shows us that there is hope -- there is path off of the shame shelf.  You just have to know stuff.... Or have IBEW friends like Pete who can advise you. 

The Woz on Homebrewing and The Right to Repair

There is a lot of wisdom and history in this Cameo video by Steve Wozniak.  

Thanks to Chuck KE5SPY for alerting us to this.  

Here a good BBC article that summarizes the Right to Repair issue and Woz's involvement.

https://www.bbc.com/news/technology-57763037

The Woz has The Knack.  

The Joy of Fixing Broken Things (a really amazing video)

This amazing 10 minute video captures very well the joy of fixing broken things. It comes to us through a recommendation from Paul VK3HN in Melbourne, Australia. Thanks Paul.

I hope we will see more from Van Neistat.  He already has a bunch of videos on his YouTube channel:   https://www.youtube.com/channel/UC5mPJA4y5G8Z6aNkY6AxgAw

I often tell the story of the OT (probably now an SK) who at hamfests would ask if a piece of old gear was working. If the vendor answered honestly and said no, OT would reply, "Good, I pay extra for that."  He too liked to fix things.

Mending vs. Ending -- The Fight Against Planned Obsolescence

https://www.ifixit.com/Manifesto

We don't get a lot of mail from Darwin, Australia, so the message coming in from Phil VK8MC immediately got our attention.  When I looked into the details I realized that it was very SolderSmoke-relevant.  The Guardian article that Phil cited even mentions hobbyists tinkering with electronic devices in their sheds (that would be us!).    Phil points to the connection between our repair efforts and the struggle to save the planet: "It's not just a hobby, it's an ethical position which contributes to the well being of the planet. A higher calling indeed!" 

Here is the article Phil pointed us to:

https://www.theguardian.com/commentisfree/2021/mar/17/ending-over-mending-planned-obsolescence-is-killing-the-planet?CMP=Share_AndroidApp_ProtonMail

The poster above (which hangs above my workbench) is from https://www.ifixit.com/Manifesto. 

Seized up Variable Capacitor -- Any ideas?

Perhaps in retaliation for all the bad things I've said about regens over the years, the main tuning cap in the old regen I've been working on suddenly went from completely loose to totally stiff.  I can turn it, but it is too tight for the old vernier drive in the regen.  I have replaced it with another cap, but this part was kind of the star of the show, situated as it was several inches above the chassis, connected to the tuning control by a long shaft.   I've tried squirting WD-40 in there -- no joy.  I can't even figure out how to open up the part of the cap where the ball bearings should be. It is an OLD Eddystone from England.   Any ideas? 

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Halogen Lamps and Heat Guns to The Rescue!

Hi Bill,

Your recent success with baking your Sony Vaio gave me the courage to attack my flat screen monitor. The most expensive thing in my entire computer setup is my "LG" brand monitor. It's the only thing that I've purchased new. Everything else came from the curb, or the surplus store. However, it started going on the fritz a few weeks ago.

While browsing around the chat groups on the internet I found out that many monitors from the past few years have had bad capacitors in them. So I opened it up, hoping to find a blob of leaking chemicals near a cap. "It should be a quick fix" I thought. However, everything looked great. No bulging caps, or leaking chemicals. I then turned the circuit board over, and instead of seeing a shining city of perfect solder joints, I saw a cloud of grey. Practically every solder joint was cold.

This is where your laptop baking got me thinking.

I didn't have a halogen lamp handy, but I did have a heat gun. So I put the gun on the high setting, and very slowly passed it over the board. It left a gleaming trail of solder joints.

When I started to connect things back together again, I heard a rattling. It seems that I heated the board up enough to allow some components to completely fall out. Luckily they were through-hole components (nothing surface mount), and were easy to solder back in.

Once everything went back together... success!

One thing to note, at one point I got a nasty zap from one of the caps on the board (I'm assuming for the back light). Even though we're not working with tubes and CRTs anymore, you still have to take heed and discharge high voltage caps before working on anything!

-Keith VE3TZF

KNACKERS OF THE WORLD UNITE! You have nothing to lose but your warranties!

The folks over at ifixit.com have come up with a Self-Repair Manifesto that readers of this blog will find inspirational. I like the line about "Repair injects soul and makes things unique!" Indeed. As of yesterday they were giving away free posters (real posters, not e-posters) in exchange for a Tweet (I got mine, and intend to put it up here in the SolderSmoke Shack.)

I find that a successful repair is almost as gratifying as a scratch-built homebrew project, especially if the problem was difficult to diagnose.

So, ifixit comrades: The SolderSmoke collective is with you! Up the Revolution!

My Frequency Counter. FIXED!

I mentioned my broken frequency counter... Tony Fishpool, G4WIF, of G-QRP sent me a replacement CMOS chip. The counter is now counting beautifully. It was a real chore to get the bad chip off the double-sided board, then I doubled my work by putting Tony's chip in upside down. It doesn't work very well that way. I did another chip extraction. By this time I had all kinds of lifted pads, broken traces, pins on the verge of breaking. I felt sure that all the heating and de-soldering had destroyed the CMOS. But no! It lives!

This was a very satisfying troubleshoot and repair. I feel like Dr. House. The whole thing was made even nicer by the fact that the repair part came from the junkbox of a friend. Thanks Tony!

Looks like the old counter is still well-calibrated. It has my QRSS sig at 10140070. ON5EX's grabber puts me at 10140050. So the counter is 20 Hz high. Not bad for flea market junk.