Category: test gear

SolderSmoke Podcast #231 — Travel, SST, Mythbusting, Filters, TIAS, NanoVNAs, DC RX in SPRAT, Drake A Line, Spillsbury, STICKERS! Mailbag


SolderSmoke # 231 is available:


Annual Field Day Special Edition

Travelogue: To the Dominican Republic!
New dog — Meet Guapo (see below).

A great Father’s Day for Pete and Bill. I got a TinySA.
Pete got some cool chick magnet glasses (see below).
Watch out Newbury Park!


Bill’s Activity

SST Transceiver. Took it to Dominican Republic.
Made only one contact, but QRP-QRP.
Not a lot of CW activity, and not a lot around 14.060.
A lot more FT8 visible on the NA5B WebSDR.
That might be better for this kind of operation.
I might try SST CW out today from the backyard. Field Day!

Fired up my 20 meter DSB NE602 rigs. Made two contacts.
Still trying to fully understand the NE602 Gilbert Cell. Lots of mystery in there.

Building “The MythBuster.” 75/20 with sideband inversion.

10 pole 5.2 MHz filter. Used Dishal and AADE.
Used NanoVNA to see the passband.
G3UUR for crystal parameters.
Cohn Constant K topology.

Also used NanoVNA to check input and output impedance on the TIA amps I will use around the filter.

Pete’s activity:

Article on DC receiver in SPRAT. FB response. 50 receivers under construction.

Work on Drake A Line.

Jim Spillsbury.

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The N5JHH IBEW SolderSmoke stickers (see above and below). How we will use them.

Mailbag:
N2SVD
K8ITY
Tom (Junkbox receiver)
N0ZIB (Curse you, SolderSmoke!)
DL6ID
N2NLY
VK2EMU
ZS1KE
AF7O
NG2E
VU2ESE
OK1RP
N5JHH

A Problem with the San Jian PLJ6-LED Counter

I had hoped to use this handy and cheap little frequency counter to add some glowing Juliano Blue to the frequency readout on my Quarantine Hodgepodge rig. I’ve used these boards with my BITX20, my HA-600A, and with my DX-100/HQ-100 rigs. But guess what — these boards do not work with the BITX40 module board that is the heart of the Quarantine Hodgepodge. And the reason why is interesting.

Here is what happens: First, you plug in the IF frequency of your rig. In my case 12 MHz. You connect your VFO output to the signal input on the PLJ6. You power up the PLJ6. You then have to select one of two IF frequency options. One of these options ADDS your IF frequency to whatever it detects at the signal input. In my case, for a 7.2 MHz signal it would detect a VFO signal at 4.8 MHz. If it were to ADD this signal to the IF freq, it would readout 16.8 MHz. And it does. But obviously that is wrong. So you go to the other option — this one SUBTRACTS the designated IF frequency FROM whatever it finds at the signal input. So here we get 4.8 – 12 = -7.2 Almost perfect right? But here is the problem: The PLJ6 can’t handle negative numbers! So it displays 000000. Not helpful.

Here is the manual:
https://www.mpja.com/download/35057tebasic%20manual.pdf

I didn’t have this trouble with any of the other rigs because none of them required the use of negative numbers. My BITX 20 for example had an IF of 11 MHz and has the VFO running a bit above 3 MHz — so the PLJ6 just adds the IF to the VFO signal and Bob is my uncle. Similar problem-free addition takes place with the other rigs.

I found some discussion on this problem on the internet. Here is one:
https://groups.io/g/BITX20/topic/bitx40_and_plj_6led_frequency/4330098?p=,,,20,0,0,0::recentpostdate%2Fsticky,,,20,2,0,4330098

Some of the respondents didn’t seem to understand the problem. Others hint that the ability to handle negative numbers was as some point in the code for the PLJ6 device, and may somehow be accessible, but no further info is provided.

I have already worked up a possible solution, but I’m interested in how you folks would approach this problem. Any thoughts or suggestions? I will reveal my solution in the days ahead.

A Lifetime of Workshops

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

It has been more than decade, but we’ve posted about Steven K. Roberts N4RVE before:

https://soldersmoke.blogspot.com/2009/09/i-didnt-care-i-had-secret-life.html

https://soldersmoke.blogspot.com/2009/09/knack-on-bike-steve-roberts-video.html

This morning I came across his recent article about the workshops he’s had over the course of his life. Very nice. Man, I should have held on to that SP-600 I once had. You folks will like this:

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

Repairing My Maplin Audio Waveform Generator

I picked this generator at the Kempton Park rally in London many years ago. I use it quite a bit, not only for circuit testing but also as an easy way to get my homebrew BITX rigs to send a signal so that I can adjust my antenna. I just plug this thing into the mic jack, crank in a small amount of 1 kHz audio, and I am ready to minimize SWR.


It never gave me any real problems until last week. I opened it up and examined the circuitry for the first time. Lots of mystery chips in there. Fortunately they are all socketed. Thank you Maplin.

Even without really knowing how each of the ICs work, it was easy to troubleshoot. See the schematic in the article that begins on page 21 in this .pdf:


My Rigol scope showed a good signal going into and coming out of IC8, the LF351 op-amp. From there the signal goes to IC5 a 4066BE. But nothing was coming out of IC5. Thus IC5 was my lead suspect. I put in a quick order to Digikey. A couple of days and a few bucks later the chips (as always, I ordered several) were on my doorstep. Within a few minutes IC5 was replaced and the generator was as good as new.

One annoying problem with this generator is that it has no automatic shut-off circuitry. So if I forget to turn it off, I soon have to buy two 9V batteries. Tony G4WIF suggested a simple timer circuit. I may do that soon. Or, given that we are already on the IC dark side with this project, there is this: https://www.youtube.com/watch?v=C4C2H_3BU3o&feature=youtu.be

I recently find myself replacing a lot of chips in various rigs and devices in my shack. It seems that chips go bad more frequently than discrete transistors or even tubes. But maybe I’m just using older gear with older, more fragile chips. What do you folks think?

SolderSmoke Podcast #228

Soldersmoke Podcast #228 is available:

http://soldersmoke.com/soldersmoke228.mp3

Of course, no travel. But vaccines are here so maybe soon we can leave our shacks.

In the meantime:

I’ve been playing chess against AI bots on chess.com.

Netflix recommendation: The Bureau. From France. A review from NPR:

https://www.npr.org/2020/06/22/881642358/addictively-suspenseful-thriller-series-the-bureau-will-keep-you-on-edge

A reading from “Conquering the Electron.” Germanium vs. Silicon.

Bill’s Bench:

The KLH Model Twenty-one II. Acoustical Suspension. First receiver WITH A PILLOW! Bad speaker? Blown AF amp finals. Hot heat sink. VBE Multiplier. Desitin.

Tony Fishpool’s recommended LM386 boards. 10 for 11 bucks. Nice. They work. Pictured in the Amazon ad at the upper right of the SolderSmoke blog page.

Putting a digital display on the Lafayette HA-600A

Test gear trouble. My Radio Shack multimeter getting flaky. I many need something better. Auto ranging? My beloved Maplin AF generator died – will have to fix. I need that thing. Probably a bad chip. Good thing they are socketed.

I almost forgot about SKN! But I remembered and I made one contact with the HT-37 and Drake 2-B.

Pete’s Bench:

Presentation to RSGB on Homebrew.

TenTek Troubleshoot.

Swan 240? Looking nice.

SDR adventures.

MAILBAG

Bill N8ET sent me some really nice Showa 9 MHz 8 pole crystal filters.

Kevin AA7YQ Smoke jumper! Building a hybrid SDR.HDR rig. Launched blog. FB

Nick M0NTV working on similar HDR/SDR project. Great video.

Grayson KJ7UM Hollow State Design – Launched a new blog. Very FB!

Thomas K4SWL of SWL Post blog. Kearsarge Mountain Transmission system. And recent events.

Peter VK2EMU Poetry. CW poetry.

Pete WB9FLW looking at DSB rigs…

Drew N7DA Feels not like a real ham because he hasn’t built a quad from bamboo. Which type of landscape bamboo is best for antennas?

Ryan Flowers of MiscDotGeek.Com blog is also watching the Tally Ho YouTube videos of Leo Sampson. Wants to put a WSPR beacon on the Tally Ho.

Joe KF5OWY Working with diode ring mixers, trying to see the mixer action on his ‘scope. 1 and -1!

Jim AB9CN sent a cool idea about how to do a 20/17 Moxon.

Roy GM4VKI – I thanked him for his article in SPRAT about putting a 2n3904 on the output of an NE602 10P mod. Brilliant.

Roger Hayward Told him that I really liked his Dad’s recent web site updates.

Farhan – Jokingly cursed me for showing him the Oscillodyne regen of Hugo Gernsback and Jean Shepherd. “Now I will have to build this!”

SolderSmoke Podcast #228

Soldersmoke Podcast #228 is available:

http://soldersmoke.com/soldersmoke228.mp3

Of course, no travel. But vaccines are here so maybe soon we can leave our shacks.

In the meantime:

I’ve been playing chess against AI bots on chess.com.

Netflix recommendation: The Bureau. From France. A review from NPR:

https://www.npr.org/2020/06/22/881642358/addictively-suspenseful-thriller-series-the-bureau-will-keep-you-on-edge

A reading from “Conquering the Electron.” Germanium vs. Silicon.

Bill’s Bench:

The KLH Model Twenty-one II. Acoustical Suspension. First receiver WITH A PILLOW! Bad speaker? Blown AF amp finals. Hot heat sink. VBE Multiplier. Desitin.

Tony Fishpool’s recommended LM386 boards. 10 for 11 bucks. Nice. They work. Pictured in the Amazon ad at the upper right of the SolderSmoke blog page.

Putting a digital display on the Lafayette HA-600A

Test gear trouble. My Radio Shack multimeter getting flaky. I many need something better. Auto ranging? My beloved Maplin AF generator died – will have to fix. I need that thing. Probably a bad chip. Good thing they are socketed.

I almost forgot about SKN! But I remembered and I made one contact with the HT-37 and Drake 2-B.

Pete’s Bench:

Presentation to RSGB on Homebrew.

TenTek Troubleshoot.

Swan 240? Looking nice.

SDR adventures.

MAILBAG

Bill N8ET sent me some really nice Showa 9 MHz 8 pole crystal filters.

Kevin AA7YQ Smoke jumper! Building a hybrid SDR.HDR rig. Launched blog. FB

Nick M0NTV working on similar HDR/SDR project. Great video.

Grayson KJ7UM Hollow State Design – Launched a new blog. Very FB!

Thomas K4SWL of SWL Post blog. Kearsarge Mountain Transmission system. And recent events.

Peter VK2EMU Poetry. CW poetry.

Pete WB9FLW looking at DSB rigs…

Drew N7DA Feels not like a real ham because he hasn’t built a quad from bamboo. Which type of landscape bamboo is best for antennas?

Ryan Flowers of MiscDotGeek.Com blog is also watching the Tally Ho YouTube videos of Leo Sampson. Wants to put a WSPR beacon on the Tally Ho.

Joe KF5OWY Working with diode ring mixers, trying to see the mixer action on his ‘scope. 1 and -1!

Jim AB9CN sent a cool idea about how to do a 20/17 Moxon.

Roy GM4VKI – I thanked him for his article in SPRAT about putting a 2n3904 on the output of an NE602 10P mod. Brilliant.

Roger Hayward Told him that I really liked his Dad’s recent web site updates.

Farhan – Jokingly cursed me for showing him the Oscillodyne regen of Hugo Gernsback and Jean Shepherd. “Now I will have to build this!”

So Many Wonderful Things on W7ZOI’s Site

There he is. Wes Hayward, W7ZOI in 1957. I had never seen this picture before. I found it on Wes’s recently updated “shackviews” web page: http://w7zoi.net/shackviews.html .

There are so many treasures on that page, and on all the other portions of Wes’s site.

Some highlights for me:

— Wes’s description of the station in the above picture.

— On his page about Doug DeMaw, Wes mentions that after Doug edited Wes’s 1968 article about direct conversion receivers, Doug built some himself, experimenting with different product detector circuits. Having used Doug’s mixer circuit in many of my rigs, and having recently experimented with different product detectors for my HA-600A, I kind of felt like Doug was watching over my shoulder, guiding me along as I experimented.

— Wes’s use of a digital Rigol oscilloscope. Makes me feel better about giving up on my Tek 465.

— The page about Farhan’s visit to Wes, and the awesome gathering of homebrew Titans that ensued…

— Wes’s meeting with Chuck Adams.

Thanks Wes. Happy New Year and best of luck in 2021!

SolderSmoke Podcast #226 The U.S. Election, Solar Cycle, uSDX, Hermes, HP8640B, SGC 600 Sig Gen, HA-600A, Mailbag

SolderSmoke Podcast # 226

http://soldersmoke.com/soldersmoke226.mp3

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About the U.S. election

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Mars: Setting early, will have to shift to evening observation. Weather has been poor.

Sunspot Cycle 25 is underway — SFI 78, SN 32

The Gliessberg cycle


Pete’s Bench: #49, #50, uSDX, Hermes Lite


Bill’s Bench: HP8640B, Global Specialties Corp 6000 counter, Lafayette HA600A.


MAILBAG:

Peter VK2EMU Sent me copy of 1947 Handbook. Thanks Peter

Brad W1BCC Spotted 10 S-38s for 80 bucks on Craig’s list. What’s going on here?

Dale K9NN sent both Pete and I care packages with very cool part, including DG Mosfets

Stuart ZL2TW sent me Les Moxon’s Antenna Book. TRGHS. Moxon will be back!

Alvin N5VZH got his receive converter with a little Tribal Knowledge from SS.

GM4OOU The Bitsy DSB rig from Scotland

Peter VK3YE DSBto DC incompatibility SOLVED

Paul VK3HN’s Digital SWR and Power Meter and Low band AM TX VFO/Controller FB Videos.

VK2BLQ alerts us to article about Jac Holzman of Elektra Records.

AA0ZZ great message on assembler language and writing software the hard way.

Chip Replaced, GSC 6000 Counter Fixed

This thing has been half-broken for a long time. I needed to get the input for 40 MHz – 650 MHz working I got the a replacement SP8630B Plessey divide-by-ten counter chip on e-bay, and yesterday I extracted the old chip and put in the replacement. I took great care NOT to solder this one in upside down (as I had done with another chip replacement in this counter). I used solder flux and solder wick to gradually get the pins free of the board. (You can see the old chip in the picture above.)

As to what happened to the original SP8630B chip, John over on the Vintage Test Gear Facebook page wrote:

The Plessey SP8630A/B is an ECL divide by 10 prescaler, with a upper working frequency of 600MHz. That generation went out of production in the late 1980s. Plessey was bought by a Canadian company now called Micrel. You may be able to find one from one of the specialist obsolete component companies, but it may be dead on arrival. Those ECL ICs had a fairly high mortality rate if they are very old.

It is the old story of “metal migration”. In early semiconductors very small impurities in the silicon structure cause minute bits of the metallisation to leach out into the essentially non-conducting silicon insulation. Many old devices, although they have never been used, were found to be very leaky and this degrades the gain of the active devices. The worst types are the very old Germanium transistors.

As the semiconductor scientist learnt more about the super cleanliness required and the better purification of the metals the problem tended to improve. The Marconi company I worked for back in the 1980s had a real problem with comms satellites failing after a few years of service. Of course you can’t go up there and swap out the faulty devices. Accelerated ageing of a backup satellite showed that some devices just stopped working after being subjected to high and low temperature cycling, which is a common problem with satellites in orbit!

I am liking this little machine more and more. It is very simple — no microcontroller, just a collection of gates. I discovered that the main main crystal oscillator is actually built inside a little oven to keep the temperature stable — oscillator and the oven stay on as long as the counter is plugged in, even when the device is switched off. I calibrated the counter with WWV and with my HP8640B and with my little Feeltech sig gen counter. I wish I knew how to calibrate the counter in the Rigol DS1102E oscilloscope.

Global Specialties Corporation 6000 Frequency Counter — Anyone have a Plessey SP8630B Chip?

Continuing my effort to improve my workbench and its test gear, this week I turned to an old frequency counter that I picked up at the Kempton Park Radio Rally in London many years ago. It was not working when I got it, but long-time SolderSmoke listeners will recall the tale of woe that resulted from my having soldered a replacement IC (that Tony Fishpool G4WIF had sent me) UPSIDE down. Tough times my friends, tough times.

Well, I’m working on it again. First I converted it from 220 to 110 power. I had a transformer in the junk box that fit nicely, both electrically and mechanically. In the course of doing this, I learned something about this counter that I did not know: As long as it is plugged in, even if you turn it off, the time-base oscillator keeps running. And get this Color Burst Liberation Army members: The oscillator runs at 3.579545 MHz. TRGHS.

With sunspots scarce and with Pete pessimistic about the solar cycle, VHF and UHF now seem more interesting. I need to have more test gear for the higher frequencies. This counter works up to 650 MHz. Yea!

When I first fixed this thing, I was quite pleased to get it going with “Input A — 5 Hz to 100 MHz.” But now I want to get “Input B — 40 MHz to 650 MHz” working also. I used a 50 MHz signal from my newly repaired HP-8640B to trouble shoot Input B. I think one of the divider chips is bad. It is a Plessey SP 8630B. Does anyone have one of these chips in their junk box?

HP8640B Internal Frequency Counter Fixed (More Repairs Pending)

The HP8640B is a complicated machine. Above you see just one sub-assembly, and the page from the manual that describes it. This is what I’ve been working on. The little spring “tine” fell out of one of those discs behind the two control knobs. So I had to open this thing up, find the spot from which the tine had fallen, and glue it back in.

I used Gorilla Super Glue, followed 24 hours later by a dab of JB Weld “minute weld” dual epoxy. One of the other tines was about to fall out, so I went ahead and gave all the tines in this assembly the glue treatment. ( I bought some “Weld On” acrylic cement but the warnings on the label were quite sobering. So I left that can sealed up.)

This morning I put the thing back together. This is not easy. At one point a spring popped and a tiny metal part that is probably irreplaceable seemed to fly away into the black hole that is the shack’s carpet. I had just about given up hope when I found the thing sitting right in front of me on the bench. TRGHS.

The HP8640B fired up right away without trouble and the internal frequency counter is working fine.

As I noted in the last SolderSmoke podcast, a very nice community devoted to the HP8640B has developed around the world. Here are some of the notable participants:

Bill at Electronics Revisited is a very nice fellow with lots of experience on the HP8640B. He offered to sell me a replacement unit for the assembly pictured above. If you have an ailing HP8640B and are looking for someone to work on it for you, Bill is the guy you should talk to: http://www.electronicsrevisited.com/ He also very kindly offers to answer any questions you may have about the HP8640B.
Here is the e-bay page of the fellow in Bangalore who makes the brass gears. Mine are on the way!
https://www.ebay.com/usr/engineeringideas?_trksid=p2047675.l2559
Marcus VE7CA has a great site devoted to the HP8640B: https://www.ve7ca.net/TstH86.htm
BH1RBG in China has a nice site describing his adventures with the HP8640B: https://sites.google.com/site/linuxdigitallab/home/hp8640b-20v-power-supply-down
K6JCA has a good blog post about fixing the tines and the gears:
http://k6jca.blogspot.com/2018/09/repair-log-hp-8640b-rotary-switches-and.html
Steve Silverman (who gave me this HP8640B) found a really useful history of the device:
http://hpmemoryproject.org/timeline/bob_devries/some_memories_05.htm#part_05_chapt_09
And of course special thanks to Dave VE3EAC who alerted me to the falling tine problem and put me on the path to a successful repair.
The gears should be here in a few weeks, so that will be another opportunity to work on this HP8640B. Also there are some tines in the attenuator assemby that might reinforce with the glue treatment.

SolderSmoke Podcast #225: Mars, uSDX, G-QRP, HP8640B, DX-390, Rotary Tools, Walla Walla SDR, MAILBAG

SolderSmoke Podcast #225 is available

http://soldersmoke.com/soldersmoke225.mp3

Mars, West Coast smoke.

Pete’s Activities:
— DC receivers.
— CW offset
— GQRP talk
— The uSDX project

Bill’s Bench
— Sliding into the Vintage Test Gear Cult: HP8640B .
— Fixing up and figuring out Radio Shack DX-390 receivers.
— 220 to 110 on a few remaining devices.
— Got myself a Dremel-like rotary device.

Tech News:
— ARRL/TAPR Convention: SDR project from Walla Walla University students. Intuitive explanation for why desired and image freqs in a mixer come out with very useful phase differences.

— Chuck Adams’ Amazing Lab Notebook. Includes a simple circuit to measure resistance and Q in crystals. FB.

MAILBAG:

— Dino KL0S SITSing in his shack, homebrewing 9 MHz filters FB Dino. Airborne!
— Dave NT1U sent us the famous 1968 QST Article by W7ZOI re DC RX.
— Ron K0EIA listening to SWBC staions with uBITX.
— Ted AJ8T Korguntubes making a 12AX7 equivalent.
— Joel N6ALT sent me a nice DX-390 manual. Thanks Joel
— Bob KD8CGH alerted us to the uSDX project — story on the blog.
— Craig AA0ZZ Sent a great message with insights on computer code — I will put up on the blog.
–Tracy KN4FHX reports on optimistic prognosis for SolarCycle 25. Some chickens may have to be sacrificed.
— Stephen M0OMO Thanks SolderSmoke for rekindling interest in this hobby.
— Paul VK3HN has a cool new rig — The Prowler — check it out
— Steve N8NM working on his Sunbeam car — Pete already knew about the carburetor synch problem. N6QW knows everything.



HP8640B — Fault Found! A very TINY and Hard-to-Fix Fault

I’ve been troubleshooting the internal counter in my HP8640B signal generator. The generator itself works fine. And the counter works fine for all signals coming in on its “external” port. But the internal counter stopped working properly above 16 MHz. So I started digging into the manuals and the schematics, re-familiarizing myself with the digital logic behind pre-microcontroller frequency counters. NOTE: If you are working on one of these, be sure to be using the correct version of the manual and schematic. At one point I found a really nice high def copy of an HP8640B manual (for one used in a Patriot Missile System!) only to discover that MY A8A3 board was significantly different from the one in this manual. BAMA provided a manual that matched my device: http://bama.edebris.com/manuals/hp/8640b/

Every dark cloud has a silver lining. Here, the silver for me came from opening up the HP8640B. What an impressive looking piece of gear. It looks like something from the Apollo command module, or perhaps from a nuclear weapon. “The RF source is a 256 to 512 MHz cavity-tuned oscillator that is mechanically tuned…” There is phase lock circuitry. The are AM and FM modulators and a really useful array of attenuators. There is a frequency counter with an external port and an internal frequency counter that measures the original 256-512 MHz signal, then divides down to give a very accurate readout of the output frequency. This is the kind of device that would generate a cult following. Count me in!

Also, I’ve sometimes lamented the lack of VHF test gear on my work bench — the HP8640B could really help me move me into the VHF range.

I started the troubleshooting with some observations and noodling. At what frequency did the internal counter stop working? What did the readout look like when it stopped working? What device failure could lead to these symptoms? I was aided in this by suggestions sent in by readers of my previous blog posts. Thanks guys.

I was just getting ready to start some intrusive testing on the logic devices in the internal counter when Dave VE3EAC sent me this:

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I think you might be overthinking the failure mode here. I had a similar problem with my unit and it was one of my early Covid-fix-it projects. There is an assembly that controls the bands on the front. It has the famous gears that crack. On the back side are two sets of rotary switches that control a lot of stuff. The switches are of a very unique HP design and offer a lot of advantages over traditional switches EXCEPT they fail in an unusual manner. A PC board has all of the interesting wiring and very tiny double leaf springs short tracks together as needed. The springs tend to break away from the plastic posts on the rotating plate and not make the needed contact. Very carefully examine the insides of the 8640 and your bench top to see if any have fallen out. These are difficult to buy or fabricate. The disk is designed to be rotated 180 and use a new set of posts to locate the springs. Use a small dab of epoxy to set in place. The totally mechanical repair fixed my unit that also would not read above 16 MHz. There are a number of web pages that give great detail of this repair. Also it is worth while to replace the Delrin gears if they are cracked. Replacement brass ones are available on eBay and they will permanently fix the gear problem.
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I had thought about the problem being in the frequency range switch, but I had sort of tested for this by slowly rocking the switch through various positions as I watched the display. A dirty rotary switch will usually allow the circuit to intermittently work as you rock the switch. But this didn’t happen. And the HP switch felt quite sturdy, so I focused on the circuitry.

When I got VE3EAC’s message, I carefully flipped the HP8640B over and for the first time opened the bottom of the compartment. The bottom view is much more impressive than the top view:

The switches that VE3EAC wrote about are just below the ribbon cable near the center front. I could see the little springs that he was discussing on the switches. They appear MUCH more delicate than the rotator on a standard rotary switch. And I didn’t see any of them lying around below the switch. But when I tried to flip the HP8640B over, something in there moved and caught my eye. I pulled out some tweezers and pulled this out:


Wow. That little spring contact fell off the switch. That was preventing the HP8640B internal counter’s time base from changing as I went above 16 MHz. It is ironic that such a big and solidly built device such as the HP8640B should be laid low by such a TINY part.

This gets me back to my original question: Discretion or valor? Getting that spring back onto that switch will not be easy. VE3EAC sent me this K6JCA link describing how to do this. Yikes, it even requires the purchase of a special tool!
http://k6jca.blogspot.com/2018/09/repair-log-hp-8640b-rotary-switches-and.html
I’m going to let the HP8640B sit there with the cover off for a while. It will be taunting me, challenging me to fix it, to make it work the way Hewlett and Packard intended. It may take a while, but I think I’m going to have to accept this challenge. I’ve become real fan of the HP8640B and it would be a shame to leave it wounded like this.

The Agony of Troubleshooting — From China

I am troubleshooting my beloved NYC HP8640B Signal Generator (thanks to Steve Silverman and Dave Bamford). Some of you may wonder why I don’t just replace this beast with something small, lighter, cheaper and newer. Well, I have not found any new sig generators that will do what this beast does: It goes all the way up to 256 MHz (higher with an extension kit). It has a great attenuator in it so you can set the output just where you want it. AM or FM modulation. Really useful. So I think I’ll fix it.

My problem is that the internal freq counter stops working above 16 MHz. Using the very extensive documentation, and without even really opening up the machine, I think I have located the fault. I think it is in the Counter Time Base Assembly board A8A3. Now of course, the fun begins. (Tips, advice, solutions, and words of encouragement would all be appreciated.)

While planning my assault on A8A3, I came across the web site of BH1RBG. He too has recently been working on an HP8640B. His problem was different, but when I read through his site I saw evidence that the agony of troubleshooting is something that is the same all around the world. Check out his description of the agony:

I even suspected the LM723 should had something bootstrapping circuit, make sure the Q4 sure start. Because the external reference VR3 is floating too, oh, my godness.

I became hopeless, and ordered several LM732,and waiting delivery for days. This beast frustrate me so deeply, changed the LM723 does not help anything. And i almost desoldering everything in the board!

Oh man, I’ve been there. Several times while in the throes of a troubleshooting battle I have actually had dreams of removing all the parts from a troublesome PC board.

BH1RBG has a very interesting site with lots of ham radio projects:

https://sites.google.com/site/linuxdigitallab/rf-ham-radio?authuser=0


Taming Glitches in a Soyuz Space Clock (Plus — Inside a Logic Chip and How Crystals Work)

Thanks to Bob KD4EBM for sending this.

There is so much good info in this video: They crack open a logic chip and look at the internal construction (it is entirely understandable by mortal minds). They use cool test gear to troubleshoot the clock from a Soyuz spacecraft. They explain very clearly the series and parallel resonances of quartz crystals, then display these resonances on a very nice spectrum analyzer.

 The creator of the video is CuriousMarc. He has many other interesting projects:

https://www.youtube.com/c/CuriousMarc/featured

 https://www.curiousmarc.com/

His bio is here:
One paragraph from his bio really resonated with me:

Working on this old stuff forces me to deal with the very fundamentals of electronics (and electro-mechanics). The principles are exactly the same as today, but nothing is hidden in mysterious circuits – you can understand and fix everything. Years of Moore’s law has sure given us gobs of transistors, oceans of memory and a glut of gigacycles, but many times, particularly in consumer hardware, these are simply used to cover up poor and inefficient designs – and resource devouring software. What Intel giveth, Microsoft taketh away, as they say. It often irritates me that my PC takes several seconds to react to a simple command, in which time it must have executed billions of unnecessary instructions and consumed a few gigabytes of memory, no one knowing exactly what for anymore. Nothing like this in old high-end hardware: designs are pure and efficient, and the lack of resources is compensated by engineering mastery and immense cleverness, which is a joy to reverse engineer. Not only does it teach us timeless electrical fundamentals and engineering tricks, but it also gives us a much better appreciation of today’s tech. How did all the technology we take for granted came to be? It will make you a far better engineer and inventor if you take the time to be a thorough student of the inventions of your illustrious predecessors.

Andreas Spiess (The Guy with Swiss Accent) — Workshop Tips

Thanks to Paul Taylor VK3HN for alerting me to the YouTube channel of Andreas Spiess. There are lots of great projects there, including several videos on building an Oscar 100 ground station.

In the video above, Andreas talks about his lab/workshop. He is more focused on digital projects than I am, but I found many of his tips applicable to the analog world. And of course the more digitally oriented readers will find Andreas’s observations especially useful.

I was sold on this video when Andreas reached to his book shelf and showed us Tracey Kidder’s “Soul of the New Machine.” That is the book that brought the word “soul” into the SolderSmoke lexicon.

There are many great videos on Andreas’s channel. I found his Playlists page to be a good way to see the many different catergories of his projects:

https://www.youtube.com/c/AndreasSpiess/playlists

 Thanks Andreas.

Mike WU2D’s Great Drake TR-3 Refurb Video — Part 2

Mike WU2D made another very nice video about his Drake TR-3 refurb.

He cracked me up when he noticed that one of the calibration oscillators was 30 Hz off. “Let’s pretend we care,” said Mike. Indeed. But it was probably wise to tackle this problem, given how upset modern hams seem to get with 30 Hz discrepancies. Mike noted that the problem was casued by “aging cystals.” Yikes! Another thing to worry about, along with the Southern Magnetic Anomaly.

Once again Mike has added a useful term to our lexicon: “The Dribble Method” of signal injection (or extraction): Just wrap a few turns of insulated wire around the tube or IF can and inject or measure away.

 Neutralization! Now there’s a blast from the Thermatron past. I haven’t done that in a long time. I liked Mike’s “reverse neutralization” method.

Mike’s video featured some real Boatanchor eye candy. That Heathkit HR-10 receiver caught my eye, as did that HP signal generator.

Thanks Mike. One hand behind your back OM.