My first RIFA

Over the years I have repaired few devices and never found a RIFA capacitor. Until today when I finally met them in all their smelly glory.

H7864-A PSU label

They are inside the PSU of a 1980's computer, a digital microPDP-11. The exact model is H7864-A, in this case the compatible part by Astec AA12131.

I had already looked into a H7864-B that had non-RIFA capacitors. Or at least not with the usual square shape. It did stay powered without blowing. It should be noted that while -A and -B have the same voltage outputs (and probably the same pinout), their current ratings are different with -A being beefier.

A RIFA capacitor!

I tried plugging a -A and after few minutes it popped and smoked. Well done, Paolo: mission completed! So I picked another -A from the pile of microPDP-11's and here it is on the bench. It was easy to spot RIFA's since they are close to the AC input, so just follow the input line. According to Internet sources the H7864-A should mount 3 RIFA's, but I found only C101 (0.47uf X2) and C102 (0.22uF Y2), while C201 (0.1uf X2) is of a different brand, shape and color. 

 

C101 was kept in place with some kind of wax that should be removed to free the component. Heat, extra solder and flux and they will come out quite easily. Just note that the leads were bent, so you need to straighten at least one.

Do C101 and C102 really need to be there? They form the filter... I should not write that, but the PSU works without the filter. At least for a smoke test it will be fine.

 

 

 

Old Capacitor Wisdom

I've received a homebuilt oscilloscope from 1950's. Scuola Radio Elettra, an Italan company back then, was very popular and helped many people to get into the eletronics world. The instruction manual was 770 pages long and it is half builder's manual, half electronics student's book.

The scope does not show a trace on screen. I was told the instrument was OK, but it has been sitting unused for months, to say the least. I read through the manual looking for the troubleshooting section and came across some wisdom on old capacitors.

"The only components that require replacement with use are the electronic tubes and the electrolytic capacitors. If the oscilloscope has been left inactive for a very long time (months or years), it will be advisable to first turn it on for about a minute and then turn it off and let it rest for at least half an hour, then turn it on again for another 10 minutes. After this, let it rest for another half an hour and finally you can use it with peace of mind. This process serves to allow the electrolytic capacitors to reform and regain the efficiency lost during the long period of inactivity."

Even in 1950's when writing the original manual they knew of electrolyic capacitors "hobby" to change their value with time. I assume that "decades" falls into "years" of inactivity, so I will try the procedure reccomended in the manual. With the covers off, so that I see filaments glowing.

 

 

 

Sony walkman WM-B12 repaired

Now that my interests are expanding to retrocomputing, I feel the need to read those C64 tapes. Which means that, somewhere, a tape/cassette player needs to be fixed.

I began from my walkman Sony WM-B12. A rather cheap unit back then. I suspected the failure was in the rubber belts. That model is just two plastic shells locked together that come apart with the usual gently-pry-here-and-there method. The remnants of the two belts were just enough to suggest their original path. They melted into a sticky dirty goo that is non-conductive. Hint: the goo is quite very filthy, so work on a disposable surface, use gloves and protect your clothes. Seriously.

The goo came away with mechanical method, so I didn't need to use chemicals. Then I needed to understand which belts I needed: square, round or flat? The remnants suggested square about 1mm per side. Maybe less, but I needed a proof it can work, I don't need perfect sound (from a tape?).

The usual Chinese sources sell a bag of 1mm square belts of assorted lengths. They came faster than expected.

I did not take any measurement. I just picked two belts that seemed right. And they were indeed! Now I have a working walkman and something to show to teenagers. Their reasoning about how we built a "playlist" back then is very interesting. Especially when they realize there were no commercials.

I was not that lucky with a later model from Aiwa with autoreverse plus AM/FM radio. It needs a longer belt, probably round and thinner. I tried the 1mm square and the result is very obviously wrong. Another time, maybe.

 

If you still have tapes and a player do consider trying a repair. It's pretty easy. Just be prepared to have a wayback machine in your ears when you succeed.

T.I. Data Books

Here they are, on my desk. It started in high-school in the 1990's. These books were a good alternative read for nerds, instead of those brick-thick romance novels from a century back. 

Few Texas Instruments Data Books

That unmistakable combination of colors and shape makes them visibile from very far away. Their content is probably everywhere online, but I think the paper format allows a better overview of available components. If we were to design circuits like in 1970's-1990's, back again.

I am afraid this is just the beginning.

FM antenna hack on a rented car

This Summer we spent 10 days driving around Greece in a rented car. Being high season I looked for cheaper alternatives to the big names. Using a local company (directly, not through a broker) I could save 20-30% and get a better deal on "options" like FDW, different drop off location, unlimited km.

 

Where is the catch? The car is not exactly new. We got a 7 years old Citroen C3 (we asked for it) with 75k km. Mechanically was OK, it even had cruise control and lane assist. No parking sensors and rear window wiper, though. Most important: it had an FM, MW, LW radio.

 

Too bad someone had hit a very low something and broke the antenna leaving an exposed PCB.

The result was that in FM we could pick whatever station was in line of sight. Greece is full of valleys and hills, so any station would last maybe 10 minutes max.

With a close inspection I noticed a pad with a hole on top of the board so we all started looking for a not-rusty wire: why not try a MacGyverism?

The exposed antenna fin PCB and my addition.

 

It is curious to note as in 2024 you don't find pieces of electric wire on the ground as it used to be (I used to carry 20 cm of hookup wire in my wallet and I should restore it). After 4 days of looking I spotted a venerable paper clip in a beach bar terrace.

In the hole it went and the FM band sprang to life. Well, at least several station could be heard vs. maximum one at any given time.

 

Mission completed.

Fairchild Multimeter Model 7050

I bought a Fairchild 7050 multimeter because it has slightly larger than usual Nixies. There was no indication of its state, but I could count the three tubes in the pictures. It looked a bit dirty as visibile in the picture below.

Picture by the seller.

When it arrived I tried powering it at half AC voltage, just in case, but nothing happened. There was no current draw as the power supply didn't sag a single Volt. As it was sold as a "low cost accurate 3-digit instrument" (quote from the manual), there is just one screw in the back keeping everything together. Also the AC cord is soldered to the board, there is no socket.

Once I could look inside I measured that the fuse was intact, so I moved to the ON/OFF switch and sure enough it did nothing: open in both positions. If everything else is OK, it will have to be replaced and shouldn't be too hard to find since it was a "low cost instrument" probably using very common parts.

I created a short across the switch and tried again the power-up sequence as before. At 120 Vac it wouldn't display anything, but there were no signs of smoke, overheating, smell, burns, exploded components, ... so we stepped to the nominal 220 Vac... whoa! It is working!

I did some tests and the readings agree with my other DVM's. Well, let's say they are in the ballpark but hardly within the 0.1% advertised in the manual. Thought there is no drift after the warm-up and nothing blew up after more than 60 minutes of doing something.

So, apart from cleaning, fixing the power switch and maybe trying to recalibrate it, this little beauty from the past should not present other challenges and is ready to go into service.

Texas Instruments Consumer Circuits Data Book 1978

I bought this book at Marzaglia fair 2024. I have never owned a data book, so this was a chance to fill that gap.

The index looks very interesting. You can see how many specialised integrated circuits were designed and, probably, produced. 

My eyes stopped on "Timekeeping Application" and "Game Chips". That's something today you can do with one microcontroller, you can even dare to squeeze the whole index of this book into a single firmware.

Zoom in on these two pages from the index (click on them) and see what you needed to build a not-so-complex application back in the 1970's.

For your convenience and for search engines, here is an OCR extract of the two images above.

CB TRANSCEIVER APPLICATION
SN76514N	DOUBLE BALANCED MIXER	399
TP0235	FREOUENCY SYNTHESIZER	408
SN76515P	DOUBLE BALANCED MIXER	414
TP55I04	PLL FREQUENCY SYNTHESIZERS	416
TP55114	PLL FREOUENCY SYNTHESIZERS	416
TP55106	PLL FREOUENCY SYNTHESIZERS	416
TP55116	PLL FREOUENCY SYNTHESIZERS	416
TP55116N	PLL FREOUENCY SYNTHESIZERS	416
TMS1022NL	CB CHANNEL CONTROLLER	427
TMS1023NL	C8 CHANNEL CONTROLLER (GERMAN BAND)	451
SN16880N	LOG. STEREO LEVEL DETECTOR/INDICATOR	452
SN16889P	LINEAR LEVEL DETECTOR/INDICATOR	456
SN16921NM	SCALE DRIVER IC	461
TIMEKEEPING APPLICATION
TMS3879NC	R.C.TIMER WITH TIME CONSTANT MULTIPLIER	465
TMS38348N	MOS/LSI CLOCK CIRCUIT	471
TMS1951NL	DIGITAL RADIO CLOCK	483
TMS1952NL	DIGITAL RADIO CLOCK	492
TM1191943NL	DIGITAL RADIO CLOCK	302
SN76825P	16/23 STAGE COUNTER CIRCUITS	514
SN76835P	16/23 STAGE COUNTER CIRCUITS	514
SN76810P	MONOSTABLE TACHODRIVER	520
TMS1121	UNIVERSAL TIMER	530
LOW COST GAME CHIP
TMS1965N1	6 GAME EUROPEAN SYSTEM	547
UNIVERSAL GAME CHIP
SN76423N	AUTOMATIC RANDOM ENGLISH	555
SN76424N	WALL GENERATOR	559
SN76425N	SYSTEM REGULATOR AND SYNC GENERATOR	562
SN76426N	DUAL CHARACTER GENERATOR	566
SN76427N	WALL BALL GENERATOR	569
SN76428N	VIDEO GAME LOGIC	573
SN76429N	HOKEY,TENNIS/HAND BALL GAME LOGIC	577
SN76430N	SYNC GENERATOR/COLOR GENERATOR VIDEO SUMMER	581
SN76431N	COMPLEX CHARACTER POSITION CONTROLLER	586
SN76440N	SPACE WAR GAME LOGIC COMPLEX CHARACTER	590
UNIVERSAL GAME CHIP
SN76432N	HOKEY/TENNIS/HANDBALL CHARACTER 592
SN76442N	RACE CAR/ROCKET SHIP/UNIVERSAL MAN CHARACTER 597
SN76443N	COMPLEX CHARACTER GENERATOR 598
SN76444N	ROCKET SHIP/HOKEY/TENNIS 599
SN76445N	GUN FIGHTER/UNIVERSAL MAN CHARACTER 600
SN76446N	EXPLODING ROCKET CHARACTER 601
SN76449N	EXPLODING HELICOPTER CHARACTER 602
SN76460N	ZERO TO WIN AT 20 DIGITAL 603
SN76462N	SCORING 603
SN76483N	SPACE WAR OBSTACLES GENERATOR 608
SN76484N	SPACE WAR SWITCHING LOGIC 612
SN76477N	COMPLEX SOUND GENERATOR 615
TELEPHONE APPUCATION
TMS3833NC	ADAPTATEUR POUR CLAVIER TELEPHONIOUE 625
TMS3851N	C-MOS LOGIC CIRCUITS 631
TMS3858N	TELEPHONE KEYBOARD ENCODER 634
TMS3EI46NC	PUSH BUTTON TELEPHONE DIALLER 652
TMS38.59N	PUSH BUTTON TELEPHONE MEMORY 662
TMS387I NC	PUSH BUTTON TELEPHONE ADAPTOR PULSE DIALING SYSTEM
TMS3872N1	TELEPHONE FREOUENCIES GENERATOR 681
TMS3872-1NL	TELEPHONE FREOUENCIES GENERATOR 681
TMS3831N	TELEPHONE KEYBOARD ENCODER 689
TMS3878N	FREQUENCY DISPLAY 698
MICROPROCESSOR/MEMORIES
TMSI000NL	ONE CHIP MICROCOMPUTER 711
TMS1000/1200C	ONE CHIP MICROCOMPUTER IN- C-MOS 725
TMSI000	SERIES MOS/LSI ONE-CHIP MICROCOM. DATA MANUAL 743
TMS1024	MICROCOMPUTER I/O EXPANDER 787
TMS1025	MICROCOMPUTER I/O EXPANDER 787
TMS1117NL	MICROWAVE OVEN CONTROLLER 790
TMS1976NL	CAPACITIVE-TOUCH KEY BOARD INTERF. CIRCUIT 815
TMS2501JC, NC	64X5X7 STATIC USASCII CHARACTER GENERATOR 857
TMS4103JC, NC	64X5X7 STATIC USASCII CHARACTER GENERATOR 858
TMS4710JL, NL	COMPLETE ASCII CHARACTER SET GENERATOR 5X7 CHARACTER. 8X8 BLOCK 859
TNIS4027-30	NH 4096 BIT DYNAMIC RANDOM-ACCESS MEMORY 868

 

 

Free coffee on Lufthansa flights (Summer 2024)

If you are going to fly with Lufthansa this Summer 2024 you might be able to secure a free coffee onboard. I discovered this by chance and it might work with other companies that have a frequent flyer program.

I enrolled in Lufthansa's Miles and More program for fun, in case it might give some advantages in case of delays or whatever. It's free, so why not?!  The only difference I noticed so far is that your boarding passes will have "M" or "M/M" printed on them.

When you enroll, if you accept to receive their newsletters you get 500M (and you can unsubscribe, of course). Then you install their frequent flyer app and they give you 500M more. And of course after flying with them you get more miles, depending on some algorithm I haven't studied.

Real frequent flyers with lots of Miles can redeem them from a selection of brand-name products. But Miles can be exchanged for onboard food and refreshments as well.

It turns out that a tea "costs" 800M while 1000M secure you a cup of coffee (a value of 3.5€, almost as much as you would pay in a German airport).

For Summer 2024 they have a promotion that gives 2000M when booking and flying with them. So I ended up with 3000M after my "go" trip.

There is one caveat: they serve food and drinks on flights longer that one hour operated by Lufthansa (but you collect Miles on partner airlines too). Also Miles are not credited in real time, so prepare everything few days in advance.

The hostess knew I could redeem miles but was not sure how. Here it is for you. You tell them what you want and that you will pay with Miles. She will scan the card code (it's in the App!) AND ask for a debit/credit card to guarantee the transaction. In case Miles are not enough the remaining amount will go on the card. 

Have a nice Summer 2024 from ik1zyw blog!

 

PS: next post will be again in-topic with electronics, radio and old stuff to be repaired.

Friedrichshafen Ham Fair mystery

Both in 2023 and 2024 I had a strange encounter in the flea market area of Friedrichshafen Ham Messe.

There is a guy from Far East (China, Japan or Korea) that buys large early valves, not even in the greatest shape. He seems to be picking them by some characteristic that is not the part number.

He came at the same stall where I bought two dekatrons. Since I noticed him also last year, I have waited he finalised his purchase and tried asking what he does with them. All that I got was "sorry I have no time" and he ran away. The seller told me she had asked him before and never got through.

Has anybody else noticed him? Do you know what could be his project?

Friedrichshafen 2024: the year of the dekatron

My visit to the largest(?) HAM radio event in Europe 2024 is over. This year I could spend the whole Friday to wander around the halls. Overall my impression was that there were fewer exhibitors and visitors than last year 2023, but that's the way our hobby is going to.

Lots of good looking stuff was up for sale. Being able to enter right in the first minutes gives higher chances to find what you will consider a good bargain. And with little experience from past editions you know where are the usual sellers so you can avoid or run to them, depending on your needs.

As far as my long lasting love for gas filled tubes goes, I was surprised to see that Nixies were still available by the end of the first day even thought the asking price was like Internet or lower. For the records, used IN-14 at 7€ and ZM1040 at 60€.

Instead I bought two Dekatrons and then found other 9. They all contain the right amount of gas. Future will tell if they actually work.

 

Additions to my Dekatron collection!

I found two HP 5082-730? NOS displays. I don't know the last digit in the part number as it has been cut away from the packaging.

Last but not least, I got an HP 5512A counter.

HP 5512A counter sold as working.

 

(Note to future self: the Bird part in the picture is for a friend.)

Virus removed, after 30 years. A tale of retrocomputing.

Armed with F-PROT 2.24 on a write-protected 3.5" floppy disk I tackled the infected machine.

First of all I wanted to be sure that the computer was infected. So I let it boot normally, then ran F-PROT from the floppy, which halted during RAM test with this warning:

It's a pretty alarming message.

So I booted it off a DOS 3.2 on a floppy dsk (write protected) and ran a second scan. This time the memory was clean but it obviously detected Junkie in the hard-disk MBR, which could not be cleaned. That was expected. Unfortunately DOS on that floppy would not recognise the hard-disk so I could not issue the [FDISK /MBR] command.

What's the infected program?

Time for a... reinstall! This time I used the three 3.5" floppies with MS-DOS 5.0, booted off the first one and followed the guided procedure. We should note that since it detected a formatted HDD, there was no need to format the disk and wipe the content: it simply copied itself over C:\DOS. Unfortunately this probably left me with an infected MBR and at the end of the install process it wanted to reboot. Hitting F-keys I managed to get a DOS prompt where I could run FDISK /MBR (maybe the setup wizard had already done that, but I preferred to avoid a second reinstall).

1996 F-PROT in 2024 action!

Rebooted from HDD. Loaded F-PROT from the floppy and let it scan the disk. It located two infected .COM files I remember I had executed, which were cleaned. Now we're ready to go. No, there's the pile of 5.25" floppies I DIR'ed to check!

So I spent more than a few minutes scanning all 5.25" disks that were at hand's reach and found nothing. In order to prevent similar mistakes I have now write-protected these apparently clean disks.

Side note on F-PROT. The executable can be run with /OLD option to bypass the "signatures expired" block. Apparently /OLD on 2.24 does not work so I simply set the system date a month later than the signature timestamp.

Limited resources. A tale of retrocomputing

Having unlimited access to the resources of a computing history museum has diverted my free time activities to different kind of equipment: (retro)computers and (retro)computing. I do miss the hiss of SSB or the smell of soldersmoke, but I don't mind following unexplored lands of lost knowledge. Regardless, there's plenty of stuff to fix, too!

I was going through a stash of 5.25" floppy disks when I found a textual adventure in Italian language for DOS from 1986. On modern Internet I found a person looking for a copy of the game since he had played it back then: why not sharing the joy of my discovery with him?

I had to transfer the file from 5.25" floppy to 3.5" floppy on a 80386 Olivetti machine (circa 1988). Then the floppy went into a modern high-end Compaq Presario 2100 laptop (2003) to be transferred on a USB stick. Finally the USB stick went into an Internet connected machine (2023) for a final backup and delivery to my new friend.

How cool is that? I've used some 40-year old media and time-traveled its content ~20 years ahead, twice.

Since the 5.25" floppies were DS/DD with 360 kB capacity, I could fit 4 of them in a 1.44 MB 3.5" floppy. Why not? So while I was at it I copied another disk with Epic Megagames shareware game, a Tetris from 1986 and a Z80MU (Z80 emulator).

When the USB stick hit the modern computer, the antivirus detected the Junkie virus in TETRIS.COM.

HORROR!

The problem is not the single infection, but all the write-enabled floppies I read on the Olivetti machine once I had played a bit of Tetris myself. And, worse, the infection in the Olivetti machine! I am not sure what was infected first: the PC or the .COM program. Nevermind, now.

While I could reinstall the 80386 computer (DOS 6.x), I chose to try to preserve its content and see what can be done. This means traveling back in time in order to have a functional antivirus software on a single 1.44 MB floppy disk. That was the preferred portable media, so a time-correct antivirus had to fit on a single disk.

Everyone agrees that the free-for-personal-use F-PROT antivirus in 1980's and 1990's was the best choice. The latest version 3.16f from 2009 is just too large at 9.2 MB. Reader, I'll boot the machine off a clean floppy disk and run the antivirus from another floppy. No fiddling with multi-volume .ZIP files, especially since it's not needed.

The biggest challenge for the unexperienced retrocomputing guy that I am, was to locate an F-PROT version released after Spring 1994.

While browsing old software on archive.org I remembered that computer magazines (yes, printed on paper) usually came with a CD full of shareware software. Then in a matter of minutes I have downloaded the .ISO image of a CD and finally found F-PROT 2.24A from August 1996.

When I finally saw the folder with the wanted piece of software (in a .ZIP file, of course) I realised why most of my searches failed. In DOS days, filenames followed the 8.3 format convention. In 8 characters you had to fit both a mnemonic for your product and a version number. So it is not F-PROT_224A.ZIP (11.3) but rather FP-224A.ZIP. "FP" reader, "FP"!

Directory listing of Pegasus 5.0 CD, 1994.

At last the unzipped antivirus went in the USB key and on a 3.5" floppy. Next step will be to scan and clean as many floppies as possible, while I came up with a safe procedure to deal with the hundreds of potentially infected removable media in the warehouse. 

Modern AV detecting 30+ years old threat!

Apologies for the text-only post. At least you know I'm alive and kicking.