14 November 2024

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.

 

 

 

21 October 2024

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.




22 September 2024

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, ranging from 1978 to 1994. With their unique yellow color with a blue stripe 3/4 way up.
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.


26 August 2024

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.

15 August 2024

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 of a dirty Fairchild model 7050 multimeter
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.

31 July 2024

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



 

 

30 July 2024

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.

01 July 2024

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?