Category Archives: Electronics

Wipe and wait

My car has a 4-position windshield wiper stalk; off, intermittent, slow, fast.

While the motor needs to be pulled and serviced because there’s little difference between slow and fast, the intermittent wipe had always been somewhat pathetic.

Selecting intermittent would make the relay click, and as soon as the wipers returned to the parked position, click again and they would almost immediately wipe again.

Pulled the dash shroud down and located the clicking box at the top left. (Top right is the key-in/seatbelt buzzer, bottom left the cruise control stalk, above that with the finned heat sink the dashboard dimmer control).

relay delay box

Took the circuit board out and drew up the circuit diagram by following the traces, to get a better understanding of the circuit and its method of operation.

board

Culprits were most likely the electrolytic capacitors. One had a high ESD and the other was meant to be 22uF, it measured in at about 100nF. Replaced them both. Now the wipers wipe and wait about 5 seconds before wiping again on intermittent, and added bonus, they now wipe 3 times after spraying screenwash onto the screen. Not bad for 45 minutes’ work and spares I had in stock.

Co-processing.

I decided to buy a little something for myself, so eBay was opened up and I hit “Buy It Now” on an item.

Package

3 weeks later, it arrived from Kowloon, Hong Kong. The reason for the package? This empty socket.

socket

As if by magic, it was filled with a suitable device:

387

Upon fitting a 387 co-processor, a jumper needed to be shorted to inform the board to use it.

jumper

CheckIt determined that the thing was working (which is good, as there are surprisingly quite a lot of fake/broken chips circulating the market).

checkit

It was then tidied up into the desk. Makes a significant improvement where a math co-processor is utilized.

lotus 3

A bit of fun, reminder of days gone by.

Film photography and a 386

I went to an estate sale at the end of last week and picked up a few things, the computer below and a camera, of the notably interesting items.

386

A 1993 Magnavox (Philips) 386 SX/20, with optional CD-ROM sitting on top. It was grimy on the outside, filthy inside as to be expected from an older system.

A1

After a thorough cleaning, the Canon A-1 camera. 35mm film camera with fully automatic exposure (AE). View through the viewfinder (this shot before I had cleaned the lens and filter, so it’s a bit hazy) shows the aperture and exposure time in f/stops and 100ths of a second respectively.

viewfinder

It’ll calculate that and set itself if you leave it in fully programmed mode.. fancy stuff. Bought a new battery for it and a foll of Fuji 400.. have been shooting some pictures so once that’s finished I’ll see if they came out OK.

wolfenstein

Got the computer running after giving it a thorough clean and fixing a couple contacts. Found a cable to replace the one in the back to link to the CD. Added a network card so it has CD interface, network and sound. Multimedia on a 386, before “multimedia” was a coined phrase!

cd working

Added a larger hard drive in (540Mb, or rather, 30Gb but partitioned down to the max the BIOS can handle without an overlay) and got the CD to read. 1x so it’s not fast but it does work!

AM Radio

This is a fun one for me- I’ve had this radio since I was about 12- I had gone to my school for the tombola/fair/jumble sale. I bought one of two radios, initially the one I god was a white plastic deal, brand I forget, and one of my friends- Alex Biffin- bought this one, for 50p (about, what, $0.75 these days). I bartered this one for his radio as this one worked better. It’s a Roberts RIC-1, the first radio to be produced in the UK to incorporate an integrated circuit (IC) into the design, making the design a lot smaller.

radio

It worked for a while until I dropped it and it stopped playing. I took it apart and determined the cause was the IF oscillator coil because it would sometimes crackle into life if I twisted the can. I tried to search around, went to the radio shop in Wells (long since gone) but nobody had the part available, so I shelved the radio.

Fast forward two decades and I decide to pull it off the shelf and try fix it, with greater knowledge, experience and Internet behind me these days. I found a service manual for it, something that was totally unavailable back in the day.

apart

Took it to bits, gave it a bit of a clean up as it was rather dusty. The loudspeaker wire had also broken off so that got re-soldered on. Still, nothing from the speaker as before.

LP1175

The offending article, a twin transformer coil in a can marked LP1175, apparently a fairly common part made by Philips back in the day.

angle

Same device, from a different angle, also the TAD100 IC that gives the radio its’ name.

can removed

De-soldered the IF can and set it aside, looking at the connections.

coils

Further dismantled the can, removing the outer shelding, and also the inner ferrite shield that surrounded the primary winding. Pointed at there with the tool is a glob of glue where the primary coil windings pass through- which was fractured and had broken the fine wire.

new wire

I managed to unravel one length of wire from one end of the coil and re-soldered it to its leg, the other one was underneath the rest of the windings and wouldn’t come undone far enough to be long enough to reach. I took a piece of regular multi-strand cable, took one strand of copper out of it and fixed it to the short leg- the rest of the windings are covered in varnish so wrapping it around wasn’t a problem.

extension

Attached the extension piece to the leg it needed to be fixed to. Put it all back into the circuit, twisted the power dial and POPCRACKLEHISS. Wonderful! Tuned in a local station, a joy to hear audio from this radio after so long.

The loudspeaker had seen better days so I carefully made some repairs with coffee filter paper and Elmer’s glue (PVA) after doing a bit of research on the Internet about basic cone repair.

coffee paper and speaker

Cutting out more pieces and carefully reshaping the edges lef to an acceptable repair that no longer vibrates with bass notes.

fixed speaker

With that done, I set up my test rig and began aligning the radio- it wasn’t bad but it is now easily capable of picking up WSM that broadcasts from Nashville, TN.

aligning

It’s nice to have this radio working again. It got the kids interested in the theory, so with the new Snap-Circuits set (circuit building set we got from Elenco) built a small, basic AM radio. Fun times!

Finding a leak that doesn’t exist, and a broken timepiece.

I’ve been having a hard time finding a few problematic issues with the Renault lately. Particularly it had started to leak power steering fluid quite badly, which would mark the floor where parked up and also get onto the auxiliary belt and make that slip.
Looking down from above, past the alternator and air conditioning compressor the pump looked rather wet, so I splashed out $14 and bought a full seal set for the pump. I decided to clean everything up with degreaser and refill the system, to hopefully see where the oil was leaking from.

dismantle

Begin by taking everything out, including battery, battery tray, moving the air conditioner comressor, remove the alternator and the brackets holding it all in.

empty

That leaves good access to the power steering pump. The corrugated plastic tube is the wiring for the front of the car, the braided hose is the gravity feed to the pump from the reservoir.

scrubbed up

Cleaned up the pump with an old toothbrush and engine degreaser. Rinsed it all down with warm water from the potato pump.

clean

Got a bit carried away as I had water left, so I cleaned down the inside of the hood where the oil had flicked off the belt, and the surrounding areas also. Topped up the oil and left it to dry overnight an in the sunshine.

full

Left it for two days, then checked on the level. Unfortunately the oil was all there still.

still oil

Another two days. Nope, there’s still all the oil left in there. The leak has miraculously fixed itself. Normally, hot, cold.. didn’t matter. It would leak regardless of it it was run or not. Now it’s not leaking!

clean pump

The pump is clean and dry, no signs of leakage.

oily frame

The only other place I can see is the return line, from the rack back up to the reservoir. If that has a crack or a pinhole it could be leaking. The engine cradle frame is a bit oily down under the back but I cannot see anything else that would be causing a leak. Further investigation to follow.

The second thing that irked me was the previously well-working clock had quit.

broken display

The display had taken to showing mostly nonsense, or nothing at all.

clock out

Took the dash to bits (again) and liberated the clock from the little cubbyhole it’s attached to.

polished

Cleaned up the smoked plastic section of the clock as it was all scratched and hazy.

components

Figured there were a couple pieces that might have failed and caused it to not work. Replaced the electrolytic capacitor and transistor. No joy.

circuit diagram

Followed the traces and built a diagram of what went where, to get a bit of an idea of how it all worked.

dead

Tested it but the chip was dead. No oscillator, just noise. The clock circuit boards are available, but they are a Jeep Wagoneer part, and as such suffer heavily from Jeep Tax and are therefore expensive.

zeroes

Upside-down image but poking power to the grid brought some nonsense up on the display so the VFD was all still good.

9

Poking about a bit more showed that some of the logic was alive, as various numbers could be liberated. Nothing sensible though.

led

Purchased a little LED clock with voltage and temperature capability for ten bucks, with the intention of fitting it into the clock as shown- looks OK but a little out of place and the very-bright display has no dimming capability.

dismantle

Decided to strip the board down and re-use the VFD, with the new clock module providing the logic. I’ve ordered a little 50V boost converter to drive the VFD, that will be proven to work first then I shall go ahead and get some high voltage transistors, pull the LED’s off the clock and use the output (multiplexed in the same way thankfully) to drive the VFD. Original clock, original display, just now with time, temperature and voltage display. Watch this space for updates.

Redux of the last few months.

It’s been a slow few months with little to report. I’ve lost faith in a few things, with a couple problems and issues with projects that had me baffled and I kinda lost interest in them.

However, things have picked up a little and I’ve gone back to the troubled projects or made some headway.

I bought some replacement tuning slugs for the Marantz receiver. They aren’t 100% the same permeability but they are the correct screw thread.

slugs

Replaced them in the transformer after carefully breaking the old ones up and getting them out of the core. Now I know what they feel like, the old ones were broken before I even started- the lack of decent radio reception certainly points to that.

radio waves

I got all set up and the thing refused to tune well. I could get a couple of strong local stations but the tuning meter and tune indicator would not light up, and those are partially controlled by the transformer. I connected my oscilloscope to the input side of the transformer to check the waveform was not distorted and all of a sudden, LOUD radio, strong signal! Uh.. yeah ok. Reflowed the solder, no effect.. touched the oscilloscope probe to the transformer again gently, and bingo. Strong signal. Touched my finger to it.. improvement. Okay, so it’s a capacitance issue. Experimented and ended up with a 10pF ceramic cap across the terminals to bolster the transformer. Now the selectivity and sensitivity are great. It’s right now the best radio I have in the house for FM stereo.

Carried on with it but now it keeps tripping out into protect. I’ve troubleshot the protect circuit, one of the other boards must have a leaky cap on it somewhere. I need to pull the boards power supplies off one by one and see what fixes it.

Next up, refinished the floors at the house. Edging strip all done in the kitchen:

kitchen skirting board

Finished up in the utility room, flooring strip and the paneling done:

utility room door

Finished up the cabinet around the water heater:

water heater

Pulled the stove to bits and thoroughly cleaned it, the glass particularly was vile.

stove

Finished the floor edge strip in the living room, split the flooring between the two rooms where it was buckling and added a divider to allow for expansion.

living room floor

Rented a floor sanding machine and sanded the floors back, as previously they had looked OK, but having painted the walls and tidied up they were the least well-finished parts of the room.

floor sander

Solid cypress flooring. Smelled real nice when lain bare.

floor stripped

A few coats of polyurethane clear varnish later:

shiny

Looking much better. Also, picked up a nice Holophane light fitting on clearance for $4 at Home Depot. Fitted an LED light to it that has 4 segments inside, looks rather like a standard light bulb:

light fitting

Been troubleshooting the brakes on the car for a while. Stumbled across a post on a Ford Explorer forum with the same symptoms as mine. Turned out to be a faulty brake booster servo. I’m going to vacuum test mine this afternoon, have my MityVac for the purpose (shown here with brake bleeding catch-can fitted):

MityVac

Also picked up a GTE Palco payphone, which has gone into service here at the house, with the requirement for coin removed.

GTE Palco payphone

I repaired a little Realistic PA amplifier that got struck by lightning, and built a cardboard speaker to test it with.

amp and speaker

Also cleaned out and got fixed up the Kerosene lantern, for hurricane use.

kero lantern

That’s about it for now.

Another stereo.

Recently was offered this hi-fi by a work colleague. Garage clear-out, it had been sat in there for years.

Marantz MR1155

It’s a Marantz MR1155, from the early malaise years of cost-cutting and design setbacks. It also didn’t work. Power was applied before I got it, and apparently it went click and made a bit of a crackle.
Sure enough, it would power up and come out of protect, but not much else happened. Evidently the protect circuit was not detecting a particular problem so that was kinda okayish.

dust werewolves

With the lid removed, the contents of the device appeared to be mostly lint. Yuk. That has to be the worst hifi I’ve owned yet in terms of dirt.

clean

Thankfully it all cleaned up nicely.

stripped down faceplate

Pulled the front off after work, removed all the buttons (they had gone green and fusty) and brought it all home to clean up. Judicious application of drill and polishing mop got it looking respectable again.

shiny

Not perfect by any means but definitely better.

lid

Cleaned up and put the lid back on. Fairly respectable.

in bits again

Brought it all home and started to poke about. Pulled up the manual off HifiEngine and set about looking for the cause of no audio. Powered it up, the main amp voltages were pretty much in spec, but the FM/AM/Phono/Preamp board was dead, with hardly any voltage. Bypassed the preamp board and fed the power amp board directly- presto, greeted with slightly clipped but definitely OK audio. The expensive amplifier modules are still OK.

caps

Ordered the full replacement of electrolytic caps to shotgun all the boards. Over the course of a couple days I replaced everything. Still no voltages, so I replaced the transistors that control the voltage and protect circuit.. nothing much. Further troubleshooting found the 14V Zener to be almost a dead short over 0.3V so I went to desolder it and it cracked into 2 pieces. With it removed, bringing up the variac got the voltages to rise. There’s the problem then. Ordered a couple 14V Zeners and whilst in town stopped at Radio Shack and picked up a couple 12V ones to see if that would get it to come to life:

alive!

Sure enough. Not very good but operational. Went to tune the FM because it was not working very well at all post e-cap replacement. Broke the discriminator tuning slug (even using a fiberglass tool of the correct size) so pulled that out and took it to bits. Ordered a couple replacement cores, so need to wait until it’s all back together before readjusting.

10.7MHz transformer

Go figure. It had to break..

Speaker grille redux

Finally, I added another coat of stain to the grille face of the speaker that I rebuilt.

drying grille

Sat on the cardboard box in the back of the truck to dry in the sunshine. Plank of plywood next to it for the PSU project I’ve been building.

Once the stain had soaked in it got buffed off and left in the sun a while, then I gave it a coat of Tung oil and let that set.

cloth

Measured and cut the cloth. Stretched and stapled it into place on the spacers.

fixed grille

Added the badge back on and put it in place. Looks sharp!

Multi-cap can

Had a bit of spare time and inclination today so I took all the connections off the back of the McIntosh after labeling the wires. That’s a task in itself.
Removed the old multi-cap can. Took to the base of it with the Dremel. I had wanted to retain the original look of the capacitor as the top of it sticks through the chassis. The old brown heat marks show the point where it shows. The Dremel cut is well below the visible line.

dermelled

Mallory’s finest. Still in surprisingly good physical shape.

can dissected

Cleaned the dregs of tar out of the case after softening it a bit in boiling water.

tarpit

Removed the old capacitor wad. Four new caps to fit inside. It would appear Nichicon listened to the classic audio crowd because these are common values and voltages the the era, designed to fit inside old cans easily.

new bits

Fitted the caps all in place. They fit nicely. Actually over the spec of the originals on voltage and temperature. They should last.

newcaps

Had to drill the base to pull the leads through. Kept the original markings intact.

square triangle semicircle

Glued back together it looks nice. Gave it a bit of a buff up with a bit of metal polish.

restuffed

Looks neat back in the chassis. Sitting listening to it now and it’s running happily.

Matchmaking

I recapped an old Dell power supply, as it has some useful voltages (-12, +12, +5, +3.3) and was more than enough powerful (160W) for most of the projects I do. Added a small load to the +5 rail and the voltages stabilised, that’s the light bulb.. spent a bit of time and built up matching circuit on Veroboard.

messy

Initial testing was good, so tidied things up a little.

board

Set about measuring transistors to see the Vbe of each. Matching at 72F to within 2mV.

measuring

Did 100 of them, they are surprisingly close (all within about 5mV) so I have more matched and/or similar pairs than I thought! That’s good, means all the transistors installed can be identical.