When I was 17 I got a summer-job at a one-man car-garage. Heaven.
One day I was replacing the wheel bearings on a car - when I noticed that using a blow-off gun made it quicker cleaning out the old-grease in the hub, so as I removed each old bearing I delighted in the sound it made when I applied the blow-off gun to it (the bearing being on my thumb). Whizzzz, another puff of the gun, WHIZZZZZZZ, another puff etc... then without thinking I wondered just how fast it would whiz round so carried on.
When the bearing exploded at probably 100,000rpm it was a miracle I didn't loose an eye....
One day I was replacing the wheel bearings on a car - when I noticed that using a blow-off gun made it quicker cleaning out the old-grease in the hub, so as I removed each old bearing I delighted in the sound it made when I applied the blow-off gun to it (the bearing being on my thumb). Whizzzz, another puff of the gun, WHIZZZZZZZ, another puff etc... then without thinking I wondered just how fast it would whiz round so carried on.
When the bearing exploded at probably 100,000rpm it was a miracle I didn't loose an eye....
Last edited:
benc, that story is funny as ****, but it's not electronics...still, I can dig it! 
It's one thing to nearly kill yourself, another to nearly kill someone else... and Health and Safety was an unknown world when I started out.
On the student entertainments committee, we were always running into lack of POWER. Seemed like we never had enough sockets for all the lights and amps for discos and gigs. I decided to build the world's longest extension cable.
I ran 40 yards of 13A cable from the equipment store up the Student Union corridor to the common room. I enlisted my friend John Alton to wire up the socket in the common room, while I fitted the plug in the equipment store. After a nifty 2 minutes work fitting the plug, I yelled up the corridor: "Are you done, John?"
No reply. Lit up a ciggie and gave it 5 minutes. "Are you done, John?"
No reply. I decided he'd done it and buggered off for coffee with one of the many Ents groupies. Plugged in my end and headed off up the corridor to plug in a test lamp.
DISASTER. John was flat on his back. He said he'd been wiring it up slowly and patiently when he suddenly got blown 10 feet across the corridor by electricity.
Well, he lived, and had a sense of humour. But I was known as "Sparks" after that. Which is the ultimate accolade for the electrical equipment manager really.
It's one thing to nearly kill yourself, another to nearly kill someone else... and Health and Safety was an unknown world when I started out.
On the student entertainments committee, we were always running into lack of POWER. Seemed like we never had enough sockets for all the lights and amps for discos and gigs. I decided to build the world's longest extension cable.
I ran 40 yards of 13A cable from the equipment store up the Student Union corridor to the common room. I enlisted my friend John Alton to wire up the socket in the common room, while I fitted the plug in the equipment store. After a nifty 2 minutes work fitting the plug, I yelled up the corridor: "Are you done, John?"
No reply. Lit up a ciggie and gave it 5 minutes. "Are you done, John?"
No reply. I decided he'd done it and buggered off for coffee with one of the many Ents groupies. Plugged in my end and headed off up the corridor to plug in a test lamp.
DISASTER. John was flat on his back. He said he'd been wiring it up slowly and patiently when he suddenly got blown 10 feet across the corridor by electricity.
Well, he lived, and had a sense of humour. But I was known as "Sparks" after that. Which is the ultimate accolade for the electrical equipment manager really.
Ok, not a strange repair but a moderately strange electronics story nonetheless. In Silicon Valley, there's a hallowed electronic surplus store called Halted that's been around for years beyond count (30+ and counting - maybe one of you even older farts than me can tell me when they started).
Anyway, back in the early to mid 80's I was there at one of the parts drawers at Halted and struck up a conversation with a guy who'd just finished a consulting job for Sili*****. It seems they were having a yield/contamination problem with their jfets. It all came down in the end to lab coats - the assemblers that were putting the teeny chips into the TO-18 packages and bonding them down were wearing their lab coats to lunch, then back into the work place, so that a bit of the day's entree got sealed in with some of the fets. One of my colleagues had similar food contamination problems with HV TO-3 bipolar transistors (a selected 2N6545) made by a certain European vendor - probably a similar type of situation.
Companies have cleaned up their acts considerably in the intervening years.
These days, there are automated production lines that take 30 inch silicon wafers in one end and spit microprocessors out the other with no intervening human contact.
On another note, I've joked for a long time that you haven't really made your mark in Silicon Valley, until one of your creations shows up in Halted for sale. You get all sorts of odds and sods (including old hand made prototypes) when corporations clean out their back rooms and sell the detritus for whatever return they can get. It happened to me a few years back, when I spotted one of the power supplies I'd designed in a previous job on the shelves there - gratifyingly enough, quite a few years after I designed it (no, I didn't buy it).
Anyway, back in the early to mid 80's I was there at one of the parts drawers at Halted and struck up a conversation with a guy who'd just finished a consulting job for Sili*****. It seems they were having a yield/contamination problem with their jfets. It all came down in the end to lab coats - the assemblers that were putting the teeny chips into the TO-18 packages and bonding them down were wearing their lab coats to lunch, then back into the work place, so that a bit of the day's entree got sealed in with some of the fets. One of my colleagues had similar food contamination problems with HV TO-3 bipolar transistors (a selected 2N6545) made by a certain European vendor - probably a similar type of situation.
Companies have cleaned up their acts considerably in the intervening years.
These days, there are automated production lines that take 30 inch silicon wafers in one end and spit microprocessors out the other with no intervening human contact.
On another note, I've joked for a long time that you haven't really made your mark in Silicon Valley, until one of your creations shows up in Halted for sale. You get all sorts of odds and sods (including old hand made prototypes) when corporations clean out their back rooms and sell the detritus for whatever return they can get. It happened to me a few years back, when I spotted one of the power supplies I'd designed in a previous job on the shelves there - gratifyingly enough, quite a few years after I designed it (no, I didn't buy it).
Just a couple weeks back I was replacing a failed FWB on my 475 o'scope. While I was contemplating replacing all of the electrolytic caps, another full wave bridge decides to self destruct.
Another story out of MCAS Cherry point.
One of those early buck regulator type switching power supplies about half a cubic foot in volume and a power density of perhaps 20 watts per kilogram came in, (it was almost enough to kill me, fixing stuff I could have designed better myself)...
It powers up fine, after swapping some modules around, one of the safe to turn on tests fail. We spent half an hour trying to meter out the problem, of course there's floating grounds, emi filters, two sets of relays, 400hz transformers with .2 ohm dc primary resistance, and no means to just plug it in with a light bulb in series, I decide and someone who'd been there a number of years agrees to bypass the safe to turn on test.
Instantly 10 feet of 20 gauge teflon coated wire goes up in smoke, a 60 amp 240vac relay is fused shut. (that was about it for the damage). Of course after the fact, we decided to ohm out the emi filter properly.
20 years of vibration and the last impact of dropping it on the bench was enough to make the toroidal inductor in the emi filter finally make contact with the brass shell.
BTW, I can neither confirm nor deny that an entire I level division was tuning travelling wave tubes for maximum power, rather than lowest SWR, for, uh.. years, at least 10.
my shop worked 3 shifts for years, lots of the techs were real geniuses. It wasn't uncommon for me to find things like broken traces 3 months and 100 man hours after everything else had been fixed.
Another story out of MCAS Cherry point.
One of those early buck regulator type switching power supplies about half a cubic foot in volume and a power density of perhaps 20 watts per kilogram came in, (it was almost enough to kill me, fixing stuff I could have designed better myself)...
It powers up fine, after swapping some modules around, one of the safe to turn on tests fail. We spent half an hour trying to meter out the problem, of course there's floating grounds, emi filters, two sets of relays, 400hz transformers with .2 ohm dc primary resistance, and no means to just plug it in with a light bulb in series, I decide and someone who'd been there a number of years agrees to bypass the safe to turn on test.
Instantly 10 feet of 20 gauge teflon coated wire goes up in smoke, a 60 amp 240vac relay is fused shut. (that was about it for the damage). Of course after the fact, we decided to ohm out the emi filter properly.
20 years of vibration and the last impact of dropping it on the bench was enough to make the toroidal inductor in the emi filter finally make contact with the brass shell.
BTW, I can neither confirm nor deny that an entire I level division was tuning travelling wave tubes for maximum power, rather than lowest SWR, for, uh.. years, at least 10.
my shop worked 3 shifts for years, lots of the techs were real geniuses. It wasn't uncommon for me to find things like broken traces 3 months and 100 man hours after everything else had been fixed.
Wrenchone, I worked for "Haltek", the other Silicon Valley surplus heaven in the late eighties. It was when I and another tech came over from Litton, Applied Technology Cal lab and began doing repairs for them that the instrumentation side really took off and got spun off as Test Lab Company. Saw some truly bizzare instruments. Worked on an old HP box with serial number "Proto-01" (Was amazingly similar to final production model.) When Test Lab was doing the official split off I used my employee discount to load up on switches, barrier strips, rolls of micro solder, Belden multi-cable and other various stuff. At one time we had quite a line of various Sillicon Valley founders and luminaries pass through. Sure miss that old store.
Doc
Doc
Let's see how this direction works...
Most common failures in test equipment.
1. Closest parts to the outside on inputs and outputs. People often cause far more failures than components.
2. Filter caps. Dry out, high ESR, or short. Look for bulges, leaks or high ripple. Consider age of equipment.
3. Local Bipass caps. Very Common failure on digital circuits.
4. Zeners. Zeners are by definition bad diodes. They get worse. High failure item.
5. Bipolar Transistors. A very quick check is that B-E should never have more voltage across it than number of junctions. Typically less than .7V Darlingtons 1.3V (if not reverse biased, but that's rare). E-C may be close, but almost never THE SAME. If the same E-C likely shorted.
6. Switches and relay contacts, edge connectors. Old waffer switches become oxidized or just plain dirty.
The best cleaner is Deoxid... A.K.A. Cramolin. Use it sparingly, not lavishly. Should never just be squirted and left. Wipe it off then very lightly re-apply. Run a piece of paper through both wafer and relay contacts. I use erasers on edge connectors then very lightly apply Deoxid. Use Deoxid blue on gold contacts.
7. IC's. Usually more digital than analog failures.
8. Resistors usually go bad in response to a problem, not as cause of it.
When looking for a problem, devide and conquer. Split circuit in half, then remainder in half....
CHECK SUPPLY VOLTAGES FIRST!
Define the problem.... leads to solution. When trouble shooting I first look at block diagram while thinking about defined problem. That will usually lead me to most probable location of problem. I usually have a good idea where I'm going to look before I ever remove covers.
If dogging out a problem for a long time and making no progress, go get a cup of coffee or tea.
Use a soldering fan. Don't trust bleeders. Don't trust others. Check for yourself.
Use your brain.
Doc
Most common failures in test equipment.
1. Closest parts to the outside on inputs and outputs. People often cause far more failures than components.
2. Filter caps. Dry out, high ESR, or short. Look for bulges, leaks or high ripple. Consider age of equipment.
3. Local Bipass caps. Very Common failure on digital circuits.
4. Zeners. Zeners are by definition bad diodes. They get worse. High failure item.
5. Bipolar Transistors. A very quick check is that B-E should never have more voltage across it than number of junctions. Typically less than .7V Darlingtons 1.3V (if not reverse biased, but that's rare). E-C may be close, but almost never THE SAME. If the same E-C likely shorted.
6. Switches and relay contacts, edge connectors. Old waffer switches become oxidized or just plain dirty.
The best cleaner is Deoxid... A.K.A. Cramolin. Use it sparingly, not lavishly. Should never just be squirted and left. Wipe it off then very lightly re-apply. Run a piece of paper through both wafer and relay contacts. I use erasers on edge connectors then very lightly apply Deoxid. Use Deoxid blue on gold contacts.
7. IC's. Usually more digital than analog failures.
8. Resistors usually go bad in response to a problem, not as cause of it.
When looking for a problem, devide and conquer. Split circuit in half, then remainder in half....
CHECK SUPPLY VOLTAGES FIRST!
Define the problem.... leads to solution. When trouble shooting I first look at block diagram while thinking about defined problem. That will usually lead me to most probable location of problem. I usually have a good idea where I'm going to look before I ever remove covers.
If dogging out a problem for a long time and making no progress, go get a cup of coffee or tea.
Use a soldering fan. Don't trust bleeders. Don't trust others. Check for yourself.
Use your brain.
Doc
Last edited:
I had an odd one when I was repairing consumer audio. One channel of a receiver - I think it was a Harman Kardon but it was long ago. The amp had a very strange distortion that made no sense. Asymmetrical clipping but all the power devices and supplies were fine and made no difference whether it had a load on it. I pulled the voltage amp device after the differential pair and put it on a curve tracer. The curve trace showed a transistor that had an apparent resistor in parallel with the E and C terminals. Replacing the faulty transistor fixed it but it was the only one like it in over 35 years.
G²
The problem with amplifiers is they are a loop so a fault anywhere can pass symptoms around the whole loop.
I had an amplifier not working right but the voltages looked OK. In the end I took out all the transistors and of course it was the last one that had failed with a gain of 1.
I spent one happy half hour trying to work out why an amplifier would not power up. Kept plugging the amp into my extension lead and it was just dead. Checked the transformer for open windings etc and it seemed ok. Of course i hadnt plugged my extension into the mains ! And thats with 30+ years experience.
I had an amplifier not working right but the voltages looked OK. In the end I took out all the transistors and of course it was the last one that had failed with a gain of 1.
I spent one happy half hour trying to work out why an amplifier would not power up. Kept plugging the amp into my extension lead and it was just dead. Checked the transformer for open windings etc and it seemed ok. Of course i hadnt plugged my extension into the mains ! And thats with 30+ years experience.
Yes, can get tricky. Same principle applies to everything from precision HV AC calibrator amplifiers (Fluke 5215), exotic high voltage high current Sorrensen Research power supplies and even more exotic Television transmitters with bandwidths from 4.5 to 20MHz opperating on UHF.
The new digital transmitters run either 25-35 KW tubes, or mountains of 1KW solid state modules that get combined in multiple stages to reach desired output power. Even the modules are made up of smaller pallet sections assembled in same manner. Power gets split coming in and runs in phase to individual pallet amps then recombined at output. Outputs are combined in banks then the banks recombined in cabinets. Cabinets combined to feed main out. Now all digital controlled down to individual pallets.
But point being that broadcast transmitters are just big amplifiers. The same principles apply from audio up to UHF, as do the same type problems.
Try recapping two transmitters with 32 drawers of 16 pallets with two big SMT caps per pallet.
Doc
Interesting on reading all the countless problems with electronic equipment and how some drove the repairer person nut's to solve the nagging fault!...
I recall one time at the local tv/video repairs centre, where we had a Hitachi a7 set that refused to stay on for more than 2 hours and then shut down to standby! these set's did a power on followed by a check of it's voltages then if all's well power up...mm! not this one...so time to get stuck in..ht set to 152v and so going over all set up's...in the end it turned out to be a 80 pin smd chip in the middle of the underside pcb that needed to be changed out and solved the fault... these day's you open a lcd and think wow where do you start!
Still I'am glad to say, I'm back to servicing/repairing audio equipment/valve amplifiers as this is where it all started way back in the 80's... you just can't beat that feeling of bring a old vintage amplifier back to full working order...
I recall one time at the local tv/video repairs centre, where we had a Hitachi a7 set that refused to stay on for more than 2 hours and then shut down to standby! these set's did a power on followed by a check of it's voltages then if all's well power up...mm! not this one...so time to get stuck in..ht set to 152v and so going over all set up's...in the end it turned out to be a 80 pin smd chip in the middle of the underside pcb that needed to be changed out and solved the fault... these day's you open a lcd and think wow where do you start!
Still I'am glad to say, I'm back to servicing/repairing audio equipment/valve amplifiers as this is where it all started way back in the 80's... you just can't beat that feeling of bring a old vintage amplifier back to full working order...
Probably with the backlight power supply.
Highest failure section on LCD's. Oddity is that it's a transformer failure as often as a driver FET. (I know question was redundant, just indicating that even in an LCD there are places to start.) Doc
Probably with the backlight power supply. Highest failure section on LCD's. Oddity is that it's a transformer failure as often as a driver FET. (I know question was redundant, just indicating that even in an LCD there are places to start.)
I would agree there.. Doc
Service places charge a high price to repair lcd's set's and one tech said 'we just change over board's 'that sort's hour's of fault finding and keeps cost down for us! what happen to good old tracking down the faulty part and getting things back to working order..
That's the part we and new diyer's enjoy learning how/why it work's and above all know how to break the circuit in the stages to get it working...
I would agree there.. Doc
Service places charge a high price to repair lcd's set's and one tech said 'we just change over board's 'that sort's hour's of fault finding and keeps cost down for us! what happen to good old tracking down the faulty part and getting things back to working order..
That's the part we and new diyer's enjoy learning how/why it work's and above all know how to break the circuit in the stages to get it working...
I understand both perspectives. As DIYers we have the luxury of dogging something out. MFG's are looking at economics of a repair. Both are valid. If you are a repair facility, you need to turn a profit to stay in business. Good generalists are hard to find. Working as senior repair person in a calibration lab I used to go through stacks of employment applications from newbies fresh out of 18 month tech school who all thought they knew it all. Very few are capable of trouble shooting complex instrumentaion. Someone with good generalist experience (DC, Audio, Video, RF, digital) can sometimes keep three other techs busy just swapping parts they tag.
I've said to others before, given enough time, information and resources, there is nothing that I can't fix. There are many things that are not ecconomical or practicle to fix, but there is nothing that I'm incapable of fixing. It's a trade off. Sometimes you just have to deal with ecconomic realities.
Doc
I've said to others before, given enough time, information and resources, there is nothing that I can't fix. There are many things that are not ecconomical or practicle to fix, but there is nothing that I'm incapable of fixing. It's a trade off. Sometimes you just have to deal with ecconomic realities.
Doc
That's one of the neat things in broadcast electronics. Some of the old machines HAVE to be kept running just to transfer to countless hours of old shows. Some of them you might even like. I try to come at it as a 'purist' to not only get it to work but restore it to its original state but I had an Amoex AVR-1 that would be more trouble and cost than its worth.
http://www.lionlamb.us/quad/avr1_3.jpg
http://www.akdart.com/vtr/jpeg/21-01a.jpg
The sync change over relays were just ridiculous trouble to find and repair. I soldered jumpers on the sockets and used a retired Grass Valley sync change over switch with an NTSC and PAL sync generator to get the pulses to run the machine. The machine does NOT take a color black but requires sync, blanking, subcarrier, burst gate and some I forget. The sync generators CAN lock to color black. That combined with the analog to serial digital adapter on the back of the machine brings it into the digital 21st century. FYI I soldered those jumpers so that it's still 'restorable' 'just in case'.
G²
http://www.lionlamb.us/quad/avr1_3.jpg
http://www.akdart.com/vtr/jpeg/21-01a.jpg
The sync change over relays were just ridiculous trouble to find and repair. I soldered jumpers on the sockets and used a retired Grass Valley sync change over switch with an NTSC and PAL sync generator to get the pulses to run the machine. The machine does NOT take a color black but requires sync, blanking, subcarrier, burst gate and some I forget. The sync generators CAN lock to color black. That combined with the analog to serial digital adapter on the back of the machine brings it into the digital 21st century. FYI I soldered those jumpers so that it's still 'restorable' 'just in case'.
G²
Last edited:
Ouch! What a dinosaur. Is it 2"? I only go back as far as 1" tape.
We just bought a 1/2 dozen video recorders that are smaller than a cigar box, record onto SSD and and do just about any video format you want. Built in monitor, too. Amazing how far things have come.
http://www.sounddevices.com/products/pix.htm
Yup, it's a 2" quad, weighs 2200 lbs, requires a 208 volt power supply and while it has an internal air compressor, it's connected to house air at 55 PSI. Standard def video and mono audio. I see it every day at work. Next week they're sending me to Sony SRW school which is the other end of the VTR spectrum.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.