Get Out of Jail Free Card (with faulty components) - Page 1
Forum section: electronics / general

author: VK3DRB
author_rank: Super Contributor
timestamp: January 30, 2014, 11:57:42 am
content: No! Today someone at work had accidentally ripped out a small 4 pin DC-DC converter (isolated) off a prototype board for a machine we are developing. The 4 pins had actually pulled out from inside the tiny potted component... no metal could be seen in the component. No equivalent parts were available locally (not unusual for Australia) and we needed the machine working - immediately.THE SOLUTION? We ground off the edge off the device until we could see the four metal pads in the guts of the IC. We also grounded off the tiny plastic standoff feet from the outer package of the device so device could sit flush on the PCB so the legs still soldered in the PCB would overlap the now exposed metal pads. We soldered on legs into the device and despite the trauma it functioned perfectly! A dab of hot-melt glue secured it.I would like to know what other component rescue stories you have experienced. That is, how have you improvised as a get out of jail free card?I remember many years ago I was to show the US Ambassador to China a tour of the first computer manufacturing plant in China, in the city of Tianjin. A critical manufacturing machine called a Rod-L hipot tester had a component failure on the morning of the tour. With no time to fix it, I modified the assembly code program in the PC connected to the hipot tester to simulate the hipot tester working properly. It fooled the US Ambassador. Mission accomplished. (Of course I replaced the defective component prior to production.)So have you improvised to get out of dire straits when an electronic component has failed? Did you rescue the dud component, or find a creative workaround?

author: Stonent
author_rank: Super Contributor
timestamp: January 30, 2014, 05:02:14 pm
content: My commodore Vic 20 had the same issue.

author: Sigmoid
author_rank: Frequent Contributor
timestamp: January 30, 2014, 06:01:10 pm
content: It's not really a component rescue, it was only after cutting traces on a veroboard, and soldering in all the jumper wires and resistors, that I realized that while the design was made for transistors with ebc leg arrangement, I only had bce ones at hand... and the board was kindof cramped...Thankfully I still had a handful of jumper wires... Not the nicest solder job I've ever done that's for certain.

author: SeanB
author_rank: Super Contributor
timestamp: January 30, 2014, 07:48:05 pm
content: I depotted a sealed amplifier in an octal base with a steel can to replace the output transistors. Took a week of soaking in acetone to soften the original resin to the point were I could pick it off the inside components, revealing the LM709 opamp and the output current booster and the 2 bias diodes. New transistors ( 2N2222a and 2N2905A) and 2 new diodes and it was working again, but it no longer fitted into the steel can. Board was pretty fragile after the soaking, had o be careful on soldering the new parts to the traces. Was still working 10 years later as a video amplifier.

author: SeanB
author_rank: Super Contributor
timestamp: January 30, 2014, 10:04:16 pm
content: I will look and see if I can find it.

author: VK3DRB
author_rank: Super Contributor
timestamp: January 31, 2014, 08:42:20 am
content: Quote from: mojo-chan on January 30, 2014, 04:46:03 pmYears ago, some el-cheapo K-Mart quality transistor radios that had dry joints were "fixed" by the manufacturer by flexing the board and pouring glue on them to keep them bent. I have heard that trick being done on low end video cassette recorders.

author: VK3DRB
author_rank: Super Contributor
timestamp: January 31, 2014, 08:50:36 am
content: Quote from: SeanB on January 30, 2014, 07:48:05 pmBrilliant.On October 29, 1941, U.K. Prime Minister Winston Churchill visited Harrow School to to hear the traditional songs he had sung there as a youth, as well as to speak to the students. When he was invited to give a speech, Churchill stood before the students and said,"Never, ever, ever, ever, ever, ever, ever, give up. Never give up. Never give up. Never give up."You could have been in the audience. (Or the son of one of his students.)There is a lot to be said for persistence.

author: SeanB
author_rank: Super Contributor
timestamp: February 01, 2014, 04:42:28 am
content: Seeing as it was part of a video duplicator fixing was the only course, as a new amplifier unit was going to be a very expensive unit, coming from the USA. I already had had one fail on it, so when the second died I needed to fix it.

author: Skimask
author_rank: Super Contributor
timestamp: February 01, 2014, 05:36:57 am
content: One night, we got stuck in the middle of (____insert name of place here because I probably can't mention it 'cause it probably violates something somehow____)...we'll just call it nowhere.Flying a C-130. We were taxiing out for takeoff and I just happened to be looking out the window and saw one of the propeller heater boots flash for a bit and go up in smoke. According to the rules, we couldn't fly without prop heaters. Taxied back, shut down engines, went out for a look. Saw the rubber coating blown out and the wires burnt to a crisp. Was going to take at least a week to get a new prop in for replacement.We broke out the pocket knives, started peeling away a bit of the rubber to expose enough extra wire so I could solder in a chunk of jumper wire. Well, the solder wouldn't bond properly with the wire. I assume either I couldn't put enough heat to it (35W pencil iron is all we had along with some old paste flux) or the wire itself was coated with garbage from being coated with all that rubber for X number of years. The best I got was a cold-ish solder joint at both ends. Wrapped the whole thing in a tin-foil like tape, and covered the whole "repair" with 15-minute epoxy. Waited about 1/2 hour. Started the engine, ran it up to speed, turned on the prop heaters and let them cycle for a couple minutes, shut it down to make sure the epoxy hadn't flung itself off. Got back in the plane, fired it up, and got the hell out of there.Would we have been all right even if we didn't fix the prop heater? Probably. Obviously it was cold at altitude, but we didn't fly thru any visible moisture, and therefore had a very low chance of icing anything up. But...a bunch of guys will do a lot of whatever it takes to get back home after X number of days in place Y.

author: vk6zgo
author_rank: Super Contributor
timestamp: February 01, 2014, 06:18:13 am
content: Pretty much standard procedure in Oz!I've had my moments,like rebuilding a SMPS unit in a Sony Picture Monitor.The rectifiers on the secondary side had gone up in smoke & burnt big holes in the board.Most of the rest of the board was uncooked.The original rectifiers had two diodes in a fairly small package,& if not unobtainium,were one of the few things Sony couldn't get for us within a couple of days.In the TV studio store,I found some small round PCBs which had been meant for some forgotten project.Luckily,they had just about the right track configuration to fit two discrete diodes on.Epoxied them in place in the (cleaned out ) holes. made the external connections,fixed the other faults,turned it on,& "Bob's your Uncle!" away it went.In another case,an Electrohome Pix Mon cooked a Bi-Polar Electrolytic cap used in the "Boost HT " circuit.Modern BP electros we obtained had too high ESR & cooked in minutes.We ended up with a "Christmas tree" of Polyester "greencaps"---this became the standard fix.LGT TV Transmitters had some "unobtainium"special ICs,which cooked up regularly,& the French were a bit "laid back" about sending spares to "Australie".The boys made a small board piggybacked on a DIL plug to replace them.I wasn't involved in making them,but I saw them in service.In one place,a Thomson 10kW TV Transmitter's 32V supply for the transistor PA's croaked,& required special parts to fix it.As luck would have it,there were some NEC 28v TRPA power supplies around,which were "tweakable" enough to get to 32V.One of these was mounted in a box,sat down alongside the Thomson,with input & output cables jury-rigged.It ran the Thomson for months!I was again,only peripherally involved.

author: VK3DRB
author_rank: Super Contributor
timestamp: February 02, 2014, 12:57:01 am
content: Quote from: vk6zgo on February 01, 2014, 06:18:13 amOne fix for the very expensive Rank Arena TV triplers that arced burnt cracks in their plastic case was to gouge out the crevice, clean it with isopropyl alcohol and cover it with silicone. There were many examples of this in the TV industry when manufacturers charged exorbitant prices for parts.

author: VK3DRB
author_rank: Super Contributor
timestamp: February 02, 2014, 11:35:06 am
content: Quote from: SeanB on February 01, 2014, 04:42:28 amIf that is flux all over the place in the photo, it is pretty good it lasted 10 years. It looks quite old, with an old carbon resistor. Good photo!

author: SeanB
author_rank: Super Contributor
timestamp: February 02, 2014, 01:01:12 pm
content: Not flux, slightly roasted epoxy filler that I was not going to remove further. The new 2R2 resistor was there because I ground through the original one with the Dremel opening the clear casting resin. Opamp Labs definitely did not want these modules to be treated as anything other than a real black box ideal opamp. Note the new bead tantalum capacitors on the back, the original ones fell apart during the soak, and the 4u7 35V ones I had on hand fitted fine in the place of them. Heatsinks were needed because the new transistors ran hot, so the clips were enough to cool them to barely warm. Flattenned the can so I would remember what it was.

author: amyk
author_rank: Super Contributor
timestamp: February 02, 2014, 02:11:00 pm
content: Mike has an interesting video related to this:

author: scientist
author_rank: Frequent Contributor
timestamp: February 05, 2014, 04:37:47 am
content: Had the same thing happen with an ATTiny84, just drilled into the packaging a bit, filled with solder, and epoxied over it.

author: Gribo
author_rank: Frequent Contributor
timestamp: February 05, 2014, 11:30:35 am
content: I had an old Intel PLD (Before they sold the line to Altera) die in a critical circuit, without any documentation about its programming. At the time, the component was obsolete for 10 years. I had to reverse engineer its logic from a working unit and used a CPLD on a small adapter board as a replacement. AFAIK it is still in use..

author: iampoor
author_rank: Frequent Contributor
timestamp: February 06, 2014, 10:18:15 pm
content: Quote from: SeanB on February 01, 2014, 04:42:28 amAre hose the same opamp labs modules that they used all over heir strange audio mixing consoles? Were they popular in video duplicators?

author: SeanB
author_rank: Super Contributor
timestamp: February 07, 2014, 05:04:55 am
content: They do do from DC to video with reasonable linearity, and as this was the first time I met them ( never saw the consoles) I do not know. At least having them in octal bases like the Philbrick units made fault finding easier.

author: schwarz-brot
author_rank: Regular Contributor
timestamp: February 08, 2014, 01:57:58 pm
content: Replacing bad caps on multilayer boards with a simple iron? Rip the old ones out with a strong and fast pull with some universal pliers. The pins will stay in the PCB, nicely connected to the corresponding layers. Then simply solder on a new cap on these posts. Works a treat and fails pretty seldom. Especially helpfull for consumer gear like PC mainboards and other cheap multilayer stuff.

author: N2IXK
author_rank: Frequent Contributor
timestamp: February 08, 2014, 11:54:49 pm
content: Opamp labs is apparently still in business, and you can buy those modules for $50 apiece:http://www.opamplabs.com/products/logic-module-plug-in/video-amps/400v.html