- Your Toughest Job - 8 Updates
- Distiibution amplifier vs. ???? - 2 Updates
| Jeff Urban <jurb6006@gmail.com>: Feb 12 04:27PM -0800 The ones that separate the Men from the boys. For me it was an RCA CTC169. The symptom was display shifted on the screen and no sound. I don't remember or sure which but IIRC shifted to the right was a known fault, but this was shifted to the left. And it was intermittent. It would never act up when I had the chassis stood up on edge for testing. Three people with good eyes already combed the board for bad connections and even resoldered everything, no good. I am not even that much a digital guy, but... This fault was caused by the 503KHz crystal for the sweep circuit. Check out this failure mode; When the unit is turned on the uProcessor had always been running to receive the remote command. However the EEPROM ran off a sweep derived source. There was only a small window of time for the EEPROM to load its data into the uProcessor and the 503KHZ crystal had not failed completely but enough to make the oscillator slow to start - sometimes. I other words the data missed the bus. (I think that is pretty damn good metaphor...) It was not easy but it was a contract job. you cannot just give back the money,it would be like if your house burnt down and the insurance company say "Well here's your premiums back". It doesn't work that way. It would not have been a nosebleed for the company, more like a decapitation. Literally, "Do not leave until this is done, we will even get you beer at midnight just DO NOT GIVE UP, DO IT". So who else has had "one of those" ? And this was not lucking out on it, I had to know much more about the theory of operation than was included in even the training manual. I actually though maybe they were going to try to take my car keys ! It was that critical to them. But if I decide to work for you I have loyalty. There are only a few things I won't do, like sabotage or wholesale ripping people off. I fired a guy from my shop for sabotaging a unit. Guy walked in and told him what he wanted and the guy did it. We do not do that and he was out the door immediately. He became a bricklayer... So, anyone have anything like that " I got others, I bet Allison also does, maybe a few others. I would like to hear about them. you are being a desk potato (or in Quaylese potatoe) on the internet, what else you gonna do ? I am not a democrat or a liberal but Dan Quayle was not an exemplary...whatever. Anything really. Should not even be trusted to teach grade school spelling and VP of the country. Man Bush 2 was really fucking stupid, couldn't find oil in Texas. Are you kidding me ? Anyway, back to the topic. Your hardest job, brainwise. |
| Phil Allison <pallison49@gmail.com>: Feb 12 10:30PM -0800 Jeff Urban wrote: ------------------ > In other words the data missed the bus. > (I think that is pretty damn good metaphor...) ** ROTFL - so do I. > So, anyone have anything like that " I got others, I bet Allison also > does, maybe a few others. I would like to hear about them. The Yamaha R1000 digital reverb unit was a nasty case. The complaint was that it made a loud noise, like white noise, after warming up for some time. Soon verified with hot air blown onto the main PCB but not able to be localised. Found that a soldering iron tip placed on the middle of the 40 pin processor reliably induced the fault - so ordered a new one and fitted it with a mating socket. Made not the tiniest difference. A call to the importers struck oil when the tech went through the service bulletins in his filing cabinet. One of them was headed " Big Noise ". The fix was to change 6 memory buffers to high speed CMOS. All R1000s in the initial batch had the same issue, loss of speed when running hot caused memory data clashes and random data produces white noise when decoded to analogue. ..... Phil |
| John Robertson <spam@flippers.com>: Feb 12 11:37PM -0800 On 2020/02/12 10:30 p.m., Phil Allison wrote: > ...... Phil One of my more memorable fixes (we all have some of those) was trying to sort out why a proven board design would not reliably read an opto switch for a game that had had 1,000s sold. This was one of the first optos used in pinball games on a game called Space Station and I knew that the original factory computer was perfectly happy with the opto, but a replacement MPU (exactly the same schematic and layout as the original) was not. The opto would read erratically in self test - essentially it flickered. DV supply was clean, MPU clock was good, the new MPU board used what appeared to be good parts. Poked at it for a little while with a 'scope and all the levels looked good. After a while I started looking at the chips this aftermarket manufacturer used for IO. The original factory TTL was LS, and it turned out this designer figured that HCT was the way to go to replace it. All well and good, except that they inserted HC instead of HCT for the IO chips... I wrote them a note suggesting they not do that any more. Today I spotted another of this same company's boards in for service (different generation MPU) and they are STILL mixing HC and HCT, with this board made about ten years after the previous one... Sigh. The board looks good, but the complaint is that it has some erratic problems from time to time... I wonder which chips I'll change first? John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
| Fox's Mercantile <jdangus@att.net>: Feb 13 04:38AM -0600 On 2/12/20 6:27 PM, Jeff Urban wrote: > Anyway, back to the topic. Your hardest job, brainwise. Being one the guys that had to make shit work in the Aerospace industry was always full of fun and excitement. Emitter Coupled Logic was the "New Big Thing(tm)" at the time. We had a project that required a huge amount of data, and it had to be correct. It wasn't. Worse than being random, it, after analysis, appeared to be pattern sensitive. We were using a Textronix DAS9600 as a logic analyzer. Not fast enough. Call Textronix. They send a "Super duper" front end snapshot capture. Oooh, this is fucking cool! It has a sample rate of 5 pico seconds. Our customer says, "Buy it!" I fill out a purchase order. Submit it. And wait for the confirmation from Textronix. Two days later, I have it, and a delivery date of six months. I notify our customer. They said, "I'll fix that." The next day, I'm at my desk and I get a call from Tektronix. It's the CEO. "Tell your customer, you'll have that in six weeks." Of course, I had to ask him how that happened. "The President called me last night and told me to make it happen." Oh my. Well, true to his word, it showed up in six weeks. Now the fun begins, trying to find the problem. I was proud of myself. I found it within a week. "Good tools = good work." There was a problem with the memory from Fairchild. And it WAS pattern sensitive. A call to them got us all new memory. There was more to it than that, but that's all you get from me. -- "I am a river to my people." Jeff-1.0 WA6FWi http:foxsmercantile.com |
| Michael Terrell <terrell.michael.a@gmail.com>: Feb 13 02:38AM -0800 On Thursday, February 13, 2020 at 1:30:46 AM UTC-5, Phil Allison wrote: > A call to the importers struck oil when the tech went through the service bulletins in his filing cabinet. One of them was headed " Big Noise ". > The fix was to change 6 memory buffers to high speed CMOS. > All R1000s in the initial batch had the same issue, loss of speed when running hot caused memory data clashes and random data produces white noise when decoded to analogue. Occasional batches of embedded controllers for a Telemetry receiver, where the MPU oscillatior wouldn't start and run. Asked the long time employees, it had been a problem since it was first released to production. Their solution was to keep changing the PU and crystal until it worked. I looked at the schematic and spotted the problem. They had designed it for a PMOS IC, which went obsolete before production started. So they went into production with the CMOS version, but they didn't change the capacitors. The original used a pair of 20 pF, the CMOS needed 200 pF for that crystal. Engineering insisted that I was wrong, because it had been in production for ten years. They refused to issue the ECO, until a large customer wanted to know where their equipment was. I told the Corporate VP that they had been sitting in shipping for a month, waiting for that ECO so they could be shipped. He turned pale. He had started as a production test tech, and he was familiar with the problem. "I'll be back in five minutes, with your ECO." So much for Design Engineering's policy of no ECOs being written from the Production floor, or on designs that were over two years old. :) |
| amdx <nojunk@knology.net>: Feb 13 07:57AM -0600 I went into a consumer electronics repair shop to apply for repair position, I had a couple dozen certificates from Manufacturer training classes with me. The owner told me he just just hired a guy or he would have hired me. I wasn't home an hour and the guy called me back and said, I noticed several of your certificates were from Sony. I have this Sony projector TV that has been a dog, if you want to take a look at it, I will pay you. So I drove the 1/2 mile from my house and got the manual out. The symptom is no light out of any of the three tubes. There was no high voltage, so I'm poking around with the scope and the owner says "Hey, you got it going". I didn't know it had lit up, being on the backside, I didn't see it, but I didn't say that. It turned out a previous tech had changed two caps in that circuit, but he replaced them with a lower value. Just the capacitance of the scope probe was enough to bring the circuit to life. Probe connected it works, disconnecting the probe it didn't work. He hired me, even though it was part time, I already had a full time job. Mikek |
| Randy Day <randy.day@sasktel.netx>: Feb 13 08:07AM -0600 In article <b4854b08-3ce9-43a5-8c5e-44a1d8e867d3@googlegroups.com>, jurb6006@gmail.com says... [snip] > Anyway, back to the topic. Your hardest job, brainwise. Big Name retailer, mall anchor store, large company customer. Symptom: Jewelry department POS terminal (full UPS, on 24/7) keeps shutting down, staff have to wait 20 minutes each morning for restart. Went on for weeks/months, different techs had tried various components, no change, lots of hair pulling, no one is happy. So I get the service call one afternoon, working away. Replaced the parts suggested in the ticket, unit runs fine. As I finish up, the store is closing, staff are turning out the lights. All of a sudden the UPS starts beeping - WTF? Turns out, that one terminal was wired to a breaker that got turned off every night - the poor UPS kept it going for a few hours after closing, so no one saw a problem... |
| Michael Terrell <terrell.michael.a@gmail.com>: Feb 13 06:56AM -0800 On Wednesday, February 12, 2020 at 7:27:04 PM UTC-5, Jeff Urban wrote: > So, anyone have anything like that " I got others, I bet Allison also does, maybe a few others. I would like to hear about them. you are being a desk potato (or in Quaylese potatoe) on the internet, what else you gonna do ? > I am not a democrat or a liberal but Dan Quayle was not an exemplary...whatever. Anything really. Should not even be trusted to teach grade school spelling and VP of the country. Man Bush 2 was really fucking stupid, couldn't find oil in Texas. Are you kidding me ? > Anyway, back to the topic. Your hardest job, brainwise. Metrodata NTSC, Motorola Exorcisor Bus based six channel character Generator. at a CATV headend. It locked up for about 10 minutes. Just long enough not to get a scope there and the covers off the rack mounted chassis. It worked about six months, and did it again, and again at shorter intervals until it locked up and stayed that way. There were no spare boards for the pair of systems, and they were essential to the system's operation. One system had a SMS disk storage subsytem with a pair of 8" floppies, but the failing system only had 32KB of RAM on a MC6800 8bit processor. No operating system, and information was stored as 'pages' so the addressing was selected by a block of RAM. The two systems and the dis system had cost us a little over $60,000, in 1980. Then the company that built the two systems promptly went bankrupt and shut down. There I was, standing on a ladder, leaning into the chassis with a logic probe. One of the address lines on the Exorcisor bus was shorted to ground. One of the address decoders had failed. a 29 cent TTL IC that took over two years to finally die. |
| tabbypurr@gmail.com: Feb 12 01:17PM -0800 On Wednesday, 12 February 2020 14:09:08 UTC, amdx wrote: > I guess I'm just mellowing as I age. > On the other hand, I have my days. > Mikek I know. I just gripe a little because 99% of questions are the same way, and a lot never provide the relevant info. NT |
| amdx <nojunk@knology.net>: Feb 12 06:23PM -0600 >> Mikek > I know. I just gripe a little because 99% of questions are the same way, and a lot never provide the relevant info. > NT Guilty! I think Jeff Liebermann is ready to file charges on me! :-) At least he makes me think about what might be needed now. Mikek |
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