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General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc. |
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5th Jun 2015, 10:15 am | #1 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
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How stock faults have changed over time
One of the many fascinations with the forum is learning how many of the 'stock faults' now are so different from stock faults back years ago.
I was thinking that the main stock faults now are: 1) Dried up grease in mechanisms; 2) Drive belts that have sagged/turned to goo; 3) Leaky paper capacitors; 4) Transistors that have packaging issues such as Tin whisker/Lockfit; 5) 'Green spot' on transformers; 6) Record cartridges that have hardened suspension or dissolved; 7) Recording tapes that are shedding oxide copiously; 8) Exploding RIFA capacitors ! Whereas back in the past the stock faults were: 1) Open circuit dropper resistor sections; 2) High value resistors going open circuit (TV frame stages); 3) Electrolytics that have dried out (again TV frame stages); 4) Small-bottle power valves that were not up to the task; 5) RF/IF valve emission failing in fringe TV areas. Of course there are all the make/maker specific stock faults, but I was trying to be general. I've no doubt I've missed some - so what do you think ! |
5th Jun 2015, 10:47 am | #2 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
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Re: How stock faults have changed over time
Interesting analysis.
I would say that electrolytics drying out and developing a high ESR is very much a problem still with us with modern gear though. N. |
5th Jun 2015, 10:58 am | #3 |
Nonode
Join Date: Jun 2009
Location: Herefordshire, UK.
Posts: 2,495
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Re: How stock faults have changed over time
Yes, Nick, you are completely correct ! - indeed I was just thinking that point before I read your post.
In my defence I ought I suppose to have limited the stock fault question to equipment of that era. However I have realised that if asked now for a stock fault with modern equipment I would have put electrolytics top of the list. |
5th Jun 2015, 11:03 am | #4 |
Octode
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
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Re: How stock faults have changed over time
Dry or failed solder joints are also far more common on modern kit.
- Joe |
5th Jun 2015, 11:08 am | #5 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
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Re: How stock faults have changed over time
Wasn't "green spot" recocgnised as a serious problem in the late 'twenties, leading to intensive developments in enamelling technology and copper purity? Mind you, it might have meant that fine wire corrosion took fifty years to manifest instead of five, thus we're still faced with duff vintage meters, LF coilsets and output and EHT transformers!
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5th Jun 2015, 11:48 am | #6 |
Dekatron
Join Date: Jan 2005
Location: Oxford, UK.
Posts: 17,843
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Re: How stock faults have changed over time
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5th Jun 2015, 12:48 pm | #7 |
Octode
Join Date: Mar 2011
Location: Sheffield, South Yorkshire, UK.
Posts: 1,453
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Re: How stock faults have changed over time
YOU might think that, Nick; I couldn't possibly comment.
- Joe |
5th Jun 2015, 3:50 pm | #8 |
Dekatron
Join Date: Jul 2008
Location: Charmouth, Dorset, UK.
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Re: How stock faults have changed over time
If we are including TVs, ion trap straps breaking, you generally knew exactly what had happened as soon as you spoke to the customer - nice quick and easy job.
Peter |
5th Jun 2015, 8:16 pm | #9 |
Dekatron
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Re: How stock faults have changed over time
I suppose what you're comparing really is what we find now after years of disuse, compared with what went wrong after years of abuse!
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Kevin |
5th Jun 2015, 10:54 pm | #10 |
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Re: How stock faults have changed over time
Add disintegrated speaker surrounds to the current stock faults.
One fault that has remained is high value carbon resistors that have gone high. These now turn up in a lot of SMPS start-up circuits David
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5th Jun 2015, 10:57 pm | #11 |
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Re: How stock faults have changed over time
I would add previous repair attempts and modifications to the list.
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6th Jun 2015, 10:23 am | #12 |
Rest in Peace
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Re: How stock faults have changed over time
Yes. A modern stock fault goes something like "I re-capped it to improve the sound but now it doesn't work".
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7th Jun 2015, 3:07 pm | #13 |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
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Re: How stock faults have changed over time
Solder joints that are cracking- common on old leaded solder. Especially in places where there was a lot of heat around. It didn't like extremes of heat. First CRT monitor was a old Sony, which worked when it felt like it and responded to the treatment seen in some old TV programs (and a lot of GPO equipment ) - no amount of training etc could equip you with the knowledge of where and how-hard to hit it to get it to work. Problem was found to be cracking solder joints.
Then there's capacitor problems. I worked for a firm which undertook warranty work for a well known firm which had brought out a cheap FAX machine in the late 80's. Low 5v rail caused problems- cure- replace certain capacitors. But the best one- of which the sign was a smell that will live( possibly to the repeater station in the sky) with BT( and previous versions) transmission blokes is the sound of a rack alarm on 51 type equipment and the smell of selenium rectifiers. No need for fancy test gear- once smelt- never forgotten. One other fault ,not often seen on domestic vale stuff is the envelope failure on valves which are on 24/7 , and then the power fails. Valve cools rapidly and glass can't contract fast enough and cracks. |
8th Jun 2015, 9:39 am | #14 |
Dekatron
Join Date: Apr 2012
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Re: How stock faults have changed over time
Dead electrolytics is definitely #1 on my list of faults - whether we're talking the modern plague of SMPS-with-caps-with-the-ends-blown-out, or the leaky red-and-black Plessey types fitted in lots of 50s/60s gear.
I also see a surprising amount of stuff like ADSL routers, set-top-boxes and the like where components associated with one or more of the input/output ports have been fried. Lightning? A while back there was a spate of TVs and camcorders where the circuitry associated with the yellow video phono-sockets often got popped because when connecting the video lead the centre pin made contact with the centre of the socket before the shield did - and any AC voltage-difference between the camcorder and the TV (due to the Y-capacitors on the mains inputs) would get applied direct to the electronics. My most recent "fault" was caused by mice. Consumer-grade PCBs and surface-mount components are nowhere near as resistant to mouse-pee attack compared to older discrete-component-and-tagstrip style assembly. |
8th Jun 2015, 10:21 am | #15 |
Octode
Join Date: Feb 2009
Location: Cornwall, UK.
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Re: How stock faults have changed over time
I would think any tape deck with decomposing belts/idler wheels etc would be a stock fault now in my book
Gary |
8th Jun 2015, 11:11 am | #16 | |
Dekatron
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Re: How stock faults have changed over time
Quote:
Most of the "failed" solder-joints I see on modern kit are more mechanically-rmediated [snagged headphone- or power-jacks breaking the solder-lands off the PCB for example] than electrical. |
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8th Jun 2015, 12:04 pm | #17 |
Dekatron
Join Date: Jul 2008
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Re: How stock faults have changed over time
My thought were similar, going back a few years to CRT days possibly 50% of the faults were down to dry joints but very rare on modern stuff. I have not had much to do with flat screen TVs since I retired but the couple I have repaired have had dried up electrolytics in the power supply - about the only part I would attempt to repair now.
Peter |
9th Jun 2015, 2:14 am | #18 |
Dekatron
Join Date: Dec 2007
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Re: How stock faults have changed over time
Some I have handled did indeed have bad soldered joints in the power supply. I think this number also peaked a bit after the first generation of RoHS compliant sets had begun to age.
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9th Jun 2015, 8:29 am | #19 |
Dekatron
Join Date: May 2008
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Re: How stock faults have changed over time
Joking apart, this is a situation where sometimes, someone with only primitive test equipment is actually at an advantage over someone armed with anything more sophisticated. If you just have a simple series lamp limiter, you can test before and after each and every component replacement; so if you do introduce a wiring fault of your own, you will know about it straight away. Whereas if you have a nice fancy rig with a variac and volt and milliamp meters, it takes a little bit longer to run the set up between component changes; therefore, it becomes easy to blow off the very tests that might well save you the most bother in the long run.
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