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Finding a difficult fault.


catman
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G'day all, not on an audio project but one of my Ham Radio transceivers wired with an external dynamic microphone by myself.  After being 'bumped' it stopped working and after replacing the RJ11 modular microphone plug and essentially rewiring everything, it still didn't work!  Grrrr.  Eventually I trotted out my Akitika 1KHz tone generator and injected tone into the transceiver via the new plug and wiring.  Ok that worked fine but still no audio from the external microphone and preamp.  I had earlier proved the two transistor microphone preamplifier fully operational, so where was the signal disappearing? 

 

Everything checked out ok, so adopting the Sherlock Holmes approach, what was left had to be the cause.  Some wiring and shielded cable, and the cable looked fine, but I replaced the shielded cable, and that was it!  Although it looked perfectly fine there must have been a minute break 'somewhere'!  Oh the joys of fault finding!  Regards, Felix (vk4fuq).            

Edited by catman
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I recall a similar fault from my Marantz days. A 22XX receiver came in for warranty repair. The customer complained of intermittent distortion on one channel. Should be pretty simple, I thought. Gotta be a dodgy electro (they used a lot of tantalums in those days and tantalums, although quite reliable, can fail catastrophically for no apparent reason. After a lot of testing, I noted that the fault was weather related. In cool, moist weather, it distorted. In dry, warm weather, it was fine. I finally traced it to a 100mm section of shielded cable. An intermittant fault was causing a low resistance to earth, thus causing the preceding stage to distort under the, now, heavy load.

 

Most frustrating!

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I had to remove my Printer network circuit board from my HP laserjet and then bake it in the oven for 8 minutes at 350F to fix a documented (on a forum) intermittent fault I had,

Came back after a year or so and baked it again in the oven for 8 minutes and all is well to this day.

Edited by rocky500
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Had a fault with a mother board (PC) would just play up and crash occasionally. Checked for all the normal software faults and identified it as hardware, dang, 12;30 on Saturday afternoon in Burnie, no PC store..

Disconnected and removed mother board, with no spare and needing to get things happening a Mate suggested to give the board a good flexing and re install. As rough as it sounds, give the board a good flexing and re installed, still running right now and sent this message. The "repair" was done over a year ago.

@@rocky500, can see the merit of the 350 degree heat treatment  :thumb:

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Wait till you guys fix any intermittent faults on a printer.... :P

 

Don't talk to me about printers! In the recent past:

 

* I had to retire my venerable, ultra-reliable, HP Laserjet 5MP, because it won't talk to Windows 7 & any modern computer.

* Throw out several ink jet printers due to dried out ink.

* Stuck with a really crappy Samsung colour laser printer, which not only caused me no end of problems every time I had a paper jam (wish these guys would learn from HP), but decided to stop working just outside warranty AND just after I bought a brand new set of toners.

* I bought a second hand HP Color LJ 3600n. Brilliant printer. Excellent print quality. Bought a new set of toners and the damned fuser failed. AUS$500.00 for a new fuser.

 

I'm now using an $80.00 Brother laser printer (mono). Surprisingly decent printer.

 

Know where I can place some new toner cartridges for an HP 3600n and a Samsung (something or other)?

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Don't talk to me about printers! In the recent past:

 

* I had to retire my venerable, ultra-reliable, HP Laserjet 5MP, because it won't talk to Windows 7 & any modern computer.

* Throw out several ink jet printers due to dried out ink.

* Stuck with a really crappy Samsung colour laser printer, which not only caused me no end of problems every time I had a paper jam (wish these guys would learn from HP), but decided to stop working just outside warranty AND just after I bought a brand new set of toners.

* I bought a second hand HP Color LJ 3600n. Brilliant printer. Excellent print quality. Bought a new set of toners and the damned fuser failed. AUS$500.00 for a new fuser.

 

I'm now using an $80.00 Brother laser printer (mono). Surprisingly decent printer.

Know where I can place some new toner cartridges for an HP 3600n and a Samsung (something or other)?

You don't fix anything that's sold in Office Works, they're buy and used once until the supplies run out and unfortunately adds to land fill.

The supplies are now more expensive than the printer themselves. You're better of going to Office Works with a USB stick and get them to print off it, it's cheaper this way.

Some places like Snap and Kwik copy will even print on line for you, if you have an account. If you decide to run a printer you need to estimate what your usage will be and the type of media you are going to to print on. Now days printers are now designed to print up to 350gsm, digisynthetics for indistructable documents that DOD uses, right up to bank statements and official documents.

With toner, always stick to the OEM, but this is how they make money, they make a loss producing marketing and selling that printer, it's the supplies and parts is where they gain profit. BTW toner supply is not the same, every model even with the same brand, they are all different. Not one type of toner is the same for that single brand, a company like Xerox can have 50 different printers, however each model will have its own designed toner.

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You don't fix anything that's sold in Office Works, they're buy and used once until the supplies run out and unfortunately adds to land fill.

The supplies are now more expensive than the printer themselves. You're better of going to Office Works with a USB stick and get them to print off it, it's cheaper this way.

Some places like Snap and Kwik copy will even print on line for you, if you have an account. If you decide to run a printer you need to estimate what your usage will be and the type of media you are going to to print on. Now days printers are now designed to print up to 350gsm, digisynthetics for indistructable documents that DOD uses, right up to bank statements and official documents.

With toner, always stick to the OEM, but this is how they make money, they make a loss producing marketing and selling that printer, it's the supplies and parts is where they gain profit. BTW toner supply is not the same, every model even with the same brand, they are all different. Not one type of toner is the same for that single brand, a company like Xerox can have 50 different printers, however each model will have its own designed toner.

 

Sadly, I need a printer on the premises. 

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I work with RF, intermittent faults are part of my daily routine.

Everything from a cracked semi-rigid coax solder joint to slightly oval RF connectors can all cause loss of or reduced signal strength.

I had a 2dB attenuator that went high to 8 dB and caused a lot of head scratching for a while.

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Get around over-priced ink supply by using an aftermarket continuous ink supply system like this

https://continuousinksupplysystem.com.au/?gclid=CPrnkK759csCFQGbvQodpNwJ3w

A bit fiddly to set up, but works really well

 

Ink jet printers? 

 

Not interested. I moved to laser printers back in 1989. I've owned inkjets before and since. They're a PITA. 

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Sadly, I need a printer on the premises.

Companies such as Ricoh, Xerox, Konica Minolta are the main players in this game. The small office color units are mainly disposables and rubbish built quality as price is a factor. Like I said, you need to know what sort of volume you are doing in A4. The above mentioned brands have service contracts where some will includes free toner. They bill you on counter usage, and the agreement is normally between 3-5yrs Max. So Everytime you hit that print button, the counter clicks over you get charge $0.04 etc depending on the deal and you have to shop around.

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Finding intermittent faults on PCBs can be a bit of a frustrating exercise. A couple of very useful tools you can use are, compressed air at low pressure through a small nozzle, for localised cooling, and a hot air gun through a small nozzle for localised heating. I have also used freezer spray cans, but they are expensive at usually around $20 per can. Both those methods are useful for dry joints that are almost invisible, and for dodgy electros.

 

In the electronics repair business I had a few years back, a low ESR meter for electros (and can also be used as a low ohms meter for track continuity), and the hot and cold treatment would have found probably 80% of faults. Apart from the catastrophic component failures of course. Oh yeah, and C411 in the vertical ccts of NEC TVs

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Know where I can place some new toner cartridges for an HP 3600n and a Samsung (something or other)?

 

Greys online has HP carts and accesories and some times in the No reserve Auctions and you can pick them up real cheap if they suit your printer.

http://www.graysonline.com/search.aspx?q=HP+Color+LJ+3600n

 

Seems like a lot of Generics now but they do have Genuine's from time to time.

Edited by rocky500
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  • 5 weeks later...

My HP laserjet printer disappeared from the network again.

I think it is the weather change as it has been a lot colder lately.

Tried the usual resetting everything but no go.

 

Baked it again for 8 minutes at 180 degrees Celsius and all working great again,

So if anyone else has a faulty HP printer card...

 

post-107190-0-03310600-1462514701_thumb.

 

 

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Ink jet printers? 

 

Not interested. I moved to laser printers back in 1989. I've owned inkjets before and since. They're a PITA. 

 

That's about when the consumer inkjets hit the market!

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That's about when the consumer inkjets hit the market!

My brother bought the 1st Canon, it was crap... The ink bleed if you used normal copying paper, but of course they didn't have inkjet graded paper back then, if they did, I wasn't aware of it, today there's also rats of media. Some pestiege government department is using digisynthetics that is waterproof and tear proof.

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