Multimeters and test equipment.

I bought an Allsun EM125 scopemeter, as it looked like a unit that was rugged, and repairable. Last night the on button failed. It is just out of the 30 day return window, so I had a go at repairing the switch.

The switch was easy to disassemble, but one of the contacts was showing signs of having been hot. The contact was so lightly built, that no matter what I tried I couldn't repair it.

I can't understand the manufacturers thinking when they put this thing together.

The rest of the internals are really well put together and they have even used spring washers on the screws that
join to earth. Why put together something so complicated and hard to engineer, then use a crappy switch?

Any way, I ended up using a switch off a Sony Walkman (the white bit in the second picture) as a replacement, and the unit works.

My recommendation is steer clear of this mob's products.

Cant believe you still have a walkman kicking about.......lol

Ha ha. Got some parts from old amplifiers that I wrecked decades ago. Hindsight is a wonderful thing. Enthusiasts pay good money for them now.

Crazy. .... i chucked stuff like that out 20 years ago..... as a kid i was wired for sound.

I'm an electronics engineer by trade but have not touched any circuit level repairs for years. I remember pulling 200 pin circuit mount chips and replacing them . Those days are gone





….................... On the move

Ask me what a NOR gate is these day and am farked





….................... On the move

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.

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Originally Posted by mudnut

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.

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One thing I will never forget is soldering and I have to say I;m ferking good at it. I'm wearing glasses these days for those short sight distances

Quote:

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Originally Posted by mudnut

Same. After countless hours at night school too. These days my eyes are letting me down. My soldering looks like bird turds. I'll have to invest in a huge magnifier/ light and hope I put it away each time I use it, so it doesn't
catch the sun and burn the house down.

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I am the same, I can still solder good but only with the assistance of a big magnifying light clamped to the workbench. I get younger guys at work to do the fine soldering these days. I used to have excellent eyesight but by the time I was 48 I could no longer do much without glasses.

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Originally Posted by Bloodyaussie

Crazy. .... i chucked stuff like that out 20 years ago..... as a kid i was wired for sound.

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When a heap of us went over to Kupang my mate brought a Walkman for $380, jaw dropping eh..?

@ TPC I have one of these http://www.ebay.com.au/itm/Double-Th...0AAOSwVL1V~8PM

A bit of one-upmanship;

http://www.ebay.com.au/itm/Helping-H...kAAOSwGvhUFoGi

Although the quality of the lens may be lacking.this sort of unit would solve a few problems.

To solder on to the PCB, I filed the soldering iron to a fine point, but I will invest in a variable heat iron, one day.

Quote:

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Originally Posted by threedogs

When a heap of us went over to Kupang my mate brought a Walkman for $380, jaw dropping eh..?

@ TPC I have one of these http://www.ebay.com.au/itm/Double-Th...0AAOSwVL1V~8PM

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Quote:

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Originally Posted by mudnut

A bit of one-upmanship;

http://www.ebay.com.au/itm/Helping-H...kAAOSwGvhUFoGi

Although the quality of the lens may be lacking.this sort of unit would solve a few problems.

To solder on to the PCB, I filed the soldering iron to a fine point, but I will invest in a variable heat iron, one day.

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We have these on the benches at work, very good when replacing surface mount components or inspecting for cause of faults.

Attachment 65025

Funny how hand skills and soldering technology have evolved...
1960's - hand soldered circuits put men on the moon (according to some)
To get High Reliability Hand Soldering certification meant submitting work pieces for microscopic examination
1980's - multi-layer circuit boards with 5 layers of conductors/printed circuits meant repairs by hand required precision die grinding tools and a low power magnifiers
I remember spending hours or in the odd case days changing components on some avionics gear
2000's - everything is crimped or robot soldered so if the board is screwed throw it away

Just about a throw away society if you ask me. ppl have lost the ability to repair things
EG old school fitter and turner, these days press some buttons and the job is done. lol Well sorta
How many mechanics [young] would know how to reco a 48mm ida Dellorto carby.
I remember on the auto sewing machines we just plugged each board in to find the faulty one,
then inspect it further for a dry joint somewhere. We were supposed to throw them away.
Received a gold star for finding and fixing them

Panel beaters is another ,,,how many could make a panel
to fit a car from a sheet of flat steel

Hey mudnut, do you want these oscilloscope leads?
Have had these sitting here and have no use for them.
BNC type connector .
Let me know your address and they're yours





….................... On the move

Oops forgot pic http://www.nissanpatrol.com.au/forum...016/02/220.jpg





….................... On the move

PM sent, mate.

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Originally Posted by the evil twin

I remember spending hours or in the odd case days changing components on some avionics gear

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Still the same, and they want to pay less per hour than a plumber, sparky or mechanic.
Graham

Quote:

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Originally Posted by the evil twin

Funny how hand skills and soldering technology have evolved...
1960's - hand soldered circuits put men on the moon (according to some)
To get High Reliability Hand Soldering certification meant submitting work pieces for microscopic examination
1980's - multi-layer circuit boards with 5 layers of conductors/printed circuits meant repairs by hand required precision die grinding tools and a low power magnifiers
I remember spending hours or in the odd case days changing components on some avionics gear
2000's - everything is crimped or robot soldered so if the board is screwed throw it away

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We used to have a shelf where we would put some of the equipment that was considered to expencive to fix and when things got quiet and I felt like a challange I would grab one and spend several hours fixing it. I could fix almost anything given enough time. Most equipment gets sent back yo the factory for board replacement these days.

Quote:

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Originally Posted by TPC

We used to have a shelf where we would put some of the equipment that was considered to expencive to fix and when things got quiet and I felt like a challange I would grab one and spend several hours fixing it. I could fix almost anything given enough time. Most equipment gets sent back yo the factory for board replacement these days.

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Ha, your post reminded me of my apprenticeship. When the grain haulage season was over, work would become sporadic. To break the monotony, we could go to the electrical room and have a go at repairing 74 volt motors. One day my tradesman decided to challenge me to a race to put a fuel pump motor together.

While we stripped the motors and began assessing them, a small crowd gathered. They were egging us on, and heckling the tradesman. When the tradie got distracted, another bloke swapped out a field winding with a dud one, and an armature with a bent shaft.

The tradie finished his motor only minutes before me, and bagged me out. It was bloody funny when we tested the motors though, because his motor growled and surged crazily.

We used to have a inqustion to replace a main board, when I took over the workshop. I found it was often cheaper in labour and parts to do board changes.

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Originally Posted by GQ TANK

We used to have a inqustion to replace a main board, when I took over the workshop. I found it was often cheaper in labour and parts to do board changes.

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Yeah, the "Golden Wheelbarrow" was rife in a lot of industries, twenty years ago. By the sounds of it repairing anything is just not worth it now.

I have a Fluke, forgot what model but it is specifically designed for automotive work and I bought it locally at the Fluke shop. Was'nt cheap but Fluke is very good, some mine sites will only let you on with a Fluke.

Yeah I have nowhere near a the money for a Fluke though.

Just sold my Fluke on Ebay too...and my scope, soldering iron and everything else...

How's this for a grab for cash. Jaycar had the QM1577 scopemeter for $399 in last year's catologue, and it is $579 this year.

Get a nice Rigol 100Mhz scope for that money! Check here...

Yeah I looked at some of their gear. I may have some luck in seeing one of the Hanteck units, as a local bloke is seriously considering buying one.

It would be good to actually see the build quality and features before ordering over the internet for once.

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Originally Posted by mudnut

It would be good to actually see the build quality and features before ordering over the internet for once.

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Emona are in Melbourne and usually have demo units. There are also places that hire gear if you want to try before you by. I can vouch for Rigol, couldn't fault them.

I found another basic unit by hantek, https://www.amazon.com/gp/offer-list...&condition=new

Still battling along with the old crappy allsun. This hantek seems to get good reviews but ...

The Uni-T 2000 series Benchtop oscilloscope is a bloody marvellous piece of kit. The sig gen I created to run speedos was having interference problems when plugged into 12v. Yet I could only see a nice looking square wave at the 555 timer chip, on the Allosun handheld. I found that having a power lead more than a few centimeters causes the rise on the wave to become fuzzy so I will purchase a small rechargeable 12v battery to install on a new sig gen I am making. I really do recommend the Uni-T as a reasonably priced unit.

Quote:

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Originally Posted by mudnut

The Uni-T 2000 series Benchtop oscilloscope is a bloody marvellous piece of kit. The sig gen I created to run speedos was having interference problems when plugged into 12v. Yet I could only see a nice looking square wave at the 555 timer chip, on the Allosun handheld. I found that having a power lead more than a few centimeters causes the rise on the wave to become fuzzy so I will purchase a small rechargeable 12v battery to install on a new sig gen I am making. I really do recommend the Uni-T as a reasonably priced unit.

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Before you bother with the battery idea, try puting a 0.1uF ceramic or vitramon or similar capacitor across the supply rails right at the 555 (pins 1 & 8). And make sure your ground rail is solid and short as possible. Digital circuits need power supply decoupling.

Quote:

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Originally Posted by Brissieboy

Before you bother with the battery idea, try puting a 0.1uF ceramic or vitramon or similar capacitor across the supply rails right at the 555 (pins 1 & 8). And make sure your ground rail is solid and short as possible. Digital circuits need power supply decoupling.

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I've tried a few ideas as well. Pi filters, common modes chokes, etc. It comes down to the length of the leads. I will try a shielded cable. Also 9v batteries seem to be going flat in no time these days.

What ripple frequency was your Pi filter designed to decouple?

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Originally Posted by BillsGU

What ripple frequency was your Pi filter designed to decouple?

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The 50hz of the power supply I use. I also found placing a small ceramic cap across pins 1 and 8 caused a weird feedback frequency. The best I have so far found is to have a sizable 12 volt gel battery with a an IC7809 to regulate its output. This gives me the option to run a Bd139 as an inverting switch on the 555 output to get a nice AC Square wave. I am now playing with different configurations to get a smooth enough signal at frequencies between 30hz and around440-480hz. I found that around 270hz is 100kph.

Have a close look at the ripple frequency. The ripple out of a full wave rectifier is 100hz. The frequency you are trying to generate is close to your filter frequency and you may be getting some feedback via the filters. You could try using an opto coupler to ensure isolation.

Or get one of these: https://www.westlab.com.au/signal-ge...b-0-1hz-100khz

Quote:

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Originally Posted by BillsGU

Have a close look at the ripple frequency. The ripple out of a full wave rectifier is 100hz. The frequency you are trying to generate is close to your filter frequency and you may be getting some feedback via the filters. You could try using an opto coupler to ensure isolation.

Or get one of these: https://www.westlab.com.au/signal-ge...b-0-1hz-100khz

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I need the sig gen to be portable, small and robust. So I can disconnect the speed sensor connector and test the wiring harness and cluster.
I've been looking into the interference. I think the configuration of the my 555 is too sensitive to outside influence. It uses a capacitor and around 120-130 kohms between pins 1and 2. I will try a different set up using pots between pins 8,7 and 6.

Yep. The 555 circuit I picked was just to sensitive. I built another one today which handles 10-18 volts, either 240v fed Power supply or 12 battery with no interference whatsoever.

Sometimes starting from scratch is the way to go. Beats chasing your tail and trying to fix problems by introducing more problems. Every extra component you put into a circuit is a potential issue.

Quote:

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Originally Posted by BillsGU

Sometimes starting from scratch is the way to go. Beats chasing your tail and trying to fix problems by introducing more problems. Every extra component you put into a circuit is a potential issue.

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Too right.

I was looking to buy a dedicated frequency meter kit online to add to the sig gen. Going to use a cheap Jaycar multimeter and strip it down just to display volts and Hz.