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dfuller

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Apr 26, 2020
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Guitar amps, as per usual. Cheap Vox hybrid amp with a bad tremolo vactrol and potentially a bad output IC. What fun, huh?
 

RayDunzl

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Central Scrutinizer
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Mar 9, 2016
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Riverview FL
Motorcycle - tires, carbs, and petcock.
 

restorer-john

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Gold Coast, Queensland, Australia
and petcock

An adult's only version of a petrock: ?

1596064714804.png
 

RayDunzl

Grand Contributor
Central Scrutinizer
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Riverview FL
Motorcycle - tires, carbs, and petcock.

Front tire change looks like a success.

Never changed a tubeless cycle tire before.

1596080501102.png


I got brave after watching this guy and getting the tools for the job.

(the local shop estimate might have had something to do with it too)
 

Instrumental

Member
Joined
Jul 4, 2020
Messages
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Location
Sweden
Tiny space but lots of tools and instruments. The IO board of a NAD 3400 in for major
surgery. Noisy or non-functional swithches opened and cleaned. The contact elements
are hidden inside the plastic parts so no chance of proper cleaning from the outside.
New op-amps, relays and capacitors in the signal paths remain. It's my "spare" amplifier
so the main goal is to get it up and running again but no more than that. This model
is a rats nest of cables inside so the "fun factor" is limited.

Bench.jpg IO-pcb.jpg Switches.jpg
 

solderdude

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Jul 21, 2018
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The Neitherlands
The K712. Nothing like the fun PMA has... :confused:
 

ahofer

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Jun 3, 2019
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New York City

restorer-john

Grand Contributor
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Mar 1, 2018
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Location
Gold Coast, Queensland, Australia
A new higher powered simulated speaker dummy load.

View attachment 75983

I see you are using your new fine tip temperature controlled soldering iron... ;)


I have a story. A short one:

My father bought a soldering iron to solder some DIN speaker terminals in around 1974. He'd never soldered before but being a doctor, he figured it couldn't be too difficult- anyone should be able to do it. I remember looking at this brand new thing and being so jealous as I'd begged for a soldering iron for a while (I was about 7yo at the time). I wasn't allowed to go near it or touch it. It was "dangerous" apparently...

What frustrated me was, he tried to use it once and gave up, put it in its box with all the attachments up in the cupboard. It was teasing me.

He asked what I wanted for my birthday and I said the soldering iron. I guess he figured that was an easy gift- he had it already, so I got it. The rest is history but here is the soldering iron (scroll down):
























weller.jpeg


Never used the "cutting" tip, maybe melted a bit of plastic with the "smoothing" tip, but went through quite a few soldering tips. I taught myself to solder with that iron. Even fine PCB work on boards I made from scratch (my mum hated ferric chloride stains). Lost count of how often the pistol grip got so hot it would burn my palm. Several years later saved up enough to get a proper fine tip iron and the temp controlled ones came later.

It is still the goto iron for big cap terminals, star earth points or soldering metal shields- nothing else has the grunt of that thing.
 

SIY

Grand Contributor
Technical Expert
Joined
Apr 6, 2018
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Location
Alfred, NY
View attachment 76073

Never used the "cutting" tip, maybe melted a bit of plastic with the "smoothing" tip, but went through quite a few soldering tips. I taught myself to solder with that iron. Even fine PCB work on boards I made from scratch (my mum hated ferric chloride stains). Lost count of how often the pistol grip got so hot it would burn my palm. Several years later saved up enough to get a proper fine tip iron and the temp controlled ones came later.

It is still the goto iron for big cap terminals, star earth points or soldering metal shields- nothing else has the grunt of that thing.

They're also great for terminals on big power resistors. I do have a temp controlled fine-tipped iron which... doesn't quite hack it for this.
 

March Audio

Master Contributor
Audio Company
Joined
Mar 1, 2016
Messages
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9,317
Location
Albany Western Australia
I see you are using your new fine tip temperature controlled soldering iron... ;)


I have a story. A short one:

My father bought a soldering iron to solder some DIN speaker terminals in around 1974. He'd never soldered before but being a doctor, he figured it couldn't be too difficult- anyone should be able to do it. I remember looking at this brand new thing and being so jealous as I'd begged for a soldering iron for a while (I was about 7yo at the time). I wasn't allowed to go near it or touch it. It was "dangerous" apparently...

What frustrated me was, he tried to use it once and gave up, put it in its box with all the attachments up in the cupboard. It was teasing me.

He asked what I wanted for my birthday and I said the soldering iron. I guess he figured that was an easy gift- he had it already, so I got it. The rest is history but here is the soldering iron (scroll down):
























View attachment 76073

Never used the "cutting" tip, maybe melted a bit of plastic with the "smoothing" tip, but went through quite a few soldering tips. I taught myself to solder with that iron. Even fine PCB work on boards I made from scratch (my mum hated ferric chloride stains). Lost count of how often the pistol grip got so hot it would burn my palm. Several years later saved up enough to get a proper fine tip iron and the temp controlled ones came later.

It is still the goto iron for big cap terminals, star earth points or soldering metal shields- nothing else has the grunt of that thing.
OMG same experience with ferric chloride trying to make pcbs. Yellowy brown fingers. ;) Sodium hydroxide (ooh whats that tingly burning sensation) involved somewhere from memory.
 
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restorer-john

Grand Contributor
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Mar 1, 2018
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Location
Gold Coast, Queensland, Australia
While discussing accuracy in meters in @watchnerd 's thread, I was testing various meters against my Time 1044 Voltage and Current calibrator. It has been a faithful device albeit seemingly a little hard on batteries of late. I put it down to poor batteries as a new 9V got rid of the "batt" symbol and all was well.

Or was it? Usually the testing is a quick confirmation, the 1044 is turned off and it's put away, often for many months. It's a physical hard switch and about six months ago, I replaced the 9V clip wire as it was getting a bit loose and I figured it was developing a resistance, enough to trigger the low batt event. Then I figured the 2.5mm external power switch could be the culprit as it had never been used so I poked the internal switch leaf NC contact, put a new battery in and the problem went away. Or did it?

Yesterday, I put a new battery in (again), lined up a few meters to test, and within a minute, the low batt indicator was on and it started giving erroneous readings. OK, there's a problem. So, I put a meter in series to monitor the current and one across the cell to watch the terminal voltage, turned it on and watched. All looked normal, around 40.00mA. I looked away and when I looked back, the "batt" indicator was on and the current consumption was 0.400A. Wait a minute, that's 400mA! And terminal voltage was below 8.2V. I repeated this several times to confirm. It was killing the batteries after a short delay.

It was time sensitive. I figured that extra 360mA at 9V (~3W) is going to produce some heat from something fast. Defintely don't power it from the bench supply unless I want smoke- the 9V battery was essentially its own current limiter. But it was somehow resetting and the unit worked perfectly after a minute's rest. There was a tiny smell I know when I sniffed the battery compartment. Tantalum caps. Bastards. I know you're in there!

IMG_3812.JPG

So in I went. Off came the colletted brass/plastic knob (lovely little thing), the nut and I hoped the unit would come apart without having to peel off the front panel (that would wreck it). And what did I see? 4 tantalums, 20 years old, nice Wimas and a heap of 25 turn trimmers (8) and quality construction. A separate A/D board for the meter etc.

DSC_1777.JPG


IMG_3816.JPG


IMG_3817.JPG


In circuit testing of the tantalums showed ESR was normal, actually good, but I wasn't convinced. Fired it up without the display A/D board and the consumption went up to 400mA after about a minute. I waited for a bit and then felt the caps. Yes! The rail decoupling 10uF 35V tantalum feeding the LM10CLN was hot- really hot. (rail is 24V). So, replaced the little bastard with a lowish ESR Nichicon Fine Gold (so audiophile huh) and all is well again. Consumption is 16-24mA when not sourcing current, a far cry from the 400mA before. The other three 2.2uF 35V tantalums were fine (only seeing 3-5V) and in parts of the circuit where I might screw up the calibration, so I left them alone.

IMG_3813.JPG

Some members wanted to see the internals of this little thing so here's a few more pics.

IMG_3814.JPG

IMG_3815.JPG


Here's the little troublemaker- he's cost me about 6x 9V Alkaline batteries.

WIN_20200908_13_20_50_Pro.jpg


And my tester thinks it's a double diode with two different voltage drops...
 
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solderdude

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Darn Tantalums.
Had to replace a whole bunch of them (most of them out of precaution) in a railway safety system.
Some of them started leaking current. Could be within a few days or months.
In this case 47uF/16V.
Replaced them all with Kemet.
DSCN8061.JPG
 

restorer-john

Grand Contributor
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Mar 1, 2018
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Location
Gold Coast, Queensland, Australia
Now I can go back to fixing this mess a "tech" made on a cracked PCB...

IMG_3786.JPG


Bit of a cap bulge going on here...
IMG_3801.JPG

The other one already blew its sleeve. The two caps are actually still within spec and ESR is excellent, but they have clearly had a hot life next to voltage regulator heatsinks...
IMG_3802.JPG

I don't know what to say.
IMG_3790.JPG


Clean them up.
IMG_3795.JPG


New joints.
IMG_3797.JPG


Quite a few like this.
IMG_3792.JPG
 

solderdude

Grand Contributor
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The Neitherlands
That'll give you something to do.
 

restorer-john

Grand Contributor
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Location
Gold Coast, Queensland, Australia
That'll give you something to do.

It was Father's day on Sunday, so my Dad gave me a job to do, when I went over to see him! God knows where or when he bought this amplifier, but he must have sneaked it in, under the radar. No surprises it has a laundry list of "issues". But I love him, so it gets the full treatment. I wouldn't even pick it up for parts if it were me.
 
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