An Interesting Mixer Fault

[dicky]

I've bought a box full of customer return Citronics CM-4 Live, CM-6 Live and CM-10 Live mixers on the intention of fixing them and keeping one or two and selling the rest

Anyway they are now repaired and the fault on the last one made me laugh

The fault on the CM-10 was channel 5 had low output levels

Upon removing about a hundred screws, nuts, washers and knobs to get the thing apart I found this! :confused: :confused: :confused:

(see pics)

A 22uF Electrolytic cap that was slighty worse for the wear IMHO

It is next to one of the mounting pillars for the PCB and I can just imagine it was a manufacturing fault. I just have this mental image of some chinese guy (or girl) in the factory wondering why the front and rear panels did not quite fit together properly - before cursing and giving it some with a screwdriver to make sure it did!! :daft:


Last mixer of this batch now fully working - just needed a capacitor.... and about 100 odd screws, nuts, washers knobs....... putting back in LOL

I should have another load of these coming in the next couple weeks if anyone interested in one


Rich

[DJ Jules]

Classic - brilliant design and assembly there ;)

[Nakatomi]

So they apparently don't do final assembly tests then... (that's testing after it's all put together) :eek:

[Excalibur]

So they apparently don't do final assembly tests then... (that's testing after it's all put together) :eek:

Err Justin, that's what customers are for nowadays. :D

[Nakatomi]

Err Justin, that's what customers are for nowadays. :D

Quite. In a former life my job was to improve test processes for electronic production lines & if it wasn't operators being lazy it was managers badgering the engineer to skip bits of the test to increase their output (curiously never the yield). Where I work now has a typical DPM (defects per million) of something like 100-200, which for any operation involving human beans is pretty damn good.

[dicky]

Ain't that the case............... I suspect someone somewhere decided it was cheaper to get rid of all the Quality Control Engineers and just swap out the odd ones that didn't work after they got sold - and stupid though it may seem at first glance' that actually most likely makes economic sense :p

And gives folks like me a nice little sideline in income :)

Rich

[ckpr2]

I am into old amplifiers.
I managed to pick up a 1980's Maplin 50 watt amplifier off ebay.
Someone had tried to fix it and had failed badly.
Some transistors were missing but I managed to source them on ebay. RS and Farnell no longer stocked them.

I fitted the new transistors and the amp sort of worked quietly.
I went through the circuit slowly and some of the voltages were wrong so checked every component with a meter and everything checked out fine.
In the end it came down to one transistor and that checked fine using a multimeter.
Then I checked it for polarity and it was wrong.
Some one had put in a PNP instead of an NPN transistor.
So I replaced it with the correct type and it sounded great.

Its hard enough fault finding with the correct components in the board never mind the wrong ones.
But I got there in the end.