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Success Stories If you have successfully repaired or restored a piece of equipment, why not write up what you did and post details here. Particularly if it was interesting, unusual or challenging. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 14th Oct 2018, 12:29 am   #1
Nymrod121
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Default Marantz SR4200 soak testing (!)

This item formed part of a recent 'bereavement-related equipment uplift & dispersal' project.

Applying power brought it to standby, after which I selected the built-in tuner's FM band as a source. The display briefly showed 87.50 MHz, followed by the word 'PROTECT' which flashed several times, after which a relay clicked and the unit reverted to standby.

After taking the top (ventilated) cover off, I found evidence of liquid spillage ... what looked like tea or coffee had got onto two of the three major PCBs. Not good news ... so on the basis of 'nothing ventured, nothing gained' - and bearing in mind some previous conversations with Craig Sawyers regarding Tektronix procedure on overhauls - I removed the affected boards and ran them through a dishwasher cycle (no tablet/salt) then put them in a fan-assisted oven at 50℃ for two hours, then overnight in the airing cupboard to dry out.

After re-assembly, I applied power via a variac having set the Marantz' power button to 'out of standby'. I heard very faint / intermittent fizzing at the 40% variac setting, so I left it at this value (whilst listening *very* intently) for ten minutes. The effect had ceased by that time so I increased the variac setting in 5% steps every ten minutes - listening/watching all the while for any signs of distress - then left it at 100% for half an hour. Nothing further untoward was noted (phew!) so I selected 'tuner' - the display again came up showing 87.50 MHz but now it stayed on. I attached a simple wire antenna and tuned to 88.30 MHz. I advanced the volume control and there was Sutton Coldfield's Radio 2 service ...

So now after two hours of further careful testing, the audio side of things seems to be working as it should but I need to check its ability to route analogue video before putting it up for disposal.



Guy
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Old 14th Oct 2018, 8:36 am   #2
mole42uk
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Default Re: Marantz SR4200 soak testing (!)

I’ve used the dishwasher several times on pcb assemblies - I just put them amongst the dishes on an ECO cycle, with tablet & salt, then dry in the airing cupboard for a few days. 100% success so far, the most satisfying was the EHT board of a very dirty Marconi 2955 which had all sorts of tracking faults before the clean and worked perfectly after.
Of course, I may have just been fortunate!
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Old 15th Oct 2018, 4:23 pm   #3
Phil G4SPZ
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Default Re: Marantz SR4200 soak testing (!)

Good tips there. Thanks Guy.
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Old 15th Oct 2018, 7:20 pm   #4
G6Tanuki
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Default Re: Marantz SR4200 soak testing (!)

In times-past I was involved with running a few thousand PCs for a large financial institution.

"Tea/coffee-with-milk in the keyboard" was a regular issue. Back then a new genuine IBM Model-M keyboard cost 100+ so we'd save up the beverage-contaminated keyboards and - out-of-hours friday night - stick them through a 'cool' cycle in one of the staff-restaurant's industrial dishwashers, using a squib of an industrial detergent called 'MS202', then stack them over the outlets of the open-plan-office's airconditioning outputs for the rest of the weekend.

We got around an 80% recovery-rate. But we still billed the clients for a new keyboard....!
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Old 15th Oct 2018, 9:49 pm   #5
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Default Re: Marantz SR4200 soak testing (!)

Back in the early seventies when I joined HP I had a 'Microwave Division preferred parts manual' parked on my bookshelf. It contained spec sheets for all the HP numbered parts I'd likely need.

Every one had the line "Shall survive a dishwasher cycle with Calgonite detergent"

Our family had never had a dishwasher. I'd never heard of "Calgonite" I did wonder if it was something that Superman ought to be wary of.

But no, it meant that parts were expected to be proof against a how wash and rinse cycle after acid flux foam and wave soldering. And yes, the wash used commercial dishwasher detergent.

Electrolytics had to be well sealed, the detergent was tough on aluminium, tough on the causes of aluminium! Pots came with a tear-off plastic seal over the screwdriver turned bit.

I now treat the dishwasher as a service aid, but might add a bit of latex solder mask to bits that need a temporary seal.

I'd have been really impressed by that amp if its display had diagnosed the contaminant.... "Tea, Earl Grey, Hot" or something like that.

David
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Old 16th Oct 2018, 10:28 am   #6
wireless_john
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Default Re: Marantz SR4200 soak testing (!)

What a good story! Never thought about using a dishwasher for this sort of thing - I'll remember that for the future!

John
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Old 17th Oct 2018, 8:14 pm   #7
kevinaston1
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Default Re: Marantz SR4200 soak testing (!)

On finding myself redundant from the music industry, with only a couple of years to retirement, I took a job working for a small AV company. One of my first jobs was the overhaul of a large audio mixing console which looked like it had been stored in a coal pit.


After sorting out the hundreds of dry joints and cleaning/relubricating potentiometers, I had a working unit which was nice and clean; but the hundreds of coloured knobs were in a right state. They went home with me that night, where I put them in a wash bag and put them in the washer.

The next day, the boss could not believe how well the unit had cleaned up; he was convinced I had found a new set of knobs for it.


Kevin
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