Modular Synth Panels

Ouch, that hurts... :-)

What I usually do is get a good DMM (a Fluke 45 in my case), and just  
measure the resistance across all the caps. Yes, we're talking 10's of  
milli-ohms difference here, but the lowest one(s) are easily found. If  
you follow a power/gnd pair of traces, you can even see if you're  
getting close because the resistance is getting lower and lower. Also  
works when finding a bad chip with an internal short.

Ben


On 28 sep 2009, at 07:43, Dave Halliday wrote:

> The tants had a really good high frequency response IIRC -- good for
> filtering out noise as well as 60Hz.
>
> My technique was to follow the power buss on the circuit board and  
> find an
> arbitrary mid-point that was away from any critical wiring and use a  
> dremel
> tool to sever it.
>
> Find out which half had the short and proceed until you had three or  
> four
> caps to test. Unsolder one lead and lift the leg and test the power  
> buss
> again.
>
> I could usually find a dead cap in 10-15 minutes. A good friend of  
> mine
> nearly fainted when I dug into his Odyssey although he had thought the
> problem was in the power supply and had disassembled it. Took me  
> longer to
> put that together than to find and replace the dead tant.
>
> Scrape the traces on each side of the dremel cut and solder a bit of  
> solid
> wire to bridge the gap.
>
> Dave
>
>> -----Original Message-----
>> From: ModularSynthPanels@yahoogroups.com
>> [mailto:ModularSynthPanels@yahoogroups.com] On Behalf Of
>> Richard Brewster
>> Sent: Sunday, September 27, 2009 6:32 AM
>> To: ModularSynthPanels@yahoogroups.com
>> Subject: Re: [ModularSynthPanels] ChaQuo Wiring Question...
>>
>> I'd not use any tantalum caps.  Their main benefit is the
>> smaller size
>> vs electrolytic of the same specs.  They also cost more.  I
>> have one of
>> my own tales from the days of yore.  I used to hand-build audio and
>> video synthesizer circuits in the seventies.  These were all
>> prototypes
>> and needed plenty of power line bypassing.  At one point we
>> used a bunch
>> of 100 nf Panasonic tantalums.  We might put 20-30 of them on
>> a board.
>> And yes, they did fail by shorting out.  But unless it fried
>> and burned,
>> we could not tell which one failed.  So, one by one, each had to be
>> clipped out until the bad ones were found.  Then all the "good" ones
>> that had been removed too had to be replaced.  Needless to say, we
>> stopped using the tantalums.  If you do want to use some, I'd
>> recommend
>> ones with at least a 35 volt rating.
>>
>> Richard Brewster
>> http://www.pugix.com
>>
>> mcb, inc. wrote:
>>> On Sat, 26 Sep 2009, Scott Deyo wrote:
>>>
>>>
>>>> Yeah, I torched a polysty on mine too. That's probably the
>> culprit. Polysty's
>>>> and tantalums are bummin' me out lately...
>>>>
>>>
>>> Speaking of tantalums, came across this interesting tale from
>>> days of yore:
>>>
>>>
>> http://www.designnews.com/blog/Made_by_Monkeys/23362-Do_You_Wa
>> nt_Butter_On_Those_Capacitors_.php?nid=3073&rid=398497
>>>
>>> --
>>> Monty Brandenberg
>>>
>>>
>>
>>
>>
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