[sdiy] finding a short in a Yamaha CS-50/CS-80

[Bob Weigel]

I just told him an easier way.  Get a 40 dollar HP milliohmeter off ebay 
:-) This method really does speed up finding the offended shorted 
component.  What is that old thing..HP3490A.  I got one for 40 bucks as 
I recall and it needed some filter capacitors but wow it works great on 
sniffing out those kinds of problems. -Bob

Csaba Zvekan wrote:

>>>> Am 28.10.2008 um 21:38 schrieb jpitt at fhcrc.org:
>>>>
>>>>> Do I have to desolder every single +15 and -15 line off every  
>>>>> board  to track down the short or is there an easier way?
>>>>
>
> jpitt
>
> Yes, you have to. Then measure it board by board. Narrow it down to  
> the board. Then measure the caps first. I don't know any other way.
>
> Csaba
>
>
>
> Bob,
>
> Which exact YAMAHA custom IC do you need ? The IG00156 or if you are  
> lucky it's just another IG00151 ? Perhaps it's a bad cap in the VCF  
> section ? Have you checked ?
>
> Csaba
>
> On Oct 29, 2008, at 7:35 PM, Bob Weigel wrote:
>
>> OH yeah absolutely check the tantalums for shorts.  The worst  
>> problems I've seen in these units though were from when the power  
>> supply of a cs-20m had a regulator problem where it overvoltaged  
>> everything.  I'm still dealing with that.  Anyone have a vcf they  
>> want to sell me?  The vcf leaks slightly making a crappy irritating  
>> subtle noise. I need to scrap something else to get VCA's and a  
>> VCF.  If you ever see an organ getting tossed from that era SNAG IT  
>> because some of the parts are the same. 1976 is too early; all  
>> transistor usually on those organs.-Bob
>>
>> Csaba Zvekan wrote:
>>
>>> Ingo is right check the tantalum capacitors . They are all over  
>>> the  place. I remember having a short on one of the TBS boards.  
>>> Check TBS1  or TBS2 boards there are plenty of tantalum 0.33uF s  
>>> there.
>>> It's a good practice to replace all of them tantalums anyway today   
>>> it's this guy here tomorrow on another board. If you know what I  mean.
>>> Is it a CS-50 or CS-80 ?
>>>
>>> Csaba
>>>
>>>
>>> On Oct 29, 2008, at 6:05 PM, Ingo Debus wrote:
>>>
>>>>
>>>> Am 28.10.2008 um 21:38 schrieb jpitt at fhcrc.org:
>>>>
>>>>> Do I have to desolder every single +15 and -15 line off every  
>>>>> board  to track down the short or is there an easier way?
>>>>
>
> jpitt
>
> Yes, you have to. Then measure it board by board. Narrow it down to  
> the board. Then measure the caps first. I don't know any other way.
>
> Csaba
>
>>>>>
>>>>
>>>>
>>>> First thing I would do is search for anything that gets hot.   
>>>> Careful, the offending component probably gets *very* hot.
>>>>
>>>> If this doesn't help, I'd take a close look at all tantalum   
>>>> capacitors (if there are any). I've seen failed ones that looked   
>>>> fine but had just a tiny silver ball (like a solder blob) on them.
>>>>
>>>> Ingo
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