[sdiy] Buchla 259a and LF13331 substitute

[mark verbos]

On Jan 8, 2009, at 12:14 AM, Dave Leith wrote:

> Thanks everyone for all the info. I do already have some LF13331 to
> experiment with.
>
> Mark I have a question for you. You recommend the DG201 as a good
> replacement (as does a cinematronics vector monitor repair guide that
> I found thru internet research) What I'm puzzled about is the both
> chips have Logic 0 < .8V and Logic 1 as > 2.4 The LF13331 is normally
> open but the DG201 is normally closed, (DG202  normally open) What am
> I missing here?

You're right,  DG202 is the one. The harris data sheet shows the  
switches open in the pin layout for the DG201, but it's the normally  
closed version. Jerks.

>
>
> The other interesting detail from the cinematronics vector monitor
> repair guide is that they say a major cause of failure (for them) with
> the LF13331 is when the the -15 supply comes up faster than the +15
> and they recommend a diode between pins 4 -5 of the LF13331 to
> protect. I'm using a Power One supply - I wonder if this is necessary?
>

I've never heard of that, but it could work. I've seen lots of those  
chips die in buchla modules. I think the other models of switches are  
more reliable.


Mark



> Dave
>
> On 1/7/09, mark verbos <mverbos at earthlink.net> wrote:
>> be careful.
>>
>> I have worked on many 259s. I own one that was built by a 3rd party  
>> and
>> this person used DG412s instead of LF13331Ns. In theory, these are  
>> better,
>> faster, lower on resistance, but they caused little glitches that  
>> went away
>> when replaced with actual LF13331Ns. I'm not saying that there's  
>> anything
>> magic about those chips, just be sure to use a replacement that is  
>> similar
>> spec'ed and not "better."
>>
>> I recommend DG201 as a replacement in the 259. The pinout is almost  
>> the
>> same, sadly a couple pins are rearranged.
>>
>> Mark
>>
>>
>>
>>
>> On Jan 7, 2009, at 2:16 AM, Aaron Lanterman wrote:
>>
>>
>>> On Jan 7, 2009, at 2:09 AM, David Ingebretsen wrote:
>>>
>>>
>>>> This page,
>> http://mysite.verizon.net/res8aiig/ICparts/ICparts.htm the
>> LF13331 for sale, a bit pricey, almost $12.00 for singles, but I  
>> don't
>> really have a feel for what a good price would be for one of these  
>> chips.
>>>>
>>>>
>>> No reason I can think of to use a LF13331 when a modern DG chip will
>> probably be better anyway.
>>>
>>> I remember Peter Grenader giving the same recommendation (IIRC).
>>>
>>> - Aaron
>>>
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