550B schemos?

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QUEEF BAG

Well-known member
Joined
Jun 12, 2009
Messages
563
Location
Seattle
i find myself in need of a schematic for a 550B
the only schematic i have found so far is a hand drawn
doc that only has the audio path. (and a bit harder to follow than
a regular schemat)

With A-2 in the -16 volt rail falls to about -1.3v
take out the op amp and volts are good.
same thing with a new op amp too.

also still looking for a schemo for the (evil) 550A-1

thanks
 
here is a 550A, it's not the same but close enough it might help you.


550Aschem.jpg
 
thanks pucho-

i have quite a few api schems, including that one, & i guess yer right
i'll just use that one.

i'm sure we all could dig those other two though

as a somewhat avid collector, still havn't seen the A-1 drawing

as a somewhat half assed tech i could use them

wow. that all sounds rather lazy of me.

i hate it when i find my self procrastinating on some pieces,

& it's probably worse the better you are at rationalizing with yourself.

ok - back to the shop.
 
Curmudgeonly, your post makes me want to find every other product with the designation 550-B, since you made me figure out what the f&% you were talking about by not saying API.  No, I have no info.  ;)
 
yeahhh....i kinda thought about that, shoulda gone w/my gut feeling.

550B is up and running again, only needed a new op amp.

550A-1 is still down about a dB or two with the eq in circuit.

haven't gotten into API repair much until the last year or so and
am a little slower than i should be.

Doug- it would just be stuff like cessna aircraft,coleman stoves, kawasaki motorcycles,
ammo loading machines, 8 ton crawler/dozers, samsung software, air circulators, etc.
 
walrus-

yeow! fantastic!

thanks, those seem to be some of the harder ones to find,
been lookin' for a while.

i was a little suprised to see how much the revision E eq that
was on my bench looked like the 550L that is in the legacy consoles

thanks again
 
pucho812 said:
I have noticed that those 2520 have a high faliure rate, More often then not I have fixed api issues by replacing those DOA
In most older units there is not a lot else to fail!  :)
 
yeah, if you think those are bad, The original black 2510 op amps in the legacy eq
suck pretty hard, in a hot environment the little pins separate from the circuit board.
they make blue dipped ones now that seem to be lots better.
 
There's the Urei 550 for one:

http://www.uaudio.com/webzine/2005/may/graphics/analog%20obsession/550-A-close-up.jpg
 
Certainly far fewer of them out there, but that tends to be the stuff I obsess over. 
 

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