990 INSIDE PICS

[ijr]

http://img.photobucket.com/albums/v436/IJR/9904.jpg
Hehe... audio archeology...
:grin:

 

[gyraf]

Great picture series!!!

 

[ijr]

A little question.
Are these yellow cap's COG type???
(newer have see before what is COG or NPO caps ;
use all time silvermica's from surplus (have 'em ~10 kg )
and very happy :razz:

 

[Marik]

Eloyim adirim!
Od ehad! Lo maspik lanu butcher ehad....
..... sichakta gam ze :green: :green: :green:

Jeeez!

Don't we have another butcher :shock:
CJ, I knew it is contengious :thumb:
:guinness: :guinness: :guinness:

 

[NewYorkDave]

Yes, JH does use C0G/NP0 caps in the 990.

He's not at all secretive about what's inside. After all, the circuit is published and well-known. In fact, he had some unpotted ones sitting on his table at AES for anyone to inspect. He probably would have sent you a photo if you asked, although I'm sure unpotting the module was a fun exercise :guinness:

It would be hard to build an equally good or better version at home for less money than he charges (about $50 each).

http://www.johnhardyco.com/pdf/990.pdf

 

[Flatpicker]

[quote author="NewYorkDave"]It would be hard to build an equally good or better version at home for less money than he charges (about $50 each).[/quote]Yes, I don't see how he makes enough money on them as it is.

BTW, Why did you hack it? Was it not working?

Anyway, thanks for posting. It's interesting to see the insides. (pssssst... would someone send ijr a 2520? :wink: )

 

[ijr]

Eloyim adirim!
Od ehad! Lo maspik lanu butcher ehad....

Ahi, freakim ba shabat lo mebazbezim zman stam!
(brother, freaks are not loose time on shabats too!)
unpotting the module was a VERY fun exercise
)))
You right, home makin' 990 will cost same money
(~$20 parts+time...)

BTW, Why did you hack it? Was it not working?

1. Yes, get it dead )
2. Never see before how those COG's looks,
and the fatest way was hack one 990...
:razz:
But really, these yellow ones are COG???

 

[NewYorkDave]

What language are you guys speaking? Hebrew?
Switch to Yiddish so that I can join in the fun!
(Actually, I don't really know Yiddish either, except for the little bit that most every New Yorker knows). :wink:

 

[ijr]

Ya, it was hebrew... 'bout iddish, I know only 5-10 words, not usefull
in normal society ))

 

[Marik]

Ahi, freakim ba shabat lo mebazbezim zman stam!

Sababa! Gam ani lo aiti fraer. :grin: Shabatot avadti b'shmira v'kibalti maskoret kfula. Ben a'siurim asiti kol minay ma'agalim v'tikunim. Ma ze a'haim a'elu :sad: :evil:



[quote author="ijr"] 'bout iddish, I know only 5-10 words, not usefull
in normal society ))[/quote]

Same here

 

[bblackwood]

Anybody know how to hack open a 2520? I have a few now and wouldn't mind donating one to science, so to speak...

 

[ijr]

Some time ago fixed 525a comp...
Old version, even have elsewhere pcb scan
and redrawn fragments of schem. -it different a bit from "c"ver.
One of opamps blew out, but (what idiot!) I returned it to customer...
Figured out hard epoxy... not easy job, but (IMHO) possible
to hack too...
@Marik:
ken, ah sheli, shmira ze hara shel' avoda....avarti gam at ze
takzhe mozhno prikalyvat'sya po-russki ili, tol'ko rebyata ne pojmut; davaj perejdem na bolee international'nyj yazyk )

 

[Flatpicker]

[quote author="ijr"]But really, these yellow ones are COG???[/quote]Yes. They are available in either axial or radial versions. They look just like any other X7R or Z5U ceramic caps.

 

[JustinS]

Hey the whole amp is mounted upside down to the way I have always thought... interesting. I wonder what the reason is for having the pins on the component side vs the other way... Anyone got any ideas??

Justin.

 

[ijr]

Hey the whole amp is mounted upside down

I wondered too why circuits containing 990 sounds great if placed upside
down and have this strange character in sound if placed right!
More transparent highs, better bass responce...
Still not tried 'em on Rane pseudoaccustic infector, but result must be great!
:razz: :razz: :razz: :razz: :razz: :razz: :razz:
And, finally got answer on my question!
YES, they are COG!!!!!
(gotta buy a buncha of those yellow yellow yellow COG's!!!)
:sam: :sam:

 

[Bryson]

Here's an older Jensen 990c with lager footprint due to load isolator on board.

http://home.earthlink.net/~redbugg/all/jpgs/990c.JPG

 

[bluebird]

Still not tried 'em on Rane pseudoaccustic infector

ijr... your a nerd :green:

 

[ijr]

'cuzz me.. what is "nerd"?
(my english... can be better )

 

[alk509]

Hey IJR,

I can't tell from the pictures... Are there any diodes thermally coupled to the outpt transistors? We were trying to clone some of these puppies a while ago, but neither me nor the other person making them (I think it was either Rafael or Peter C) could keep them from overheating and blowing up... :sad:

I now have a copy of the original AES paper and it says something about clamping the output transistors with their biasing diodes (as opposed to with each other). I'll actually sit down and read it and I'll come back with more...

Peace,
Al.

PS:
Nerd, nurd (noun, slang): 1. A foolish, inept, or unattractive person. 2. A person who is single-minded or accomplished in scientific or technical pursuits but is felt to be socially inept. 3. A Group DIY member :green:

 

[Flatpicker]

[quote author="alk509"]...but neither me nor the other person making them (I think it was either Rafael or Peter C) could keep them from overheating and blowing up...[/quote]It was Peter C. I was wondering about that - did you guys have big heat sinks on the output transistors like the ones shown here? I bet the epoxy helped to distribute some heat, too.