Oh! IC

[Reeltarded]

Long story short.. guy covered his work by dabbing a color coded dot on top of the ICs he used in my Hammond B3 chopper's custom preamp board.

There are 4. 2 with green dots, one red dot, one yellow dot. Nice. What a dick.

Is there any hope of discovering a range of IC series that would be purposed for such a thing? Close would be close enough, I AM GUESSING.

I guess a lot. I guess better than chance, on average. Too much chance and I am a loser!

[vibratoking]

This may already be obvious, but if he did not grind off the factory marking, you could remove his marking and see what is underneath. If the ICs are standard 8 or 16 or whatever pin DIP packages, then there is little chance of identifying them without a factory marking. There are no telltale signs other than the factory marking that I am aware of. Totally generic without the marking.

No chance of contacting the offender? If he won't give you the information then at least you will have the opportunity to call him a dick directly. Won't help your problem, but it might make you feel better.

[Aurora]

You could try to pry the whole blob off with a scalpel or thin knife....
depends on what kind of paint he used... you may be lucky....

what kind of packages? Only 8 pins? Is this just a preamp, or are there any other functions on that board? Picture?

[Reeltarded]

He's dead.. I dare say if he weren't already I would see about that.

8-pin and socketed board. It is a simple preamp. I am guessing that they are either TI or Hitachi, and that is as far as I will guess. The parts are cleaned of any markings, and then dotted with freaking acrylic nail polish or something like it.

I think I need a primer on where to start as far as function goes. If I guess low I can go up? No? I am going to Radio Shack in the AM to try for a miracle.. I suppose.

Wish me luck.

Here is to Bill Beers, brilliant genius, Hammond hater. Cheers.

[Structo]

If you have any other junk chips on hand, experiment with solvents to see if the factory marking will survive the solvent.

I would try acetone or lacquer thinner first.

[Reeltarded]

The markings were sanded off and he dabbed paint on to keep track.

Radio Shack shows 2 op amps 8-pin.

What would happen to the rest of the circuit if I chose poorly?

[johnnyreece]

The markings were sanded off and he dabbed paint on to keep track.

Radio Shack shows 2 op amps 8-pin.

What would happen to the rest of the circuit if I chose poorly?

I get a vision of something like this from Indiana Jones (He chose...poorly...and yeah, the info's there, just read through it a bit ): http://www.benjamingran.com/2012/01/27/ ... up-comedy/

[Reeltarded]

lol

I thought of the same scene as I said it. Yes.

[Aurora]

Then you're in for some diggin'...
First you have to determine wether they are singles or duals...
Does the amp have a dual voltage supply? Singles usually have power input on pin 4 and 7 ( neg-pos), duals on 4 and 8....
TL071 and 072, single and dual resp. could be a substitute...
Look up the datasheets on www.ti.com and see what you can make of it...

EDIT: Does the thing have more than one input channel...?

[Aurora]

BTW - a short description of what this board does would help...... how old is it???? Might give a clue as to what ICs ar used.

[vibratoking]

I would measure what pins the power is on and then try to substitute a sensible part like TL071, 072 as suggested. Part could also likely be Burr Brown, which is now owned by TI, I think.

BTW, what makes you think the opamps are bad? Those things don't blow often IME. Have you scoped inputs and outputs?

[Reeltarded]

This is info I can use.

No, have not scoped anything. The Hammond specialist in this area looked it over and told me this is the same thing that happens when the chips go on another preamp that he *is* familiar with. That is all I have to go on, barring a massive pile of money thrown at something that has to be so simple.. yet nearly impossible to guess right he first time.

It has to be mid-eighties manufacture. I read a post on another forum where someone said in '07 that the parts were common and at Radio Shack. They only carry 2 models of 8-pin op amps under their brand. They have them here in town. I am going to look it over once more in the morning, and throw the big switch...

If the lights dim... say a little prayer. Jesus will say, "Hey! You aren't supposed to be here yet!" and I will reply, "Where is Bill Beers?".

[Structo]

What is a chopper?

Is that a chopped down B3 cabinet?

I think Vibratoking's idea has some merit.

If you can figure out the pinout, it will go a long way to identify them.


For example a TL071 is a single opamp.

[img:351:195]http://www.synthdiy.com/files/2004/tl071a.gif[/img]

Where as a TL072 or 4558 is a dually.

[img:377:352]http://www.media.supplyframe.com/produc ... pinout.jpg[/img]

[Reeltarded]

Yes, a chopper is a portable B3 made from a normal B3.

THANKS TOM! That makes so sense even caveman do it! I am pretty sure they are singles because of neaky spicions, but nice to have a ref of what the heck look at, unga..

[catears]

Not so fast. There are many types of components that are made in DIL packages aside from your normal/what would pop into your mind at first glance "operational amplifier". Single/dual Op amps are most common in the 8 pin DIL, but if they are color coded, it's probably for a reason.

I would suspect OTA chips to be in a Hammond type deal, especially if there is any leslie sim going on . You may have a voltage regulator/doubler in there as well. Try putting a dual op amp in place of an OTA or doubler= square peg, round hole. Like others said, if get your voltages you can try to guess/match. Personally I would trace the signal along with metering voltage (if the unit still works), then socket the IC holes and choose wisely. You probably wont hurt the circuit if you go plugging in random sh*t, but there is a chance you could ruin the part. The great thing is you are dealing with far less current/voltage with a circuit like that, so you can work on it while it's alive with little caution. Just don't jump in the bathtub with it

Post some pictures of the top and the back of the board if you can, it might help. Best of luck!