Unknown IC - any one have a clue what it is ?

[Rasputin_2]

I have a samson ML140 and I can't find a schematic for it any where. Does any one have a clue what this IC is (it has 8 legs) ?



There are four channels and each channel has one of these IC's. One channel is hissing and the only thing I could find wrong was one micro phonic cap and I replaced it. That leaves this IC, but the IC is unmarked and with out a schematic, well, I'm not sure just what it is or how to test it properly. I have used the ohm setting on my multimeter to check it against the other IC's, they all seem about the same, but whether that is telling me anything with this IC I haven't a clue.

Thanks...

[Jazz P Bass]

It looks like an inline op amp.
If you remove it, the part number is most probably stamped on it.

[Enzo]

I agree, if you pull it, there likely is a number on it. Might be hard to see from this angle.

It is a SIP, for single inline package , as opposed to a DIP for Dual inline package.

And I doubt it is anything special, just a dual op amp probably. They used a SIP for space savings.

[Rasputin_2]

You both are correct. I couldn't see anything on it for nothing when it was installed. But, once I pulled it it was indeed labeled. The NJM2068L is a high performance, low noise dual operational
amplifier. Thanks for the quick replies. I was hoping not to remove it, but what do you do. If I find this is causing the noise or not I'll try to remember to update this thread. I've found the data sheet, now to test it. Thanks, again.

[Enzo]

I looked at other Samson models after posting earlier, and saw they used 2068's a lot, so I was about to suggest 2068L.

Mouser has them in stock for 60 cents.

http://www.mouser.com/ProductDetail/...FL8KNwD4IVM%3d

If you have other SIP dual op amps in stock, they will probably work just as well. I looked at my inventory and happen to stock 2068L, but I also found 4580L, TL072L and a couple other odd ones, and would use them if i had to. 2068 is a "low noise" type, but often as not, regular op amps sound as clean.

[Rasputin_2]

Thanks for the info Enzo. I bought a couple from mouser (sorry, edited it, had samson, should have been mouser). The static/noise issue is directly related to the tone controls of the one channel and the volume control of that channel and the other channels have no effect on it. If you turn the three tone controls down to zero the static/noise pretty much disappears. This is the first time I've had this issue and it not be a pot, cap, resistor type thing.

[Jazz P Bass]

It may very well be the controls.

Try a little DeOxit dribbled down the control shaft (as they are probably sealed pots)

[Rasputin_2]

I cleaned the pots a couple times with DeOxit and it didn't even begin to change the static/noise. The pots seem to be in great shape, but if the 2068L doesn't fix it I guess the next step is to replace the tone pots.

[Enzo]

Not likely pots. Pots make noise when you turn them, if they are dirty or worn. But I don;t recall one ever making noise just sitting there.

If you are itching for this, swap this IC for the similar one in another channel. Did the noise move to the other channel with the IC?

[Rasputin_2]

To be honest, the IC's were so cheap I just decided to buy two; figured I put one in and have a spare. I'm not thinking it's the tone controls either, but. I have seen the little variable resistors used to adjust voltages get noisy, but not like this, and the preamp board has none on it and even if it did it'd effect more than just the tone controls on one channel, so. Will see if it's the IC is the issue here soon.

[nickb]

I have had some success using freezer spray to narrow down the problem. It seems to work about 50% of the time. Sometimes the change is slight so you need to listen carefully.

[Rasputin_2]

Someone else told me about that freezer spray once before, but I have never used it.
Is there any you prefer or ?
Guy I knew said they used it in his dads shop a lot to find issues.

[Enzo]

Any proper shop should have a can of it. Brand is not important, any more than the brand of ice cubes you buy from the store to chill your beer matters.

Circuit chiller is useful especially where a circuit changes as it warms up - we can unwarm it in an instant. But also even in non-thermal situations, the thermal shock of freezing can reveal iffy parts.

Plus is is great for removing hot melt glue. A quick freeze of a glob of hot melt makes it brittle and you can shatter it and it crumbles away easily.

[Rasputin_2]

That's pretty much what guy that worked at his dad's shop said. I guess I need to get off my butt and get some. Ya, proper shop I am not; hobby, back room, for the hey of it I am. But, it sure sounds like the Circuit Chiller would be something nice to have on hand.

Edit Starts -------------------------------------

Well, I ordered two of these: NTE RX100-10

Hopefully I got the right goods the first time

[nosaj]

Any proper shop should have a can of it. Brand is not important, any more than the brand of ice cubes you buy from the store to chill your beer matters.

Circuit chiller is useful especially where a circuit changes as it warms up - we can unwarm it in an instant. But also even in non-thermal situations, the thermal shock of freezing can reveal iffy parts.

Plus is is great for removing hot melt glue. A quick freeze of a glob of hot melt makes it brittle and you can shatter it and it crumbles away easily.

Is there a difference in freeze spray versus using canned air upside down?

nosaj