jbl 6260 circuit question

[NickH]

Does anyone know what op amps are used in the front end of the 6260?

Thanks,
Nick

[hjames]

Does anyone know what op amps are used in the front end of the 6260?

Thanks,
Nick

See page 31 - http://www.jblproservice.com/pdf/Vin...6260manual.pdf

According to the schematic it says either Op amp type 7L084 or 71084 (its kind of a smeary PDF)

Based on some googling, I'm guessing its 7L084

[NickH]

Thanks Heather.

I did download the manual but I didn't recall seeing it on the schematic. Or maybe I just couldn't make it out.

Thanks again,
Nick

[hjames]

Thanks Heather.

I did download the manual but I didn't recall seeing it on the schematic. Or maybe I just couldn't make it out.

Thanks again,
Nick

Bottom left corner of page 31 ... but as I said, it is blurry.

[Baron030]

I agree the manual looks very blurry. But, to me the font looks to be Italic. So, what appears to be a “7” could very well be a “T” instead. And my google searches do not turn up any 71084 or 7L084 op-amps. On the other hand, a TL084 is a common 4 unit op-amp. If the chips appear to be 14 pin dual in line packages then most likely to be they are TL084 chips.

Here is a Texas Instruments product Link: http://www.ti.com/lit/ds/symlink/tl084.pdf

And where you can find a replacement part if that is what is needed: http://www.mouser.com

Mouse Part # 595-TL084CN

Baron030

[NickH]

Well I'll find out tomorrow for sure since mine will be delivered by FedEx sometime Saturday. Tl084 would make more since being the old school opamps prefix. But I find it odd that the 6260 uses a different opamp then the 6290 which by the manual looks to be a tl072. The only person who probably knows this by heart is subwoof. I'd love to find a discrete opamp that will work in its place.

I guess I'll find out soon.


Thanks for the help though,
Nick

[Allanvh5150]

Go with TL084.

Allan.

[NickH]

I'll have to do some research and find a modern superior opamp that will work in its place.

[martin2395]

Nick, you might want to take a look at Burson and Audio-GD's offerings, they do have discrete opamps in their lineup but I don't know the details.

[NickH]

Hi Martin,

I've been looking at bursons discrete opamps. But they don't make a quad though. I got the amp today. I've got to put it on the bench tomorrow. It doesn't seem to be working at 100%. I hooked it up to the speakers and the output seems to be low.

I talked to my friend who's an analog engineer he actually said the tl074 would be a good upgrade. But I'm leaning more toward the opa4134. I thinking a full electrolytic capacitor change is also in order.

I'll have to look into audio GD.

Nick

[Allanvh5150]

Each of the 074 and 084 have their own merits, however, in this application, the 084 is more than adequate.

Allan.

[NickH]

I've bought the parts to overhaul this unit. All new electrolytics except for the power supply caps. Mouser didn't carry the right type. Mundorf makes a cap that I think will fit but I'm not certain though. I'm replacing all the others with nichicon muse caps. I know its probably over kill, but they were cheap. I'm also pulling the tl084 opamps and putting sockets in there place. I will be trying tl074's in here first as they are a bit better noise performance. I plan to eventually put opa4134's in there place but they need a adapter since there smt.


I checked the bias on the unit. One side was in spec but the other was over .4 volts. I lowered it to .280 which matches the other channel.
The one thing I found odd is if I was monitoring the voltage between the base and emitter on one channel if changed that channel input attenuation setting the base to emitter voltage would change. But I didn't do the same on the other channel. I'm sure this is nothing unusual but it seemed a little odd to me.


Other then that the units in pretty good shape. I'm hoping it will serve me well for many years after the overhaul.

Just wish I could find 2 knobs for it though, or at the very least the security covers.

Nick