Where to get chip for Ross Phaser?

[eric]

Hi,

Does anyone know where to get a single AM97C11CN chip (it's an AMD chip) for a Ross Phaser (an old orange one)?

They are available in bulk, but I only need one.

Thanks for any help.

[Enzo]

Without me looking it up, what is the chip? What does it do in the circuit?

[eric]

I don't know what it's function is...

...just that it's a 16-pin AMD chip. Also, there are two horizontal wavy lines and the number 929 on it.

While I'm at it, there are also four RC4558P chips (with AB/PEP-3 and with the number 910 written vertically) .

The phaser works, but there's some slight distortion when hitting strings hard, so I thought I would try new chip(s).

[Enzo]

I suspect it is not the chips then. More likely weak power supply filtration - how old are those filter caps? Or low voltage. You might be overdriving the input. Stuff like that.

[xFallen]

Hi,

Does anyone know where to get a single AM97C11CN chip (it's an AMD chip) for a Ross Phaser (an old orange one)?

They are available in bulk, but I only need one.

Thanks for any help.

I am not sure what makes you think it is an AMD chip. Is AMD marked on the chip somewhere? The squiggley lines constitute a trademark of National Semiconductor.

A quick look through my old CMOS references indicates it was manufactured by NS and is an analog quad SPST switch. No cross reference that I could see. The 'C' in 97C11 is typical of CMOS devices since many non-CMOS devices were often the same p/n but without the 'C'.

As to locating one, google or other search engine. Sometimes the smaller companies have this oddball stuff and they may not have inventory published on the web. For example, dckits.com has been known to have some goofy things on the shelf from time to time. While they are just a hole in the wall operation they have also been around a long while. All inventory is not on their website, in fact most of it is not. There are many smaller places like this that may have old inventory.


Barry

[eric]

Thanks - I think I've confused things by referring to AMD.

A web site I searched showed one in inventory manufactured by AMD, and I assumed that's what the "AM" prefix referred to. But on further investigation, it seems the AM97C11CN chip could be manufactured by any of Advanced Micro Devices, Atmel, Datel, National Semiconductor, SGS-Thompson ST Microelectronics, TI Texas Instruments.
So as you point out, this one is probably from National Semiconductor.

When I contact some distributers, they usually have a minimum order of $200 or $300. I'm not sure what a reasonable cost would be for just one, but I wouldn't want to pay that much.

[eric]

Thanks for the suggestion.

Actually, I have now discovered a working AM97C11CN chip in another device I have. I could swap them out as an experiment to isolate whether it's the chip. But the chips seems very well seated in their sockets and I don't want to risk damage.

Is there a safe technique to remove the chip from it's base?

(Perhaps I shouldn't be doing this myself, eh?)

[Mark Hammer]

The 97C11 is long-since out of production. It is essentially a JFET transistor array, not unlike the LM3046 bipolar transistor array or similar devices. As such, it shares all the advantages and disadvantages of JFETs in a phaser. One of the disadvantages is distortion. One of the advantages the 97C11 had was that the JFETs are matched, such that more even sweep is produced.

Here is the schematic of the pedal in question, or at least the schematic of one of the pedal issues/versions: http://www.home-wrecker.com/ross_phaser_orange2.png

One of the things you will see here is a 10nf/10k network between the gate and drain (e.g., pins 9 & 10, 16 & 15, etc). This network is known to reduce FET distortion in response to peaks, so I suspect the pedal is already designed to reduce distortion as much as possible. That means that swapping out chips will likely do little to improve the situation.

One thing you might try instead is to attenuate the input signal a bit, and keep the signal level away from the critical clipping point. Then, complement that with a slight boost in the output stage to maintain overall signal level. The attenuation up front might be something like a 4k7 - 10k resistor in between C1 and where it connects to R2. That's not a lot of attenuation but the intent is to keep the overall signal level as hot as is possible to keep S/N ratio manageable. Remember that the circuit itself adds noise so the hotter the input signal the less noise will seem to be added by the circuit. The complementary boost could be as simple as adding a 1-1.5k fixed resistor in series with R29. A 1500pf cap in the feedback loop of U4A could also help to keep hiss under control.

[eric]

Thanks for the detailed info.
One thing I mentioned was that I do have another 97C11 to try - but I was concerned about how to replace it. I didn't want to damage either of them.

Does the chip just pull off the base?

Thanks.

[Enzo]

The chip is either soldered to the board, or it is in a socket, and the socket is soldered. A socket would be readily noticable. If it is socketed, then it pulls straight up and out. DOn't use your fingers, as one end will pop free before hte other and the chip will yank out and bend hte pins. Get under each end with a small screwdriver or pointed object and gently pry each end up, alternating ends until it is free, THEN pick it up with your fingers.

If the new chcip is actually new, the rows of pins may slant outwards some, to fit in a socket or holes on the board, the rows of pins need to be bent straight down.

[bizzle]

Problem with later version of Ross Phaser

My Phaser is the later version with three LM13600N chips and one RC4558N chip. When switched on, I can hear the phased output, but it is very quiet. I would imagine there's a problem with the amplifier circuit, but I don't really know how to troubleshoot it. I'm pretty sure this is the correct schematic: http://www.tonepad.com/getFile.asp?id=99. Can anyone provide some insight as to how to go about troubleshooting the problem? I'm armed with my pocket multimeter...

[Mark Hammer]

Pop over to the DIY Stompbox Forum. There are enough folks there who have built the Tonepad clone that they can help you out.

[bizzle]

DIY Stompox is slow in approving new members. Any info while I wait?

[Mark Hammer]

The slowness is a holiday-related thing. Try again now.