SAD1024 & SAD512

[thedefog]

Got another SAD question for all of you,

I have an SAD1024 with a bad B channel and was able to get a hold of an SAD512. I had hopes of wiring the working 1024 channel in combination with a 512 to restore a Ross Flanger. However I must be doing something wrong.

I have pins 1, 4, and 10-16 tied to GND on the SAD1024, and pins 1, 4, 10, 13, 14, 15 & 16 tied to GND on the SAD512. Pins 11 and 12 on the 512 are connected to Vdd- as instructed in the datasheet. Vdd and Vbb are jumpered between the two ICs, as well as gnd, then I just ran bus wire to create the respective pins. My pin out wiring has been checked over multiple times. No bridges, etc.

The guitar signal now passes through when the effect is engaged (it had no output previously due to the bad second channel on the SAD1024), but I still have no flanging effect. I checked voltages on the chip and scoped the clock, and it looks healthy. Am I not supposed to ground all of the unused pins on the bad channel of the SAD1024?

[Govmnt_Lacky]

According to the last page of the SAD1024 datasheet from Reticon:

"... In some instances, SAD1024 devices having an inoperative B section may be used to make SAD512 devices. It is, therefore, essential that unused pins 10, 14, and 15 be connected to ground, and that pins 11 and 12 be connected to Vdd."

Looks like you need to UN-TIE pins 11 and 12 of the 1024 from GND and tie them to Vdd according to the quote.

Good Luck  

EDIT: After looking at this a bit more, it almost appears that you need to swap the 1024 and the 512. If you did that, you would have the proper pins connected to the proper destinations according to the datasheet 

[thedefog]

I'll tie those pins to Vdd and check it out tonight. Thanks!

[Govmnt_Lacky]

OK. I think it would benefit if we clarified something.

Here are the pins that should be tied to GND and Vdd for the particular chips according to the datasheet:

SAD1024 (with BAD B-side) - 1, 4, 10, 13, 14, 15, and 16 to GND. 7, 11, and 12 to Vdd

SAD512 - 1, 4, 10, 11, 12, 13, 14, 15, and 16 to GND. Only pin 7 to Vdd.

Using this and what you have posted above, it looks like you could just SWAP the two chips and accomplish the same thing without having to re-locate anything.

May want to double check the reasoning but it looks correct electrically 

[thedefog]

OK. I think it would benefit if we clarified something.

Here are the pins that should be tied to GND and Vdd for the particular chips according to the datasheet:

SAD1024 (with BAD B-side) - 1, 4, 10, 13, 14, 15, and 16 to GND. 7, 11, and 12 to Vdd

SAD512 - 1, 4, 10, 11, 12, 13, 14, 15, and 16 to GND. Only pin 7 to Vdd.

Using this and what you have posted above, it looks like you could just SWAP the two chips and accomplish the same thing without having to re-locate anything.

May want to double check the reasoning but it looks correct electrically 

The Vbb and Vdd points are on separate sides though, so they'd still have to be jumpered together between the two chips, correct?

[Govmnt_Lacky]

The Vbb and Vdd points are on separate sides though, so they'd still have to be jumpered together between the two chips, correct?

Yes. Pin 7 (Vdd) and Pin 9 (Vbb) will need to be tied together on BOTH chips. Also, you will need to connect this trace to Pins 11 and 12 of the SAD1024.

The datasheet says that unused outputs (a.k.a. SIDE B of SAD1024) need to be connected to Vdd... which TECHNICALLY is the same as Pin 7. Now, in most cases, Pin 7 is connected to Pin 9 so I guess they could just all be connected together to Vdd.

[thedefog]

I checked it when I got home, and it turns out I had it wired correctly with pins 11 & 12 on the SAD1024 going to Vdd on the bad channel.  

I wish I had a SAD1024 to try and sub in to see if that is actually the issue. I'm going to probe and scope around a little more on it tonight and see if another part is to blame. Thanks for your help Govmnt_Lacky. Much appreciated.

[jdub]

Hey man- This thread here http://www.diystompboxes.com/smfforum/index.php?topic=93646.40 has an exchange between Fender3D and Govmnt Lackey here on modding an MXR flanger to use just the B-side of a 1024; I was able to do the same thing to my MXR clone, but only using the A-side, and it sounds mighty good. If I'm not mistaken, the Ross is basically the same as the MXR, so you should be able to do an analogous move on it (I couldn't find a schem for the Ross, though...). See page 3 of the above thread for info. Since the 512 is basically a 1024 with bad B-side, you could plug in either your 1024 or a 512. Lemme know if you wanna try it; a bit tricky, but doable- it also depends on if you're willing to mod a vintage Ross board, o' course... 

[thedefog]

Hey man- This thread here http://www.diystompboxes.com/smfforum/index.php?topic=93646.40 has an exchange between Fender3D and Govmnt Lackey here on modding an MXR flanger to use just the B-side of a 1024; I was able to do the same thing to my MXR clone, but only using the A-side, and it sounds mighty good. If I'm not mistaken, the Ross is basically the same as the MXR, so you should be able to do an analogous move on it (I couldn't find a schem for the Ross, though...). See page 3 of the above thread for info. Since the 512 is basically a 1024 with bad B-side, you could plug in either your 1024 or a 512. Lemme know if you wanna try it; a bit tricky, but doable- it also depends on if you're willing to mod a vintage Ross board, o' course... 

Hey, thanks for chiming in. This isn't my pedal, but a friends, and he doesn't want to modify it in case he wants to sell it in the future.  But I'm personally interested in how the pedal works. I was unable to find a schematic online.

[thedefog]

nevermind, just realised it is identical to the mxr.

[jdub]

This isn't my pedal, but a friends, and he doesn't want to modify it in case he wants to sell it in the future.

Certainly can't blame him for that!  Might be that the best bet, then, is to shell out $$ for a good 1024, unfortunately...   Out of curiosity, though, what voltage are you reading for pins 11 & 12 on the SAD? 0?  You're sure it's bad?