HT8955 echo (H-Echo, SH-echo) - not working - DRAM fried?

[Taylor]

I built up a simple echo using the HT8955 and associated DRAM on the breadboard. I pretty much built it from this schematic, but I did not build the in and out buffers, and instead I'm feeding it from another pedal.

So basically what I have on the breadboard is just the HT8955, DRAM, 78L05 and the surrounding parts. I also read over the datasheet to get a feel for what was going on and if I missed any important info. I'm not using a bipolar supply because only the opamps are run bipolar.

I do have audio going through the circuit, but there's no delay, even adjusting the delay time knob all over. I pulled the feedback path out to verify it wasn't just going through there, and indeed audio is going into and coming out of the HT8955. I scoped the digital bit pins and I do seem to have bit streams coming out of the 8955. I have verified power voltages, all good. I then pulled the power from the DRAM, and it acted exactly the same as with power.

I'm wondering if the DRAM chip is fried. My previous experience is that it's usually way more likely that I messed up than that a chip is dead, but I also remember reading that DRAM may be more static-sensitive than most parts we normally deal with. I'm thinking perhaps my nonchalance as a result of never having killed EEPROMs or CMOS logic by handling them has claimed its first victim.

Probing has gotten me as far as I think it can. Anyone have any thoughts on how to determine if the DRAM is in fact dead?

[Galego]

What does "feeding if from another pedal mean"?

[Taylor]

guitar - buffered pedal - breadboard - buffered headphone preamp

In other words, I'm using the buffers in other, working pedals to do the buffering so as to simplify what's on the breadboard.

[Govmnt_Lacky]

Looks like another Hazelwanter project 

I spent a lot of time, effort, and money into the Holtek Pitch Shifter project from him only to find out that the project was a bust! I could not find 1 person who sucessfully built it.  I did manage to find A LOT of people who built it and wracked their brains for a long time like me only to scrap it!

Good Luck with it Taylor. I hope you get it going.

[Taylor]

Looks like another Hazelwanter project  

I spent a lot of time, effort, and money into the Holtek Pitch Shifter project from him only to find out that the project was a bust! I could not find 1 person who sucessfully built it.

Actually, you just found somebody who built the DH pitch shifter successfully: me!   I posted a bunch of info on how to get it working (fixes for some of the traps I stepped in, which suspect you may have done also) here:

http://www.diystompboxes.com/smfforum/index.php?topic=88829.20

The thing is that these are old projects. The one I'm playing with is from 1998, very early in the game for DIY digital delays. All the same, it's basically straight from the datasheet, so I don't think the issue is Dean's design (apart from the audio section, which IMO is needlessly inconvenient, which is why I skipped it). I think the issue has more to do with either my build or the DRAM having been zapped.

I don't so much want this circuit itself, but I have some ideas for some unique stuff using this kind of delay, so I wanted to build it and then try some ideas - but I can't even get the basic thing working.