[Filburt]

Quote:

Originally Posted by Teerawit It takes alot more to kill these chips You should redo those cold joints.

Haha. Cold joints make a difference, but what he's describing is somewhat similar to what I've encountered with bad chips in a variety of situations, although very similar to what I encountered with the PINT. It was just an idea, though.

 

[FallenAngel]

Hey guys

Well, more bad news on my side here.

I redid ALL of the joints using Wonder silver solder (flows really nicely) and I think that none of them are cold anymore. I also used a little extra flux to being with, and thoroughly cleaned it off using rubbing alcohol.

The bad news is though... offsets are even bigger. Ugh!
OG->OR: 5.72v
OG->OL: 4.99v

Here are new pics, does anybody spot anything amiss?
If nothing comes up pretty soon, I'll be ripping that AD8620AR from the BrownDog and sticking it to straight to a dip8 socket.




Thanks!

 

[tomb]

The good thing is that your solder joints look fantastic, now - on a par with anybody's. The bad thing is that if your measurements are still bad, that probably means you have some bad chips.

This was probably mentioned before, but sockets should be required equipment for anyone but experts. I'm lucky if I don't melt the sockets, much less chips. If I was soldering them directly, they'd all go bad.

 

[Teerawit]

Agreed....a DIP8 socket is a good safety measure. Not a bad trade off - 35 cents to avoid soldering a $5+ opamp.

 

[FallenAngel]

Well great news guys. I've found the culprit, it was the funky Drowndog or DIP8 adapter. I didn't exactly take your advice on using another one, and just went ahead and surface mounted the AD8620AR straight onto the underside of the pimeta. Damn! If I had known it was going to be that easy to do it, I would have probably made a PINT

!

In either case, the DC offsets are less than 2mV on each channel and the Pimeta sounds incredible with my Grados.

Here are the finished pics (no case yet, ordering one now). Thanks for all the help guys, would have never finished it without the generous help of this great forum

 

[MASantos]

I found your problem!!! I don't know how nobody saw this!!! Folks, take a look at the brown dog where the AD8620 is... It is a single SOIC to DIP adapter. It should be a double SOIC to DIP adapter. YOu got that adapter from tangent right? THe DOuble SOIC to DIP adapter has some yellow marking s on it.

Manuel

 

[FallenAngel]

Since the correct adapter was sent, I retract my comment about www.cimarrontechnology.com. Most likely the huge DC offset was because I screwed up the pin on the adapter and maybe because of some very funky soldering.

 

[Jam_Master_J]

Looks good and nice work soldering that SMD op-amp.

 

[tangent]

Quote:

Originally Posted by FallenAngel I got the chip already on the BrownDog from... BrownDog

In defense of Cimarron, Phil Maltby (the proprietor) has always been good about replacing adapters with manufacturing errors. There's probably nothing you can do now that you've resoldered the chip, but FYI...

Quote:

If I had known it was going to be that easy to do it, I would have probably made a PINT

Heh. Another way to look at it is, if you had this much trouble with a PIMETA, imagine the fun you could have had with a PINT.

Quote:

Originally Posted by MASantos It should be a double SOIC to DIP adapter.

Why do you believe that? The dual SOIC adapter is for taking two single-channel SO-8 op-amps and using them in place of a dual channel DIP-8 op-amp. An example of where you might use that adapter is for taking two AD8610s and adapting them for OPALR in the PIMETA. For the AD8620 in OPALR, the simple SO-8 to DIP-8 adapter is the correct one.

 

[FallenAngel]

Thanks for the clear up Tangent, I removed my unjust comments about www.cimarrontechnology.com

Just one question... so what's next?

I'm thinking of adding a battery charging circuit to this thing.
Or at least finding a way to run battery and wall power at the same time without using an actual switch to change between the two.

 

[tomb]

Whew! I had a heck of a time searching for this - apparently, Head-Fi is working on their search engine. They keep switching back and forth from theirs to a Google search engine.

HEAD-FI - Dont' use Google's search engine for your site - it sucks!

Anyway, check out this thread from __redruM. He constructs a super-small and super-simple charging circuit for 2x9V for a 24V power source, a perfect combination for a PIMETA. I'm going to try it. Later in the thread, Tangent also recommends a TO-92 case LM317L, which will make it even smaller:
http://www6.head-fi.org/forums/showthread.php?t=110663

EDIT: Well, he actually constructs it for a Mint and 1x9V, but the circuit doesn't change for 2x9V (he does show that for a PIMETA), but the charge voltage goes to 24V.

 

[FallenAngel]

Thanks Tomb, I'll be building one of these for the pimeta, just ordered the parts from Mouser, but of course, I couldn't just order those from there so... to answer Tangent, I did have lots of fun building your Pimeta, and as you say that I might have even more fun building a PINT... well, I just oredred enough parts for 2

(I bought a box of Altoids mints, and just couldn't resist ordering PINT parts to fill it - it makes sense to me).