Suggestions for "liberating" MN3006 & MN3007 BBD chips from old circuits?

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I picked up this old archer "video sound processor" (surround sound simulator) from the 80's at a junk store.

It has one each  of MN3006 (128 stage) & MN3007 (1024 stage) BBD chips in it. Any suggestions for how to get them de-soldered with the least chance of damaging them?

It's been hacked up in a weird way by someone in the past, but I was able to get enough out of it to see that the delay part still worked.

Are the delay times long enough on either of these to do a proper delay? (not flange/chorus)

Any suggestions of interesting/downright weird effects using them?

There is also a LM1894 Dynamic Noise Reduction System chip in there... I wonder if that could be used for anything interesting...

[Mark Hammer]

I picked up this old archer "video sound processor" (surround sound simulator) from the 80's at a junk store.

It has one each  of MN3006 (128 stage) & MN3007 (1024 stage) BBD chips in it. Any suggestions for how to get them de-soldered with the least chance of damaging them?
First scrub/brush the copper side clean since there will likely be some atospheric crud accumulated over the years that will interfere with good heat transfer.  A little brass bristle brush might be useful.  Then, use solder wick, preferably a smaller gauge (it comes in different szes), and impreganted with a wee bit of liquid flux to facilitate solder flow.  That will do a good job of getting the solder off the pins quickly and cleanly.  Try not to do all the pins at once since the heat buildup might damage the chip.  Wait a bit between pins.  Not 10 minutes, but wait a bit.

It's been hacked up in a weird way by someone in the past, but I was able to get enough out of it to see that the delay part still worked.

Are the delay times long enough on either of these to do a proper delay? (not flange/chorus)
Short answer is no.  At the same time, a flanger or chorus that involves being processed by an MN3007 first and then an MN3006 could make for some bitchin stereo effects.

Any suggestions of interesting/downright weird effects using them?

There is also a LM1894 Dynamic Noise Reduction System chip in there... I wonder if that could be used for anything interesting...
Absolutely.  makes a great single-ended NR system that is less instrusive than a gate, since it is simply a sliding filter, and a cousin of the the Rocktron HUSH chip.  Plenty of sample circuits posted around.  My back issues of Popular Electronics, radio Electronics, and Electronics Today have a bunch of them.

[jkokura]

Nice find. How much did you pay, cause MN3007's can be expensive.

Jacob

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Thanks for the info Mark.

And jkokura, I paid $5 total for two boxes (the other is an oldschool printer switcher in a nice steel box). I assumed right off that I would just be using both for parts. Didn't even realize the video sound processor would have delay chips in it. The delay knob was on the back of the box and I didn't notice it when I was in the shop. It's got a dozen or so dual opamp chips too.

[R.G.]

Salvaging parts comes down to three main paths:
1. You want to save the parts, don't care if you destroy the old board as long as you don't hurt the part.
2. You want to save the board, don't care if you destroy the part getting it out as long as you don't hurt the board.
3. You have to save both parts and board. This one is hardest, of course.

You have situation 1, I think. In this case, there is a radical trick that is the absolute easiest on the parts that can be done, although it doesn't sound like it. The trick is to melt the solder on all pins at the same time from the bottom of the PCB while putting the gentlest of pull on the part from the top. There are U shaped IC pullers that have a hook that fits under each end of a DIP that makes this easy.

For solder melting, I have a dual soldering tweezer: http://www.mcmelectronics.com/product/TENMA-21-8230-/21-8230 It takes a little practice - what doesn't? - but you can melt all the pins at the same time and the IC pulls right out. Some ICs have pins clinched over, and that makes it harder. In that case I use a soldering iron per pin and unbend the clinched pin first. But when the solder melts, the IC pops out the other side. There have been soldering irons made with little inverse - U shaped tips which melt all the solder at the same time. I never liked them, too fussy.

The winner here, if you can get used to destroying the PCB, is the propane torch. This is a heat gun on steroids. Clamp the PCB in a vise, clip the IC extractor which you have so carefully made out of a bit of tin can onto the IC, and wave the lit torch on the solder side. You want the widest, softest flame you can get, and you do NOT want the flame itselft touching the PCB. The idea is to get the jet of hot air outside the flame to hit the PCB, so the torch will be 2-4 inches (50-100mm...  ) away from the PCB, and aimed a little below the IC to allow for heated air rising. If you have practiced a time or two on throwaway boards, the solder will melt on all pins at about the same time; you can feel it turn loose with the tiny tension you're holding on the extractor. Then it will suddenly turn molten, the IC will pop out, and you're done. I used to remove memory chips from boards back when memory chips were $20 each this way. Some boards had big holes for the IC leads, and you could suspend the board chip side down over a bucket of water, then torch the solder side. The chips ... dropped... out into the water.

If you have to save a PCB with a bad DIP, don't mess with desoldering. Clip off the lead next to the IC body, then lift each lead out separately with the soldering iron. A little solder wick now gives you pristine holes. Or it did before RoHS. Lead free solder will not wick out well enough in any board I've ever tried it on. The trick is to flow some 60-40 leaded solder into the joint. This alloys with the lead-free, making a much more fluid stuff that can be wicked out. Use a carefully-whittled wood splint to poke into a hole full of molten solder to push the molten stuff out instead of wick if you are short of wick.

If you simply must save both board and part, you're in trouble. Solder wick, suction soldering irons, solder bulbs, prayer, etc. may help.