Reliability of suspected clone ICs - Page 1
Forum section: electronics / beginners

author: Ampere
author_rank: Regular Contributor
timestamp: December 09, 2015, 06:29:29 am
content: A while ago I realized that I had hit a brick wall. I was reading through my books and trying to absorb more of the basics, but what I could try for myself was limited by the fact that I don't own a function generator. This made it very difficult to do my own experiments with AC signals.I looked for function generators and most of the ones in my price range seemed very limited. Then I found a project which promised 20MHz for far less than most 5MHz scopes sell for:Project (It wasn't until I reached the end of the page that I realized who had created it!)http://alternatezone.com/electronics/hsfg.htmSchematichttp://alternatezone.com/electronics/images/hsfglc11.gifI needed to buy the vital MAX038 IC on eBay from China because I couldn't find any other supplier who still carried it, and I couldn't find any other similar IC currently in production. So I waited a few weeks for the chip to arrive and then I built the circuit. Immediately the current limiter light came on in my power supply. I looked it over and couldn't find anything wrong. So I tore everything out and built it again from scratch. Same problem. Then I looked over again and noticed that R6 which should be 6.8 ohms and connected to ground was actually 6.8k ohms and connected to -5V.After checking all other connections once more, I started it up again. Current limited.At this point I wasn't sure whether there was another problem with the circuit or if I'd made the IC so crispy that the short was permanent or if the IC was a dud. I decided that I could always get another IC and went ahead with some troubleshooting. First I removed the IC and applied a voltage to the circuit. There was no short. Then I put the IC back in and checked the current through each individual pin, only keeping the circuit powered for as long as it took my meter to register. I checked all of the grounds. Nothing. Then I checked VEEand saw a large amount of current. I figured that the current must be coming from V+ or VCCso I removed each of them one at a time. Bingo. Having V+ but not VCCconnected solves the shorting problem. The circuit still doesn't work, but I figure that I abused the IC so much that it's beyond help.Fast forward a few more weeks. I have a new IC and I've dropped it into the modified circuit (after checking it again). The new IC immediately activated the current limiter (which was set much lower this time). As a sanity check I put the old IC in its place. Still didn't work, but there was no short. I can't imagine why the new one is shorting but not the old one. Or why all of the current appears to be shorting straight from +5V to -5V.In short (pun not intended), I have a few questions:How reliable are these clone (at least I assume they are) ICs? I expected it to at least work long enough to verify that the circuit works.Is the chip at fault or have I overlooked something huge?Where is a good place to buy old parts? 99% of the MAX038 sellers are in China and I suspect that the other 1% could have easily bought the clone version and are reselling at a premium.

author: Ampere
author_rank: Regular Contributor
timestamp: December 09, 2015, 03:47:42 pm
content: Quote from: blueskull on December 09, 2015, 06:36:27 amThanks for the advice. I hate not knowing whether the chip is at fault or I am. I'll be sure to use the sites you've mentioned and ask for genuine parts next time in order to avoid further headaches.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 09, 2015, 03:51:44 pm
content: The Max0038 is an old rare chip. I don't know of any clone chip - you either get a real one, a broken one or just a fake. I don't think a similar (but slower) ICL8038 has the same pin layout.Sometimes it's ppossible to recognize fakes from a ggod picture.Chips like the max038 are today mostly replaced by DDS Cips like the AD9835 / AD9850. Modules based on the AD9850 are relatively cheap.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: December 09, 2015, 04:10:41 pm
content: if a genuine pic can help to ID it, here is 1. the top n sides have a diff texture (matte n gloss)*edit the bottom of the IC are also diff, with stamping and ink codes

author: AlxDroidDev
author_rank: Frequent Contributor
timestamp: December 09, 2015, 04:44:22 pm
content: Quote from: 3roomlab on December 09, 2015, 04:10:41 pmIf you decide to sell that MAX038, please let me know. I've been wanting one for a long time.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: December 09, 2015, 05:23:36 pm
content: sorry i cant sell it, it is from my IC "museum"

author: Joule Thief
author_rank: Regular Contributor
timestamp: December 09, 2015, 06:07:51 pm
content: a possible sourcehttp://www.futurlec.com/ICMaxim.shtml

author: Ampere
author_rank: Regular Contributor
timestamp: December 09, 2015, 08:38:57 pm
content: Quote from: Kleinstein on December 09, 2015, 03:51:44 pmI think that I'll give the AD9850 a try. It would be much more convenient to have something that can easily be controlled via an Arduino or a PIC.Quote from: 3roomlab on December 09, 2015, 04:10:41 pmThis is definitely not what I have. Both of my chips are smooth all over and don't have any stamping on the bottom.Quote from: Joule Thief on December 09, 2015, 06:07:51 pmGood find. I'll bookmark this in case I ever come back to this MAX038 project, but I think that it would make more sense to use the AD9850 as Kleinstein suggested.