Reliability of suspected clone ICs

[Ampere]

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.htm

Schematic
http://alternatezone.com/electronics/images/hsfglc11.gif

I 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 V_EE and saw a large amount of current. I figured that the current must be coming from V+ or V_CC so I removed each of them one at a time. Bingo. Having V+ but not V_CC connected 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.

[Ampere]

1. Clone chips are usually not exact copy, most likely just "equivalent" in function, not specifications.
2.I don't know.
3. From my experience, most Chinese chip sellers know their products are fake or not, so ask them and tell then you need the absolute authentic ones. Pretty much 90% Shenzhen part brokers do not have stock of obscure chips, so they will manage to get them for you, as long as you are willing to pay the authentic price for the authentic chips. Also, AliExpress or Alibaba or Taobao, every Alibaba Group's eCommerce system protects buyers more than sellers, so the sellers usually won't fuck around if you explicitly told them you need the real ones.

Thanks 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.

[Kleinstein]

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.

[3roomlab]

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

[AlxDroidDev]

if a genuine pic can help to ID it, here is 1. the top n sides have a diff texture (matte n gloss)

If you decide to sell that MAX038, please let me know. I've been wanting one for a long time.

[3roomlab]

sorry i cant sell it, it is from my IC "museum"

[Joule Thief]

a possible source

http://www.futurlec.com/ICMaxim.shtml

[Ampere]

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.

I 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.

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

This is definitely not what I have. Both of my chips are smooth all over and don't have any stamping on the bottom.

a possible source

http://www.futurlec.com/ICMaxim.shtml

Good 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.