I'm troubleshooting a little voice recorder kit from Kitsrus.
It is a K188.

My son soldered all of the resistors, diodes, capacitors, speaker, mic, aux. and power parts into place, and I've tested for voltage at each solder joint, and they all look ok to me.

The instructions were skectchy, and assumed we knew the orientation of the capacitors. The photo provided didn't show capacitor orientation at all.

Has anyone built one of these, and if so, can you share any insights with us?

I'm a novice, but everything looks right to me. We even get the required voltage at pins 1 and 28, on the IC. But the LED never lights up, and the device doesn't work.

Any insights would be helpful, specs can be seen on their web site, WWW.Kitsrus.com/kits/K188 (rightmost lower quadrant).

Thanks, Gary D

 

The correct link is:
http://kitsrus.com/pdf/k188.pdf
Having a look...

[eta]
The orientation of the electrolytic caps is clearly shown on the placement diagram. Positive is towards the top of the board.

This is not a beginner's circuit. Improper soldering or electrostatic discharge could quickly kill the main IC.

I don't know what experience level your son has. Proper soldering skills take time to develop. Proper ESD precautions are not obvious to newcomers.

If you can walk across the room and get a shock from a switchplate or doorknob, you have an ESD problem - and it's likely that the IC was destroyed by improper handling.

 

Sgt.

That's probably it, he was joking about ESD when working on his Nephews laptop today (fortunately it still works).

I'll recheck the orientation of the caps, and if no help, I will salvage parts for other projects.

I bought his son (age 7) a Fry's Electronics beginners kit for Christmas. Maybe when he (dad) works on that, he will gain some experience.

Many thanks, and Merry Christmas / Happy New Year!!!

Your a hero to those of us who are technically challenged.

Gary

 

Gary:

I have a similar board purchased from Electronics 123 , (DIY K188 K189) but my guess is that they are all made by the same Chi-Com company.
Prior to assembling mine, I discovered a mistake on the Board !

If you look at the top surface of the board, with the LED at the top right corner, focus on resistor R4, located near the lower right corner of the IC socket. It is the ROSC, the oscillator resistor, and is supposed to connect from pin 20 to through the resistor to ground. On my board, there was a trace shorting the bottom of R4 directly to the trace coming from Pin 20, which is the plus side of C4. The bottom of R4 also connected to ground (through the board) , like is is supposed to. The result of the mistake was that C4 had ground connected to both sides, and R4 was connected directly across pins 18 and 20, then to ground, and C4 was essentially not in the circuit. I caught it prior to assembly, so I simply cut the offending trace with an exacto knife. Mine now works perfectly. I bought the board for ease of programming several voice chips to be used in other projects, and it works just as I expected.

I called Electronics 123 and told them of the problem - they in turn called the board manufacturer, and they acknowledged the mistake, however they both said they have shipped thousands of these, and that the board works anyway. Perhaps it would, but it sure seems like it would affect the ACG, as well as the oscillator frequency.

As a side note, if you cannot get it to work, you might want to check out another board, fully assembled and much cheaper. It is an evaluation board for the ISD 17240,( a 240 second chip). Available from DigiKey, for $13.30. It is a slightly smaller board, fully assembled, and the IC is a surface mount under a blob of epoxy. It has all 6 pushbuttons, and a built-in electret mic. The differences are that it does not have jacks for Aux IN and Aux Out, nor does it have a jack for the power supply, or a terminal block for speaker connections. The power and speaker connections must be made via male header pins on the board. The Aux in and out are via male headers as well.

DigiKey part number is ISD-COB17249-ND

Good Luck

Ken

 

WHOOPS !

That part number should be ISD-COB17240-ND

 

Thanks Ken, I'll give it another try.

Gary