74LS190 issue has me baffled...

[robkwil61]

It's been a long time since I've done any digital design but my neighbor asked me if I could build him a digital scoreboard for his shuffle board table. Thought it would be pretty easy. I created the design in MultiSim and it works perfectly. I ordered all my parts and started putting it together. Works great except for one tiny problem. My 74LS190 is counting past 9. It goes from 0 to 9 and then 10, 11, 12, 13, 14, 15 before it triggers the carry over. I thought after the chip hits binary 1001 it should reset on its own to 0000. But it does not. What am I missing? I have all the inputs tied low. CTEN is low so it only changes on the clock pulse. It will count up or down depending on the status of pin 5. Load is set high so when it powers up I get a zero on the 7 segment display.

I ordered the counters off eBay from China. Is it possible I got a bad batch? I ordered 10 of them and have tried at least 4 or 5 of them but they all seem to do the same thing. The only other thing that makes any sense is that I was actually sent 74LS191 chips, although they are clearly marked 74LS190.

Thanks for reading,
Rob

 

[Ian Rogers]

Makes sense 191 is a binary counter whilst the 190 is a BCD counter.... It seems as though that is your problem... Just re-order the correct ones.... Are they expensive in your part of the world?

 

[tunedwolf]

I agree, the 190 is a bcd decade counter, it should never be able to go beyond the range 0-9

 

[robkwil61]

Thanks Ian and tunedwolf.. I pretty much confirmed what I thought. Although the chips are marked as LS190s they are LS191s. Motorola muffed that batch. I substituted a 191 in my MultiSim circuit and it does exactly what my real circuit is doing. I see the exact same bogus segments light up on the 7 segment display. I found some locally for about $2 a pop. No more cheap Chinese purchases for me.

 

[robkwil61]

BTW... Ian... what do you pay for Jack D in your part of the world?

 

[Ian Rogers]

I only drink it occasionally....

ASDA do it for £15 for 700ml every now and again.... I mainly drink The Macallan now or dalwhinnie... Both are about £32 ish..

 

[tunedwolf]

I like the Macallan, not so keen on the Dalwhinnie. Last bottle I bought was 25yr old Bowmore, mmmm

 

[Ian Rogers]

Last bottle I bought was 25yr old Bowmore

I just finished a bowmore double wood!! I'm sure that knackered up my throat.... I haven't been able to speak since!!!

 

[tunedwolf]

I just finished a bowmore double wood!! I'm sure that knackered up my throat.... I haven't been able to speak since!!!

Naw, that would hae been the singin' afterwards

 

[Ian Rogers]

I hope we have answered the OP's question... All this whisky talk makes me thirsty....