7408 chip replacement - WMS System 11b

[Steevsee]

Hi to all.
Slowly working through some issues on my recently aquired WMS Cyclone.
So far I have discovered a bad Diode(IN4764 - 100v Zener) on the power supply board and have ordered full rebuild kit from GPE.

Also checking the CPU board as the knocker coil was locked on. The Driver and Pre-driver transistors for this coil both test ok, so I think possibly the 7408 (Quad 2 input AND gate) may be faulty.
Unfortunately GPE are sold out of this chip.  Jaycar have an LS and HC version of 7408 listed but I'm not sure if these can be substituted or not. 
(I did read somewhere online that these should generally not be sustituted as they may or may not work).

Any advice greatly appreciated.

BTW, I see Greg (RTBB) has the LS version listed on his site.

[ddstoys]

These can besubstituted and work fine for something but does not work on all

[FirePower]

74L can be replace by 74LS, 74 or 74S
74LS can be replaced by 74 or 74S
74 can be replaced by 74S
74S cannot be replaced

not sure about HC, haven't checked a spec sheet, but it only comes down to chip speed and current capacity  or fan out ratio. Speed will not be a problem in pins as they are slow. Read the spec sheet for the HC device and compare it to the 74 spec sheet. I've got a feeling they will be ok - I think 74HC were released as a universal replace all series, but check the current rating to be sure.

[ajlaird]

74L can be replace by 74LS, 74 or 74S
74LS can be replaced by 74 or 74S
74 can be replaced by 74S
74S cannot be replaced

not sure about HC, haven't checked a spec sheet, but it only comes down to chip speed and current capacity  or fan out ratio. Speed will not be a problem in pins as they are slow. Read the spec sheet for the HC device and compare it to the 74 spec sheet. I've got a feeling they will be ok - I think 74HC were released as a universal replace all series, but check the current rating to be sure.

HC were designed to run off 5V or 3.3V and shouldn't be a problem - as you say, they were designed as a universal replacement.

[Steevsee]

Thanks for sharing your knowledge guys.
I guess since i'll install a socket anyway, I can easily try them out, and change them if neccessary.

[studley67]

steve,try rs (radiospares) they will have one pluss order online and they will even couriur it to your door free,no min spend,i think.good luck

http://australia.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=2175566