Help with finding IC or a equivilent

[roadrash]

I am looking for a t74ls0081 chip that may be damaged after a short out and I need to replace to eliminate it possibly being faulty now.
can someone help me find one or is there a equivalent that will do the same job.

many thanks

[stj]

Re: Help with finding IC or a equivilent

got a foto?
i suspect it's just a 74ls00
and can usually be replaced with a 74HCT00
not that there is any problem getting LS series.

[roadrash]

Re: Help with finding IC or a equivilent

Thanks here is a picture. Can you also tell me if the equivalent is also pin compatible so i can just solder it straight in.

[stj]

Re: Help with finding IC or a equivilent

just a 74ls00 - they are all pin compatable from different suppliers.
is that an amiga rom switcher? just wondering.

why do you think the chip is bad?

[stj]

Re: Help with finding IC or a equivilent

oops - that price / quantity limit must be an error.

quick, buy one with free postage before they fix it!!!
http://uk.rs-online.com/web/p/standa...gates/2175702/

[petehall347]

Re: Help with finding IC or a equivilent

oops - that price / quantity limit must be an error.

quick, buy one with free postage before they fix it!!!
http://uk.rs-online.com/web/p/standa...gates/2175702/

looks about right for RS ..

[roadrash]

Re: Help with finding IC or a equivilent

yes it was a Amiga Rom switcher that I stupidly put in the wrong way in a spare amiga and it burnt out a wire in the ribbon cable and got a MC74F244N chip on the motherboard bloody hot. Ive ordered a couple of new MC74F244N chips and fitted a new length of ribbon cable. I checked the kickstart rom chip that was not selected by the rom switcher (a KS 2.04 rom) and it is still ok. However I am not sure its good to try the rom that was selected (a KS 1.3 rom) in case it will damage my main amiga 2000 plugging it in. I cant believe I did that. That switcher has no markings to say which way it goes and I got it oriented wrong damn it. Just hope it hasnt taken anything else to much out like the MC68000.

[stj]

Re: Help with finding IC or a equivilent

it could have trashed the 1.3 rom, but test it to see - it cant damage anything else.

[roadrash]

Re: Help with finding IC or a equivilent

Oh will do, but wanted to check first. Dont want to damage another Amiga. Can you tell me where Amiga keeps its real time clock? because thats how this all started. I replaced the onboard ni-cad battery as I have done many times before but this time I put that in the wrong way round too and when I realised & corrected almost straight away, I tested the Amiga and it didn't boot into kickstart so thats when I took the kickstart roms out of my other Amiga 2000 to see if it was that that had been damaged and it just all got worse. I thought the realtime clock was in its own chip but if its in the processor then that would explain why it didnt boot after replacing the battery.
I really am going to have to take photos of everything I do before starting work, no matter how trivial, as short term memory issues & confusion caused by my progressive M.S. are getting ridiculous or give up repairs altogether.

[stj]

Re: Help with finding IC or a equivilent

RTC is near the battery, it has about 18pins and has a small crystal next to it.
i prefer to mod the amiga's to use a lithium coincell like pc's - because they never leak.

[roadrash]

Re: Help with finding IC or a equivilent

arnt the coin cells a different voltage and have to be changed moe regulary

[stj]

Re: Help with finding IC or a equivilent

maybe, nicad/nimi are 2.4 or 3.6v - lithium are 3v
but the rtc is designed to operate down to 2v or less - so not a problem.

[roadrash]

Re: Help with finding IC or a equivilent

Thank you stj. you were spot on with the SN74HCT00N i soldered it in and my rom switcher is working again. I also tested that other kickstart rom and your right it wasnt damaged so that's more good news. Now just have to wait for the two MC74F244N chips that got hot on the other amiga to come and I can then see if that fixes that one too. If it did damage the cpu I have a HT68000 which I could use which I think is just a Hitachi equivalent and it might have even come from another amiga years ago.

[stj]

Re: Help with finding IC or a equivilent

all 68000's are compatable, even the speed rating is not too important - i'v overclocked 8MHz parts to 14MHz without any problem!!!