Non-working Commodore PET 3016

[ortek_service]

Originally Posted by ortek_service

Yes, that's quite helpful - Although technically it shows is that the MC3446AP is a direct or similar replacement for the (Texas Instruments only) MC3446N or MC3446J. However TI themselves claim these area a replacement for the original Motorola MC3446P.

I haven't seen anywhere (yet) where Motorola say the MC3446A(P) replaces the original MC3446(P)
- With no mention of difference in the later datasheets.
But I would expect it to be, and now I've found the original datasheets, I've OCR'd that
(along with TI one, tidying it up so pages are straight & cropped), plus played spot-the-difference on these.

Many of these datasheets are rather vague about operating-voltage range (for Motorola ones) or packages suffix differences (for TI one).


I have now found that the specifications for the original Motorola MC3446(P) & the TI MC3446N (or extremely similar with MC3446J & MC3446D very similar) are basically all the same.

Whereas the later (replacement?) MC3446A(P) has a couple of differences:
- It is compliant with later GPIB / IEEE standard dated 1978 (compared to 1975) and still has termination resistors but only shows 'T' on symbol.
- It has a wider operating voltage range of 4.5-5.5V (compared to 4.75-5.25V)
- It has reduced typical hysteresis on the Receiver Inputs Threshold Voltage High to Low Output Logic State, which is now typically 1.0V rather than 0.8V. (However, it seems they forgot to update the hysteresis-loop graph, as this is the same as before!)

Datasheets for all versions are attached.

Although the TI Datasheet seems to imply that D suffix are also DIL Package, unless TI have changed their package suffix letter meanings, then D was used for (Half-pitch Small-Outline) Surface-Mount.

So although Aliexpress etc have MC3446D's quite cheap, they do show a picture of a Surface-Mount one - So not suitable.

And these are TI's package details that are not in their datasheet, but found from: https://www.ti.com/packaging/docs/se...tipackages.tsp

D (R-PDSO-G16) Plastic Small Outline Package: https://www.ti.com/lit/ml/mpds178g/mpds178g.pdf
J (R-GDIP-T**) Ceramic Dual In-Line Package: https://www.ti.com/lit/ml/mgdi003/mgdi003.pdf
N (R-PDIP-T**) Plastic Dual In-Line Package: https://www.ti.com/lit/ml/mpdi002c/mpdi002c.pdf

So shows that MC3446N or MC3446J would also be OK for original MC3446P

[SiriusHardware]

I agree that 'D' almost always means surface-mount, where 'N' almost always means DIP, although confusingly DIP ICs may not always end in 'N'.

[SiriusHardware]

I presume we are still agreed that MC3446AP is an acceptable substitute for MC3446N? Otherwise we may be causing Colin some anxiety here in our desire to be meticulous.

[ajgriff]

I think Colin can rest easy.

Alan