"Weird Device" : Nutone Door Bell LA60

[goontron]

Re: "Weird Device" : Nutone Door Bell LA60

this doesnt really make sense. z105 controls not only the sound, but also the display. the display will show numbers (not always the one i press), seemingly never a few of them, such as 8 and 0 and a few more. this could be a bad keypad, but then why is it when i hit the test button the display does not go blank like the manual says it should. (test button works confirmed by measuring resistance between 5,6 on keypad. this makes me think either only part of the z105 is dead, bad socket as stj suggested (how to tell?), or z106,z107,or z108 causing problems though this would make me wonder if it would stop z105 from playing the default chime on power, assuming it does in fact do this by itself.

edit: just tried shorting keypad pins with a bit of wire. 2 and 9 are '0' and 4 and 9 are '1'
whenever i short 2 and 9, i get '1' or '3' most often random, never '0'. but shorting 4 and 9 almost always gives me '1' as expected.

i also noticed that pin 12 on z106 has 3k resistance to +5v while powered off? found this while checking to see if any buttons were bad.

it makes sense that if the keypad has a short it would be acting up. It might hold z105 busy as well. Have you tried desoldering the keypad and seeing if it chimes?

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

it makes sense that if the keypad has a short it would be acting up. It might hold z105 busy as well. Have you tried desoldering the keypad and seeing if it chimes?

i have not removed the kaypad, though i have tried lifting d114 and keypad pin 2. i'll get some solder wick after work today and remove the keypad.

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

removed the keypad, no change. i can still get the lights to come up by shorting where they keypad would, still getting 1 or 3 randomly on doing so.
z105-z108 are the only possible culprits, right?

[goontron]

Re: "Weird Device" : Nutone Door Bell LA60

removed the keypad, no change. i can still get the lights to come up by shorting where they keypad would, still getting 1 or 3 randomly on doing so.
z105-z108 are the only possible culprits, right?

Z106 could be bad... it would be a long shot though.... Yeah, probably one of the two. At this point i would pull z106 then retest, if that failed install z106 and remove z108 and test. If that fails, well, it's probably z105, yeah. Simple logic like z107 rarely fail, and wouldn't hold z105 busy.

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

i was reading the input notes section and it mentioned binary data lines on a through e. does this mean on z105 pins pa0-pa4 are actually just a binary number, 5v being a 1 and 0v being a 0? and then pa-5 is the keystroke "trigger"?

Pa-0 (pin 20 of z105) has 3v on it... pa-1 through pa-5 have less than .3 on them. unknown if it is coming from z105 or z106. but seeing as how z105's pa-0 is probably just a digital read it wouldnt give a voltage ever, right?
now that i see this, it makes sense why i never saw the thing put up an even number on this display. that also explains in part why the chime test button does no work, since it can never send the value '14' (tone test) and would instead send '15' (tone select).

should i just break the trace temporarily to pa-0 and see then if it will chime?

[keeney123]

Re: "Weird Device" : Nutone Door Bell LA60

So here is the data sheet for that key decoder you should be able to figure it out from this http://pdf1.alldatasheet.com/datashe...LD/74C923.html

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

Partial success!!!

this time i cut the trace for pa0 and found the 3v is coming from z105, somehow? but when i pulled it to ground and hit test tone (by shorting where they keypress would be) it played the tone.

my idea is to put a high value resistor, such as 20k and see if that hold it low whilst z106 might be able to supply enough current to push it back up. not sure whats going on here whether z106 is supposed to be able to sink a small bit of current or only be able to source.

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

while looking further into this, i find that it is pin 19 on z106 is dead. shorting key '0' and key '1' gives no change to pin 19, while pin 18 will go high and low (as it should).

are there any replacements for this encoder anywhere?

[keeney123]

Re: "Weird Device" : Nutone Door Bell LA60

while looking further into this, i find that it is pin 19 on z106 is dead. shorting key '0' and key '1' gives no change to pin 19, while pin 18 will go high and low (as it should).

are there any replacements for this encoder anywhere?

Here is one place
http://www.jameco.com/shop/keyword=key-encoder-ic

[jasonbay13]

Re: "Weird Device" : Nutone Door Bell LA60

ship in 112 days? and i'm assuming theres shipping on that. so expensive. maybe i could rig a switch. kinda inconvenient, but it only gets used twice a year (the control part).

[stj]

Re: "Weird Device" : Nutone Door Bell LA60

https://www.aliexpress.com/item/Free...664438304.html

[keeney123]

Re: "Weird Device" : Nutone Door Bell LA60

ship in 112 days? and i'm assuming theres shipping on that. so expensive. maybe i could rig a switch. kinda inconvenient, but it only gets used twice a year (the control part).

Is that what Jamco Customer Care told you, 112 days?

[keeney123]

Re: "Weird Device" : Nutone Door Bell LA60

https://www.aliexpress.com/item/Free...664438304.html

This one is interesting as they have the Fairchild logo on it even thou Fairchild is no longer making them.

[stj]

Re: "Weird Device" : Nutone Door Bell LA60

a lot of chinese stuff is either old/surplus stock from manufacturing, or it's stuff desoldered/pulled from unsold products.
it's actually very rarely fake.

i buy a lot of old memory from china - eproms etc, and they are all the real deal.

[stj]

Re: "Weird Device" : Nutone Door Bell LA60

btw, the picture has "F", but the part numbers look like it may have been from national semiconductor.
was it licensed?

[keeney123]

Re: "Weird Device" : Nutone Door Bell LA60

btw, the picture has "F", but the part numbers look like it may have been from national semiconductor.
was it licensed?

It is definitely a Fairchild logo and part number. I had looked it up on the Fairchild site, but if you have had good experience buying from them then why not buy as it is cheap enough.