Check DTACK resistance to 0v (with power off of course) something doesn't seem right there.stween wrote: Sun Dec 18, 2022 8:27 pm A quick check between festive tasks: with no glue, no CPU, address fc0000: DTACK is low.
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It helps build a picture where our "good traffic" is coming from..
Thanks :)
It helps build a picture where our "good traffic" is coming from..
Thanks :)
stween's build
Re: stween's build
Re: stween's build
Doesn't sound right. Should be open circuit really.
Not sure without looking , but remove the other chips which have dtack on them. Likely MMU, MFP, etc
Re: stween's build
Mmm. Okay, I removed all chips I see DTACK on. I still see 1k to ground.
Not sure if this is relevant:
Decided to go fishing and look at resistance on adjacent pins to DTACK on each socket. Figured sharing the same path might be indicative of ... something. What I did so far is NOT AT ALL thorough because I didn't map the top of the socket to the grid layout on the back, but looking at immediately adjacent pins on the top of the sockets didn't show the same resistance as DTACK on any socket, except on the GLUE.
On GLUE: pins 28 through 33 show the same 1k resistance. That's: RDY, VPA, BERR, DTACK, IPL1, IPL2.
Re: stween's build
What does DTACK measure to 5v then ?
EDIT
With no chips on the board and unrelated signals.. I wonder if your aware of this fix ? viewtopic.php?f=89&t=5256
You could remove the inductors and see if those pins go high then...
There should be noting at all on DTACK.. Basically blitter, CPU, MMu,GLUE,68K sockets, MFP. 3.3V buffers.
Aside from RDY which isn't on the CPU.. The others are unrelated aside from the 3.3V buffers. and even then different ones!
EDIT
With no chips on the board and unrelated signals.. I wonder if your aware of this fix ? viewtopic.php?f=89&t=5256
You could remove the inductors and see if those pins go high then...
There should be noting at all on DTACK.. Basically blitter, CPU, MMu,GLUE,68K sockets, MFP. 3.3V buffers.
- Capture.PNG (1.08 MiB) Viewed 1682 times
Aside from RDY which isn't on the CPU.. The others are unrelated aside from the 3.3V buffers. and even then different ones!
- Capture.PNG (58.04 KiB) Viewed 1682 times
Re: stween's build
Just under 1k to 5V. (To ground is actually just over, like 1.1k. To 5V, it's 0.9k.)
DTACK is open circuit to ground from the 3.3V expansion slots; I figured those are separated off from the rest of the board anyway so forgot to mention.
I have definitely never seen this page beforeWith no chips on the board and unrelated signals.. I wonder if your aware of this fix ? viewtopic.php?f=89&t=5256
Replacing those might be beyond me and my tools though!Re: stween's build
Just blob them with a solder blob and they will ease off.. clean off the pads with braid. Not sure how the buffers will react, but cant make things any worse. In theory just the 3.3V bus won't work, but that's not important right now anyway.stween wrote: Tue Dec 20, 2022 1:38 pm I have definitely never seen this page before
Re: stween's build
Okay. Specifically, just the highlighted resistor-shaped packages to the top left of each of the larger chips? (the bus converters?)exxos wrote: Tue Dec 20, 2022 1:50 pmJust blob them with a solder blob and they will ease off.. clean off the pads with braid. Not sure how the buffers will react, but cant make things any worse. In theory just the 3.3V bus won't work, but that's not important right now anyway.stween wrote: Tue Dec 20, 2022 1:38 pm I have definitely never seen this page before
I can futz with it this evening. If not this evening ... then I'll probably have to park it until mid January/early February!
Re: stween's build
I removed them in this post.stween wrote: Tue Dec 20, 2022 3:06 pm Okay. Specifically, just the highlighted resistor-shaped packages to the top left of each of the larger chips? (the bus converters?)
viewtopic.php?p=87527#p87527
You cannot keep us in suspense that longstween wrote: Tue Dec 20, 2022 3:06 pm I can futz with it this evening. If not this evening ... then I'll probably have to park it until mid January/early February!
Though if it is not those bus converters then I give up
Re: stween's build
Useful, thanks!exxos wrote: Tue Dec 20, 2022 3:17 pmI removed them in this post.stween wrote: Tue Dec 20, 2022 3:06 pm Okay. Specifically, just the highlighted resistor-shaped packages to the top left of each of the larger chips? (the bus converters?)
viewtopic.php?p=87527#p87527
haha I'll be away from home, that's the real problem! I probably have time tonight. I've just got the fear about components so small!You cannot keep us in suspense that longstween wrote: Tue Dec 20, 2022 3:06 pm I can futz with it this evening. If not this evening ... then I'll probably have to park it until mid January/early February!
Though if it is not those bus converters then I give up