Build debugging
#1
If this is posted in the wrong place, please let me know.

I'm nearly done with my ICS64 build and just waiting for a couple more IC sockets to show up in the mail.

While testing, I ran into some issues with the 5v rail, which doesn't seem to be working at all?

I suspected that I might have a problem with the 1A 7805 regulator @ VR2, so I replaced it with a Recom R-78B-1.5, but so far this hasn't made a difference?


Here are the voltages I'm readings at various test points:

TP1 12.38 DC
TP2 9.23 DC
TP3 9.23 DC
TP4 9.34 DC
TP5 GND
TP6 0 (this should be the 5v rail?)
TP7 6.3 AC
TP8 6.14 AC

VIC Pin 40 9.22 DC
SID Pin 28 9.29 DC
RF Mod 12.4 DC


Here are the jumper settings I've selected on the bottom of the board:

JP2 Open (what does this one do?)
JP3 5v (using an 8565 R2 @ 5v)
JP4 24 (will use standard ROM)
JP5 24
JP6 24
JP10 24 (will use standard ROM)
JP11 24
JP12 24
A13 - A15 Open (plan to use Kernal switcher)

   

   


Any tips or leads?
Thanks!
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#2
I found a short on my 7 Pin DIN power connector, which was clearly the culprit for the issue with the 5v rail.
Once that was cleaned up, almost all of the 5v source voltages are testing correctly now.

The key exception is the VICII circuit, which for some reason reads 9v everywhere a 5v source voltage should be?

BTW - I've triple-confirmed that JP3 is definitely set for 5v VIC... 

Irrespective, what could be causing all of the source voltages on U29-U32 to hit 9v, instead of 5v?

New voltage readings:

TP1  12.01 VDC
TP2  8.75 VDC
TP3  8.73 VDC
TP4  8.9 VDC
TP5 GND
TP6 5.20 VDC
TP7  6.17 VAC
TP8  6.08 VAC

VIC Pin 40  9 VDC
SID Pin 28 9 VDC
RF Mod 12 VDC
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#3
Re-download the manual! I made a change a week or so ago for something I had forgotten. Refer to page 73. You MUST cut the trace between 12V and the center pad of JP3. Otherwise, you are tying 12V to 5V and you will get between 8V and 9V!!

JP2 is for a special PAL mode.
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#4
(10-18-2021, 07:34 PM)admin Wrote: ...You MUST cut the trace between 12V and the center pad of JP3.  Otherwise, you are tying 12V to 5V...

Uhg! That was it. Wasn't aware of the v1.2 manual update. Thanks!

I cut the referenced pad and now all voltages are testing correctly (nice!).

I also noticed that my 7812 and Recom 5v SReg are running much cooler now.
Guessing the short was causing them to fight with each other.

Attaching a view of all the voltages I'm reading on the unpopulated board...

   
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#5
Looks like I spoke too soon!

The 14 pin sockets I was waiting on showed up last night, so I finally completed the build and attempted to power up, only to be greeted with the black/blank screen!

I noticed that the VIC and left-most CIAs were getting warm, but the Basic ROM was actually getting hot!

I powered down again and proceeded to look for shorts & solder-bridges, but so far I haven't found any.

Wondering if the voltage readings I attached in my last post provide any clues?

Any helpful troubleshooting insights would be appreciated.

Thanks!
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#6
The voltages look good. Do you have a dead test cartridge? When you turn on the power do you see any changes in the video output?
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#7
(10-27-2021, 11:51 AM)admin Wrote: The voltages look good.  Do you have a dead test cartridge?  When you turn on the power do you see any changes in the video output?

Thanks for response, and for confirming that my voltage measurements look OK.
I do have a Dead Test and Diag cart, but I'm not getting any video output at the moment - Not even a flashing screen?
I also tried swapping the VIC with another 8565R2 (5v PAL) which is tested and known to be good, but still nothing.

I'm curious about what could be causing the BASIC ROM to heat up so much. I definitely don't see any obvious shorts.

Thanks again.
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#8
None of the ROMs should run hot at all.  Are you using the OLED screen or LED strip?

Even without the VIC-II plugged in, you should see some change the video output when power is applied.

With the real dead test cartridge ($E000 version) you don't need any ROMs even plugged in.  Try removing all of the ROMs.  Have you verified that your PLA is ok?
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#9
(10-28-2021, 11:08 AM)admin Wrote: None of the ROMs should run hot at all.  Are you using the OLED screen or LED strip?

Yep - that's what I assumed, which is why I'm puzzled by what I'm seeing...
Not using the OLED screen or an LED Strip (yet).

Quote:admin
Even without the VIC-II plugged in, you should see some change the video output when power is applied.

Oddly, there is no video output of any kind. Not even a screen flicker, or any kind of noise pattern, which is very strange.


Quote:admin
With the real dead test cartridge ($E000 version) you don't need any ROMs even plugged in.  Try removing all of the ROMs. 

Yep - tried this, but the effect is the same with the dead test - no video output at all.


Quote:admin
Have you verified that your PLA is ok?

I've tried a couple different PLAs, including the GAL and a 251913-01. Neither made a difference.
I tested both PLAs using the BackBit Chip Tester, where they "Passed" multiple rounds of testing.
Although, I don't have another working 407 board to test these PLAs with, so I can't confirm with 100% confidence that either are working. 


Appreciate the responses...
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#10
Check to make sure that your solder joints are good at the 8 pin video connector, as well as the VIC-II chip.

The 74LS629, MC4044, and 74LS74 along with the crystal (and of course VIC-II) are responsible for the video output. Check all of these to make sure that they are inserted in the proper direction... in fact, check all of the chips to make sure that all of the notched at facing towards the rear of the board.
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