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Cbm dual drive 3040 disk - two red lights

AndyG said:
This could point to bad Rom or RIOT chip. Have you re-seated the IC’s ? Also do the drives spin up at all ?
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Hi Andy, yes i re-seated all socket ic's...drives sometimes spin up and sometimes not :(
 
Ummm… I did encounter a similar issue today and it was badly seated ROMS and RIOT chip (bent the legs in slightly to get them to work but that was because I was upgrading it from Dos 1 to 2). The fact that it sometimes spins up the drives suggests it’s trying to startup. Check the continuity for all the sockets to be sure as those white sockets are terrible: replacing the roms can be a challenge as the chip select is reversed - active high on pin 21 and low pin 20 …. (worth checking as don’t recall all the details ). You can get suitable adapters. Indeed I built a 2532 adapter for my Eprom programmer that enabled them to be read at least.

Found this link which maybe of help later in your quest

 
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AndyG said:
Ummm… I did encounter a similar issue today and it was badly seated ROMS and RIOT chip (bent the legs in slightly to get them to work but that was because I was upgrading it from Dos 1 to 2). The fact that it sometimes spins up the drives suggests it’s trying to startup. Check the continuity for all the sockets to be sure as those white sockets are terrible: replacing the roms can be a challenge as the chip select is reversed - active high on pin 21 and low pin 20 …. (worth checking as don’t recall all the details ). You can get suitable adapters. Indeed I built a 2532 adapter for my Eprom programmer that enabled them to be read at least.

Found this link which maybe of help later in your quest

Click to expand...
OK thanks! Which socket is the Rriot in?
 
I am afraid everyone is distracting Desperado...

He thinks he has ascertained that the RESET signal is permanently active. If this is the case, until he gets to the bottom of this problem, everything else is sort of secondary until we have a working RESET signal...

Dave
 
It’s a 40pin if with rev 034 on it(901466-04) if you have dos 2 and i think 901466-02 for dos 1
 
Looking at you photo it is the 40 pin IC 901466-02. What is the code on the rom chip in the left and right sockets … ending -06 and -07 (checking they are in the right order)
 
AndyG said:
Looking at you photo it is the 40 pin IC 901466-02. What is the code on the rom chip in the left and right sockets … ending -06 and -07 (checking they are in the right order)
Click to expand...
901468-07 in UH1
901468-06 in UL1
 
daver2 said:
I am afraid everyone is distracting Desperado...

He thinks he has ascertained that the RESET signal is permanently active. If this is the case, until he gets to the bottom of this problem, everything else is sort of secondary until we have a working RESET signal...

Dave
Click to expand...
Dave maybe can use my scope to see if i have waveform on reset signal?
 
The RESET signal is either HIGH or LOW. There isn't a 'signal' as such. A voltmeter or logic probe would (in my opinion) be the tools to use. You can use an oscilloscope...

You have monitored the RESET signal before on all of your previous PET repairs with success. This should be no different...

The time that the RESET pulse is present for may be the only difference.

Dave
 
daver2 said:
The RESET signal is either HIGH or LOW. There isn't a 'signal' as such. A voltmeter or logic probe would (in my opinion) be the tools to use. You can use an oscilloscope...

You have monitored the RESET signal before on all of your previous PET repairs with success. This should be no different...

The time that the RESET pulse is present for may be the only difference.

Dave
Click to expand...
Can be 555 bad maybe?
 
The test that is proposed will identify that. Will you please stop guessing and perform the test...

This is the whole point about having tools such as a multimeter, a logic probe and an oscilloscope. You can perform a test to work out where the fault is without guessing.

Dave
 
daver2 said:
The test that is proposed will identify that. Will you please stop guessing and perform the test...

This is the whole point about having tools such as a multimeter, a logic probe and an oscilloscope. You can perform a test to work out where the fault is without guessing.

Dave
Click to expand...
but I have already done the test you proposed ... I do not see high signals but only low :(
 
My apologies - I missed it - too many posts...

With the button pressed, the output from the 555 (UM2/3 - which is also UL2/13) should be HIGH and the output from UL2/12 should be LOW.

When you release the button, after a short period of time, UM2/3 (UL2/13) should go LOW and the output from UL2/12 should go HIGH.

So, if your logic probe indicates neither a HIGH nor a LOW when the button is pressed this indicates that the output from the 555 is not a valid logic level. Faced with this - I would measure the DC voltage on UM2/3 with the button pressed. Post back what the voltage is.

I suspect that both the 555 (UM2) AND UL2 are both faulty. However, it could also be UL2 affecting the output from UM2.

With UM2/3 LOW (UL2/13 LOW) this should make UL2/12 HIGH. Hence the reason I suspect UL2 is faulty (but, as I have stated before, there could be something after UL2/12 holding the pin LOW).

Either way, if the UL2/12 output is permanently LOW, this is holding everything in RESET, so you have to resolve this issue FIRST before moving on with any further fault finding.

If you replace UL2 first, then perform the test again to see if you need to replace UM2 as well.

Are the capacitors C19 and C22 electrolytics or tantalum beads? They could also be faulty - but this will only affect the subsequent timing of the 555 reset pulse.

Dave
 
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