2600 Jr. with boot delay & raspberry sound

[+x=usr(1536)]

Apologies in advance for the camera work; I don't have a direct capture device at the moment.

 

Here's one I can't find any info for: a 2600 Junior that has about a three-second boot delay, along with a raspberry sound while the delay is taking place.  This happens both with the Harmony Encore and retail cartridges, and, once it gets past the delay, works perfectly.

 

 

Disregard the on-screen noise; that seems to be down to the modern 9V, 1A power supply that I'm using.

 

I'm guessing that a cap is shot and is taking its sweet time to charge, but none of them appear to be damaged and/or leaking.  Has anyone run across this before and, if so, what was the fix?

[+Stephen Moss]

There may be other causes but I can only think of two things off the top of my head that might create that delay...

1) Power issue that result in a slow rise to the required supply voltage or

2) An issue with the Reset (RES) pin on either the RIOT or 6507 that results in a slow rise to 5V 

 

Usually for both the voltage should rise from 0V to 5V too fast to really notice any rise on multi-meter (maybe 0.1 seconds max), so if you have a multi-meter try checking if the voltage change seems instantaneous or changes over a few seconds.

If there is a slow voltage rise on the supply voltage that may take some tracking down, if the issue is with a Reset pin then it could be an internal issue with the IC or a problem with either the Capacitor or resistor value going high resulting in a longer capacitor charge time.     

[+x=usr(1536)]

5 hours ago, Stephen Moss said:

There may be other causes but I can only think of two things off the top of my head that might create that delay...

1) Power issue that result in a slow rise to the required supply voltage or

FWIW, this was happening before changing PSUs.  The voltage regulator was also replaced with a Traco 2-2450 DC-DC converter and the behaviour took place both before and after.  The Traco is measuring a steady 5VDC out.

 

Would it be reasonable to suspect C26 (the 2200µF main axial capacitor) as a possibility?  Note that I have no specific reason for the suspicion, just that it's early on in the power chain and is the first thing I can think of that may take a while to come up to spec.

5 hours ago, Stephen Moss said:

2) An issue with the Reset (RES) pin on either the RIOT or 6507 that results in a slow rise to 5V

Good point.  More:

5 hours ago, Stephen Moss said:

Usually for both the voltage should rise from 0V to 5V too fast to really notice any rise on multi-meter (maybe 0.1 seconds max), so if you have a multi-meter try checking if the voltage change seems instantaneous or changes over a few seconds.

Thank you for that; it's extremely helpful.  I'll check both the RIOT and 6507 and report back.

5 hours ago, Stephen Moss said:

If there is a slow voltage rise on the supply voltage that may take some tracking down, if the issue is with a Reset pin then it could be an internal issue with the IC or a problem with either the Capacitor or resistor value going high resulting in a longer capacitor charge time.     

Got it.  Fortunately, I do have known-good spares of all three main ICs to hand, so if socketing and swapping is required it's a realistic proposition.

[+Stephen Moss]

On 3/31/2023 at 1:56 PM, x=usr(1536) said:

Would it be reasonable to suspect C26 (the 2200µF main axial capacitor) as a possibility?  Note that I have no specific reason for the suspicion, just that it's early on in the power chain and is the first thing I can think of that may take a while to come up to spec.

Well at this point it could be anything so in that regard it is reasonable, but if the Traco is immediately putting out 5V at switch on then it is probably OK, but the only way to be sure is to check it.

[+x=usr(1536)]

Did some brief checking of the RIOT, 6507, and TIA to make sure that power was getting to them as expected.  Everything there seems normal - no delays were seen when watching them as the machine powered on.

 

One possibility I hadn't considered was the 4050, since that can control CPU reset.  If it's flaking out, it could be possible that at power-on it's taking longer than usual to ramp up, leading to the issue I'm seeing.  FWIW, the joysticks' buttons are working OK, so I'm not 100% convinced that this is the problem.

 

In any event, for right now I'd like to work on a couple of other projects for a bit that have been sitting on the back burner.  If the 4050 is going to be changed out, it should be socketed at the same time - along with the other three main ICs in the machine.  Making those changes isn't an issue, but I'd like to fiddle with something else before getting back to them.