Value of C21 on NTSC short-rainbow Junior PCB?

[+x=usr(1536)]

If you happen to have a short-rainbow NTSC Junior and could check the value of C21, I would greatly appreciate it.  Inadvertently crunched it while doing other stuff and cannot read the markings as a result.

 

FWIW, it's the capacitor circled just above the power switch in the following picture:

 

[+-^CrossBow^-]

Looks to be a 100nf 50v if the high res shots of other jr boards I found online are to be believed. I assume it is the small smd in a glass tube cap upper right of the large filter cap above the power switch you are talking about?

 

[+x=usr(1536)]

3 hours ago, -^CrossBow^- said:

Looks to be a 100nf 50v if the high res shots of other jr boards I found online are to be believed. I assume it is the small smd in a glass tube cap upper right of the large filter cap above the power switch you are talking about?

Yep, that's the correct location, but my board had the same blue axial cap as highlighted in the picture that I posted.  If I had to hazard a guess, I'd say that it's probably ceramic, at least based on the sound one of its type elsewhere on the board makes when tapped with a screwdriver.

 

I've also been searching for hi-res photos with readable markings, but no luck yet.

[+-^CrossBow^-]

10 hours ago, x=usr(1536) said:

Yep, that's the correct location, but my board had the same blue axial cap as highlighted in the picture that I posted.  If I had to hazard a guess, I'd say that it's probably ceramic, at least based on the sound one of its type elsewhere on the board makes when tapped with a screwdriver.

 

I've also been searching for hi-res photos with readable markings, but no luck yet.

Probably the same value and you just have mlcc type vs the SMD encapsulated one shown in the pics. I do know that the other cap just opposite it on the south end of the large filter cap is the same value. If you can read that one, it should be the same.

 

[+x=usr(1536)]

1 hour ago, -^CrossBow^- said:

Probably the same value and you just have mlcc type vs the SMD encapsulated one shown in the pics. I do know that the other cap just opposite it on the south end of the large filter cap is the same value. If you can read that one, it should be the same.

Ah, cool, thanks.  Appreciate it!

 

FWIW, I did take a look at the Jerzy Sobola schematics for the 2600 Jr., but I have two reservations about them: one, they're for a PAL machine; two, I tend to question their accuracy given some of the things I've run into with them.

 

They do give the value as 1nF; I'm just not sure how far I should trust that.  Will read the other cap later and see how it compares.

[+-^CrossBow^-]

7 minutes ago, x=usr(1536) said:

Ah, cool, thanks.  Appreciate it!

 

FWIW, I did take a look at the Jerzy Sobola schematics for the 2600 Jr., but I have two reservations about them: one, they're for a PAL machine; two, I tend to question their accuracy given some of the things I've run into with them.

 

They do give the value as 1nF; I'm just not sure how far I should trust that.  Will read the other cap later and see how it compares.

Those caps in the image I found are clearly marked as 104 type. That is .1µf or 100nf and I sure it is the same value used regardless of which specific type was installed. MLCC, or even an older ceramic disc type could be used there.

 

 

[+x=usr(1536)]

11 hours ago, -^CrossBow^- said:

Those caps in the image I found are clearly marked as 104 type. That is .1µf or 100nf and I sure it is the same value used regardless of which specific type was installed. MLCC, or even an older ceramic disc type could be used there.

Which is a fair point.  I'm going to stop stressing over the value and install a .1µF; they're available and if that's what was on that board, that works for me.  Can't read the complementary one on my machine's board without unsoldering it, which I really don't feel like doing this evening.

[+x=usr(1536)]

Just to close the loop on this: C21's value is .1µF, at least based the value of the cap I removed from C12.  Both caps perform the same function (smoothing Pin 7 / +5VDC on the joystick ports), so values should match.

 

FWIW, the Sobola schematics call for 1nF for both C21 and C12, which seems too small to be useful.  Not gonna go so far as to say that they're wrong, because that may be correct for the PAL machines his schematics are based on, but the NTSC model I have here definitely had a .1µF at C12.