S.E.X. 2.1 C4S No connection between 23U and OA/OB [solved]

[JosephDuffy]

Hi guys,

I finally got round to installing my C4S upgrade (for the second time, some of you will note) and whilst doing the resistance checks I noticed that I'm not getting a reading between 23U and OA/OB and between 23U and A5/B5.

I've checked the board's soldered in the correct places, and uploaded an image to be doubly sure (sorry for the flash. It's night time now so I can't take a great photo)

What joints can I be looking  at to try and reflow/diagnose the problem?

Thanks,
Joseph Duffy

[fullheadofnothing]

23 is ground. If any of the other terminals you listed were connected to ground, your amplifier wouldn't work. Additionally, what resistance checks are you using? There are none listed in the manual.

[JosephDuffy]

23 is ground. If any of the other terminals you listed were connected to ground, your amplifier wouldn't work. Additionally, what resistance checks are you using? There are none listed in the manual.

The original (S.E.X. 2.1) manual has the resistance checks on page 38. On there it recommends using terminal 23 to test the various terminals. It states that A5,B5 should be "*" (vary from ohmmeter to ohmmeter)

Do these values no longer apply with the C4S installed?

By "not getting a reading" I don't mean that I get a 0; the ohmmeter shows the default value

[Paul Birkeland]

The original (S.E.X. 2.1) manual has the resistance checks on page 38. On there it recommends using terminal 23 to test the various terminals. It states that A5,B5 should be "*" (vary from ohmmeter to ohmmeter)

whilst doing the resistance checks I noticed that I'm not getting a reading between 23U and OA/OB and between 23U and A5/B5.

I don't see what the issue is here?  There's no default value because this isn't really a measurable terminal. 

[JosephDuffy]

The original (S.E.X. 2.1) manual has the resistance checks on page 38. On there it recommends using terminal 23 to test the various terminals. It states that A5,B5 should be "*" (vary from ohmmeter to ohmmeter)

whilst doing the resistance checks I noticed that I'm not getting a reading between 23U and OA/OB and between 23U and A5/B5.

I don't see what the issue is here?  There's no default value because this isn't really a measurable terminal.

I should have a reading, though? When I take a reading over another terminal marked as "*" (such as between 23 and C1) I get an actual reading on my ohmmeter (in this case ~100), but when I measure it over 23 and A5 the ohmmeter shows no reading (like then neither probe is connected to anything)

[fullheadofnothing]

Terminals marked with an asterisk will vary from meter to meter because they are connected to reactive, and not purely resistive, components. Another meter will most likely give a different result; you can buy one if you feel it is necessary to see a "result." The important thing is that it is not reading 0 on these terminals.

[JosephDuffy]

Terminals marked with an asterisk will vary from meter to meter because they are connected to reactive, and not purely resistive, components. Another meter will most likely give a different result; you can buy one if you feel it is necessary to see a "result." The important thing is that it is not reading 0 on these terminals.

I've taken a few photos to clarify what I mean:

Not connected (no reading)

Black on 23U, red on 1 (a reading)

Black on 23U, red on B5 (no reading)

If this is correct and I'm just going mad then my apologies. I'm being a bit over cautious since I messed it up last time!

[Paul Birkeland]

I will reiterate that the terminals with an asterisk will read various values depending on the meter and the terminal itself.

As long as these aren't close to zero, you're OK.

The fact that one terminal may show some large number doesn't automatically imply that every asterisk terminal will show that same number. (because the readings will vary)

[JosephDuffy]

I will reiterate that the terminals with an asterisk will read various values depending on the meter and the terminal itself.

As long as these aren't close to zero, you're OK.

The fact that one terminal may show some large number doesn't automatically imply that every asterisk terminal will show that same number. (because the readings will vary)

I realise they won't all show the same, but the one in question (A5/B5) isn't showing a reading at all (i.e. not 0, not connected, the default value for the multimeter). If this is the correct behaviour then I will assume that it's safe to switch on. My only concern is that if there's meant to be some resistance and there's a voltage check to do across these terminals then I'd at least be seeing a reading of some description across these terminals, even when the amp is turned off. However, if there's not meant to be a connection then this won't be a worry.

My apologies if I am simply not understanding this

[Doc B.]

Yes the one reading you are concerned about is infinite resistance as far as your meter is concerned. So it's fine.

[JosephDuffy]

Thanks everyone, you were correct. I turned it on last night and all the LEDs lit up and the voltage checks were correct.

Sorry for my misunderstanding and thank you for everyone's patience. Now enjoying my new upgrade