Misreadings and maybe bad RCA jack?

Netsky · 1200

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Offline Netsky

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on: December 26, 2019, 06:50:31 AM
Hello,

I have a few things about the readings of my crack.
At both terminal 2 and 4 there is a 0 ohms reading, I think those aren't supposed to be 0 because those values are signified with a *?
Terminal 1 and 3, which are also signified with a *, both have a 22.2k ohms reading, I think this is okay, and maybe those are the only 2 * terminals not supposed to have a 0 reading?

Another thing, I have no reading at all on the center pin of the black RCA jack, the red one has a 95k ohms reading.
I think maybe the black RCA jack is broken, because the center pin on the black one where the wire goes in is loose, I can move it up and down, which is not the case with the red one, no movement at all there.
There is also way too much solder at the terminal of the potentiometer where the white wire from the black RCA jack is connected to, but not so much that it connects directly to the other terminals or the metal from the potentiometer itself.

The rest of the readings are good. What could be the problem?

Netsky



Online Paul Birkeland

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Reply #1 on: December 26, 2019, 07:07:14 AM
At both terminal 2 and 4 there is a 0 ohms reading, I think those aren't supposed to be 0 because those values are signified with a *?
It's very important that you not power up your Crack until this is resolved.  Are you certain this is 0 and not OL?

Terminal 1 and 3, which are also signified with a *, both have a 22.2k ohms reading, I think this is okay, and maybe those are the only 2 * terminals not supposed to have a 0 reading?
That would tend to suggest that 2 and 4 are indeed 0.  Can you post some build photos?


Another thing, I have no reading at all on the center pin of the black RCA jack, the red one has a 95k ohms reading.
What does "no reading" mean?  What does the meter say? 

I think maybe the black RCA jack is broken, because the center pin on the black one where the wire goes in is loose, I can move it up and down, which is not the case with the red one, no movement at all there.
I bet if you plug a cable in, it doesn't move.  I wouldn't worry about this.

There is also way too much solder at the terminal of the potentiometer where the white wire from the black RCA jack is connected to, but not so much that it connects directly to the other terminals or the metal from the potentiometer itself.

The rest of the readings are good. What could be the problem?
So you didn't get 0 ohms at terminal 13?  Terminal 13 connects with wire to B5, then B2, then 2, then 4.  If you didn't get 0 ohms at 13 but you get 0 ohms at 2 and 4, then there is a miswire.  (We can probably see it from some build photos)

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Netsky

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Reply #2 on: December 26, 2019, 07:27:58 AM
It's very important that you not power up your Crack until this is resolved.  Are you certain this is 0 and not OL?
That would tend to suggest that 2 and 4 are indeed 0.  Can you post some build photos?

What does "no reading" mean?  What does the meter say? 
I bet if you plug a cable in, it doesn't move.  I wouldn't worry about this.

So you didn't get 0 ohms at terminal 13?  Terminal 13 connects with wire to B5, then B2, then 2, then 4.  If you didn't get 0 ohms at 13 but you get 0 ohms at 2 and 4, then there is a miswire.  (We can probably see it from some build photos)

Yes the readings on terminals 2 and 4 are 0, when I try to read the terminals it goes to 0.00.

I didnt get 0 ohms at terminal 13, it climbs slowly toward 270k ohms.

The reading at the center pin of the black RCA jack does nothing, there is always a 1 or l ? by default on the meter and if I measure the other terminals it goes to 0.00 ohms or for example to 95.0k ohms on the red RCA jack center pin.

I will try to check for the miswiring.
« Last Edit: December 26, 2019, 07:32:31 AM by Netsky »



Online Paul Birkeland

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Reply #3 on: December 26, 2019, 07:37:55 AM
So we can be nearly certain that there is a miswire then.  The red wire that leaves the 6 lug strip and goes to the octal socket may not be connected to the correct terminal at the 6 lug strip, though I would check all of the wiring at the 6 lug strips.

The 1 at the black center pin of the RCA jack would make me wonder if the reading is just over 100K, and thus over the range of your meter, but you were able to resolve a 270K reading elsewhere.  What I would then wonder is if you have the jumper between the lugs on the volume pot where the black wires connect?

Posting some build photos is still a very good idea.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Netsky

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Reply #4 on: December 26, 2019, 11:53:27 AM
So we can be nearly certain that there is a miswire then.  The red wire that leaves the 6 lug strip and goes to the octal socket may not be connected to the correct terminal at the 6 lug strip, though I would check all of the wiring at the 6 lug strips.

The 1 at the black center pin of the RCA jack would make me wonder if the reading is just over 100K, and thus over the range of your meter, but you were able to resolve a 270K reading elsewhere.  What I would then wonder is if you have the jumper between the lugs on the volume pot where the black wires connect?

Posting some build photos is still a very good idea.

I found and corrected the miswire, it was the red wire going from B5 to terminal B12, it should have been terminal B13. All the wires should be wired correctly now.

Now the readings on terminal 1, 2, 4 and 5 are all the same. They are 30k ohms and still climbing, exactly the same as terminal 13, I suppose that is correct? If those readings are correct then all the readings are correct now except for the black center pin where there is still no reading at all.

The 1 at the black center pin is not because the reading is over 100k I think, because the reading is capable to read up to 2000k.
Where the 2 black wires connect at the bottom of the volume pot there is a wire going up so that is okay I think.
I have included a photo of the point where the white wire from the black RCA jack is soldered to the volume pot, and there is way too much solder there in comparison with the others, the little hole (not the hole that the wire goes through) connected directly on the volume pot itself is completely filled up with solder in comparison with the other connections, maybe this is the cause that there is no reading at the black center pin? The solder is not so much that it is soldered directly to other important parts or connections though.

I have also checked readings of all the 6 connections directly at the volume pot, and the only one that doesn't give a reading is the white wire connected to the black center pin.

Tomorrow I can make more photo's of the whole if those are still necessary now. Now there is too little light for good visibility.
« Last Edit: December 26, 2019, 12:17:46 PM by Netsky »



Online Paul Birkeland

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Reply #5 on: December 26, 2019, 01:06:39 PM
Although that image is not totally in focus, it's completely possible that you've damaged the pot with all that solder.

To solder successfully to the pot, just wrap each wire around the terminal on the pot, then solder just where the wire is wrapped.  There is absolutely no need to fill the hole on the pot terminal with solder if you have the wires wrapped and squeezed onto the terminal.

In your case, there's solder going all the way into the pot where the white wire connects in the photo, so there's some potential for damage to have been done.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Netsky

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Reply #6 on: December 26, 2019, 01:18:07 PM
Although that image is not totally in focus, it's completely possible that you've damaged the pot with all that solder.

To solder successfully to the pot, just wrap each wire around the terminal on the pot, then solder just where the wire is wrapped.  There is absolutely no need to fill the hole on the pot terminal with solder if you have the wires wrapped and squeezed onto the terminal.

In your case, there's solder going all the way into the pot where the white wire connects in the photo, so there's some potential for damage to have been done.

If the volume pot is damaged, how can I get a replacement?

Tomorrow I will try to remove some of that solder, maybe it will fix the problem.

Is there no way that the black RCA jack is the problem if the wires are correct?



Online Paul Birkeland

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Reply #7 on: December 26, 2019, 01:21:37 PM
I would e-mail replacementparts(at)bottlehead(dot)com about getting a new pot.  If you're not in the US, I can help you find a local source in your country if international shipping is a problem.

Sucking the solder out might help, but then again it may not. 

The black RCA jack will not create infinite resistance in that manner, it's the carbon track in the pot that is approximately 100K, and not seeing 100K there means the outer lug is no longer connected to the carbon track (probably from that solder flowing in there).

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Netsky

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Reply #8 on: December 27, 2019, 03:22:32 AM
I would e-mail replacementparts(at)bottlehead(dot)com about getting a new pot.  If you're not in the US, I can help you find a local source in your country if international shipping is a problem.

Sucking the solder out might help, but then again it may not. 

The black RCA jack will not create infinite resistance in that manner, it's the carbon track in the pot that is approximately 100K, and not seeing 100K there means the outer lug is no longer connected to the carbon track (probably from that solder flowing in there).

I fixed the connection at the volume pot! I sucked some solder away and now it gives a reading at the black center pin, 101k ohms, it is 1k more than what is the max in the manual, is that okay? Also, the red center pin has a reading of 95k ohms, is that difference normal?

Another thing, the terminals 6, 7, 9, 10, B3 and B6 all have a 0.1K ohms reading higher (2.5K / 3K instead of 2.4K / 2.9K) than whats on the manual, is that okay too?

Before I fire up the crack, I have to know that these things are alright.
« Last Edit: December 27, 2019, 03:27:42 AM by Netsky »



Online Paul Birkeland

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Reply #9 on: December 27, 2019, 05:05:10 AM
Yes, resistors have a tolerance range that will mean those readings aren't spot on (some meters aren't spot on too).  The difference in DC resistance of the volume pot is a frequent question here but rest assured that this difference is completely normal and won't cause operational issues.  I would go ahead and fire up your Crack now that you have the resistances sorted out.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man