Resistance check question [solved]

[DenverDude]

I just finished assembling the Crack this weekend (lots of fun ... haven't assembled anything like this since I was a kid doing school projects), and so I'm a bit tentative about plugging this in for the voltage check before I doublechecked a few resistance readings I'm getting.

For the following terminals, I'm getting these readings on my analog multimeter:
6 - 3.0K
7 - 3.5K
9 - 3.5K
10 - 3.0K
13 - It shoots quickly to 2.0K and stays there
B3 - 3.5K
B6 - 3.5K

Is this normal variance? If so, am I good to move on to the voltage check? If not, what might be the issue?
All other resistance readings are either in range or spot on.

Thanks a bunch in advance your your help ... the manual and kit have been excellent so far.

[Paul Birkeland]

What kind of meter are you using? 

Terminal 7 has a 3K resistor to terminal 3, can you confirm that this is installed, then measure it in-circuit (one probe on 7, one on 3).  What do you get?

You have readings that are all a little on the high side, which is why I think it's a meter issue.

Terminal 13 is a bit of a problem, can you look at the finished photo in the manual and check your work?  Of interest would be the red/black wires, and where they are going to and coming from.

At this point, do not move on to the voltage checks. 

-PB

[DenverDude]

Thanks for the quick reply, Paul.

So the Terminal 7 to Terminal 3 reading was 3.4K ohms. The meter I'm using is a Radio Shack Model 2200037 19 range analog multimeter.

As for Terminal 13, everything seems to be in place as depicted in the manual. The only wire on that terminal is a red wire that is connected to terminals B5 then B2. And the rest that is connected to that terminal is the unstriped end of the 220uF 250V capacitor, the red striped end of the 270k ohm 1W resistor and one lead of a 270ohm 5W resistor (bottom terminal). I tested it again and same result ... just goes immediately to 2.0K ohms.

I'm not very experienced with assembling electronics, so I'm sure I'm doing something wrong. I have attached pics that show this terminal ... thanks for your help.

http://blog.planningpod.com/wp-content/uploads/2014/02/DenverDudeCrack2.png

http://blog.planningpod.com/wp-content/uploads/2014/02/DenverDudeCrack1.png

[Paul Birkeland]

Is the single black wire coming from power transformer Terminal 4 or 5 going to 13 or 14?

You have an analog meter, they respond very quickly, you never really get an exact number.

T13 is wired to T2 and T3, the funky resistances should also show up there? (As well as B2/B5)

[DenverDude]

Single black wire is going from Transformer terminal 4 to Terminal 14L.

As for other readings, here's what I measured:
Ground to T2 = 2.0K
Ground to T3 = 0
T13 to T2 = 0
T13 to T3 = slow climb from 80K to 270K

And yes, the resistances for B2 and B5 are:
Ground to B2 = 2.0K
Ground to B5 = 2.0K

I hope that helps ... thanks.

[Paul Birkeland]

Remove the red wire from 13 and repeat the measurements.

We need to figure out where this is coming from.

Also, I'd be triple-sure that you are indeed getting 2.0K on your meter, and not 200K or 2M, which can be less than clear on an analog meter.

[DenverDude]

Hello Paul -

I'm fairly certain that I'm reading the meter correctly, and I even installed new batteries in it.

I removed the red wire from Terminal 13, and here are my new readings:
Ground to T2 - The meter does not register a reading (i.e., it does not move)
Ground to T3 - 0
Ground to T13 - 1.9K
T13 to T2 - The meter does not register a reading (i.e., it does not move)
T13-T3 - Slow rise from 20K to 270K

Also, just want to double check, but the tubes SHOULD NOT be in, correct?
Thanks...

[Paul Birkeland]

You can pull the tubes out and recheck, just to be certain.

What is the resistance between T3 and 20
T3 and 21
T3 and 15

Can you post an overhead shot of the power supply?

[DenverDude]

So, there are no tubes installed (and I have not installed them for any of the resistance testing), and the red wire from T13 to B5/B2 is not connected to T13.

Here are the readings:
T3 to T20 = 0
T3 to T21 = 950 ohms
T3 to T15 = slow rise from 20K to 270K

Here are three overhead shots of the power supply area:
http://blog.planningpod.com/wp-content/uploads/2014/02/2014-02-26-15.04.37.jpg
http://blog.planningpod.com/wp-content/uploads/2014/02/2014-02-26-15.05.30.jpg
http://blog.planningpod.com/wp-content/uploads/2014/02/2014-02-26-15.05.42.jpg

Thanks...

[Paul Birkeland]

So, there are no tubes installed (and I have not installed them for any of the resistance testing), and the red wire from T13 to B5/B2 is not connected to T13.

Here are the readings:
T3 to T20 = 0
T3 to T21 = 950 ohms
T3 to T15 = slow rise from 20K to 270K

OK, I'm going to go ahead and say that this is a meter issue.  T15 and T21 are connected by a 270 Ohm resistor.  If T21 is 950 Ohms, T15 should be ~1.2K, but it is not. 

Go ahead and install the tubes and move on to the voltage checks (And reconnect the disconnected wires).  For future kit builds, I'd look online for a $15-ish digital multimeter. 

-PB

[DenverDude]

So, Paul, I owe you a big apology ... it definitely was the analog multimeter I was using. I just bought it at Radio Shack a few weeks back, so I returned it today and picked up a digital multimeter. And that made all the difference.

All the resistances tested in range, all the voltages tested in range, and I am now listening to wonderfully warm, rich music through my new Crack and my Sennheiser HD600s. It sounds awesome!!!

I owe you a drink (or a couple). If you are ever in Denver, let me know. I go to Rcky Mtn Audio Fest every year.

Thanks a bunch...

[Paul Birkeland]

Ah, I'm glad everything worked out!  I suspect you may find us in Denver later this year...

As a funny story about Radio Shack meters, I taught an amplifier building class at the last VSAC trade show.  Needing a bunch of cheap meters to do final voltage checks on each amplifier, I bought 5 of their inexpensive digital pocket volt meters. 

When it came time to use these, all 5 of them were completely defective.  None of them could measure the 120V coming out of the wall, none of them could measure ~0 Ohms when the meter probes were touched together, and I concluded at that point that I wouldn't ever buy anything from Radio Shack again! 

Enjoy the tunes,
-PB

[DenverDude]

Interesting ... that's sort of sad, because I always relied on the Shack harkening back to the days when I was a kid fiddling around with making radios.

I had another quick, completely unrelated question. Do you have any recommendations for books or resources for beginner electronics builders? I'm wanting to get more into building amps and preamps, but I need to know more about basic circuitry and the like before I feel comfortable diving into building more complicated kits (or even something from scratch). Any advice would be much appreciated ... thanks again, you are an awesome resource.

[Grainger49]

There are a number of Bottleheads in the Denver/Boulder area.  You might reach out to some. 

Just post in the General forum and ask for Bottleheads in that area.

[Paul Birkeland]

The NEETS texts are a good place to start, and are available in PDF form online.

NEETS

Morgan Jones's book is also popular, but I'd read through the NEETS texts too. 

-PB