News: Trouble logging in? Log in from the login page.
August 17, 2019, 11:47:34 AM

Author Topic: Resistance checks failed  (Read 3362 times)

0 Members and 1 Guest are viewing this topic.

Offline brando666

  • Jr. Member
  • **
  • Posts: 13
Resistance checks failed
« on: September 09, 2012, 02:16:08 PM »
Hey guys,
Hopefully this isn't a doublepost. Something went wrong when I was submitting my first post.

This is my second kit I've ever completed, first being a simple opamp headphone amplifier. I really took my time putting this thing together and making sure I had good solder connections. Really great job on the manual, very clear and concise even for a beginner. I did follow the revision for 14U to 22L.

Got to the end and started doing the resistance checks and uh-oh. Things are not looking right. Would really appreciate some assistance. I feel like there's one thing out of place that I'm missing, and as soon as I figure that out it's all going to fall into place. Here's the readings and attached is a picture for reference.

1   *
2   *
3   .2
4   *
5   *
6   *
7   *
8   .2
9   *
10   *
12   .2
13   *
14   0
20   0
22   .1

B3   *
B6   *

Offline Grainger49

  • Hero Member
  • *****
  • Posts: 7175
Re: Resistance checks failed
« Reply #1 on: September 09, 2012, 02:38:34 PM »
Dan's advice in the General Folder:

http://www.bottlehead.com/smf/index.php/topic,1667.0.html

At least 80% of the initial problems are caused by a solder joint that isn't quite right; a few are swapped parts.  Rewetting is the fix.  This means to heat the soldering iron, touch a tiny bit of solder to it and use that wet solder to heat every solder joint in the kit.

Look here for a little help (question 7) on understanding your meter readings:

http://www.bottlehead.com/smf/index.php/topic,2408.0.html

A recent Crack was bad because the main grounding lug (either terminal 3 or 6) had never been soldered.  That screws up all the resistance measurements.  

Once that is done post only those measurements that are greater than 15% out of spec.  Post the terminal number, expected value and your reading.  Be aware that some meters might read 0.600 k ohms instead of 600 ohms.  You have to watch the multiplier.

« Last Edit: September 11, 2012, 04:46:01 AM by Grainger49 »

Offline Paul Joppa

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4854
Re: Resistance checks failed
« Reply #2 on: September 09, 2012, 02:52:07 PM »
Given that everything is either ~0 or * I have to wonder if you are using the correct range and lead connections on the meter. There are 3K cathode resistors (big ones) which you should be able to measure with one lead on each end of the resistor to prove your meter is working correctly.
Paul Joppa

Offline brando666

  • Jr. Member
  • **
  • Posts: 13
Re: Resistance checks failed
« Reply #3 on: September 09, 2012, 03:16:29 PM »
Sure enough, switched from my Fluke to a $5 ratshack meter and am getting readings. Must be broken or need batteries. Kinda feel stupid now :X Thanks for tips! You guys rock.

Offline Laudanum

  • Sr. Member
  • ****
  • Posts: 888
Re: Resistance checks failed
« Reply #4 on: September 10, 2012, 12:24:02 AM »
Ya know ... lots of guys here recommend Fluke meters and shun the cheap ones.  I used a Fluke at work.   I have nothing but "cheaper" meters at home.  Actually 3 of them.  Two are older meters, from Rat Shack, bought years ago, probably both in the early and mid 90's.   One is a 2 year old Tenma.   I wont argue with the Flukes being better meters or the cheap ones often being junk ... the modern cheap ones especially.  Actually, those two Rat Shack meters werent exactly "cheap" (over $50 for each, one was $70 if memory serves), neither was the Tenma.  They were very cheap relative to a comparably featured Fluke.   One of the Rat Shack meters reminds me very much of a Fluke and may well have been made by Fluke for all I know (edit, out of curiosity, I checked, it's not made by Fluke but they tried to make it look like it could have been ... on the older models anyway).   The other is a true RMS meter.   But anyway ... get your Fluke working, obviously they are good meters.  And good to hear that it was the meter and not you.

By the way, both those R.S. meters still work fine.  It's the newer Tenma that is a piece of junk and works when it wants to.   All that said, my recommendation would be with the rest for a Fluke or other quality meter, not a cheapie.   I dont need a Fluke as I know those two older meters are good.  But I wouldnt trust the cheap meters made today.  That Tenma was a waste of $40 that could have been put toward a Fluke or other quality meter.  I only bought it because I thought the one RS meter was going (it was a lead) and I couldnt find the other at the time.

Now that you have the resistance checks done, and I assume OK,  get that Fluke up and running and check those voltages.
« Last Edit: September 10, 2012, 12:38:46 AM by Laudanum »
Desmond G.

Offline Grainger49

  • Hero Member
  • *****
  • Posts: 7175
Re: Resistance checks failed
« Reply #5 on: September 10, 2012, 12:39:03 AM »
Desmond,

Keeping in mind that you said "cheaper" I'm against a dirt cheap meter.  The trouble with a $6 meter is that no one can know if they will get a good one.  I would expect that even if you have one that works the next three from the same batch might give faulty readings. 

Doctors don't buy cheap stethoscopes, mechanics buy good sockets and ratchets, and you and I used Fluke meters at work.  All are professional grade products.  (At Alcoa I had an analog Simpson, an older version of today's 270.)

But the original point that started this was that an inexpensive soldering iron can result in bad solder joints.  I did have a Radio Shack pen way back when, the 1960s.  But soon I used a good one and bought a WTCP, Weller.

Offline Laudanum

  • Sr. Member
  • ****
  • Posts: 888
Re: Resistance checks failed
« Reply #6 on: September 10, 2012, 01:48:19 AM »
Grainger, agreed that "cheap" is a relative term.  But I wouldnt buy another $40 chinese made off brand meter today.   If I had to buy a new meter today, it would be a Fluke or other well regarded name brand.  We are on the same page here.  The $50 Rat Shack meters I bought that were made 15 or 20 years ago are decent meters and have served me well.  But forget a $5 meter, a $50 off brand meter made today is probably a crap shoot.  From my last experience with that $40 Tenma, I wouldnt buy another semi-off or off brand meter at that price.  It was a waste of money that could have gone toward a Fluke, maybe would have even paid for a good condition, used, entry level Fluke.   Agree also on the pencil/pen irons.   I went through several $5 pencil irons until I finally bought a decent station.   Funny though, my station is a Tenma brand as well.  Difference is, it was bought a dozen years ago and is heavy and solid.   That $40 Tenma meter feels like cheap junk, and it is.  I dont want to bad mouth the entire brand, they probably still make some decent stuff.  But that meter isnt a good example if they still do.  
Desmond G.

Offline brando666

  • Jr. Member
  • **
  • Posts: 13
Re: Resistance checks failed
« Reply #7 on: September 10, 2012, 08:11:34 AM »
Got the fluke up and running and did the voltage checks. Everything is looking great!

Man this thing sounds like a dream.

Thanks for all the input guys, this community truly lives up to its reputation.

Offline Laudanum

  • Sr. Member
  • ****
  • Posts: 888
Re: Resistance checks failed
« Reply #8 on: September 10, 2012, 09:18:34 AM »
Nice to hear.  Enjoy!
Desmond G.

Offline Nick Tam

  • Full Member
  • ***
  • Posts: 66
  • "Crack on Crack"
Re: Resistance checks failed
« Reply #9 on: September 10, 2012, 02:15:32 PM »
Somewhere in the manual, cheapo meters should be noted as a cause of failure
Bottlehead Crack

Source: Fostex HP-A4
Cans: Sennheiser HD700
Sylvania GB6080 + Sylvania VT-231

Offline Laudanum

  • Sr. Member
  • ****
  • Posts: 888
Re: Resistance checks failed
« Reply #10 on: September 11, 2012, 01:52:40 AM »
Nope, this one doesnt count in the bad cheap meter sweepstakes.  The $5 meter worked for resistance checks in this case when the Fluke didnt (probably just dead battery for resistance checks).  The OP got the Fluke running for the voltage checks.   Still doesnt make a good case for cheapo meters, it just wasnt the cheap meters fault in this example.  It was just a fluke  ;D
Desmond G.

Offline Grainger49

  • Hero Member
  • *****
  • Posts: 7175
Re: Resistance checks failed
« Reply #11 on: September 11, 2012, 04:44:41 AM »
Ok, deleting all cheap meter references.  (In the voice of ObiWan saying, "these are not the droids you are looking for)  This horse is dead.


(https://forum.bottlehead.com/proxy.php?request=http%3A%2F%2Fi244.photobucket.com%2Falbums%2Fgg7%2FGrainger49%2Fdeadhorse.gif&hash=33d5c7338faaa912bbddeb99b76d00d5)
« Last Edit: September 12, 2012, 04:04:01 AM by Grainger49 »

Offline brando666

  • Jr. Member
  • **
  • Posts: 13
Re: Resistance checks failed
« Reply #12 on: September 11, 2012, 04:48:01 AM »
In all fairness, it was a cheap $5 meter I bought from ratshack probably fifteen years ago :)

Offline Laudanum

  • Sr. Member
  • ****
  • Posts: 888
Re: Resistance checks failed
« Reply #13 on: September 11, 2012, 08:27:45 AM »
I think that they can make them for so little money now that it's more a question of them working or not working.  Or rather, how long they last.  If they work, they work.   But then they seem to be more quirky with some measurements based on what some members report here (with their measurements).   Maybe having 3 or more meters is the key to using the cheap ones.  You have back-ups in case one breaks and you have a back-up to confirm what you are measuring from the one in use in the event it seems funky.   It's definitely an approach one could take that would probably work out ok, or atleast better than relying on only one cheapy.
Desmond G.