Resistance problems

[Maynard]

Hi guys, just finished the resistance check for the crack. All the terminal readings were fine except as follows...
I'm using an auto ranging multimeter. Its not expensive neither is it a cheap one though!
3 no response. Meter reads "O.L>"
7 no response. Meter reads "O.L"
8 no response. Meter reads "O.L"
9 no response. Meter reads "O.L"
13 manual says it will creep lowly up to 270k, but it comes down from approx 7.0 m ohms
22 no response. Meter reads "O.L"

B3 + B6 no response. Meter reads "O.L"

Left ground tab of rca Ranges around the display says "O.L".

Left center pin display reads O.L.

As I'm a total beginner I'd really appreciate some help!!
Thanks!

 

[Doc B]

For starters check your soldering at terminal 3. The readings suggest something is not properly connected to ground, possibly at that point.

Or possibly the black lead of your meter was not properly connected to the circuit.

 

[Maynard]

Thanks for your reply Doc. First of all, when I attach the alligator clip to T12 to ground, does it matter where on the terminal I place it? Its just straddling the top of t12 at the moment, over the resistor and a black wire. Also there are a couple of places where I singed the insulation on the wire, but I do not think I singed it to the wire within. Would this matter?

 

[Doc B]

What you are looking for is if you have good electrical contact at both where the test lead is connecting to T12 or at terminal 3 and the wires connected to it.

Making sure everything that should be connected to T3 is connected is the place to start. At terminal 3 visually inspect for a wire that didn't get properly soldered. Once you have confirmed that everything that should be attached is attached reheat the joint to reflow the solder.

Once that is done redo your measurements. For the test lead at T12, wiggle it to make sure that the teeth are making good contact with the terminal's metal after you clip it on.

 

[Maynard]

OK thanks have wiggled the black lead and it is making good contact with the T12. Now I'm getting a reading of 39.53 M ohms that is wandering up. At least I'm getting a reading now. Everything looks like it is in place after double checking the correct connection. I suppose the next step is to reflow the connections.

 

[Paul Birkeland]

OK thanks have wiggled the black lead and it is making good contact with the T12. Now I'm getting a reading of 39.53 M ohms that is wandering up.

That's not really a connection at all.

Touch your meter probes together, then note that resistance.  It probably won't be 0 Ohms, but certainly less than one.  You want to see that reading, or just a little bit more between 3 and 12.

One place that is very problematic for builders is where the two black wires solder to the headphone jack.  I have found many loose wires there, which essentially disconnects the power supply from the amplifier circuit.  I have even seen some working amps that sounded terrible until this connection was well soldered.

-PB

 

[Maynard]

Cheers for that guys will check.

 

[Maynard]

just finished resistance check, and it all reads fine except for t13. t13 does not climb up to 270k but starts in the m ohm region and goes down. hmmm is this ok? Have reflowed a lot of wires and it's obviously helped! 

 

[fullheadofnothing]

That's fine. Different meters will read it differently because of the large capacitor.

 

[Maynard]

Sweet!! Thanks!