Finished build. Resistance issues. Need help troubleshooting.

[Paul Birkeland]

I would avoid the temptation to turn your amp on and seek out a different meter.

[Deke609]

And be sure you're testing resistance with the amp unpowered - I imagine you are, but thought it worth saying just in case.

And before getting a new meter, try a putting a fresh battery into the existing one. they can do weird things with a low battery.

cheers, Derek

[vaplen]

Didn't realize the posts continued on page 2.  I did try a different battery but that one seemed more dead than the one I was using... thanks for the suggestion though.  And yep unplugged when testing.  Does the power switch position make a difference?

I am not going to power it on until I am able to test it, the initial readings made me weary to try.  I think the meter I was using was not functioning properly though.

I will probably have access to another manual meter tomorrow, hopefully that will change things for the better.  Otherwise I will have to wait until I can get an automatic meter.

[vaplen]

Hi All,

So I tested with a different meter and got better results.  I am now convinced there is something wrong in the circuit.  I tested all terminals at the 2k selector.  There are some terminals I tested at a different range notated with '# tested at ____'

Terminal

1=0
2=1
3=1
4=1 #tested at 2M
5=1
6=1
7=1
8=0
9=0
10=1
11=1
12=1
13=1
14=0
15=0
16=1
17=1
18=1 #tested at 2M
19=1
20=1
21=1
22=0
23=1
24=1
25=1
26=1
27=1
30=.213
31=.213
32=.213
33=1
34=1
35=1
36=1

H1=0
H2=.213
H3=1.380
H4=.215
H5=.215
H6=1.380
H7=.215
H8=0

RCA Jacks
L center pin =1  Ground tab =1 #tested at 200k
R center pin =94.2 Ground tab = 0 #tested at 200k

[Paul Birkeland]

Yeah, so when you get a "1", you would go up in values until you get a reading. 

I would strongly suggest getting an autoranging meter. 

[Deke609]

To see if the meter is working, why not measure across one of the cathode resistors? I don't have an S.E.X., so I can't point to the terminal numbers. But you may be able to figure that out from the schematic and build instructions.

cheers, Derek

[Paul Birkeland]

I had him do that already, which mostly worked, but not being able to resolve the output stage cathode resistances points to a sub-par meter or one that just isn't working properly.

[vaplen]

So I bought an autoranging meter today. Here are the results.  Really not sure what to do.  I can't even measure the resistor on A9 or B9.  Maybe I used bad solder or something (Sn60/Pb40). but it worked fine for the glow test which would make me think it was something further into the wiring.  Any ideas would be great.

Terminal

1=0.4
2=OL
3=OL
4=OL
5=OL
6=OL
7=OL
8=0.2
9=0.3
10=OL
11=OL
12=OL
13=OL
14=0.1
15=0.4
16=OL
17=OL
18=OL
19=OL
20=OL
21=OL
22=0.1
23=OL
24=OL
25=OL
26=OL
27=OL

30=220
31=217
32=215
33=OL
34=OL
35=OL
36=OL

H1=0.4
H2=217.2
H3=OL
H4=215
H5=217
H6=OL
H7=215
H8=0

RCA Jacks
L center pin = OL  Ground tab = OL
R center pin = OL Ground tab = 0.4

[Thermioniclife]

Wow, I have been loosely following this thread and I think there is something fundamentally wrong with your testing procedure. And also the solder joints still look suspect. First does the solder have a rosin core flux? I can see at some joints it appears not. Next what kind of soldering iron do you have? is it adjustable or a fixed wattage? If a fixed wattage perhaps it is to low. I think a minimum would be a 40 watt iron. If adjustable crank it up. I run my Iron at 650-700 deg. F. very occasionally higher.
Next Please turn on your meter and set it to ohms and touch the tips together and note what the display shows. Post a pic. Next set the meter to DC volts which may be expressed by Vdc or a V with a solid line with a dashed line underneath find a 9 volt battery or a
AA or AAA battery and touch the probe tips to the battery terminals. Take a pic and post. It's easy hold the probes with your 2 hands and hold the camera with your third hand.
So lets start there Then we will proceed ok?

[Thermioniclife]

Also can you take a pic of the label on the roll of solder and your soldering iron or station?

[Paul Birkeland]

Let's start with the left grounding tab reading OL.

The left input jack/pot grounds all wire to 23, which you have with an OL, but it should be grounded.  23 attaches to 26, and your 26 is also OL, but should be grounded.  36 connects to 26, which both should also be grounded, but are not.  That's one entire side of the amp not grounded.  36 is also basically the output of the power supply, so it's a good idea not to turn the amp on until this is resolved.

On the other channel, the ground leaving 36 goes to 12, which also isn't grounded.  12 should go to 5 with a black wire, and that wire doesn't look well connected at 5. In that area be sure the drain wire on the shielded twisted pair wire is pushed down close to the chassis and the foil in that cable doesn't touch anything other than the chassis if necessary. 

Terminal 12 is wired to terminal 9, and you skipped that step.  I would imagine if you install the wire that should be there, things will start looking better.

[Thermioniclife]

OH I apologize I confused your thread with someone else building a Crack. So I will reread your thread to get it straight and get back to you.

[Thermioniclife]

PB to the rescue. What a Guy!

[vaplen]

Thank you very much Paul for breaking it down.  Thank you Thermionic as well.

This may be a dumb question, but how do I ground 23-etc.?  Is there something specific I should look for?  I went through the instructions over and it seems like everything is wired correctly.  I must be overlooking something.

I would imagine since they are all connected to 23 that it would be best to start there.

[Paul Birkeland]

I called out the specific mistake that you made in my last post.