Resistance Issues

[JL23]

Hi everyone,

I had my crack up and running, but the 6080 tube didn't sit properly in its socket. I got a new one and installed it--everything peachy, except a bit of static.  I have tried desoldering and resoldering joints, but I am pretty horrible at getting desoldering braid to actually pick up any solder, and fear I am just doing more damage by burning and blackening the current solder.

Since my resoldering escapades, I have been having some issues with some terminal readings having resistance values that climb to 200k, when they should be 0.

I assume that I am going to have to figure out how to properly desolder and then resolder everything... but I have decided to stop fiddling with it and hope that someone can provide some insight before I accidentally destroy the whole set-up.


Below are the readings and pictures of my circuit. Any help would be greatly appreciated!

1. Climbs past 200k
2. Climbs past 200k
3 0 ohms
4 Climbs past 200k
5 Climbs past 200k
6 2.4K ohms
7 2.9K ohms
8 0 ohms
9 2.9K ohms
10 2.4K ohms
12 0 ohms
13 Climbs past 200k
14 0 ohms
20 0 ohms
22 0 ohms
B3 2.9K ohms
B6 2.9K ohms
RCA jacks:
Ground lug 0 ohms
Center pin 100K ohms

[Paul Birkeland]

Tell us about the solder, iron, and needlenose pliers you're using.

To get a good quality solder joint, generally you want to pass leads through the hole on the terminal strip or tube socket, then bend them up and solder between the hole and the bent elbow of the lead.  This gives your solder a good place to flow into and stay put.

From what I can see of your photos, it's likely that either your iron is a little light on the heat or you might have lead free solder.

[JL23]

Tell us about the solder, iron, and needlenose pliers you're using.

To get a good quality solder joint, generally you want to pass leads through the hole on the terminal strip or tube socket, then bend them up and solder between the hole and the bent elbow of the lead.  This gives your solder a good place to flow into and stay put.

From what I can see of your photos, it's likely that either your iron is a little light on the heat or you might have lead free solder.

So I'm pretty sure I did follow that technique, but for clarification: I would pass the wire through and bend it around the strip/socket. I would heat up the joint by putting the iron on the socket opposite to where the wire was bent. I would hold the solder on the junction between the wire and the socket, and would flow a bit in when the metal was hot enough to melt the solder.

I originally used a tin/lead solder, but it basically just burnt and bubbled brown and black as soon as it touched the metal. From there I went to a lead/silver solder, the ratio on it says 62/36/2.

I am using a 40 watt soldering station. I generally have the heat on 4.5 (https://www.amazon.ca/Weller-WLC100CUL-40-Watt-Soldering-Station/dp/B00PVV6T1C/ref=sr_1_14?ie=UTF8&qid=1534694460&sr=8-14&keywords=soldering+station)

[Doc B.]

The brown and black bubbling stuff is flux. You need to hold the iron on long enough that the solder melts and flows over and through the flux.

[Deluk]

Make sure the tip is clean, by sponge or wire mesh pad. Use distilled water on the sponge. Flow a little solder on the tip so it's nice and silvery, not black and crunchy. Wipe tip again and add a small amount of solder to the tip. Place tip on the joint. The new "wet" solder will transfer the heat quicker. When hot and the small amount of solder starts to flow add just enough solder to make a good looking joint. It doesn't have to be a lot to make a good joint. I will use braid sometimes but generally prefer a spring loaded solder sucker. Once you get used to using one it is easy. Be careful if you use it on a board as the suction is pretty fierce and can lift solder pads if you've got the joint over hot.

[SpeedyDad]

Does the wiring of the headphone jack matter? I see that the resistors are grounded but the other joints are not grounded. Not sure how much that can be the cause of the issues you are seeing but it probably needs addressing.
When you get the hang of solder wick and have desoldered a part, be careful not to touch the wick too quickly. I got a nice burn a day ago.

[Paul Birkeland]

Does the wiring of the headphone jack matter? I see that the resistors are grounded but the other joints are not grounded. Not sure how much that can be the cause of the issues you are seeing but it probably needs addressing.

This wiring (and the PT-3 power transformer) just dates the Crack to be 2+ years old.

[JL23]

Tell us about the solder, iron, and needlenose pliers you're using.

To get a good quality solder joint, generally you want to pass leads through the hole on the terminal strip or tube socket, then bend them up and solder between the hole and the bent elbow of the lead.  This gives your solder a good place to flow into and stay put.

From what I can see of your photos, it's likely that either your iron is a little light on the heat or you might have lead free solder.

The brown and black bubbling stuff is flux. You need to hold the iron on long enough that the solder melts and flows over and through the flux.

I desoldered and resoldered everything today. The joints all look way better, all of them are shiny, solid connections. Unfortunately, this didn't resolve the issue. The resistance still climbs on terminals 1,2, 4, 5 when they should be *.

[Doc B.]

. The resistance still climbs on terminals 1,2, 4, 5 when they should be *.

That's what it's supposed to do, and why we don't publish a fixed number but rather a *.

[JL23]

That's what it's supposed to do, and why we don't publish a fixed number but rather a *.

Thanks. I have one more question, will 2A 250V fuses be safe to use in the amp? During a my voltage check I made contact with two points and there was a spark and now my current fuse is toast. My local store only carries 2 amp fuses.

[Paul Birkeland]

A 2A fuse is OK.

[JL23]

Since my last post I have rolled both types of tubes and replaced the 9 pin socket. Still getting the static in the left channel. I am at a loss for what to do.

[Paul Birkeland]

You can poke around the amp with a wood chopstick while it's running (with cheap headphones plugged in).  When you find the solder joint that's causing this issue, poking at it with the chopstick will produce audible results through the headphones.

[JL23]

You can poke around the amp with a wood chopstick while it's running (with cheap headphones plugged in).  When you find the solder joint that's causing this issue, poking at it with the chopstick will produce audible results through the headphones.

Hi, yes! I saw you recommend this in another thread. I tried it and there was no effect of poking any of the joints with the chopstick.

[Paul Birkeland]

You'll need to poke at the tube socket pins and the terminal strip terminals.