Advice needed. Terminal 46 over limit for resistance check.

CuriousMister · 17624

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Offline CuriousMister

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All other resistance readings are good. This is the only one out of range. I checked connections and reflowed a couple joints to see if it’d make a difference. Do I need to add more solder to the binding post areas?  I know my soldering skills aren’t great.  Before I do any harm, I’d like to seek your advice. Am i missing something?



Offline Paul Birkeland

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Reply #1 on: December 17, 2023, 06:28:27 AM
46 gets its ground reference from the solder lug on the chassis, does this show proper resistance if you test it?  If it doesn't, there may be some reason that your ground wires up front aren't contacting the chassis, so this is definitely something to get sorted out before turning on the amp for the first time.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline CuriousMister

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Reply #2 on: December 17, 2023, 09:16:05 AM
Yes, the solder lug on the chassis reads correctly at near zero.  That’s what led me to reflow some more.  It worked.  46 is back on track.  Appreciate the help Paul!  I appeciate it!



Offline CuriousMister

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Reply #3 on: December 18, 2023, 05:05:18 AM
Man. I hit another snag during DC measurements. Terminal 30 ranges from 111-118 (should be 398) and terminal 17 ranges from 15-19 (should be 0). Reflowing doesn’t seem to be working. Attached a few more photos. I’m sure I’m missing something again. So close!



Offline Paul Birkeland

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Reply #4 on: December 18, 2023, 05:42:14 AM
A 2A3 has two fat pins and two skinny pins.  The fat pins go into the fat holes on the socket, which have the 3W resistors soldered to them.  If you are off on how you plug the tube in, you'll get results like this and you can damage your amplifier.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline CuriousMister

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Reply #5 on: December 18, 2023, 12:22:59 PM
So I swore I had 2A3 tubes dropped in correctly. I checked and did. Even swapped the tubes to see if it made a difference. It didn’t. The fat pins connected to the 3w resistors are receiving the fatter pins. I took another couple photos to illustrated it. What else do you think may be happening? I wish it was as easy as you suggested?



Offline Paul Birkeland

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Reply #6 on: December 18, 2023, 01:36:34 PM
Those voltages are actually on opposite sides of the amp.  What DC resistance do you get between 16 and 13?

The 100V or so at terminal 30 should come with smoking hot 130 ohm resistors as well.  If that isn't happening, then it's more probable that there's a solder joint problem on the resistor between 30 and 44.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline CuriousMister

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Reply #7 on: December 18, 2023, 04:49:45 PM
13=0
14=153
15=65
16=0.1

I’m giving up for the evening and will try again tomorrow night.  I wicked and soldered at lot between 30 and 44 to no avail.  17 hops around a lot when reading too.  I noticed terminal 27 is off as well.  Maybe the joint between the transistor at 27 and 30 is a problem now. That’s where I plan to to start again.

Thank you for your continued patience and help trouble shooting.  I really appreciate it.



Offline Paul Birkeland

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Reply #8 on: December 18, 2023, 05:29:15 PM
I would start by trying to measure the resistance of each 130 ohm resistor with the amp off to see if one has opened up. I think if you do accidentally plug in a 2A3 the wrong way, one of those 130 ohm resistors will open up pretty quickly. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline CuriousMister

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Reply #9 on: December 19, 2023, 12:26:36 PM
Great idea! Am I correct the only way to measure resistance on these is to detach them from the amp?



Offline Paul Birkeland

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Reply #10 on: December 19, 2023, 12:45:43 PM
You should be able to measure them with your meter while they are installed, just be sure the amp is off and you get 0V DC at each of the 450V rated capacitors.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline CuriousMister

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Reply #11 on: December 20, 2023, 06:36:49 AM
Here’s what I got for DC readings at the 450v capacitors.
Between 41/42: 0.8 probe, 0.8 alligator
Between 44/45: -0.7 probe, -0.7 alligator
Between 26/27: 61.3 probe, -3.0 alligator
Between 29/30: 35.8 probe, -29 alligator
Between 31/32: -27.3 probe, -13.6 alligator
Between 34/35: -28.7 probe, -14 alligator

31/32 and 34/35 readings seem to move together.

Now, I’m super confused. I measured resistance at the 130ohm resistors just to see what I got. Only the one connected at 31/34 read correctly. Not sure if this is meaningful.



Offline Paul Birkeland

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Reply #12 on: December 20, 2023, 06:43:15 AM
I am strongly suspicious that a 2A3 or two got plugged in the wrong way.  You'll have to remove the 130 ohm resistors that aren't measuring properly in circuit, then double check them out of the circuit (you can just disconnect one end to double check them), then replace any that aren't working properly. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man


Offline Thermioniclife

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Reply #13 on: December 20, 2023, 10:48:14 AM
It appears that your four pin sockets are oriented 90 degrees off. It looks like the large pin holes are facing toward the center of the amp and not the back as they should. If that is the case your filiment connections will go pin 1 and pin 2 which is the plate,  this is a bad situation. Just one man's opinion.

Lee R.


Offline Paul Birkeland

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Reply #14 on: December 20, 2023, 11:01:42 AM
It appears that your four pin sockets are oriented 90 degrees off.
The photos are just taken looking from the side.  Thankfully the sockets weren't improperly manufactured, that would be a fun one to chase down!

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man