Where's there smoke... (extended upgrade)

[Paul Joppa]

The regulators are not regulating; otherwise it looks good.

Do the heaters on the regulator tube (center tube) glow? You said something about the "lights" but I don't know whether you meant the heaters inside the tube, or the LEDs on the regulator board. If the tube filaments are not getting power, then the regulators won't regulate.

If they are getting heater power, try swapping with one of the signal tubes, A or B. That is just to confirm that it's not a bad tube. Unlikely, but best to be sure about assumptions.

If the tube is good and is getting heater power, then it must not be connected to the regulator board correctly, or there is a problem on the board. If the resistances at 21 and 32 are correct (83K and 150K respectively) then the voltage divider string on the board (R3 and R4) are correctly connected to the circuit. That leaves two possibilities I can see - tube pins 3 and 8 are not connected to the board, or the TL431 chip is inserted backwards.

 

[Steve Reese]

Paul, I have removed the regulator board and examined every solder connection. The chips are inserted correctly. On the board both R3 and R4 are connected correctly. I rechecked their resistance, and R3 is what it's supposed to be at 2.49K, but R4 on both sides A and B is off for some reason. Their color code is correct, and I know that they were the correct resistance before I installed them. But on the B side R4 reads at 82.5K and on A is reads 115.3K. Another strange reading on both pin R3 and R8 reads 1 volt instead of 0. What I meant about the lights, is that the diodes glow is really low. On the tube compared to the other tubes, there is no glow at the bottom of the tube. And the tube is cool to the touch.

 

[Paul Joppa]

No glow, and a cool tube, suggests that the heater is not getting power. Since there are two heaters in parallel, it is unlikely that they are both broken, but swapping in another tube would test for that.

The tube should have pins 4 and 5 connected together, and wired to the 6.3vDC heater supply that powers the other tubes as well. The other side of the heater supply goes to pin 9. Ypou should be able to measure 6.3vDC between tube socket pins 9 and 4-5, on each of the three tubes. If you don't find a bad or missing connection that way, it is always possible that the socket itself is not making good contact with the tube pins. Others have posted ways to deal with that problem; and have more experience with it than I do - hopefully if you determine that is the problem, one of them will contribute! (Grainger?...  :^)

 

[Grainger49]

Steve,

If it does indeed turn out to be the socket I first go through the insert, remove, insert, remove scenario.  Try it 6 times first.  Not only does it work 50% of the time it sounds dirty too.

If that fails turn it off, wait a couple of minutes and flip it over.  Then I use a sewing needle to coax the tube socket receptacle more closed for the offending pins.  Do it gently and the socket will really grab the tube pins.  Do it roughly and you might end up with a broken ceramic socket.  Just keep your eye on the metal inside the socket.

 

[Steve Reese]

After reading Paul's last post yesterday afternoon, I immediately began searching over in Audio Asylum to try and find out how to "tighten"the tube sockets. I went and found a saftey pin and began trying to push the metal pieces together. Socket 6 through 9 were no trouble, as was socket 1 and 2. But 3 through 5 was much harder for some reason, and I was just about ready to give up after powering up, taking readings, and seeing no lights on the regulator board. So this morning I read Grainger's suggestion about using a sewing needle, and after asking my patient wife where they were, I went back at it. The first time I didn't see a change, so I repeat inserting/removing the tube at least 8 times. Last week I had tried different tubes I have around, but this time I bought out an Ameperex industrial looking 12AU7 with weird shaped grid plates. Sanded the pins, and once again, I inserted/removed the tube... No luck. I took the sewing needle and began messing with all the sockets, but paying more attention to socket 3 through 5. I turn it on... and no lights. I was taking reading on all of the pins on each tube, when I look over at the regulator board, and man they were shinning bright!! They were brighter than either A or B side. I took the voltage readings, and they were spot on. I let it stay on for about an hour just to make sure it wasn't going to short out or anything.

After that, I took it back upstairs and hooked it back up in the system. My first impression was that it sounded more precise. As what has been my source CD throughout the years, Frank Zappa's One Size Fits All, the highhat and cymbals reminded me how Klipsch Hersheys sound... with air. That's how my Straight 8's sounded. On the third song, Sofa #1, a bass Moog drops maybe down to30 some hertz. The bass was tight and precise along with the Dan and Paul Sub that they graciously gave us all the plans to try. Now mind you, our 5 year old daughter stayed home with me as my wife ran some errands, so to say I was distracted some is putting it mild.  So after Zappa was done, I put in one of her favorite CD's They Might Be Giants -- Here Comes Science.  I went into the kitchen to do some stuff... then she'd run in and say 'Did you hear that (now imagine a 5 yr old making an instrument sound). She's only heard it in both of our cars so..... She had a good time... plus I also allowed her to make some basic solder connections with some spare wirel...

I want to thank Dan who began trying to help me, but I can't thank Paul enough. You two have been blessed with patients of a saint. And Grainger, thank you, I always love reading your insights... the sewing needle... can't wait to tell this over some pints later with the guys... And now the addition is back.... with a vengence...

 

[Paul Joppa]

This one has been a long road getting there, I'm so happy you were able to fix it yourself - feels so much better than throwing in the towel and hiring someone. Congratulations!

Also I'm happy it got resolved before I left town, I just hate to leave things like this unresolved. :^)

 

[Grainger49]

I'm always happy to help and amuse.