2204 makes loud noise on the speaker

[Mehfuzhoss]

Hello,

I finished building 2204 from a kit. ceriatone kit and hammond OT PT and Choke.

- the amp power on when switch it on
- it make a continous "low booooom" noise when it turn on the standy

I want to verify my OT wiring with you. please correct if wrong.

primary side:
- Blu-white-red 3200 ohm CT connected to EL34 pin 3, EL 34 pin 3 and Can cap positive sides respectively

secondary side:
- black - common connected to speaker's negative pole and then grounded to the chasis
-yellow - 4 ohms
-orange - 8 ohms I am using this one.
-violet   - 16 ohms

** the 100K resistor off of the Presence is connected to 4 ohms tap only.

pic attached. any suggestion?

[sluckey]

Blue goes to one tube pin 3. Red goes to the other tube pin 3. White goes to B+. Is this the way you have it wired?

If so, swap the blue and red wires. Any better?

[Mehfuzhoss]

blue is on tube 1 pin 3. red to other tube pin 3. white is connected to choke and left most can cap's positive end. (is this the B+ of 2204? I am new to amp building sorry for the noob question...lol) now the amp is working but very very low powered and thinnnn sounding! what should i check next. thank you for your help guyz.

[shooter]

what should i check next

http://el34world.com/Forum/index.php?topic=23286.0
http://el34world.com/Forum/index.php?topic=21999.0

http://el34world.com/Forum/index.php?topic=5.0

[Mehfuzhoss]

Hello,

The amp worked fine for a day. but when switch it to full power (ceriatone 2204 has a half/full switch in the back) the amp makes really loud noise continously, so i have to turn off the amp. then after a while i can turn it back on with half powered switched in, the amp works fine but very low powered. I left the amp aside for few days, turned it on today with the half/full switch removed from the circuit and it makes that loud noise. any suggestion for this situation? is my OT going bad? how can i test the OT?

Thank you.

[Mehfuzhoss]

voltage reading while the amp is operating :

v1 (input signal, furthest from power tube)
pin 9: 0v
     8: 3.37
     7: 0
     6: 173.9
     4/5: 0
     3: 4.8
     2: 0
     1: 226
V2
pin 1: 113
     2: 0
     3: 1.8
 4/5: 0
    6: 320
    7: 113
    8: 117
    9: 0

V3 (closest to power tube1)
Pin 1: 202
     2: 40.6
  3/8:58.9
  4/5: 0
      6: 190
      7: 42
      9: 0

Powertube V4:
Pin 1/8: .03
         2: 0
         3: 464
         4: 460
         5: 46
         6: 463
         7: 0

Powertube 2:
pin1/8: .03
        2: 0
        3: 464
        4: 458
        5: 46
        6: 464
        7: 0

Bias trim pot:
pin 3: 0v
    1/2: 18.6

Can cap1 (left most)
464volt

can cap2
373 and 465 respectively

are voltages showing okay?

[shooter]

now the amp is working but very very low powered and thinnnn sounding!

what changed from above to;

The amp worked fine for a day.

did you;

swap the blue and red wires.

?

[Mehfuzhoss]

Lol. So the mystery lie in these two wire but not the white.  Hmmmm

[shooter]

IF;
white is your B+

then maybe, we're testing to make sure you are phased correctly, otherwise you're feeding an in-phase signal back into the amp, causing positive feedback, which drives the PA harder until it screams UNCLE 

[sluckey]

Lol. So the mystery lie in these two wire but not the white.  Hmmmm

Maybe, maybe not. But it has to be ruled out. So, did you swap the red and blue wires as I suggested a week ago? If no, then do it now. There's a 50/50 chance that these wires are already correct. If so, the amp will really squeal when you swap them. In that case swap them back like they were. There's also a 50/50 chance that swapping the wires will cure the problem. This is just one of those things that you must verify anytime you build an amp such as this.

This is what I mean when I say swap the red and blue wires... Unsolder the red wire on one socket. Unsolder the blue wire on the other socket. Now solder the red wire to the socket that previously had the blue wire. And solder the blue wire to the socket that previously had the red wire. Should take about a couple minutes if the wires are not too short.