voltages for 5f6a?

[chuckb]

Hey guys , I have the 5f6a up and running but I have very very low volume? Can someone tell me what kind of voltages I'm supposed to be getting on V1,V2 and the PI. I'm getting 373vac on the red wires on the PT and 500vdc taken at the juction of the two diodes with amp on. Pins #4 of the power tubes give me a reading of 449vdc and pins #5 are -50vdc. Pin #1 of the PI is 286vdc and Pin#6 is 296vdc. Is this high for the PI?

Chuck.

[Diablo]

Here's what I have with a 12AY7 tube in V1, and NOS 5881 tubes. My amp works fine at these voltages.

v5(5881)
pin 3: 463
pin 4: 460
pin 5: -51
pin 6: 463
v4(5881)
pin 3: 463
pin 4: 463
pin 5: -51
pin 6: 463
v3
pin1: 272
pin3: 46
pin6: 275
pin 8: 46
v2
pin1:210
pin3: 1.16
pin6: 350
pin8: 211
v1
pin1: 177
pin3: 2.88
pin6: 174
pin8: 2.88

[chuckb]

Thanks for the info. I'm using 2x6L6's and 3x 12ax7's. I'll compare the voltages and see how much of a difference there is compared to these.

[chuckb]

I have some readings and they are as follows:

V1
Pin1: 289
Pin3: 2.62
Pin6: 298
Pin8: 2.62

V2

Pin1: 370
Pin3: 15.5
Pin6: 384
Pin8: 191

V3
Pin1: 255
Pin3: 43.9
Pin6: 264
Pin8: 44.7

V4&5
Pin3: 500
Pin4: 458
Pin5: -51.5

I have nothing on pin 6 because it is N/O.

How do these numbers look?

[JoeM]

Here's the clone of the 5F6A I did with some of the voltages. Mine works great. Hope this helps. I typically run the 6L6s at 60% dissipation more or less.

[chuckb]

I still have no sound,but everything powers up ok. I do get a little bit of sound but it's very very faint. I can't seem to track down the problem. I have all new tubes,did the chopstick thing with no noticable signs of loose connections etc. I do have a 5k/5w resistor in place of where the choke is supposed to be. I tried a 1k/5w there also but I got some poping noise when I took the amp off standby. I removed the 1k/5w and replaced it with the 5k/5w and the problem disappeared. If anyone can help me here it would be greatly appreciated? Thanks.

Chuck.

[tubeswell]

I have some readings and they are as follows:

V2

Pin1: 370
Pin3: 15.5
Pin6: 384
Pin8: 191

How do these numbers look?

(Edit - whoops I got pins 3 and 8 out of order before. Pin 8 is the CF cathode and the voltage there doesn't look too bad, but) the voltage on pin 3 (the 1st part of the DC coupled pair) is way too high (you should only be getting something like 1.5 - 2 volts max. You probably have the wrong value cathode resistor there. Its supposed to be 820R (820 Ohms)

[chuckb]

Hey tubeswell,I have a 100k resistor on Pin#8 going to ground. I also have a 100k resistor tied across Pin#1 and Pin#6 as it is shown in the schematic. This 100k resistor is then tied into a 20uf/450v cap.

[chuckb]

I also checked the voltage on pin1 with the amp fully on and I got a reading od 363vdc, and 370vdc on pin6.

[chuckb]

On pin3 it calls for a 820ohm but I have a 1m there going to ground.

[JoeM]

On pin3 it calls for a 820ohm but I have a 1m there going to ground.

1m? Do you mean 1K (1000) ohms? Check the actual value with a DMM.

[chuckb]

Hey, I did have a 1meg 1/2 watt resistor there in place of the 820 ohm. I removed it and put two 470ohm in series and now I have alot more sound but still not close to where it should be.

[Diablo]

You should measure all your resistors and compare to the schematic values. I like to measure each component as I'm building the amp to make sure I don't make a whoops. After soldering them in place, you can also check to make sure you made a good solder joint via the multimeter by checking resistance values.

[chuckb]

Hey Diablo, yes I almost always do measure before installig the resistors,but things always have a way of getting by me. I believe what had happened was I didn't have any 830ohm and I thought that i had used a 1k instead. I'm still not getting any volume that's worth talking about. I have two 4n007 diodes for my rectification,would I need more? also I have a 100k resistor tied across pins 1 and 6 of V2 going to a 22uf/450v cap, does this seem right? It shows that it is on the schematic.

[Diablo]

Yes there should be a 100K resistor between pins 1 and 6 on V2. Pin 6 is connected to an 8mfd cap on my schematic. Pin 1 is also connected to pin 7 with a wire jumper. What schematic and layout are you using?