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Got my jacks sorted out and fixed a wire that was not connected to the right spot (negative feedback). Fired up the amp and took my voltage readings.

A/C Mains Voltage - 123.6
B+ No tubes installed - I forgot to take this reading before putting the tubes in.
B+ Tubes installed, VRM set to 400v
B+2 - 395v
B+3 - 393v The schematic shows 340v.


12AX7
Pin 1- 191
Pin 2 - grid
Pin 3 - 1.7
Pin 4 - heater
Pin 5 - heater
Pin 6 - 182.3
Pin 7 - grid
Pin 8 - 1.67
Pin 9 - heater

6V6
Pin 1 - 0
Pin 2 - heater
Pin 3 - 392
Pin 4 - 382
Pin 5 - grid
Pin 6 - 182.3
Pin 7 - heater
Pin 8 - 28.1



My voltage at B+3 appears to be a lot higher than it should be. I'll have to check the resistor (R10) that sits across C6 and C7 to see if it's good. I'm not sure what to make of the voltage of Pin 8 on V1/12AX7. According to the schematic, the voltage should read 1.7 and I have 1.67. What does Off On refer to? There is one other odd thing that's happening. After I've had my amp turned on for a while and have been playing it the volume just disappears. I have to shut the amp off and wait, then turn it back on. I also noticed that the power tube seems to be glowing pretty brightly. What part of the tube is the outer metal part? Plate and Cathode? I'm going to try and take a picture of it.

Should come down when tubes are installed (per Coco aka Stephen)

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"The only problem with being retired is you never get a day off"

Oops, saw that the B+3 was with tubes installed. I forget who said it, should only vary only by about 10%. And it looks like it's over by about 20 volts.

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"The only problem with being retired is you never get a day off"

Re-checked the voltage at B+ 3 again based on the layout location. It's reading 323v now. I probably measured the voltage at the wrong location. Tomorrow I'll try playing my guitar through the amp again with VRM set at 400v and see how long it takes until the volume drops off. Then I'll take a picture of what the power tube looks like.

Tube is red-plating and that ain't good The only thing I can see is the two 47 uF filter caps (mine were 50 uF)and the resistor on the gate side of the VRM doesn't look like a power resistor(I have a blue, ceramic looking one there) , it looks more like 1/2 W carbon film. You have what looks like a power resistor in the R4 position next to the large .47uF yellow cap, but I don't know whether any of that could be causing your problem. I'm still learning, too. You might PM Stephen (Coco) from your User Control Panel (top right on screen). You can e-mail him directly from there. I wouldn't play it until you get some definite advice

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"The only problem with being retired is you never get a day off"

Also, check your bias and OT settings depending on which tube you're running.

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"The only problem with being retired is you never get a day off"

Sorry, I don't mean to be an alarmist, but the heaters should be the only things glowing. The long plates in the tube shouldn't, attached a diagram of 6L6 , the anatomy should be about the same as 6V6. https://www.tubesandmore.com/tech-corne ... be-diagram

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"The only problem with being retired is you never get a day off"

I took some pictures of the power tube with the VRM set at 3 different settings, 10, 6 and idle. The glow became less as I went to the lower VRM settings. I've rechecked my voltages again and they all were within spec.

I checked my bias and output settings. My switches are set for a 6V6. The 750ohm resistor is in play as is the 5K impedance from the output transformer. I'll have another look. I'm rechecking all my voltages again as well. Thanks.

Not to worry. I'm alarmed on my own . Red plating is definitely not good! Thanks for the link.

Double check your load switch and make sure that the load switch is putting the right voltage/load to pin3 of V2. I say this because that's the plate pin for V2. Also, the output jacks should be grounded to provide a reference ground for the OT (per joe6v6's 3rd post in OSD forum "Grounding Question"). It's might be possible that when you plug into the output jack you are lifting the ground to the chassis. So you might try removing the insulating washers and see if that has any effect. There has to be a reason that Stephen does it the way he does. Have you tried e-mailing Stephen thru the User Account Control panel? Just throwing ideas out at this point. Good luck.

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"The only problem with being retired is you never get a day off"

I tried something really simple. I flipped the switch for the bias setting from the low to the high setting. I figured if I had the 1K resistor for the EL34 wired to the wrong side of the switch, flipping the switch to the other position would put the bias to the low setting. It worked! With VRM@400vdc the tube doesn't start glowing like it did before. Amp seems to be working fine. The reason I decided to just flip the switch were two fold. For one, when I measured the voltage at pin 8 of the power tube I was getting 23.5vdc. This is way out of whack of where the pin voltage should be of 29v so I figured I must have the switch wired incorrectly. The second reason I just flipped the switch was that if I did have the 1K resistor wired to the wrong side of the switch, flipping it should give me the correct bias I need and I could verify it by measuring the voltage as well as checking the tube for any red plating. I guess I didn't really understand what hi and low bias meant in terms of the voltages that should be present at the cathode. I guess I understand that now. Now all I have to do is put the 1K resistor to the other side of the switch and all should be good. The link to the article you sent was my light bulb moment!

Cheers!

Your voltages look OK.

If you make some measurements, you can calculate the power dissipation of the 6V6 and it should be within spec. The JJ 6V6S supplied with the kit is good for 14 watts. With the numbers you provided (29V & 750R resistor), the dissipation is 13.2 watts.
There are several on-line calculators that can help you. https://robrobinette.com/Tube_Bias_Calculator.htm

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Just change the labeling and mark it so it won't cause any confusion in the future. Glad you got it working!!

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"The only problem with being retired is you never get a day off"

Thanks Stephen. Now that I got the bias sorted out I'm getting 27.5v at the cathode. No more red plating. I must not have understand how the bias switch works and which resistors come into play for the 6V6 and EL34. When referring to Lo Bias and Hi Bias, does Lo bias mean there's a lower voltage at the cathode and Hi bias means there's a higher voltage at the cathode?

Thanks.

I re-soldered the bias switch (I'm to anal to just re-label) . Everything is working as it should now. My bias voltage is 27.5v which is a bit below the 29v shown on the schematic but I don't think it's a problem. What confused me was how the actual switch functions itself. When the switch is put in one direction, the connection is actually made with the terminals at the opposite end of the switch. Now everything makes sense. I'm looking forward to trying the EL34 in it now. Can't get enough of it now!

Thanks for your help.