What could Account for This? RCA 9TC-240 Power Issue

[bandersen]

6BC5 is an excellent sub for the 6AG5

[Yamamaya42]

Originally Posted by Chris K

I did trace it out and it is all wired correctly...but still no sound so I'm going to need to start tracing backwards through the audio circuit. Before I had some pops and cracks when I moved tubes around but now the speaker is silent...and it was before I did the re-wiring work. Also, somewhere along the line, someone replaced the 6AG5 converter and RF amp in the tuner with two 6BC5 tubes. There doesn't seem to be too much of a difference in performance when I went back to the 6AG5s.

Well, if you touch the center of the pot with a screwdriver (2) with it set midway while touching the screwdriver, you should hear the telltale hum, and you know at lead the pre amp and output works.

[Chris K]

Fed a modulated signal into the audio amp tube and could hear it so all from there to the speaker is good. Headed more upstream

[Chris K]

Fed the same tone into the pin 5 cathode of the 6AL5 (V118) discriminator and hear a very faint tone with full modulation gain on the generator that isn't changing with the TV volume control in fact, it's the easiest to hear with the volume control turned full down to minimum. It's very faint though I do hear it.

[Chris K]

Well...I think I found the answer. There was a 6AU6 in the 1st audio/bias clamp socket and not a 6AV6 that's supposed to be in there.

[Chris K]

Working...that was it

[Yamamaya42]

Originally Posted by Chris K

Well...I think I found the answer. There was a 6AU6 in the 1st audio/bias clamp socket and not a 6AV6 that's supposed to be in there.

Big dif between the two!

[Chris K]

Sure is except one partially rubbed off U mistaken for a V. Sound getting through the if but the video and sound are misaligned. Par for the course for me. Now that the bottom of the chassis is sorted, I need to get the bench cleaned up and reorganized and put the focus coil back on and the 10BP4 back in. A reset in my head is needed before I go on the next adventure with this!

[Yamamaya42]

Originally Posted by Chris K

Sure is except one partially rubbed off U mistaken for a V. Sound getting through the if but the video and sound are misaligned. Par for the course for me. Now that the bottom of the chassis is sorted, I need to get the bench cleaned up and reorganized and put the focus coil back on and the 10BP4 back in. A reset in my head is needed before I go on the next adventure with this!

Numbering aside, I mean that one is a pentode and the other a duplex-diode, high-mu triode, they look very different from each other, after you have seen many of both, they are easy to tell apart, as they are distinctive.

[maxhifi]

Looks like the back side to me, since that's a drawing of the inside of the chassis, and the only way the drawing of those terminal strips makes any sense is if you're looking at the back of the controls.

[Chris K]

Originally Posted by Yamamaya42

Numbering aside, I mean that one is a pentode and the other a duplex-diode, high-mu triode, they look very different from each other, after you have seen many of both, they are easy to tell apart, as they are distinctive.

Yes I looked them up and saw the difference. That's why I was confident the issue would be resolved by making the substitution. I'm still not happy with the power situation. The TV is still only pulling about 1 1/2 amps when fully functioning. That's why I want to get the 10BP4 installed and see where I am with the picture as it needs to be. I've checked the voltages in and around the bleeder circuit and all of them are close to what they should be. Still I feel like I'm missing something. I need to check the HV again now that everything is sorted correctly on the underside.

[Chris K]

Originally Posted by maxhifi

Looks like the back side to me, since that's a drawing of the inside of the chassis, and the only way the drawing of those terminal strips makes any sense is if you're looking at the back of the controls.

Yes that's the way I did it. Didn't want maximum volume blasting through at the minimum setting!!!

[Yamamaya42]

Keep in mind that the general AC voltage in the USA has risen a bit since the TV was made by 10+ volts, this will tend to make all the bias voltages a bit higher, and the amp draw slightly lower, if it says 2.5 amps @ 117vAC, that will change at higher and lower vAC, and also, no 2 sets are alike!

[Electronic M]

One thing I've noticed is wattage and current of tube gear tends to be based on inrush surge at switch on rather than steady state draw of a warmed up set for most tube gear out there.

[Chris K]

Originally Posted by Electronic M

One thing I've noticed is wattage and current of tube gear tends to be based on inrush surge at switch on rather than steady state draw of a warmed up set for most tube gear out there.

Well if that's the case, it does zoom up to a bit over 2.0 amps when initially turned on.