I've rolled a lot of tubes & am positive the ones I have in the sockets are good, and can find no broken connection's, I don't know how to test if I am getting any power to the two 12AX7's in the phono stage I've followed every wire all the way and can see nothing obvious..Once you find the problem (about the only thing it can be is a bad tube, dirty socket, or broken/bad connection), recheck the quiescent current of the output tubes if you have installed the means. If you have installed adjustable bias and it was set with these tubes not lighting, then the output stage current draw will rise notably now due to the increased drop across the DC heater/bias supply filter/dropping resistor when these tubes are brought on line.
Dave
Tim D I'm doing this piece for a friend, He gave it to some guy to work on years ago and it came back not working so he knowing that I like ~as a hobby~ to bring back to life tube gear " fairly successfully with a lot of research and questions & mostly help" I've learned to recap and a amount more, I have a multimeter and have not done any thing with it but check continuity but if I am to move forward in my hobby/past time/passion I will and am willing to learn to us it to it fullest!Given that the V14 and V15 are apparently lighting up, Dave is spot on as to what the likely causes must be for the , filaments not lighting up on V16 and V17 and the impacts to other circuits - particularly after you get it fixed.
Some other things to consider....
- Was it working for you and then it stopped? Or did you purchase it in this condition from someone else?
- If you purchased it this way, does it look like someone was in there modifying any of the wiring around those sockets?
- Could there be a short somewhere in that leg of the filament circuit? This is probably less likely because it would affect the tubes on the parallel circuit (V14 and V15) and possibly would have damaged the power supply for the filament circuit, but it is something to consider.
Do you know how to use a multimeter to check the DC voltages and do you have a multimeter with a high enough DC Voltage range? Are you comfortable with measuring high voltages safely? If not, do you have access to someone that can do it for you (safely)?
..... I have a multimeter and have not done any thing with it but check continuity but if I am to move forward in my hobby/past time/passion I will and am willing to learn to us it to it fullest!
It's grounded Dave.On the phono preamp tube closest to the volume control, check the wiring for pin 5. There is a short jumper connecting this pin to the center ground barrel in the middle of the socket, but then the ground barrel itself needs to be grounded to the chassis as well, and does not appear to be in the photo provided. Check if this is so -- as if so, then the heaters of the phono preamp tubes will not light until a ground connection is made to the center ground barrel of this socket.
Dave
OK the Continuity of the yellow wire from pin 4 on V16 to pin 5 on V17 is good, here is a photo of the V17 socket wiring.Good. That eliminates that possibility. It was hard to be certain with the original pic. OK. Make certain there are no internal breaks in the yellow wire going from pin 4 of this tube over to the other phono preamp tube. A closeup of the other phono preamp tube's wiring would help as well.
Dave
I have checked the continuity of the pins in question and the V17 pins seem to be fine, I've rolled the 12AX7 with tubes I know to be good and still nothing...OK, it's narrowing down pretty quick then. The only things it can be are:
1. The tube in V17 is bad, or
2. The pins 4 and 5 of the tube or tube socket at V17 are dirty, or
3. The pin 4 and/or 5 receptor terminals inside the V17 tube socket are broken.
Based on the information supplied, it must be one of these three things.
Dave
I will retest and rethink, thank you Dave.Mike -- What you have is conflicting evidence, which is not uncommon in the initial stages of troubleshooting. In the current example, you state that (relative to ground) there is -25 vdc at pin 4 of V17 while 0v at pin 5, and 0v at pin 4 of V16 with pin 5 of that socket confirmed as grounded. And, you've stated that neither tube is glowing. In taking these as absolute facts, then either:
1. One of the items in my post 16 must be true, or if not, then
2. One or more of the facts as given are in error.
There can be no other possible outcomes here if the facts as stated are true. What happens so often however, is that something you think is true, is in fact not true.
Think of it this way. If the product of a multiplication problem is 20, and one factor is 5, then the other factor must be 4. What's happening here however is that we're saying that the product is 20, one factor is 5, but the other factor is (say) 6, which cannot be true. Either the product is incorrect, or one or both of the factors are incorrect -- one or the other, but as is, something presented as true is clearly not true.
For the case at hand, IF there actually is -25 vdc at pin 4 of V17 as stated, and IF there is 0V at pin 5 as stated, then either:
1. The tube or tube socket's pins are dirty, or
2. The tube is bad (as in an open heater), or
3. The receptor pins in the socket are broken (as in breaking the circuit).
The only other possible scenario if there is -25 vdc on pin 4 of V17 and 0 v on pin 5, would be the case of pin 5 of V17 somehow being shorted to ground. But if that were the case, and the tube's and socket's pins are all good, and tube is good, then its heater would be glowing wildly, since it would be receiving twice the normal working voltage. But you stated that the heaters are not glowing. So once again, the facts as offered don't fit. Maybe you have multiple bad tubes that you are assuming as good, but are not, or various other possibilities.
It sounds rediculously elementary, but assume nothing, and retest everything. The answer lies in going back and finding out what you think is true that is not. Once you find that, then you can find the answer to the problem. That is the only way to solve problems that otherwise would seem to defy explanation, like the one you have in front of you.
Dave
Dave