Official C12 Clone - Build and Support Thread

[Reverend]

Got my mic built...2nd one now, but, when I probe the heater section on the tube, to test my heater voltage, I'm getting 163V! What could be wrong? Thanks.

I should also mention that since this is my second one, I'm building it using the right side of the tube. I think I may be testing it wrong, or, better said, with the probe in the wrong place. Which pin of the tube should I touch to measure the heater? I'm also not getting any sound from the test tube with the stock capsule. Thanks.

 

[dmnieto]

I guess you tested the H+ voltage in the power supply?

163V is very close to what you could get if your power supply was unloaded and testing on the B+ point...

 

[Matador]

Pin 9 should be ground.  Pin 4 is used to heat "side 1", and pin 5 is used to heat "side 2".  So measuring between 5 and 9 should allow you to see the 6.3V if you are using "side 2".

Remember that to pick a side to use, you must short across either R3 or R4.  R3 puts the heater supply on pin 4, which picks side 1.  R3 puts the heater supply on pin 5, which picks side 2.  This is done with either a) the zero ohm jumper resistor that Chunger supplies, or b) a little piece of wire or solder braid.

 

[Matador]

I guess you tested the H+ voltage in the power supply?

163V is very close to what you could get if your power supply was unloaded and testing on the B+ point...

If the tube isn't heated, it will draw no current, and pin 1 (or pin 6, if you are using side 2) will show the full B+ voltage.

 

[Reverend]

Ok. I've got the right readings on my multi-meter. Thanks. I just needed to know where to probe. Now, I've got the original capsule hooked up and I'm not getting any sound. One thing I want to ask about - I've got a jumper wire from TK2 to C11 (cathode), should it go somewhere else? C10? Thanks for your quick response.

 

[Reverend]

I guess you tested the H+ voltage in the power supply?

163V is very close to what you could get if your power supply was unloaded and testing on the B+ point...

If the tube isn't heated, it will draw no current, and pin 1 (or pin 6, if you are using side 2) will show the full B+ voltage.

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch. 

 

[Matador]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

 

[Reverend]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

 

[Matador]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

Just to be sure - if you take the mike into a completely dark room, can you see the heater glowing?

If you substitute a 150K resistance for the mike (plug it directly into the 7-pin xlr socket at the PSU between the B+ node and the ground node), do you measure 120V(ish) at B+ inside the PSU?

And BTW be careful when doing this...

 

[Reverend]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

Just to be sure - if you take the mike into a completely dark room, can you see the heater glowing?

If you substitute a 150K resistance for the mike (plug it directly into the 7-pin xlr socket at the PSU between the B+ node and the ground node), do you measure 120V(ish) at B+ inside the PSU?

And BTW be careful when doing this...

I see the heater glowing when the lights are out (and on too). With a 150K load between B+ and ground, it's measuring 96.7.

 

[Reverend]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

Just to be sure - if you take the mike into a completely dark room, can you see the heater glowing?

If you substitute a 150K resistance for the mike (plug it directly into the 7-pin xlr socket at the PSU between the B+ node and the ground node), do you measure 120V(ish) at B+ inside the PSU?

And BTW be careful when doing this...

I see the heater glowing when the lights are out (and on too). With a 150K load between B+ and ground, it's measuring 96.7.

To be clearer - I see the tube glowing. Unplugging the mic and putting a 150K resistor between B+ and Ground, I get a measuring of 96.7.

 

[dmnieto]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

Just to be sure - if you take the mike into a completely dark room, can you see the heater glowing?

If you substitute a 150K resistance for the mike (plug it directly into the 7-pin xlr socket at the PSU between the B+ node and the ground node), do you measure 120V(ish) at B+ inside the PSU?

And BTW be careful when doing this...

I see the heater glowing when the lights are out (and on too). With a 150K load between B+ and ground, it's measuring 96.7.

To be clearer - I see the tube glowing. Unplugging the mic and putting a 150K resistor between B+ and Ground, I get a measuring of 96.7.

Which side of the tube glows?

 

[Reverend]

Yes. The power supply tested out correctly. Maybe the tube isn't getting heated now, hence no sound. I just check the B+ reading in the power supply with the mic plugged in and it reads about 162. I've tried this with two different tubes and both are about the same. Maybe my tube socket is not holding the tube good? The tube is not very hot to the touch.

Do you show 6.3V between the tube pins 5 and 9?

Yes. 6.3V between pins 5 and 9.

Just to be sure - if you take the mike into a completely dark room, can you see the heater glowing?

If you substitute a 150K resistance for the mike (plug it directly into the 7-pin xlr socket at the PSU between the B+ node and the ground node), do you measure 120V(ish) at B+ inside the PSU?

And BTW be careful when doing this...

I see the heater glowing when the lights are out (and on too). With a 150K load between B+ and ground, it's measuring 96.7.

To be clearer - I see the tube glowing. Unplugging the mic and putting a 150K resistor between B+ and Ground, I get a measuring of 96.7.

Which side of the tube glows?

The right side. This is my second mic, so I'm utilizing the right (TK2,etc..)side. It's glowing on the side of TK2.

 

[dmnieto]

The right side. This is my second mic, so I'm utilizing the right (TK2,etc..)side. It's glowing on the side of TK2.

It has to be something related with soldering or wiring... If you have 160V after R17, the only way is that:
1. The anode or the cathode are floating. or inverted: did you double check that you wired the plate and the cathode to TP2 and TK2? Be careful that because the geometry of the tube the TP2 is up and TK2 is down (TP1 is down and TK1 is up)

2. Your grid voltage is massively negative with respect to the cathode... Did you calibrate the bias voltage?

 

[Reverend]

The right side. This is my second mic, so I'm utilizing the right (TK2,etc..)side. It's glowing on the side of TK2.

It has to be something related with soldering or wiring... If you have 160V after R17, the only way is that:
1. The anode or the cathode are floating. or inverted: did you double check that you wired the plate and the cathode to TP2 and TK2? Be careful that because the geometry of the tube the TP2 is up and TK2 is down (TP1 is down and TK1 is up)

2. Your grid voltage is massively negative with respect to the cathode... Did you calibrate the bias voltage?

Plate is to TP2 and Cathode is to TK2. Grid to TG2.
With the mic unplugged, and a 150V resistor pushed into pin 1 and pin 7 of the psu, I get a B+/ground reading of about 96.6v. Is that something wrong with the power supply? Thanks so much.

 

[Category 5]

Sounds like you got the 175v transformer instead of the 200v one.  If so, you need to change a couple of resistor values to get the voltage up where it needs to be.

 

[Reverend]

Sounds like you got the 175v transformer instead of the 200v one.  If so, you need to change a couple of resistor values to get the voltage up where it needs to be.

The transformer in my psu is 200V. Thanks so much.

 

[dmnieto]

Plate is to TP2 and Cathode is to TK2. Grid to TG2.
With the mic unplugged, and a 150V resistor pushed into pin 1 and pin 7 of the psu, I get a B+/ground reading of about 96.6v. Is that something wrong with the power supply? Thanks so much.

No, it does not look like it is wrong... you could re-calibrate the B+ in the psu so you have something like 120V when the resistor is plugged in.

When you do that, plug the mic and measure not only B+, but also the polarization voltage (P3 I think)

 

[Matador]

The tube isn't drawing current if the plate voltage is that high:  TP2 should be reading 50(ish) volts.

Assuming the heater is working correctly, and it is indeed heating the "#2" side, please confirm (WITH THE MIKE UNPLUGGED):

1) you have 0 ohms between TK2 and ground.
2) you measure 100K between TP2 and B+ node (this is the plate resistance)

 

[omribgr]

Hey Everyone!
does anyone know what is the best way to assemble Gotham GAC-7 cable? (for the C12 Clone)

Thanks a lot !