Re: [AMRadio] Current on 6146s
Mark W1EOF wrote: Isn't 15ma *WAY* too much grid current for a pair of 6146s? In my Viking II I used to run about 6-8 if I recall correctly. They can be easily destroyed pretty quickly by too much grid current. Sure it is. 7.5mA is what's required on a pair, according to Johnson, and the book on the Ranger says -never- run the grid current on a single 6146 in Class C higher than around 3mA. BTW, Mark - I don't know if I ever thanked you for that plate switch for the Viking II. I think I did tell you that I stumbled across one out there in the junk and slapped it in, and all was right with the world, again. I've got this switch you sent in front of me, and I'm gonna -leave- it in the house (until I need it) so I know where the damn thing is! I just hope I can -remember- where it's at, when I need to remember ~sigh~ -- 73 -Geoff/W5OMR __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Current on 6146s
CCS rating is 3.5 ma max. per tube ICAS rating is 4.0 ma max. per tube. Pete, wa2cwa On Sun, 11 Feb 2007 22:48:32 -0500 Mark W1EOF <[EMAIL PROTECTED]> writes: > Isn't 15ma *WAY* too much grid current for a pair of 6146s? In my > Viking > II I used to run about 6-8 if I recall correctly. They can be easily > > destroyed pretty quickly by too much grid current. > > 73, > > Mark W1EOF __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Current on 6146s
On Sun, 11 Feb 2007, [EMAIL PROTECTED] wrote: Hi Mike, You are correct. The max grid current for the Viking II pair of 6146s is 8MA. Additionaly, the Valiant (3 6146s) calls for 10 mA of grid current. Cheers John KB6SCO DM09fg __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Current on 6146s
Hi Mike, You are correct. The max grid current for the Viking II pair of 6146s is 8MA. 73, John, W4AWM __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
Re: [AMRadio] Current on 6146s
Isn't 15ma *WAY* too much grid current for a pair of 6146s? In my Viking II I used to run about 6-8 if I recall correctly. They can be easily destroyed pretty quickly by too much grid current. 73, Mark W1EOF Jim candela wrote: >From John E. Coleman (ARS WA5BXO): I have found it to be very important to make measurements while in operation. Except that RF will mess up the meter readings. This is why I said to ground the grid directly and then kick the rig to XMIT and make the measurements then. Checking the plate voltage on the plate while the tube is cut off is not conclusive as there may be a high resistance between the plate point and the power supply point (all the way back in the power supply circuit) and same could be true of the screen. This would cause the plate voltage to appear normal until you draw current then it may drop real low at the plate point but still be good at the power supply. RF at the plate will cause the meter to read wrong and grounding the grid will kill the bias and RF. If the rig were operating normal then grounding the grid would cause excessive plate current so this is a good check any way. 1. While in XMIT mode, when you ground the grid, the plate current should go above 200 ma. If it does, then troubleshoot the grid circuit. 2. If it does not, then leave the ground on the grid and stay in XMIT mode. Then measure the plate and screen voltages. One of them is surely wrong. The only other possibility would be the filaments are not lit up good. Rule for the day: You can't have a 100 volt drop across a good 5ft #12 wire with out a fire. John Reply by Jim, WD5JKJO: John, all good points for sure. I take a different approach that seems to work here. I have two HV probes, a 40KV probe at 1000X, and a 6 KV probe at 1000X . The resistors in these probes combined with the coax cable capacitance make a very effective low pass filter. This filters out the RF leaving just the DC. I touch the probe directly to the RF hot plate of a tube to read the plate voltage with my trusty DVM. I recently tried this on my 8877 amplifier, and it worked well even though the amplifier was running full boar into a dummy load (900w carrier or 2100w PEP SSB). These probes are not that expensive. Those of us that need to measure above 600 volts with a DVM should use a HV probe. It is safer for both the HAM, and the DVM. Here is one on Ebay: Item number: 290080656981 Regards, Jim JKO -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.17.32/677 - Release Date: 2/8/2007 9:04 PM __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body. __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
RE: [AMRadio] Current on 6146s
>From John E. Coleman (ARS WA5BXO): I have found it to be very important to make measurements while in operation. Except that RF will mess up the meter readings. This is why I said to ground the grid directly and then kick the rig to XMIT and make the measurements then. Checking the plate voltage on the plate while the tube is cut off is not conclusive as there may be a high resistance between the plate point and the power supply point (all the way back in the power supply circuit) and same could be true of the screen. This would cause the plate voltage to appear normal until you draw current then it may drop real low at the plate point but still be good at the power supply. RF at the plate will cause the meter to read wrong and grounding the grid will kill the bias and RF. If the rig were operating normal then grounding the grid would cause excessive plate current so this is a good check any way. 1. While in XMIT mode, when you ground the grid, the plate current should go above 200 ma. If it does, then troubleshoot the grid circuit. 2. If it does not, then leave the ground on the grid and stay in XMIT mode. Then measure the plate and screen voltages. One of them is surely wrong. The only other possibility would be the filaments are not lit up good. Rule for the day: You can't have a 100 volt drop across a good 5ft #12 wire with out a fire. John Reply by Jim, WD5JKJO: John, all good points for sure. I take a different approach that seems to work here. I have two HV probes, a 40KV probe at 1000X, and a 6 KV probe at 1000X . The resistors in these probes combined with the coax cable capacitance make a very effective low pass filter. This filters out the RF leaving just the DC. I touch the probe directly to the RF hot plate of a tube to read the plate voltage with my trusty DVM. I recently tried this on my 8877 amplifier, and it worked well even though the amplifier was running full boar into a dummy load (900w carrier or 2100w PEP SSB). These probes are not that expensive. Those of us that need to measure above 600 volts with a DVM should use a HV probe. It is safer for both the HAM, and the DVM. Here is one on Ebay: Item number: 290080656981 Regards, Jim JKO -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.17.32/677 - Release Date: 2/8/2007 9:04 PM __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
[AMRadio] Current on 6146s
I have found it to be very important to make measurements while in operation. Except that RF will mess up the meter readings. This is why I said to ground the grid directly and then kick the rig to XMIT and make the measurements then. Checking the plate voltage on the plate while the tube is cut off is not conclusive as there may be a high resistance between the plate point and the power supply point (all the way back in the power supply circuit) and same could be true of the screen. This would cause the plate voltage to appear normal until you draw current then it may drop real low at the plate point but still be good at the power supply. RF at the plate will cause the meter to read wrong and grounding the grid will kill the bias and RF. If the rig were operating normal then grounding the grid would cause excessive plate current so this is a good check any way. 1. While in XMIT mode, when you ground the grid, the plate current should go above 200 ma. If it does, then troubleshoot the grid circuit. 2. If it does not, then leave the ground on the grid and stay in XMIT mode. Then measure the plate and screen voltages. One of them is surely wrong. The only other possibility would be the filaments are not lit up good. Rule for the day: You can't have a 100 volt drop across a good 5ft #12 wire with out a fire. John Previous message: John E. Coleman (ARS WA5BXO) wrote: > What you're saying is that at no time, can you get more that 20 ma of > plate current? Try grounding the control grid and see if the finals > draw current then. If not be sure to check the screen voltage and > plate voltage while the grid is grounded. And check these directly on > the plate and screen connection. Of course, that was -not- supposed to go to the whole list. No worries though... 5 landers? 3.880 in the morning, if you're not interested in the Traders net on 3.890? __ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:AMRadio@mailman.qth.net To unsubscribe, send an email to [EMAIL PROTECTED] with the word unsubscribe in the message body.
