In regards to pinning the needle I only meant that I could do it easily thus at least demonstrating that I am getting signal to the tubes... I keep the grid considerably down. Nevertheless as I stated in my last statement output is low.
Thanks for suggesting the circuit change to the relay itself. That was what I was also thinking.
I also have not been having the other prob's since I have left the switch in normal mode. However I am having another issue. Low output all of a sudden. Approx 300 watts. Previously 750... Tubes look real good and are new. No signs of flashover or shorts etc. Voltage on plates is 2500. I can pin the grid meter on transmit.. So I think the signal is getting in. Plate current seems to max at about 280 ma.. + or - a bit. Resting amps when keyed only is approx 80 to 90 ma.
Then another issue that seems to add to the puzzle. Last evening while transmitting I noticed all of a sudden 'zero' output on the amp. No grid reading or plate except for the 90 ma. Moved the bandswitch and then power again but only 300 watts peak. I thought of the relay but I cleaned it and it at least 'clicks' when I transmit. I checked resisters in the grid circuit. All seem fine. Band switch seems fine also. So if my signal was not getting through the relay how could I pin the meter in the grid position. And if I had all that 'drive' why only 300 watts peak.
Thanks Tom for your imput. It sounds like a reasonable possiblity. Will carefully check into it. I am waiting to install both soft key and soft start before I try again to operate the amp. These tubes were almost brand new and it would be a shame if they were smoked! Again thanks! Joel
Once again I'll try to explain myself. I understand that amps don't recieve. I have built numerous devices including an 800 watt amplifier from scratch that I still use today. I get the basic idea but I'm not an engineer. Whoever owned it already installed a standby switch that cuts off the - voltage entirely at the transformer winding. But as I understand amps and the manual the -137 volts on the grids during recieve is to keep the tubes 'cut off' entirely. With out this voltage applied (or when this standby mod switch is engaged) I have on occasionly watched the meter on the amp blip as the electric fence was firing. Is it not possible that the large voltage charge produced by the fence could get into the cathode circuit especially if the tube is not entirely cut off with the -137 voltage?
Now the second problem is this. AFter a minute or so of operating out of my ts 830 the meter on my 830 will "Pin" itself on transmit into the amp. If I turn off the amp it recovers and transmits fine through the amp but if I try to go through the amp it pins itself again. Am I to assume that I might have a failed tube (shorted etc.) Recently the output has dropped significantly!
Incidentally I have checked all of the crucial resisters etc. on the amp. All seem fine.
I wrote earlier about a problem with my sb 201 and its standby mod. After receiving quick responses it was apparent that I failed to be real clear. First my mistake about the grounding of the grids. Yes they are grounded through the cap. I had confused being grounded with "cut off voltage". So what the circuit now does is illiminate the cut off voltage by simply disconnecting the 120 -v supply in receive mode. That's what I meant by 'floating'. I say that because as I was observing last time while in recieve mode the amp was recieving and amplifying the signal off my electric fence in the back! I'm assuming it is because the circuit eliminates the cut off voltage! So what might be a practical solution?
Been troubleshooting my sb201. It came with a standby mod that merely disconnected the 112 v bias line from the circuit leaving the tube grids to "float". Needless to say that caused trouble. Is there a better way to rout the standby? Perhaps switching off just the relay itself? Is there a standard way to doing this?
Thanks for the quick responses! On re-examining the rig I discovered that apparently on route to my home one of the many circuit board connectors had been jarred just enough to break connection on the PLL board. So everything is up and running!
Thanks again for the imput. It good to know that there are those that are willing to give help.
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