Hi,
I have the Aikido ALL in One 9 pin board. I'm using a LM1084 5A V.Reg.
The trafo is an antek 1T250 which has dual secondary 6.3V 3A. I wired them in series for 12.6V going into the FWB to the V.Reg.
On the aikido board, I've jumpered J2 and J5 to use it as series parallel heaters. The issue is when I plug in ALL 4 tubes, the heater voltage is only 0.920V!
If I plug in a pair of tubes at a time, either one pair in the input or output, the heater voltage comes up properly at 12V. I see the heater tube glow.
Thinking maybe I have a defective V. Reg., I've pulled it out and replaced it with another V. Reg and still getting the 0.920V.
Since the 6N1P tubes are working as a pair, I don't think there is an issue with the tubes. Any ideas?
Thanks for your help!
I have the Aikido ALL in One 9 pin board. I'm using a LM1084 5A V.Reg.
The trafo is an antek 1T250 which has dual secondary 6.3V 3A. I wired them in series for 12.6V going into the FWB to the V.Reg.
On the aikido board, I've jumpered J2 and J5 to use it as series parallel heaters. The issue is when I plug in ALL 4 tubes, the heater voltage is only 0.920V!
If I plug in a pair of tubes at a time, either one pair in the input or output, the heater voltage comes up properly at 12V. I see the heater tube glow.
Thinking maybe I have a defective V. Reg., I've pulled it out and replaced it with another V. Reg and still getting the 0.920V.
Since the 6N1P tubes are working as a pair, I don't think there is an issue with the tubes. Any ideas?
Thanks for your help!
I'm doing my Aikido point-point, but I'm looking at the Aikido filament schedule and for a 12v PS and all 6v tubes (if yours are 6N1P in all positions) then you should use J1 and J4.
J2 and J5 will put 12v on the 6v heater, and cause the 1084 to shut down as you've seen.
The 6N1P cannot be run on 12v, unlike a 12a*7 which can be strapped for either 6 or 12v heaters.
Gary
J2 and J5 will put 12v on the 6v heater, and cause the 1084 to shut down as you've seen.
The 6N1P cannot be run on 12v, unlike a 12a*7 which can be strapped for either 6 or 12v heaters.
Gary
yes, most definately, big to-220 heatsink on board.
J2 and J5 puts out 12V, that is correct, J2 ties V1 and V2 heaters in series, J5ties V3&V4 in series so it should be fine.
the curious thing is if I only plug in one pair of tubes, it works just fine.
I see 12V at the heater and the tubes glow fine. The problem is when all 4 tubes are plugged in. I don't get it.
Hi,
I rewired for 6.3V, change the V.Reg. R19 to output 6V.
Works now. I still don't know why it would not work with series parallel
with J2 and J5.
Thanks.
I rewired for 6.3V, change the V.Reg. R19 to output 6V.
Works now. I still don't know why it would not work with series parallel
with J2 and J5.
Thanks.
On the diagrams I have (Rev A and C), J2 puts PS voltage directly across V1, and J5 put PS voltage directly across V2. V3 and V4 would not receive heater PS at all unless other jumpers were installed as well.
Maybe the all-in-one PCB has different jumper numbers than the standard 9-pin PCB
Maybe the all-in-one PCB has different jumper numbers than the standard 9-pin PCB
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yes, I believe all in one board has different wiring then standard board.
It's working now, been listening for about 40minutes until it started smelling bad. the trafo is really hot to the touch. not sure if this is normal. maybe it needs to cook some more to burn off the smell? 😕
Thanks again Gary. I over read your comment. So the 6N1P cannot be strapped for 12V heaters, too bad. I wanted to have the flexibility of
trying other tubes. not a big deal though.
what tubes are you using?
NOT NORMAL!
There is excessive current being consumed somewhere.
Transformers should run no more than warm to the touch.
Double check your component placement and polarity (in the case of electrolytic capacitors.
I haven't looked yet at the all-in-one board, so I can't be of much more help until I see the schematic.
I have a reasonably wide range of Russian tubes to choose from, but 6N1P-EV for input tubes and 12AU7A for output tubes is one combo I really want to try. I will probably start up with 6N1P-EV all round.
One reason I didn't opt for a PCB (aside from the fact that it has to come to New Zealand from the US), is so that I could try some tubes not supported.
The other reason is that I already had a console chassis that suited the 4-tube Aikido design, and already had the power supply (EZ80 tube rectifier) mounted.
One of the PCB-unsupported tubes I have had some luck with in my little SE amps is the 6N3P-EV driving EL84/6BQ5 outputs. It's the easiest to get low distortion at B+ less than 300v, out of all the 6N1, 6N2, 6N3 variants I have tried. It's not compatible with the PCB only because of the strange pinout, but it's a nice sounding tube.
I'm a fairly newbie at this BTW. The Aikido is only my 3rd build.
Gary
cap polairty is correct. I'll have to measure the heater current with all tubes in place.
attached is trafo spec. I tied the two 6.3V coils in parallel.
thx
I originally wanted to use the 6CG7 but ended up trying the 6N1P's since they are much cheaper. My +B for this build is 260V.
My 2nd aikido build, 1st one was the 6SN7 octal. very nice sound.
will build another one again some day.
this one sounds pretty good as well, now I just need to figure out
why the trafo is over heating.
Try separating the 6.3v windings again, and just connect one of them to the board.
4 of the 6N1P will draw about 2.5 amps, so you should be OK as the trafo is rated at 3A per winding.
The reason I mention this, is in case the windings have been crossed (out of phase), which will heat up the transformer even without the Aikido connected, and may have been the reason for the strangeness with the 12v connection as well.
4 of the 6N1P will draw about 2.5 amps, so you should be OK as the trafo is rated at 3A per winding.
The reason I mention this, is in case the windings have been crossed (out of phase), which will heat up the transformer even without the Aikido connected, and may have been the reason for the strangeness with the 12v connection as well.
I pulled off the cathodes of D9 and D10 and tied a wire to it.
Connected my meter to measure current at the input of the V. Reg.
I'm getting 2.43A which is about right for the 4 tubes.
trafo is still very hot. I'm going to reconnect the diodes to the pcb.
then pull off both the 250VAC and 6.3VAC lines to remove the load from
trafo. See if the trafo still get hot.
darn, I hope the trafo has not gone bad.
Connected my meter to measure current at the input of the V. Reg.
I'm getting 2.43A which is about right for the 4 tubes.
trafo is still very hot. I'm going to reconnect the diodes to the pcb.
then pull off both the 250VAC and 6.3VAC lines to remove the load from
trafo. See if the trafo still get hot.
darn, I hope the trafo has not gone bad.
thanks. I could give that a try. I pulled the loads off the trafo for both HV and LV. the transformer starts to get warm even without any load. that is not normal? I'll have to let it cool down completely and try again tomorrow.
I'll try again without load and see if it heats up. If it heats up, then there is some short internally in the trafo?
It does sound like a bad trafo 🙁
One sure test:
Disconnect all secondary windings, break one of the primary leads and measure AC current. Should only be a few tens of milliamps. If much larger than 100mA, trafo is toast.
Normally trafo's take some time to get even warm to the touch without load.
If you are using heater voltage boosting (biased to B+/4 or so), check that it is correctly configured, as toroidal trafo's hate DC current through them. They saturate and heat up.
One more thing occurred to me:
Check that the mounting bolt or a burr in the mounting hole in the chassis hasn't grazed the winding. This is THE most common failure mode for toroids in DIY
One more thing occurred to me:
Check that the mounting bolt or a burr in the mounting hole in the chassis hasn't grazed the winding. This is THE most common failure mode for toroids in DIY
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great idea. I did just that. measured 900mA (AC current) on the primary 🙁
I guess it's toasted. it did not take long for it to warm up, only few seconds.
that really sucks. hopefully I can get a replacement.
that smell was the indicator it went south. probably some internal windings are touching.
no nicks on the transformer.
thanks for your help. much appreciated.
the 6N1P's can only handle 250V? reason I ask is my +B voltage
on the all in one is at 260V. I should be able to to plug in 6CG7's without
any resistor changes?
I'm not sure what spec I should be looking at for the +B voltage.
thanks.
No, they will handle 300v on the plate directly (i.e 300v directly across the tube from plate to cathode), which means your B+ can be much higher. I have seen designs with 6N1P and B+ of close to 400v, it's all a matter of getting the right resistor values to suit the current you want through the tube. The resistor can be on the plate end or the cathode end of the tube, or in the Aikido series-tube configuration, a mixture of both.
What I meant about distortion in a sub-300v B+ stage is this:
Generally, in a plate loaded circuit (the Aikido is not quite that simple) a higher B+ makes it easier to achieve low distortion, and as the 6N1P likes more than 5mA of quiescent plate current, high B+ and suitable plate resistors are the best choice. Once you get down to B+ around 250v, the 6N1P starts to run out of room to maneuver and the distortion goes up (not enough voltage left across the tube == non-linearity and clipping).
Take a hypothetical example: with 400v B+ and 5mA, you want to drop say 150v to put the plate voltage in a safe but not too low area, which means a resistor of 30k.
The 6CG7 may only prefer say 3mA, which means a different resistor value.
Those were just examples, I haven't actually done the math for 6CG7.
Generally speaking, if the quiescent voltage and current conditions are the same between tubes, the resistors will be the same too. The actual values chosen are done so according to the plate characteristic data of each type of tube, found from the tube data sheets.
The Aikido 9-pin documentation I have shows a big chart of suitable tubes, and methods of calculating critical resistor values for them. Ah, just looked at the all-in-one docs and it is on page 16. There are some other charts in there as well, but I haven't read it all yet.
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