Adding wire to the leads on the mosfets can cause oscillation. The 10M45's might work OK on wire extensions if the 1K gate stopper and the 330 ohm current set resistor were mounted right at the part. These parts produce less heat than the same parts in the original TSE since they run on a reduced voltage. There is a large resistor, R36 that reduces the voltage to the mosfets. It dissipates about 3 or 4 watts depending on the B+ voltage. It can be mounted on a heat sink off board. Use one of those aluminum cased resistors made to be mounted on a heat sink:
RH00510K00FE02
I have not tried to run the filament regulator off board, but some stability issues might occur if the input and output capacitors aren't close to the part.
The usual parts availability issues have me looking for alternatives again.
Digikey currently has the IXCP10M45S parts in stock. Mouser does not.
The "mosfet of the week" is the STP2N80K5. They are in stock at Mouser and Digikey.
The MIC29502WT is out of stock. The MIC29503WT will work if pin #1 is cut off. See post #1214 in this thread. Digikey has 160 of them today. Mouser has none.
Digikey currently has the IXCP10M45S parts in stock. Mouser does not.
The "mosfet of the week" is the STP2N80K5. They are in stock at Mouser and Digikey.
The MIC29502WT is out of stock. The MIC29503WT will work if pin #1 is cut off. See post #1214 in this thread. Digikey has 160 of them today. Mouser has none.
I found MIC29502WT in China, they work. I can share the source if needed.
The 10M45S I originally got from China were fake, but Digikey came to the rescue.
I went ahead with STF3N80K5 and that seems to work so far. It didn’t blow up, at least.
The Edcor PT mechanically buzzes a bit, but I am working on it.
Wrangling and wrestling with the needed parts is the biggest challenge of this project so far.
Well, that and avoiding having my best arm pulled off by drills while I cut tube socket holes with step bits.
George,
I've been going over and over my wacky negative 700 vDC on KT66 Plates SSE build. Tested the output from the 5AR4 every which way, testing with and without choke and supplemental cap, etc, etc.
I have a printout of the schematic I've been referring to but just now I went back to your "schematic" page and re-read the first paragraph where it says:
"The mode (Triode / UL) switch, the Cathode feedback switch, the standby switch, and the rectifier switch are optional, and should be hard wired into the desired position if they are not used.
So the switches need to be installed, not just left out? I passed right by them on the BOM which reads, "USED IF DESIRED". Still, I can't see how the full voltage of the 6K7VG is reaching the outputs.
HELP!!
I've been going over and over my wacky negative 700 vDC on KT66 Plates SSE build. Tested the output from the 5AR4 every which way, testing with and without choke and supplemental cap, etc, etc.
I have a printout of the schematic I've been referring to but just now I went back to your "schematic" page and re-read the first paragraph where it says:
"The mode (Triode / UL) switch, the Cathode feedback switch, the standby switch, and the rectifier switch are optional, and should be hard wired into the desired position if they are not used.
So the switches need to be installed, not just left out? I passed right by them on the BOM which reads, "USED IF DESIRED". Still, I can't see how the full voltage of the 6K7VG is reaching the outputs.
HELP!!
The new board has three components added to cope with the junk 5AR4's that came out of all three new production factories around the time I had to change the name of the board to keep the lawyers away (2012). Diodes D3 and D4 should be a 1N4007 or UF4007 and TR-1 should be a CL140 inrush current limiter. All three can be replaced with wire jumpers and the new board will be exactly like the old board. Adding the parts will help any 5AR4 live longer though.
So, chassis fabrication is almost complete.
Thinking about wiring now..
All of my secondaries have CTs, I am planning to hook them all to the chassis star ground bolt without any detour.
Is that fine?
RCA input will be grounded via the board.
The board will have a single wire going to the chassis star ground bolt. (from one of the T1-RED_YEL pads)
The negative speaker binding posts will also be connected to the chassis star ground bolt.
The chassis star ground bolt will be connected to IEC inlet earth pin.
Is there anything wrong with any of that?
Lastly, I am wondering if all the transformer bell covers and cores should also be connected to the star ground chassis bolt.
Edcor seems to prefer to have the bells isolated from the cores, so I guess it would not make sense to lead them all to the star ground chassis bolt.
@Tubelab_com
Thinking about wiring now..
All of my secondaries have CTs, I am planning to hook them all to the chassis star ground bolt without any detour.
Is that fine?
RCA input will be grounded via the board.
The board will have a single wire going to the chassis star ground bolt. (from one of the T1-RED_YEL pads)
The negative speaker binding posts will also be connected to the chassis star ground bolt.
The chassis star ground bolt will be connected to IEC inlet earth pin.
Is there anything wrong with any of that?
Lastly, I am wondering if all the transformer bell covers and cores should also be connected to the star ground chassis bolt.
Edcor seems to prefer to have the bells isolated from the cores, so I guess it would not make sense to lead them all to the star ground chassis bolt.
@Tubelab_com
Do NOT ground the CT on the 6.3 volt or the 5 volt windings. Grounding the 5 volt CT will short your B+ to ground likely ruining the rectifier tube. The CT on the 6.3 volt winding is controlled by a jumper setting on the board. The CT must be connected to the terminal on the board for this to work.
@Tubelab_com
But the doc says a 6.3V CT is not required for 300B builds.
So, I’m guessing only the HV CT needs to be connected to the board in my case.
And I should terminate and tie out of the way both the 5V CT and the 6.3V CT.
Correct?
I also assume the rest of the stuff I posted above is correct.
But the doc says a 6.3V CT is not required for 300B builds.
So, I’m guessing only the HV CT needs to be connected to the board in my case.
And I should terminate and tie out of the way both the 5V CT and the 6.3V CT.
Correct?
I also assume the rest of the stuff I posted above is correct.
True, the 6.3V CT is not used in a 300B build, but it cannot be grounded. It should be left unconnected or connected to the PC board terminal where it does nothing. The 5V CT must also be left unconnected. The HV CT must be connected to the board where it is grounded. Connecting it to chassis ground and the board T1-red-yel terminal is OK.
Thank you, George. I’ll go with that plan.
I’ll leave the transformer cores and covers alone. After looking at 2 dozen pictures of builds by various people, no one bothers with those. The code may disagree, but I figure they would have to be made wrong in the first place to be a danger.
Of course, the chassis will still be earthed anyhow.