Thanks for that advise, djn. I haven't decided on the final layout yet. I agree with the aesthetics of having the tubes standing front and centre but I'm limited by the size of the 3 transformers I'm using. Hopefully they will arrive here in the next hour and then I will have a better idea.
The usual practice is to use Teflon washers, that is if you are mounting the socket beneath the chassis surface. The idea is to space it slightly to increase air flow.
I don't think vacuum tube rectifiers are well suited to an OTL amplifier. You need HT supplies that are capable of providing currents of order 1 amp or more (at peak volume), not milli-amps, and you don't want the voltage to drop substantially when the current draw rises to these rather substantial values.
Chris
The heat would build up with just the 6c33c alone. If you mount a 12V dc fan runs on 6V or so, on bottom chassis that blows air upwards, thus allows stream of air to flow out the top through all tube spaces, cool off the tube as well as any heat (transformers, capacitor etc) inside the enclosure. This is more effective than a sucking fan which tends to suck hot air inside from top where the tubes are.
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If you mount the socket under the chassis, 3-5 mm is enough, the socket itself has about 1 mm of spacer at the 4 corners. You can go down as far as you can if you cut the opening bigger than the tube glass base which is about 52 mm diameter and hole 55 mm so space of tube to chassis is about 2-3 mm (not to cut too big). You use a hand turn hole punch to make the real clean cut esp on steel.
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Similar to attached.
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I wonder if there would be interference between the two transformers? Maybe a grounded copper sheet between them would mitigate it.....if there is any.
You might want to cut a hole for a fan then see if it gets hot enough to actually mount one and yes, if you run it at 6v, you won't hear it.
PSU Cap revisted
Sometimes ago I reported this problem, and I have put in a new set of 8 pcs same NOS 1000u/200V. After 4 months of use I discovered 4 were budging (one is opened circuit) C5-C8, all after R1 and R2 which is 1 ohm each maybe this is causing too high rippled current and thus heat causing the budging. The other 4 C1-C4 are still reasonably good, after replace another 4 nos cap, I also drop R1/R2 to zero ohm. I hope to see what happens in next few months.
Attached is also the remake of PSU, if I were to build TM amp or others where -430V and +145 is required, their AC input are derived from same transformer for the +-150V. If +-150V rail dropped to +-140V at full power, the -430V and +145V would also drop and thus maintained the almost same bias level for top and bottom. The advantage over the original is that it output level is depended on transformer power output drop instead of voltage of -150V rail, which is too rough a ride IMO for the bias. And beside the bias would not change very much should there be a problem with the bottom tube and -150V rail. If you are to build independent supply for -430V, the bias level for the tubes would be out when the power output varied. So just a note for those who I have advised in private mail, I will just post this for all to see.
Sometimes ago I reported this problem, and I have put in a new set of 8 pcs same NOS 1000u/200V. After 4 months of use I discovered 4 were budging (one is opened circuit) C5-C8, all after R1 and R2 which is 1 ohm each maybe this is causing too high rippled current and thus heat causing the budging. The other 4 C1-C4 are still reasonably good, after replace another 4 nos cap, I also drop R1/R2 to zero ohm. I hope to see what happens in next few months.
Attached is also the remake of PSU, if I were to build TM amp or others where -430V and +145 is required, their AC input are derived from same transformer for the +-150V. If +-150V rail dropped to +-140V at full power, the -430V and +145V would also drop and thus maintained the almost same bias level for top and bottom. The advantage over the original is that it output level is depended on transformer power output drop instead of voltage of -150V rail, which is too rough a ride IMO for the bias. And beside the bias would not change very much should there be a problem with the bottom tube and -150V rail. If you are to build independent supply for -430V, the bias level for the tubes would be out when the power output varied. So just a note for those who I have advised in private mail, I will just post this for all to see.
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