I have some 4E27 tubes in my possession that I'm looking to make anode caps for (the old EIMAC anode caps for these are hard to find). These tubes will be exposed outside of the chassis and therefore pose a risk should any hands accidentally touch the anode caps. The anode will be at approx 1000V so the cap must insulate them well against accidental contact.
Anyone have any ideas on how to build some insulated plate caps that are still able to dissipate the needed heat?
I'd also like to have some insulated solid core wire coming out of the plate cap to go into the chassis, so there needs to be a way to attach it to the plate cap as well.
Thanks everyone!
Anyone have any ideas on how to build some insulated plate caps that are still able to dissipate the needed heat?
I'd also like to have some insulated solid core wire coming out of the plate cap to go into the chassis, so there needs to be a way to attach it to the plate cap as well.
Thanks everyone!
I bought these. I'll let you know how they are when they arrive? I think they are the same size judging by the datasheet... 4pcs Brown Bakelite Tube Anode Cap for FU29 FU32 829 829B 823 Audio Valve Amp | eBay
Unfortunately those caps don't give much heat dissipation. I think the original HR-5 plate caps were quite a bit more hefty.
I'm thinking of potentially milling some aluminum, but need a way to electrically insulate the milled aluminium, such as an epoxy or coating.
I'm thinking of potentially milling some aluminum, but need a way to electrically insulate the milled aluminium, such as an epoxy or coating.
Perhaps something like this? ***** Gold mine of DI¥ audio tubes schematics from Japan ***** post#31.
Does that mean you're not worried about accidental touching of very hot parts?
A 4 or 6 mm2 PV cable would conduct away substantial thermal power - common cable specs are 1kVDC and 1.8kVDC.
Check to see if any cartridge fuses have a similar diameter to the anode cap - there may be a suitable fuse holder that can be modified to suit.
A 4 or 6 mm2 PV cable would conduct away substantial thermal power - common cable specs are 1kVDC and 1.8kVDC.
Check to see if any cartridge fuses have a similar diameter to the anode cap - there may be a suitable fuse holder that can be modified to suit.
That is an accident waiting to happen.
EXPOSED 1000VDC in an open chassis? Are you CRAZY??????
And you want to kludge a homemade connector?
EXPOSED 1000VDC in an open chassis? Are you CRAZY??????
And you want to kludge a homemade connector?
You can manufacture the caps yourself out of aluminium rod but you'll need access to a lathe . I had some caps custom made for use with VT127A a few years ago
RFparts.com should have suitable heatsink caps in stock . These types of tubes need the correct caps , usual shrouded topcaps will be unsuitable and any soldered connections to these caps will not last very long . Also , if unheatsinked caps are used then the glass to topcap seals may give out . The tubes also need to be enclosed .
316a
Exactly what JMFahey said. This thread should be shut down. Heck, they will not allow discussions about "hot Chassis" amps on here and your talking about something way more lethal than that.
BillWojo
BillWojo
How? the OP is looking for INSULATED caps, right? The ones I suggested he says aren't up for the heat. I say they're bakelite and last I checked bakelite was oven safe so i think they'll work.
Agreed running exposed 1kv is dangerous!! However, I don't think that's what is being discussed here.
Agreed running exposed 1kv is dangerous!! However, I don't think that's what is being discussed here.
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The discussion of making your own caps is what the discussion is turning into. OP says he wants to machine them out of aluminum and epoxy coat them or coat them with? This is not something to be screwing around with.
Exposed high voltage connectors need to be insulated so that the curious can not fry themselves. Bread boarding an amp on the bench and building an amp to be used in the living room or man cave are two totally different things.
Someday that amp may not be in your possession anymore for a variety of reasons, it should be built with safety in mind.
BillWojo
Exposed high voltage connectors need to be insulated so that the curious can not fry themselves. Bread boarding an amp on the bench and building an amp to be used in the living room or man cave are two totally different things.
Someday that amp may not be in your possession anymore for a variety of reasons, it should be built with safety in mind.
BillWojo
I should start by saying that there are no kids or pets that could touch the amp. These highly insulated plate caps that I am looking to build are moreso to assure my own safety should the unfortunate event occur of a hand slipping.
BillWojo, I understand your sentiment, and this is the exact reason why it is important that these are made correctly and with long term safety in mind.
So far MagicBus has linked to a good thread where they used a glass shroud to protect the tube/anode and also form an air tunnel to conduct heat away from the tube. I am also considering this IN ADDITION to having a plate cap that is electrically insulated well enough that it would eliminate any potential hazards.
I had also thought about trobbins suggestion of using substantially thick cable that can conduct the heat away, but I'd still like to get more suggestions on ideas and possibilities that others have come up with in their past.
Safety is of upmost concern here, so this is not being taken lightly. I have access to a CNC lathe and CNC machines to make this properly.
BillWojo, I understand your sentiment, and this is the exact reason why it is important that these are made correctly and with long term safety in mind.
So far MagicBus has linked to a good thread where they used a glass shroud to protect the tube/anode and also form an air tunnel to conduct heat away from the tube. I am also considering this IN ADDITION to having a plate cap that is electrically insulated well enough that it would eliminate any potential hazards.
I had also thought about trobbins suggestion of using substantially thick cable that can conduct the heat away, but I'd still like to get more suggestions on ideas and possibilities that others have come up with in their past.
Safety is of upmost concern here, so this is not being taken lightly. I have access to a CNC lathe and CNC machines to make this properly.
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Hi swich401,
Use commercial valve caps, like the ones you ordered. Yout HT is high, so you absolutely need to follow HAM practice and at least cage those tubes, and include a safety interlock system that removes AC power as soon as the cage begins to be lifted. A microswitch located under a screw for the cage would be appropriate for a safety switch.
Without this feature, equipment like this does have a track record of killing the owner of the equipment. Darwin would approve of your project.
If you can't find the caps, look into the HAM groups and I'm certain that they can also give you guidance. Whatever you do, do not homebrew these items.
Wire. Grab some old CRT monitors and use the high voltage leads they use. These will be good for a number of KV and are generally heavy enough copper to handle your requirements. This wire is stranded, but will be stiff due to the insulation. Use a grommet where the wire passes though any holes. I have seen high voltage punch through wire rated at 600 volts and leading through a hole protected with a grommet. This is a messy failure as the track quickly burns the insulation and then burns it if the (now) burned wire is combustible.
This is a reasonably dangerous project due to the higher B+ you are running. You must plan and build in safety. Your cages will also prevent burns due to hot glass, but that high voltage can come and get you. You don't have to touch a conductor to receive a big shock. That is when the amplifier is working. The plate voltage will be considerably higher than your B+ resting state. So mentally treat this as a 3 KV ~ 5 KV line. If the load opens while operating, your voltages will rise to levels beyond B+ X2. The only limit will be insulation breakdown in the wiring or transformer. This can short your output transformer pretty quickly. If you can find some spark-gap capacitors rated for 1.5 KV, place them on your B+ line.
Be safe, Chris
Use commercial valve caps, like the ones you ordered. Yout HT is high, so you absolutely need to follow HAM practice and at least cage those tubes, and include a safety interlock system that removes AC power as soon as the cage begins to be lifted. A microswitch located under a screw for the cage would be appropriate for a safety switch.
Without this feature, equipment like this does have a track record of killing the owner of the equipment. Darwin would approve of your project.
If you can't find the caps, look into the HAM groups and I'm certain that they can also give you guidance. Whatever you do, do not homebrew these items.
Wire. Grab some old CRT monitors and use the high voltage leads they use. These will be good for a number of KV and are generally heavy enough copper to handle your requirements. This wire is stranded, but will be stiff due to the insulation. Use a grommet where the wire passes though any holes. I have seen high voltage punch through wire rated at 600 volts and leading through a hole protected with a grommet. This is a messy failure as the track quickly burns the insulation and then burns it if the (now) burned wire is combustible.
This is a reasonably dangerous project due to the higher B+ you are running. You must plan and build in safety. Your cages will also prevent burns due to hot glass, but that high voltage can come and get you. You don't have to touch a conductor to receive a big shock. That is when the amplifier is working. The plate voltage will be considerably higher than your B+ resting state. So mentally treat this as a 3 KV ~ 5 KV line. If the load opens while operating, your voltages will rise to levels beyond B+ X2. The only limit will be insulation breakdown in the wiring or transformer. This can short your output transformer pretty quickly. If you can find some spark-gap capacitors rated for 1.5 KV, place them on your B+ line.
Be safe, Chris
Use 8899-002 it is rated to 5KV (20KV Breakdown), 18AWG wire so plenty of current carrying capacity. https://www.alliedelec.com/belden-8...lden&msclkid=eb047833903e1474760222fdacbfa75f
Caging that animal would be prudent.
Caging that animal would be prudent.
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