You don't need separate cathodes for FW rectifier unless your transformer lacks central tap. Normal FW rectifiers such as EZ80/81 have common cathode and two separate anodes which connect to both ends of the secondary while cathode connects to CT.But if you insist, there are quite some diodes avaliable in noval version with top caps (check out EY8x/PY8x types).
hey-Hey!!!,
WE 412 has two independant diodes. As pointed out, a single cathode is fine; consider the octal directly heated types like 5U4...no separating that cathode between two diodes. In any case, with your full wave( or even a hybrid bridge ), the tube diodes are fine sharing the cathode...look at the schematic; even with SS the banded end are together at the positive output.
cheers,
Douglas
WE 412 has two independant diodes. As pointed out, a single cathode is fine; consider the octal directly heated types like 5U4...no separating that cathode between two diodes. In any case, with your full wave( or even a hybrid bridge ), the tube diodes are fine sharing the cathode...look at the schematic; even with SS the banded end are together at the positive output.
cheers,
Douglas
hey-Hey!!!,
The Bendix Hy-G-300 series also has a 412 equivalent, type 6754. True +30 second warm-up to conduction time, and not too damn expensive. Given the use, I'd go with 6CA4/EZ81, as I don't think individual cathodes are really needed for the full wave, grounded CT operation.
cheers,
Douglas
The Bendix Hy-G-300 series also has a 412 equivalent, type 6754. True +30 second warm-up to conduction time, and not too damn expensive. Given the use, I'd go with 6CA4/EZ81, as I don't think individual cathodes are really needed for the full wave, grounded CT operation.
cheers,
Douglas
This would be for a 280vac 2A transformer without a center tap, but it has two 6.3v 3A, and one 12.6v 1.5A winding. It's an older custom job that was given to me. I'd like to stick with noval, as it's for an el84 design, and I have plenty of the proper sockets. The 6754 and 26z5 look promising, and not terribly expensive for the 26z5. Any places online that carry the 6754? AES only shows a cross reference.
Lingwendil said:
You'll need two SS diodes to complete the bridge; 5A/600V Cree SiC Schottky types would be at the top of my list for this app...and it would allow the use of the 6CA4, a high performance IDH twin diode rectifier.
I've found it easier to source the WE 412 than the 6754.
cheers,
Douglas
Doug's suggestion of a hybrid bridge rectifier is (IMO) correct. However, I think you can do better cost wise. $2.22 buys Mouser stock # 726-IDT02S60C, which is a 3 A./600 PIV Infineon Schottky diode. A pair of those "puppies" will do just fine under a slow starting regime. That "12.6" VAC winding provides another opportunity to save some cash. The Noval based 12BW4 can support a 100 mA. PSU. If more capability is needed, use a pair of 12BW4s with the plates connected in parallel.
The 150 mA. rated 6CA4/EZ81 is very popular, which drives its price up.
The 150 mA. rated 6CA4/EZ81 is very popular, which drives its price up.
What I'm trying to do is just a four diode full wave bridge, but with all vacuum diodes, no silicon. I've done it with parallel- plate connected 5ar4's, but want to do the same without having to go parallel, for space's sake. An EZ81 would be ideal if it's cathode was split into two sections. I've only seen this kind of setup once, in an old octal tube radio, not sure what manufacture.
Lingwendil said:
Ah-kay, I was thinking steady-state = idle... still, that's a gigantic supply. For EL84s, I would normally estimate ~125mA per channel at clipping, ~75mA at idle. A 250mA capable supply would be notably oversized (in a good way) compared to typical vintage stereo EL84 amps, for example.
Nothing wrong with over-engineering, but 280VAC at 2A is absolutely massive. Is that a 15 lbs transformer? Are you sure about this rating?
An all vacuum bridge rectifier is a BAD idea. Does the fact of doubled forward voltage drop register?
A hybrid bridge, 1/2 Schottky and 1/2 indirectly heated vacuum, is "perfect". Schottky diodes are "noiseless" and exhibit an extremely small forward drop of approx. 0.5 V. The sonic signature is TOTALLY dominated by the vacuum diodes and the presence of cathode sleeving yields a nice, slow, B+ rise.
A pair of EZ81/6CA4s will allow you to draw 300 mA., safely. You must abandon the idea of Noval basing to pull more B+ current. A pair of 6AU4 damper diodes should do quite nicely. The 6AU4 is rated for (sic) 190 mA. of continuous DC draw.
BTW, if Magnoval sockets and tiny cathode top caps are acceptable, the current production 6Д22С (6d22s) might work out well.
It's about ten pounds toroidaljon_010101 said:
Ah-kay, I was thinking steady-state = idle... still, that's a gigantic supply. For EL84s, I would normally estimate ~125mA per channel at clipping, ~75mA at idle. A 250mA capable supply would be notably oversized (in a good way) compared to typical vintage stereo EL84 amps, for example.
Nothing wrong with over-engineering, but 280VAC at 2A is absolutely massive. Is that a 15 lbs transformer? Are you sure about this rating?
Maybe I could just go 5U4G and do a parallel PP design so I can use that extra size for some good This is the route I think I'll go then. I'll just use hybrid bridge per channel. The Trafo was originaly for a 6550 SE project a friend started, but instead of finishing it, he decided to restore a 1958 VW beetle, so I got it for 25 bucksEli Duttman said:
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