Could be hazardous, Jack.
Suppose the dame totally freaks out, and switches back to Purdey mode ?
http://www.bbc.co.uk/comedy/clips/p00bpk0g/absolutely_fabulous_eddy_and_patsys_rave/
Still no buttons : www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-276.html#post2368101
Suppose the dame totally freaks out, and switches back to Purdey mode ?
http://www.bbc.co.uk/comedy/clips/p00bpk0g/absolutely_fabulous_eddy_and_patsys_rave/
Still no buttons : www.diyaudio.com/forums/pass-labs/124889-b1-buffer-preamp-276.html#post2368101
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Use a choke input to drop the voltage. A 2 mH 15 ga choke placed after the rectifiers and before the caps will drop the voltage. Provide superior filtering then resistors and will reduce stress on your transformer, bride rectifier and caps. Partsexpress sells them. Not as a cheap as resistors but a way more tricked out and better power supply. Used in better tube equipment of yore. This is what I am doing in my F5.
I have lost track of what this references. This 2mH 15ga choke is dropping what voltage to what voltage.
2x Mono Speaker Protection Module - each for on Channel on eBay.ca (item 300498437584 end time 28-Dec-10 15:21:31 EST)
They work great.
32A max current, 0.5V DC sensitivity, PCBs are mirrored so you can mount them symmetrically. They have RC anti-oscillation protection which I removed, because F5 doesn't' need it.
They can be connected to main transformer secondaries. They can be directly mounted to speaker terminals.
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That will depend on the series resistance and the current running through it.
I think CLC would be better than LC.
Almost ready to fire up my F5. I have a few questions first though.
- How critical is the value for the capacitor used across the transformer primary? I have a .022uF that is paper in oil and pretty beefy. Russian surplus. I also just purchased a little ceramic disc capacitor that is .0047uF. The schematic calls for .0033uF.
- My chassis is mainly wood with circuit boards and heat sinks attached. What should I use as the ground plane? Will tying the two grounds from the power supply board together with the ground from the mains cord be enough? Or should I choose one heat sink to use? Or should I tie the heat sinks together with another small piece of metal and use a point midway between them? Or I was also thinking i could put a piece of aluminum in between them and just use that. Any ideas on what would be best?
Thanks in advance. Can't wait to fire this baby up. I'll be posting photos once it's finished.
- How critical is the value for the capacitor used across the transformer primary? I have a .022uF that is paper in oil and pretty beefy. Russian surplus. I also just purchased a little ceramic disc capacitor that is .0047uF. The schematic calls for .0033uF.
- My chassis is mainly wood with circuit boards and heat sinks attached. What should I use as the ground plane? Will tying the two grounds from the power supply board together with the ground from the mains cord be enough? Or should I choose one heat sink to use? Or should I tie the heat sinks together with another small piece of metal and use a point midway between them? Or I was also thinking i could put a piece of aluminum in between them and just use that. Any ideas on what would be best?
Thanks in advance. Can't wait to fire this baby up. I'll be posting photos once it's finished.
The value hardly matters.
The type is safety critical.
Across the primaries, you should be using an X or Y rated capacitor, nothing else.
From Line to Earth you must use Y rated only.
I think you mean to say an X or Y rated "film" capacitor. Ceramic disc caps, 1kV rating, were used on most of the high power ham radio tube transmitters I've owned or built and none failed.
Hi,
what works and what is guaranteed to be safe are different.
I meant X or Y rated for mains use.
There are X & Y rated that are not film type.
what works and what is guaranteed to be safe are different.
I meant X or Y rated for mains use.
There are X & Y rated that are not film type.
How would I tell what they are rated? The reason i wanted to use the paper-in-oil cap is because it seems like it would hold up. It's rated for 1000V and has very thick lead wires. The little ceramic disc (which is all radioshack had) is 500WVDC and had very thin leads.
I wondered that some times, is a 1.000v capacitor as safe as an X or Y for line applications? In theory it should, and should be even more secure. But that's theory 😉
Hi,
an X rated capacitor suitable for mains use, will have X1 or X2 and the Vac voltage stated.
A Y rated capacitor suitable for mains to earth use, will have Y1 or Y2 and the Vac voltage stated.
an X rated capacitor suitable for mains use, will have X1 or X2 and the Vac voltage stated.
A Y rated capacitor suitable for mains to earth use, will have Y1 or Y2 and the Vac voltage stated.
Yes X1 X2 Y1 and Y2 are specifications for one thing a Y1 cap can handle an 8KV spike.
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After reading up, it would appear that X1 can withstand 4000V spikes and X2 can withstand 2500V spikes.
Thanks! That's actually what I just ordered. I had been trying to avoid placing an order and just using something on hand. In the end I guess it's worth it for piece of mind.
Choke input or LC is good if you have to drop a few volts if the transformer voltage is too high. Its alternative to using wasteful resistors to drop voltage. You get better filtering with a choke. I suggested a 2 mH 15 ga aircore inductor. The voltage drops about .9 X the transformer secondary.