Ok folks...time to coddl a newbie with a lot of dead brain cells...if you don't mind that is. I remember reading about using 2 IN4007 diodes on the rectifier socket to replace the rectifier tube, but I can't remember how it was done. I'm guessing the anode goes on the AC side of the socket and the cathode on the DC side?? Is this also the way to add surge protection with the rectifier tube in place ?? I'm thinking the voltage increase is about 20 volts versus a 5Y3 tube? Please correct me if I am wrong...and as usual, thanks for all the advice on my previous threads....
Afterthought...I have some 1000 volt, 1.5 amp diodes here...they would work not ? I think the IN4007 is 1000 volt, 1 amp ???
Afterthought...I have some 1000 volt, 1.5 amp diodes here...they would work not ? I think the IN4007 is 1000 volt, 1 amp ???
bereanbill said:
Yes, that's right. However, there are other issues with doing this. Replacing a hollow state diode with an Si diode will result in a significantly higher DC output voltage. The forward drop for an Si diode is about 0.7V, and doesn't rise much higher with increasing current. The forward drop for a hollow state diode is much higher.
In a project I did, I needed 350Vdc at about 100mA. In the junk box, I had a Stancor power xfmr rated at 650Vct @ 150mA. Looked good so far as current. However, connecting that to Si diodes gave a no-load voltage of 458V, and even under load, that didn't drop below 400V. It was either get a new xfmr, or include some sort of voltage dropper, or go with hollow state. A 5U4GB had just the forward drop I needed to get the DC where I needed it.
Is this also the way to add surge protection with the rectifier tube in place ?? I'm thinking the voltage increase is about 20 volts versus a 5Y3 tube? Please correct me if I am wrong...and as usual, thanks for all the advice on my previous threads....
Paralleling solid state and hollow state diodes doesn't work. The hollow state diode will have less than a volt across it, and will draw microamps.
If your PRV is high enough, the 1KV / 1.5A diodes will certainly work. Any reasonable DC ripple filter won't come close to its Isurge rating.
Thanks...I can always rely on you, Kevin and Miles. One other ?...is it safe to run a tube rectifier with the diodes in place? If so, what is the result...do I end up with the voltage drop accross the 5Y3 or the increased voltage of the diodes???
This is really beginning to be fun !!!
BTW...anyone following my first build...I replaced the OT with a higher output/quality one and the result was almost unbelieveable...output and sound quality improved remarkably !! Thanks for all your input everyone !!!!
This is really beginning to be fun !!!
BTW...anyone following my first build...I replaced the OT with a higher output/quality one and the result was almost unbelieveable...output and sound quality improved remarkably !! Thanks for all your input everyone !!!!
bereanbill said:Thanks...I can always rely on you, Kevin and Miles. One other ?...is it safe to run a tube rectifier with the diodes in place? If so, what is the result...do I end up with the voltage drop accross the 5Y3 or the increased voltage of the diodes???
This is really beginning to be fun !!!
BTW...anyone following my first build...I replaced the OT with a higher output/quality one and the result was almost unbelieveable...output and sound quality improved remarkably !! Thanks for all your input everyone !!!!
Yes it's safe to run them in parallel, however in this scenario because the forward drop of the silicon diodes is so much lower than the 5Y3 all of the load current will flow through the ss diodes and not the tube rectifier - the voltage drop experienced will be that of the SS diodes exclusively. Basically the 5Y3 becomes a decoration.. You can also configure things with a switch to select which one you want - at its simplest just tie the two ss diode cathodes together at a spst toggle switch rated to handle the voltage, and connect the other side of that switch to the cathode of your rectifier tube, voila switch open - tube rectified, switch closed < possibly small to not so small POP> and then the SS diodes take over.
OK, I tried this and got smoke...not a good thing, but I shut it down quickly. I connected the anodes of the diodes to the plates of the rectifier, tieds the cathodes of the diodes together to one leg of an SPST switch rated at 250VAC@6A. Then I ran the cathodes of the rectifier tube to the other leg of the switch...smoke was the result. What did I do wrong ? The PT is ok...I undid the ss rectifier and it works fine....????
bereanbill said:Ok folks...time to coddl a newbie with a lot of dead brain cells...if you don't mind that is. I remember reading about using 2 IN4007 diodes on the rectifier socket to replace the rectifier tube, but I can't remember how it was done. I'm guessing the anode goes on the AC side of the socket and the cathode on the DC side?? Is this also the way to add surge protection with the rectifier tube in place ?? I'm thinking the voltage increase is about 20 volts versus a 5Y3 tube? Please correct me if I am wrong...and as usual, thanks for all the advice on my previous threads....
Afterthought...I have some 1000 volt, 1.5 amp diodes here...they would work not ? I think the IN4007 is 1000 volt, 1 amp ???
I used diodes instead of a rectifier tube in my preamp and the diodes gave off big switching spikes. I had to add a capacitor from the diode output to zero volts to kill the spikes.
Please confirm you understand the markings on the rectifier body.
Hint anodes are NOT the banded end. Verify that those diodes are really what you think they are - often best accomplished by replacing them with new ones from a trusted source. Hint2: Not the local RS...
Also this rectifier tube has just one "cathode" connection ignoring the fact that there are two filament connections.. (You didn't mix it up with the plates?)
Please also confirm that this is a conventional CLC or CRC pi-filter input circuit and not a choke input. Finally how large is the input capacitor?
Hint anodes are NOT the banded end. Verify that those diodes are really what you think they are - often best accomplished by replacing them with new ones from a trusted source. Hint2: Not the local RS...
Also this rectifier tube has just one "cathode" connection ignoring the fact that there are two filament connections.. (You didn't mix it up with the plates?)
Please also confirm that this is a conventional CLC or CRC pi-filter input circuit and not a choke input. Finally how large is the input capacitor?
OK...looking at the basing diagram for the 5Y3 it shows pins 4 and 6 as the plates, and pins 2 and 8 as filaments...no cathode. Is this tube an indirectly heated cathode ? Is that what is known as a cold cathode ? Can I not do this mod to this circut ? And yes, I know that the banded end is the cathode...these are 1KV1.5A diodes NOT from RS...
No the 5Y3 is a direct heated filamentary rectifier, filaments pins 2 & 8, you can take the dc off of either of those pins (not both) or off the center tap of the rectifier filament winding, if that winding is center - tapped.
Examples of indirect heated rectifiers would include the 5AR4/GZ34, but note that it is pinned out to be pin compatible with various direct heated rectifier types like the 5U4.
Other indirect heated types include the 6V4, 6CA4, 6X4, and various damper diodes - none of these share filament and cathode connections effectively isolating the filaments from the rectified B+.
In direct heated types the filament heats an emissive coating on the filament wires or the filament wires themselves emit electrons. In an indirect heated type the filament heats a separate cathode structure that then emits the electrons - hence the term direct vs indirect heating. (respectively)
Cold cathode types exist, but most common types are used for voltage regulation. Examples include the 0A2, etc.
Sounds like you wired it correctly, but something else is going on, what is the value of that first capacitor and the filter configuration?
Also what is the AC voltage present at the high voltage secondary of your transformer? 1KV diodes are ok with 600VCT transformers and 400Vdc, but with relatively little margin to spare for high line voltage or transients. You can put two in series on each leg to withstand higher voltages, but you should parallel each diode with a 1M 1/2W resistor, and 0.01uF/1KV disc ceramic (cap) if you elect to do this. (This insures reverse leakage currents are equalized, also equalizing the reverse voltage assuring that the PIV rating of the individual diodes is not exceeded. It also reduces rectifier hash somewhat.)
Hopefully you'll get this sorted out soon.
Examples of indirect heated rectifiers would include the 5AR4/GZ34, but note that it is pinned out to be pin compatible with various direct heated rectifier types like the 5U4.
Other indirect heated types include the 6V4, 6CA4, 6X4, and various damper diodes - none of these share filament and cathode connections effectively isolating the filaments from the rectified B+.
In direct heated types the filament heats an emissive coating on the filament wires or the filament wires themselves emit electrons. In an indirect heated type the filament heats a separate cathode structure that then emits the electrons - hence the term direct vs indirect heating. (respectively)
Cold cathode types exist, but most common types are used for voltage regulation. Examples include the 0A2, etc.
Sounds like you wired it correctly, but something else is going on, what is the value of that first capacitor and the filter configuration?
Also what is the AC voltage present at the high voltage secondary of your transformer? 1KV diodes are ok with 600VCT transformers and 400Vdc, but with relatively little margin to spare for high line voltage or transients. You can put two in series on each leg to withstand higher voltages, but you should parallel each diode with a 1M 1/2W resistor, and 0.01uF/1KV disc ceramic (cap) if you elect to do this. (This insures reverse leakage currents are equalized, also equalizing the reverse voltage assuring that the PIV rating of the individual diodes is not exceeded. It also reduces rectifier hash somewhat.)
Hopefully you'll get this sorted out soon.
Yes - it sound like you shorted the filament supply by connecting pins 2 and 8 together either directly or via the added diodes. The extra connection (from both solid state diode cathodes connected together) should be to ONLY one of these pins, which ever is the one being used as the high voltage output.
If the "short" was via the diodes then they may well be "toast".
That would certainly cause "smoke" and (joke) as we all know from our Electricty 101 course its the smoke inside the wire that make things work, we know that because when you let the smoke out, it stops working.
Review what you did and re-read the above posts.
Cheers,
Ian
If the "short" was via the diodes then they may well be "toast".
That would certainly cause "smoke" and (joke) as we all know from our Electricty 101 course its the smoke inside the wire that make things work, we know that because when you let the smoke out, it stops working.
Review what you did and re-read the above posts.
Cheers,
Ian
Sweet sucess !!!
Thanks Kevin, Miles, and Ian...Thanks to you I have sucessfully done this mod. Ya know, when I first wired it up to both cathodes, I'm thinkin' " This is not right". So now, the prototype (my first build) is all but complete. I think I'm going to call it " The Severed Head " if for no other reason than it sounds cool !?!?!? 
Thanks Kevin, Miles, and Ian...Thanks to you I have sucessfully done this mod. Ya know, when I first wired it up to both cathodes, I'm thinkin' " This is not right". So now, the prototype (my first build) is all but complete. I think I'm going to call it " The Severed Head " if for no other reason than it sounds cool !?!?!?
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