| Electronics > Projects, Designs, and Technical Stuff |
| What is a good value for B+ ripple on 480VDC |
| << < (6/7) > >> |
| Planobilly:
--- Quote from: calexanian on December 04, 2016, 07:51:35 am ---Based on that you may want to eliminate that fuse and connect that tap to the mid point of your main filter caps. http://www.thevintagesound.com/ffg/schem/twin_reverb_sf_135_schem.jpg Have a look at how it is implemented here. --- End quote --- I have seen several schematics with this sort of HT rail design. The one thing that is never shown is the AC values of the power transformer. Based on the power transformer I have which has a 377 VAC ( measured RMS unloaded voltage end to end) HT secondary which has a center tap, do you think the schematic you linked will work? Secondly, The way I have the current HT circuit built is providing the acceptable voltages and acceptable amounts of ripple (I think). I can draw a as built schematic if needed but in general the HT center tap is going to ground through a fuse atm. The B+ voltage measures 478 V RMS. Having said all that my gut level feeling is the power supply as built needs to be redesigned and rebuilt. Obviously the stand by switch is not connected in the correct place and there is the "pop" most of the time on shut down. I think for us to have a meaningful conversation, I need to bite the bullet and draw a as built set of drawings. Removing the DC components for the preamp heaters also gives me the room to place the HT caps on a new board that fits in that space. Here is a link to the EVH 5150 that I took channel two from and the power supply that I sort of copied. http://support.evhgear.com/schematics/EVH_5150III_AmpHead_Schematics.pdf Cheers, Billy BTW...If you look at the EVH schematic, do you think we need to also install the zener diodes to clamp the voltage? |
| calexanian:
Connecting the center tap will improve power supply filtering and regulation. The caps will be happier too. |
| vk6zgo:
The grounded centre-tap shown in your schematic in reply 11 is a major 'no-no". On every half cycle,one diode will be directly across half the secondary,effectively shorting it out. This is not good for the transformer or the diode. I think the reason that your supply works at all is that the fuse probably blew on the first half cycle. Returning the centre tap to the junction of your two series connected filter capacitors as suggested by calexanian is a good idea,as it allows you to use the full capacitance of each cap,as well as reducing the ESR as compared to the standard series connection. It is really a "work-around" to allow the use of high capacitance,but lower voltage rated capacitors. This kind of connection was rarely seen during the heyday of valve/tube amplifiers,as 600v rated electrolytics were common in the values usually used. The high overall values of capacitance common today & which are necessary with RC filtering were not readily available or required using LC filtering,which was all but universal. |
| calexanian:
The bridge rectifier circuit in fenders was a Ed Jhans thing. You could get better quality lower voltage capacitors in the 70's. 600 and even 500 volt caps were already on their way out and the lower voltage caps were getting better and more compact and with far lower ESR. Additionally your power rectifiers could have a lover PIV because they will never see more than rectified and filtered DC max potential across then rather than double that in the traditional full wave rectifier circuit. Also you are taking advantage of the entire secondary and you could make the gauge of the secondary winding with a larger gauge wire thereby reducing losses and heat. Bridge rectifier for these circuits is the most efficient way to go. |
| wagnerlip:
It is just me and my 50+ yrs knowledge of vacuum tubes is just vanishing away, or those output 6L6's have the cathodes floating? |
| Navigation |
| Message Index |
| Next page |
| Previous page |