HRDlx Rectification

[NTBluesGuitar]

I've been studying the schematics for the HRDlx lately, more specifically, the rectifier circuit and the question I have is: What is C53 doing in there? It's an 8200pF, 1kV ceramic disc cap and it was actually missing from my HRDlx when I bought it. I've put a new one in, just in case it's keeping something from fryin' in there...but didn't notice any difference from when it was missing.

Otherwise, it looks like a normal center tapped, full-wave filtered rectifier circuit. If anyone has any ideas, I'd be most appreciative. Thanks!

[JAM]

Looks like it's there to reduce transient switching noise from the rectifiers. Sometimes they're placed directly across each diode.

[NTBluesGuitar]

Outstanding...thanks for your help on that.

[Guitar_Mc]

NT,

If you are planning on reusing the power XFMR, I think most Full wave Rectifiers need a center tapped Power XFMR. The one in the HRDx is not center tapped. I think you can use 2 diodes in combination with the rectifier tube. Kind of like the following diagram (but different tubes of course).



Does anyone else have any input in this? Does this sound right?

[NTBluesGuitar]

Ahh...the plot thickens...

I was brainstorming a plan that would have me going solid state and following the schematic, not modifying the power supply or putting in some new setup.

However, it's good to know that there might be a possiblilty on using a tube rectifier with the current transformer.

I like having options.

[Guitar_Mc]

However, it's good to know that there might be a possiblilty on using a tube rectifier with the current transformer.

And its always nice when those options let you reuse the single most expensive component.

[NTBluesGuitar]

Indeed!

Anyway, here's my working version of the rectifier build from the schematics:



I thought about a bridge rectifier, too, but didn't want to stray too far from the original to be safe.

[Guitar_Mc]

PSU Designer II is VERY helpful in designing the power source. It takes a bit of playing around with though.

http://www.duncanamps.com/software.html

Its free.

There is also some other good amp design software there too.

[JAM]

Indeed!

Anyway, here's my working version of the rectifier build from the schematics:



I thought about a bridge rectifier, too, but didn't want to stray too far from the original to be safe.

You should redraw this, as is it appears there's a short circuit across the secondary.

[NTBluesGuitar]

You should redraw this, as is it appears there's a short circuit across the secondary.

Thanks for the advice...I really appreciate it!

Where exactly do you see the short? I'm relatively new to this, but I checked and double checked and can't see it. I'm planning to sketch out the traces from the PCB next chance I get, but as it stands, I'm at a loss regarding the short you mention.

I guess it's good that I'm drawing it out first. I'd hate to fry my protoype circuit. ;)

[JAM]

Thanks for the advice...I really appreciate it!

Where exactly do you see the short? I'm relatively new to this, but I checked and double checked and can't see it. I'm planning to sketch out the traces from the PCB next chance I get, but as it stands, I'm at a loss regarding the short you mention.

I guess it's good that I'm drawing it out first. I'd hate to fry my protoype circuit. ;)

Look where you've got the cap hooked to the two diodes, the way it's drawn the cap is just shorted too.

[NTBluesGuitar]

Look where you've got the cap hooked to the two diodes, the way it's drawn the cap is just shorted too.

Ahhhh...I think I get it now. The schematic showed the diodes and cap in common, so I consolitated connection points in the drawing. Kind of renders the cap useless this way, huh?

[JAM]

Exactly, the two diodes hooked to the cap as shown should connect to the secondary (at opposite sides) and the cap hooks across the secondary.

[Guitar_Mc]

Nice save JAM.

[NTBluesGuitar]

...the two diodes hooked to the cap as shown should connect to the secondary (at opposite sides) and the cap hooks across the secondary.

Like this (upside-down from previous version)?

[Guitar_Mc]

NT

Here is a good sheet on rectifiers that might help you out.

Hammond Power Transformer Guide

It actually has good rectifier drawings and equations.

Look at the 'Full Wave Bridge Choke input load'

[JAM]

Like this (upside-down from previous version)?

Now you've got the diodes in parallel, the ones that are connected to the cap should connect to the opposite sides of the secondary from the other pair. Why not just copy it from the HRDx schem?

[NTBluesGuitar]

Why not just copy it from the HRDx schem?

I am...apparently unsuccessfully. I see what you're saying now and it's starting to clear up now. Your help so far has been great, and I appreciate it...cool cats like you helping newbs like me is the reason I came on board here!

Anyway, this is my first attempt at 'building' from a schematic, and I'm teaching myself, so bear with me...I'll get this next try, I know that now...let me consult my paper sketches. I think I have it right in my notes there.

[JAM]

I've got a redrawn schem, if you get me your e-mail I'll send it.

[NTBluesGuitar]

Does it look anything like these:



BTW, my email is now available through my profile...I'll be in touch, too. Thanks again.

[JAM]

Yep, like #1.

[NTBluesGuitar]

Yep, like #1.

Cool... options #2 and #3 are attempts at a more streamlined component layout (if I got it right, that is) as suggested by Guitar_Mc and following your advice regarding the schematic.

Looks like there's a chance at using a bridge rectifier now, too?

[JAM]

Looks like there's a chance at using a bridge rectifier now, too?

Well that's what it is, only using separate diodes. But why?

[NTBluesGuitar]

Well that's what it is, only using separate diodes. But why?

Just exploring another possible component option is all.