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Old 14th June 2004, 08:53 PM   #1
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Default How do I replace this 40+ year old selenium rectifier?

Hello,

In early May I asked questions at this forum in regard to my Pentron tube open reel stereo Hi-Fi system. "WHAT TYPE OF PART IS THIS?"

I hope to upgrade the electronics inside to make it sound better just for the fun of it.

After clearing some things off my desk I now have time to work on this project.

Here is my problem I know how to remove and replace all of the capacitors and resistors but am absolutely lost when it comes to selenium rectifiers.

You guys have been of great help so far. I have the recommended 1N4007s on hand and am ready to start.

However, how is the proper way to replace the selenium rectifier with these?

I diagram that was provided by planet10 in the "WHAT TYPE OF PART IS THIS?" thread was helpful and I think I understand it but want to make sure I got it right.

Here is a rough diagram showing the current circuit layout including the selenium rectifier.

This drawing of mine shows just the stuff going from the power supply > the selenium rectifier > to the tube.
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Old 14th June 2004, 09:01 PM   #2
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Default My understanding on how to do this

Here is my understanding on how these are to be soldered in place of the selenium rectifier.

Remove the selenium rectifier.

Solder in its place one diode with the cathode in one direction and another with the cathode in the other.

At the power source end I solder one diode with the cathode in one direction and another with the cathode in the other. The opposite ends of each solder to ground.
Is this correct?

I drew up the below attached diagram for clairification.
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Old 14th June 2004, 09:04 PM   #3
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One side of the selenium rectifier will be marked with a plus (+). The new rectifier will replace the old one, but the striped end goes to where the + end of the selenium was. By process of elimination, the unstriped end goes to where the other selenium rectifier lead was. The selenium rectifier should be discarded.

Edit: I'm not sure I understand your drawings.
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Old 14th June 2004, 09:14 PM   #4
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Quote:
Originally posted by SY
One side of the selenium rectifier will be marked with a plus (+). The new rectifier will replace the old one, but the striped end goes to where the + end of the selenium was. By process of elimination, the unstriped end goes to where the other selenium rectifier lead was. The selenium rectifier should be discarded.
Hello,

Here is the problem. There isn't a "+" on the old recitifier. Attached is a close up.

The diagram provided to me in the afore mentioned thread suggests that I use four 1N4007s to create a "half wave" recitifer as a replacement.

[ QUOTE] Edit: I'm not sure I understand your drawings. [/QUOTE]

I can do a better one if need be. the schematic was something I quicly scribbled down.
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Old 14th June 2004, 09:17 PM   #5
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Here is the diode recitifier schematic that was suggested last month
Click the image to open in full size.

It is what I hope to duplicate.

Attached is a picture of the 1N4007 diodes that were recommended.

Darren
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Old 14th June 2004, 09:51 PM   #6
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Normally, the + sign is on one of the outside flat faces or near the bottom of the lugs. Do you have a photo from that angle?
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Old 14th June 2004, 10:08 PM   #7
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here attached is a close up of the recitifer showing the end that factes the tube side of the circuit.

I just looked it over and this is the side of the "+." Barely noticable in the scans, however.

How would I solder in the 4 diodes to replace it?
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Old 14th June 2004, 10:12 PM   #8
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Quote:
Originally posted by darren01

How would I solder in the 4 diodes to replace it?
BTW, the metalic bar shown immeditely to the left of the recitifier in that attachment is the ground terminal.
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Old 14th June 2004, 10:21 PM   #9
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It looks from your photo like it's just a two terminal device, i.e., a half-wave rectifier. So all you need is one of the silicon diodes to replace it. The earlier discussion with planet 10 involved using 4 diodes for a redesign/rebuild of that supply. You can do that, but given where you are at the moment, I'd just do the one-for-one swap, get the thing working, and save the other 3 diodes for when you're ready to take the next step to a full-wave bridge.

Make sure you replace the electrolytic capacitors, too; they tend to go pretty leaky with age.
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Old 14th June 2004, 10:29 PM   #10
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Default What would a full wave bridge do to improve the sonics of the unit over a half wave?

Quote:
Originally posted by SY
It looks from your photo like it's just a two terminal device, i.e., a half-wave rectifier. So all you need is one of the silicon diodes to replace it. The earlier discussion with planet 10 involved using 4 diodes for a redesign/rebuild of that supply. You can do that, but given where you are at the moment, I'd just do the one-for-one swap, get the thing working, and save the other 3 diodes for when you're ready to take the next step to a full-wave bridge.
Check.

Thanks for the advice. You just made the project much more easier for me to figure out.

BTW, What would a full wave bridge do to improve the sonics of the unit over a half wave?

Quote:
Make sure you replace the electrolytic capacitors, too; they tend to go pretty leaky with age.
That is the next step. A couple of the capacitors in this unit are 60uf. I checked and they don't make them like that any more. I can get several different ones to get it near 60uf but would rather use jsut one.

However, that is a topic for another thread.

Darren
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