Can someone tell me a little about selenium rectifiers, how to check them in a circuit, and how to replace them with a diode, and how to know what type of diode?
Tube radio fan here. Thanks, Richard. Rnktapp said:. Click to expand Selenium rectifiers are allso semiconductor devices but amorphouse. In old days we used to say taht each plate of rectifier can whithstand about 30V of reverse voltage and that each square centimeter of it's surface can whitstand mA of current.
You should count number of plates connected in series and calculate area of plate. One of the characteristics of selenium rectifier is: they have about V voltage drop when they are designed for V AC. Klaus New Member.
And another peculiarity about selenium rectifiers is that they require the evacuation of the room if accidentally or deliberatly :twisted shortened :lol: Who here is old enough to remember using these things? I'm putting my hand up :wink:. I remember them I remember the local pharmacy in our small town, had a tube tester, as did other stores, and quite the selection of tubes. It was not uncommon for my dad to get some advice from a friend and swap some tubes of the tv didn't work right. Sometimes that worked - if not the repairman was called.
Klaus said:. That was a funny story! It was amusing to read about the old days, and the smell if the rectifier got shorted Thanks for a laugh to start my day! Re: That was a funny story! Thanks Rnktapp said:. I did measure the AC in and the DC out, and the rectifier is still good. Dean Huster Well-Known Member. If you fail to add the additional series resistance, you may end up raising the power supply's output by more than the "one volt per plate" that is often assumed.
And it's clear that all of us who have been posting here have a pretty deep understanding of all the issues you raise above, so I 'm not sure what you're getting at. To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind. I had a hard time finding the Gramels article yesterday using the link that I originally had. I had begun to think that maybe just a series resistor is enough, but adding more resistance could also help mitigate today's higher line voltages.
Also, different manufacturer's had developed their own techniques to improve the current density amps per sq. Most of that doesn't have relevance today. No one is going to design a power supply with selenium stacks and any NOS selenium stacks today bear questionable relationship to their original specs. Back around , I helped Anocut Engineering electrochemical machining replace cabinets about 20 cu.
Water cooled and less than two cubic feet. I was just a kid! On those that don't draw anything from the first filter cap, it's obviously fine to add resistance between the two filters, although voltage on the first filter may be quite bit higher than originally intended. Overall, it looks like there is pretty good agreement here on how this works.
The small variations make no practical difference to the real world. This is especially true when one considers the typical daily variations on the mains lines feeding the radio. The only situation I know of where this voltage is important is in sets using a 50C5 output tube. That tube has a max plate voltage of v and a max screen voltage of volts. If you find either of those exceeded after installing a silicon rectifier, adjustments MUST be made. Permit me to note that the voltage drop per plate is at full load current.
This is obvious from a glance at the voltage drop graph that I posted earlier. I thought the number of tissues was determined by how hard you intended to blow.
Thanks guys learned a lot here. Thanks Leigh for the PDFs. All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowl edged. Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics , published October - April All copyrights are hereby acknowledged. Per Wikipedia , "A selenium rectifier is a type of metal rectifier, invented in They were used to replace vacuum tube rectifiers in power supplies for electronic equipment, and in high current battery charger applications.
The photoelectric and rectifying properties of selenium were observed by C. Fitts around but practical rectifier devices were not manufactured routinely until the s.
Compared with the earlier copper oxide rectifier, the selenium cell could withstand higher voltage but at a lower current capacity per unit area. The forward direction in the selenium is from alloy to baseplate. Thus, the alloy is comparable to the cathode and the baseplate to the plate of a vacuum-tube rectifier.
This photo shows a large 5-amp. Resting on top of a modern selenium of the power variety is an old-type copper oxide rectifier. Although almost three times the size of the copper oxide unit, the selenium weighs less.
Both can handle 5 amperes, but the selenium is rated at a five-times higher voltage, hence the extra length. Here, density is highest at corners of pyramid. High resistance direction B is opposite. Selenium rectifiers have long been accepted as an efficient means of converting a. Their use has recently been expanded to include radio and TV receivers as well as all types of electronic control gear and mobile equipment. But although many millions of these units are now being employed, most experimenters are dangerously ignorant of their characteristics and limitations.
Figure 1 is a cross section of a finished selenium cell. The etched-aluminum baseplate serves as the negative electrode and the low-temperature alloy as the positive electrode. In operation, electrons flow readily from the alloy to the baseplate but encounter high resistance in the opposite direction. The alloy plating behaves like the cathode of a vacuum tube and the aluminum baseplate serves as the anode or plate, with the selenium crystal layer actually performing the rectifying action Fig.
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