Replaced Rectifier

March 25, 2022 Post a Comment

Replacing a selenium rectifier

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	Post subject: Replacing a selenium rectifier Posted: Jul Wed 20, 2005 3:41 pm
Fellow member Joined: Jan Thu 01, 1970 1:00 am Posts: 94 Location: Baden, PA 15005	I'm gathering parts for a Silvertone 8020 that I am recapping, and decided to replace the selenium rectifier that is in it. I have read on a few sites that a bridge rectifier can be used, just I'm not sure how that would be possible, since, in the schematic, the rectifier appears equally a single diode.<P>If this is the case, what size diode should I use? I accept a bunch of silicon diodes that I've pulled from old computer power supplies - would one of these be sufficient, or would I demand something that would handle more ability?<P>------------------<BR>~general0ne~
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zenith82	Post subject: Replacing a selenium rectifier Posted: Jul Wednesday 20, 2005 5:33 pm
Joined: Jan Thu 01, 1970 one:00 am Posts: 8131 Location: Baltimore, MD	I use a 1N4005 silicon diode. Inexpensive, easy to find, and does a proficient job. As Neb said, be conscientious with the polarity and add together at least a 5W resistor in serial with it. In the few I've had to replace, the ideal resistor has been 100 ohms or less, just there may be cases where a dissimilar value is needed. <P>You might want to motility this thread to the restoration forum to get more than communication.<P>Tom<P>------------------<BR>
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general0ne	Postal service subject: Replacing a selenium rectifier Posted: Jul Wed twenty, 2005 7:17 pm
Joined: Jan Thu 01, 1970 one:00 am Posts: 94 Location: Baden, PA 15005	I put a mail in the restoration forum. <P>Getting the polarity isn't a trouble, since the anode and cathode are marked on the schematic, and the cathode is always the banded or marked finish on the diode itself.<P>What is the purpose of wiring a resistor in series with the diode? Is information technology just to recoup since the selenium rectifier has a higher resistance than the silicon diode? Is there a way to check the rectifier (it is still operational - it hasn't blown yet) to figure out what value resistor I should use, or is it pretty much a "try one and see how it works" approach?<P>I have about 10 or 15 1N4005's from the old power supplies (plus a whole pile of united nations-dissected supplies), so if i or two get toasted trying to find the correct resistor value, it wouldn't be that big of a loss.<P>------------------<BR>~general0ne~
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mario2	Post subject: Replacing a selenium rectifier Posted: Jul Wed 20, 2005 vii:thirty pm
Joined: January Thu 01, 1970 i:00 am Posts: 632 Location: Buenos Aires, Argentina	mario2 wrote: <font>quote:</font><Hour>Originally posted past general0ne:<BR><B>I put a postal service in the restoration forum. <P>Getting the polarity isn't a trouble, since the anode and cathode are marked on the schematic, and the cathode is e'er the banded or marked end on the diode itself.<P>What is the purpose of wiring a resistor in serial with the diode? Is it but to compensate since the selenium rectifier has a higher resistance than the silicon diode? Is at that place a way to bank check the rectifier (it is yet operational - it hasn't blown however) to effigy out what value resistor I should use, or is information technology pretty much a "endeavor one and see how it works" approach?<P>I have about x or 15 1N4005'southward from the old ability supplies (plus a whole pile of un-dissected supplies), and then if ane or two become toasted trying to find the correct resistor value, information technology wouldn't be that large of a loss.<P></B><Hour> <P>The purpose of the resistor is to drop same voltage that gets dropped past the selenium rectifier. A silicon diode will drop 0.7v while the selenium rectifier may drop anywhere between 5 and 20 Volts (or more) Measure the drop is a good starting point just go along in listen it might not exist accurate every bit it tends to drop more as it ages (I approximate that's why they overheat and burn)<P>Experiment by carefully testing voltages on the dissimilar stages (plates and filaments) this is the safest mode<P>adept luck<P><BR>Mario<P>------------------<BR>I know the voices aren't real, simply they have some pretty practiced ideas!
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exray	Post subject area: Replacing a selenium rectifier Posted: Jul Wednesday 20, 2005 7:34 pm
Joined: Jan Thu 01, 1970 1:00 am Posts: 6175 Location: Vieques, PR, United states of america	A low value resistor serves for surge protection (current limiting) of the diode. The selenium should already take one in place.<P>You generally don't need one on transformer operated sets, though.<P>A good six-stack selenium loses about 5.four volts 'by the book' (0.9v per section) compared to 0.7 volts for a single silicon diode. Thats ordinarily not a problem just if you accept high line voltage issues every bit well then information technology doesn't injure to adjust the resistor accordingly to keep the B+ downwards.<P>-Bill<P>------------------<BR>
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Leigh

Post subject field: Replacing a selenium rectifier

Posted: Jul Wed 20, 2005 8:08 pm

Silent Key

Joined: Jan Thu 01, 1970 1:00 am
Posts: 31285
Location: Maryland 20709, Us

Leigh wrote:

quote:<Hr>Originally posted by general0ne: ...I have about x or 15 1N4005's from the old power supplies<HR>

The 1N4005 is rated 600 volts PIV, which would be marginal in this application. At a 120 volt line, the bodily PIV across the diode is well-nigh 490 volts. The 600 volt rating leaves very little safety margin.I employ R1800 diodes (catalog number 583-R1800F) from Mouser <A HREF="http://world wide web.mouser.com" TARGET=_blank>http://www.mouser.com</A> , rated 1800 volts PIV. They cost about $0.12 each.------------------ 73 de Leigh W3NLB | |

Leigh@AtwaterKent.Info

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Norm Leal	Post subject field: Replacing a selenium rectifier Posted: Jul Thu 21, 2005 ii:50 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 30905 Location: Livermore, CA	Hello Leigh<P> Always adept to utilise higher rated diodes but 400 PIV (1N4004) are usable on our Ac lines.. 1N4004 has been used for years although spikes can blow them or well-nigh whatever diode. Those 1800 PIV diodes sound great.<P> PIV of a 125 volt AC line is only 354 volts. (125 x 2.828)<P> When ability silicon diodes first became available people would endeavour to use 200 PIV. (1N2069) Some times they got away with this equally diodes are usually higher. In that location were none rated 300 so 200 may actually be higher and hold up. Series resistance can too be added. <P>------------------<BR>Norm
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exray	Post subject: Replacing a selenium rectifier Posted: Jul Thu 21, 2005 8:03 am
Joined: January Thu 01, 1970 ane:00 am Posts: 6175 Location: Vieques, PR, USA	US voltage has never been rated at 100 volts. Y'all may find an detail labelled at 110 from time to time but the practice has always been 115-120.<BR>True, many folks do run into high line voltage. I've experienced (twice) a spell of it >124 at all hours and it did a off-white amount of harm before they corrected information technology.<P>In a typical selenium rectified fix running with the air-conditioning voltage x% "too high", yes, adding an boosted five volts by changing to a silicon diode may tip the scale on B+ ratings. Hence my previous post about mayhap needing to add resistance.<P>Thats not a cure-all, though...the filaments are still running high...and so is your refrigerator, VCR, etc.<P>If you have high line voltage and cannot get it corrected you might indeed accept to have some extra precautions. Modifying the set is ane valid option because even with the actress resistance information technology volition still perform for the next guy (should you lot sell it) who is not suffering from "todays college line voltages".<P>You shouldn't be blowing filaments in battery powered sets regardless of the line voltage <IMG SRC="http://antiqueradios.com/forums/smile.gif"><P>-Bill<P><P>------------------<BR>
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Leigh

Post subject: Replacing a selenium rectifier

Posted: Jul Thu 21, 2005 seven:30 pm

Silent Key

Joined: January Thu 01, 1970 one:00 am
Posts: 31285
Location: Maryland 20709, USA

Leigh wrote:

quote:<Hr>Originally posted by Bill Cahill: Remember, guys, while y'all are giving this expert advice, that yesterday's line voltages were rated anywhere from 100v to 117v air-conditioning.<60 minutes>

117 volts was the average of service voltages around the state, so half of the service areas were higher. Many Atwater Kent voltage table readings were done at 120 volts nominal.------------------ 73 de Leigh W3NLB | |

Leigh@AtwaterKent.Info

<A HREF="http://www.AtwaterKent.info" TARGET=_blank>http://www.AtwaterKent.info</A> | | <A HREF="http://www.Synchrophase.info" TARGET=_blank>http://www.Synchrophase.info</A>

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Omer	Post subject: Replacing a selenium rectifier Posted: Jul Sat xxx, 2005 8:53 am
Joined: January Thu 01, 1970 ane:00 am Posts: 296 Location: Beverly Hills, CA, The states	What's incorrect with using a silicon bridge rectifier, snubbed with four 0.0047 mf ceramic caps?<P>Likewise, what's the differnece between a "christmas" tree bridge, with four 1N4007 and a premade bridge rectifier?<P>Vacuum Tube Valley sells bridge rectifiers for vacuum tube applications.
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Tom Albrecht

Postal service bailiwick: Replacing a selenium rectifier

Posted: Jul Sat 30, 2005 10:29 am

Member

Joined: Jan Thu 01, 1970 one:00 am
Posts: 12064
Location: San Jose, CA U.s.

Hi Omer,Bridge rectifiers are "full wave" rectifiers and put out a different waveform than a single diode "half moving ridge" rectifier.Although the output from a full wave rectifier requires less filtering (and therefore smaller capacitors) than one for a half wave rectifier, in the old days, rectifiers were expensive. You either used a tube or a selenium rectifier, and using four of them to make a bridge was considered also expensive. In those days, whenever a full-wave rectifier was desired, a centertapped transformer was used. With a centertapped transformer, y'all can brand a total-moving ridge rectifier with but two diodes, and this was usually done with a dual diode tube like 5Y3 or 5U4 or 80.In the cheapest radios (and in those used for Air-conditioning-DC performance), no transformer was used, and then a half-wave single diode rectifier was the solution, either using a single diode tube like 35Z5 or 35W4, or a selenium rectifier. Bigger filter caps were needed (typically 50 uF + xxx uF), merely this was cheaper overall than either a centertapped transformer or a four-diode bridge.If you lot replace a single diode half-wave rectifier with a full-wave bridge rectifier today, yous'll end up with smoother (ameliorate filtered ) DC, only too a B+ voltage that is higher than originally intended. You lot could add resistance to compensate.In the end, you wouldn't really exist restoring, but "improving" on the original. Nothing wrong with that, simply I don't hear of people doing this detail modification very often.At that place is no functional difference between a span made with four separate diodes versus a single-unit bridge. It's just packaging.Tom------------------

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Omer	Post bailiwick: Replacing a selenium rectifier Posted: Jul Sat 30, 2005 ten:57 am
Joined: Jan Thu 01, 1970 i:00 am Posts: 296 Location: Beverly Hills, CA, USA	In the German radios I have been restoring, their radios already have the full wave selenium rectifiers. This is the reason I was posing this question.<P>As for the half wave rectifiers, I call back the principles of radio restoration would be violated past changing the circuit to something else!<P>Other than,hiding mylars in wax caps, hiding new electrolytics in old cans, and replacing bad cords with polarized ones, radio restoration should do its all-time to go on what's going on within the radio as much as its designers intended, lookwise and circuitry wise!<P>
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Tom Albrecht

Mail service subject: Replacing a selenium rectifier

Posted: Jul Sat thirty, 2005 eleven:xix am

Fellow member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 12064
Location: San Jose, CA Us

Omer, you enhance a skilful betoken. Yes, lots of German radios had full-wave selenium bridge rectifiers. Replacing those with full-moving ridge silicon span units makes a lot of sense.Siemens and other German companies seemed to take a good inexpensive process to manufacture those bridge rectifiers in the 1950s. The packaging was very compact also (in some cases the mod Si bridge is bigger!).Those radios about e'er have a power transformer as well. For the Germans, it was apparently cheaper to use those little bridge units instead of a centertapped transformer.That'southward ane of the fun things almost collecting antique radios from different countries. In unlike places, people came up with different solutions.Today, with our worldwide marketplace, designs seem to be very like everywhere.Tom------------------

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Short Circuit	Postal service subject: Replacing a selenium rectifier Posted: Jul Sun 31, 2005 3:40 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 28 Location: Loserana	The only problem I can see with installing a bridge rect. is there enough room to mount in lodge to provide a a heat sink.<BR>As far as diodes I utilize ECG 125, (NTE)<BR>g PIV and 2.five amp<BR>Got bags of 'em effectually<P>------------------<BR>There was this actually bright wink and loud bang.....
Peak

general0ne	Postal service discipline: Replacing a selenium rectifier Posted: Jul Sun 31, 2005 3:51 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 94 Location: Baden, PA 15005	If you go the square style, that has a mounting hole in the middle, information technology may be possible to mount it to the chassis, using the chassis as a heatsink. I'm not sure if that would provide enough estrus dissipation, though.<P>------------------<BR>~general0ne~
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Norm Leal	Post subject: Replacing a selenium rectifier Posted: Jul Sun 31, 2005 5:29 am
Joined: Jan Thu 01, 1970 1:00 am Posts: 30905 Location: Livermore, CA	Hi<P> Radios don't draw a lot of current. You lot may not need a estrus sink? 100 MA times .7 volts is just .07 watts. Even with a bridge shouldn't get in a higher place 1/four watt. A bridge uses iv diodes simply each is treatment less current.<P>------------------<BR>Norm
Peak