20070228.ba v04_n021.bam.20070228 >From ???@??? Wed Feb 28 05:57:55 2007 -0600 Date: Wed, 28 Feb 2007 11:56:52 GMT From: Old Tube Radios To: Old Tube Radios Subject: BOATANCHORS digest 4021 Message-Id: <20070228115653.C74813183C5@srvr1.theporch.com> BOATANCHORS Digest 4021 Topics covered in this issue include: 1) RE: Solid State Rectifier Replacement for 51JX by "Thomas Frobase" 2) Re: Lowering power supply output voltage. by "vilgotch@bigpond.net.au" 3) Re: 838 Tubes Needed by stuck in 50s 4) Re: DX-100 Power Supply by wb3fau@att.net 5) RE: Lowering power supply output voltage. by "Thomas Frobase" 6) Re: Lowering power supply output voltage. by "Tom Rauch" 7) FW: Lowering power supply output voltage. by "Thomas Frobase" 8) Re: Lowering power supply output voltage. by "Tom Rauch" 9) Re: Lowering power supply output voltage. by "Arden Allen" 10) Re: Lowering power supply output voltage. by "David Stinson" 11) Looking for SX-28 parts by "Joe Watson" 12) Re: ARRL - end of code / duct tape by John Kolb 13) Re: Lowering power supply output voltage. by Richard Post 14) Re: Lowering power supply output voltage. by W7QHO@aol.com 15) Re: Lowering power supply output voltage. by Scott Robinson 16) Re: ARRL - end of code / duct tape by "David Stinson" 17) Re: Lowering power supply output voltage. by "Tom Rauch" 18) Re: Lowering power supply output voltage. by "Ken Hickman" ---------------------------------------------------------------------- From: "Thomas Frobase" To: Old Tube Radios Subject: RE: Solid State Rectifier Replacement for 51JX Date: Mon, 26 Feb 2007 20:54:29 -0600 Message-ID: <03c201c75a1a$9aede540$0c01010a@tfrobase1> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit I like the idea, the 5 volt ac winding could supply the trigger supply, and the sense circuit would require a ground, ok so add one additional wire to an unused pin on the rectifier socket. If the module is pulled the replacement tube does not care! Now, on SS replacements Why hasn't anyone put SCRs as substitutes for s-s diodes? If each SCR turn-on delayed on it's half-cycle, then DC system voltage preserved - nirvanna No heat build-up from a series resistor. Problem is 'floating' the trigger ckt. on each diode. NJE did this well in LV power supplies a half century back. Underline LV. Nothing's easy but if there's HP progeny out here in BA arena, maybe one wil I-N-V-E-N-T Marty ------------------------------ Message-ID: <4244321.1172548208250.JavaMail.root@web02sl> Date: Tue, 27 Feb 2007 14:50:08 +1100 From: "vilgotch@bigpond.net.au" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Cc: Old Tube Radios Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit ---- Ken Hickman wrote: > Since you are replacing the hi voltage vacuum rectifier(s) that leaves the > rectifier filament > winding idle - wire it in series with the transformer primary winding Theoretically that's quite a good idea. The only snag might be that the filament winding is on the wrong side of any electrostatic shield. That might let a bit of noise through into a receiver. Otherwise it makes good sense. 73, Morris ------------------------------ Date: Tue, 27 Feb 2007 09:56:04 -0500 (EST) From: stuck in 50s Message-Id: <200702271456.l1REu4SE023496@fracas.netboobie.org> Cc: boatanchors@theporch.com, kx4r@earthlink.net Subject: Re: 838 Tubes Needed To: Old Tube Radios Greg, the 805 is a 838 with a plate cap. Easy to fine! Marty ------------------------------ From: wb3fau@att.net To: Old Tube Radios Cc: "Mike" Subject: Re: DX-100 Power Supply Date: Tue, 27 Feb 2007 15:15:36 +0000 Message-Id: <022720071515.7263.45E44B0F0004A20100001C5F21612436469A0E00CC0D99@att.net> I can not answer your question about the value of that resistor, in a similar situation, Barker and Williamson, in their BW 5100, they used a pair of 60k resistors. I know about them, because they were open in my 5100. I would not worry too much about stress on those potted chicago transformers in a DX-100. I had one come into the shop with the transformer smoking. It had a shorted 5R4, it worked fine after replacing the tube,and no ill effects . I stayed with 5R4s in the DX-100 and Apaches and replaced 125uf cans with 100uf Nichicons. They work well. Russ. ------------------------------ From: "Thomas Frobase" To: Old Tube Radios Subject: RE: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 18:11:19 -0600 Message-ID: <03d401c75acc$fc296cf0$0c01010a@tfrobase1> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit If a zero crossing detector should keep the noise low or not existent. On another subject, I have long wanted to build a primary side regulated power supply using a set of zero crossing triac's. I have seen several HP high current supplies done this way. Simple 12 volt brute power no pass transistors. ---- Ken Hickman wrote: > Since you are replacing the hi voltage vacuum rectifier(s) that leaves the > rectifier filament > winding idle - wire it in series with the transformer primary winding Theoretically that's quite a good idea. The only snag might be that the filament winding is on the wrong side of any electrostatic shield. That might let a bit of noise through into a receiver. Otherwise it makes good sense. 73, Morris ------------------------------ Message-ID: <02d401c75ad3$8b5b1530$640fa8c0@radioroom> From: "Tom Rauch" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 19:58:09 -0500 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit > If a zero crossing detector should keep the noise low or > not existent. I'm missing something. Help me. If a triac starts at zero it can't shut off until the next zero, or until the forward voltage gets so low it drops off. So we start it someplace up the cycle or we drop whole halves of a cycle. The only way to have high efficiency or low heat is to have a switching device that is either on or off. Any series device other than a pure reactance that drops voltage would make heat. Anything that switches fast makes noise unless we start and stop it at zeros. If we start and stop at zeros to not make noise, we then reduce the frequency by skipping whole portions of the cycle. So the way I see it is the only way we can reduce voltage is to change the waveshape. Either we chop up one cycle making noise, or we drop some entire positive, negative, or whole cycles which effectively reduces the frequency. None of this is generally good on transformer operated devices, especially those with high power factor. Great for lights, and great for a supply we design to have all sorts of input waveform distortion, but bad for devices that depend on a sine wave and a certain power line frequency. Or.... We can use the filament transformer winding or some other winding to buck the power line, reducing line voltage. If the Faraday shield really does anything (which is questionable) and if we bypass the Faraday shield we would only have to add a couple line bypass caps and we would be right back in business. Or....we could just use an external autotransformer or LV transformer to buck the power line with an out -of- phase voltage. Why do I think the easiest thing to do would be to just reduce the line voltage with a small transformer and forget all the rest of this? What am I missing? 73 Tom ------------------------------ From: "Thomas Frobase" To: Old Tube Radios Subject: FW: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 19:08:46 -0600 Message-ID: <03f801c75ad5$006c9b40$0c01010a@tfrobase1> MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit They way it works is you steal away alternations. The frequency stays the same the duty cycle changes. -----Original Message----- From: Tom Rauch [mailto:w8ji@contesting.com] Sent: Tuesday, February 27, 2007 6:58 PM To: tfrobase@kitparts.com; Old Tube Radios Subject: Re: Lowering power supply output voltage. > If a zero crossing detector should keep the noise low or > not existent. I'm missing something. Help me. If a triac starts at zero it can't shut off until the next zero, or until the forward voltage gets so low it drops off. So we start it someplace up the cycle or we drop whole halves of a cycle. The only way to have high efficiency or low heat is to have a switching device that is either on or off. Any series device other than a pure reactance that drops voltage would make heat. Anything that switches fast makes noise unless we start and stop it at zeros. If we start and stop at zeros to not make noise, we then reduce the frequency by skipping whole portions of the cycle. So the way I see it is the only way we can reduce voltage is to change the waveshape. Either we chop up one cycle making noise, or we drop some entire positive, negative, or whole cycles which effectively reduces the frequency. None of this is generally good on transformer operated devices, especially those with high power factor. Great for lights, and great for a supply we design to have all sorts of input waveform distortion, but bad for devices that depend on a sine wave and a certain power line frequency. Or.... We can use the filament transformer winding or some other winding to buck the power line, reducing line voltage. If the Faraday shield really does anything (which is questionable) and if we bypass the Faraday shield we would only have to add a couple line bypass caps and we would be right back in business. Or....we could just use an external autotransformer or LV transformer to buck the power line with an out -of- phase voltage. Why do I think the easiest thing to do would be to just reduce the line voltage with a small transformer and forget all the rest of this? What am I missing? 73 Tom ------------------------------ Message-ID: <02ef01c75ae0$a4f93c80$640fa8c0@radioroom> From: "Tom Rauch" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 21:31:56 -0500 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit > They way it works is you steal away alternations. The > frequency stays the > same the duty cycle changes. When we punch a hole in the sine wave by dropping cycles periodically it's just like superimposing a really low frequency waveform on the sinewave. That old fart Fourier figured that out long ago. It works fine for lights and fine for things that are designed with the dynamic regulation to hold the voltage up and not be hurt by the surges, but old tube radios really don't fit that criteria. Old radios don't like to have the power removed and restored every few cycles. They like nice steady sine waves without interruption. 73 Tom ------------------------------ Message-ID: <004a01c75ae2$ea68bd70$b5e47443@KB6NAX> From: "Arden Allen" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 18:37:52 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit > If a zero crossing detector should keep the noise low or not existent. > > On another subject, I have long wanted to build a primary side regulated > power supply using a set of zero crossing triac's. I have seen several HP > high current supplies done this way. Simple 12 volt brute power no pass > transistors. Tom beat me to the punch but here's what I was thinking: The problem with zero crossing triac triggers is the line frequency gets divided by various factors depending on regulation requirements. You end up with the derived B+ varying by a few Hertz. Then you have to smooth that out by following with a dissipative regulator. There goes your voltage. Or you can come up with a high frequency switching regulator but then you don't need the zero crossing preregulator. Now you are stuck with even more noise to quash. Arden Allen KB6NAX ------------------------------ Message-ID: <000b01c75ae9$1c0de160$fa01fea9@Default> From: "David Stinson" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Tue, 27 Feb 2007 21:32:41 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit OK; we've heard a basket of "it won't work." Here's the deal: I have a BA receiver with standard +250 VDC B+, full-wave rect. center tap grounded, pi-type cap input/output filter, 5 and 6 volt AC for fils just like a bi-zillion radios out there. I want to run the B+ at 100 volts, not 250. I will change nothing whatsoever in the receiver except the power supply, having run it on 100 volts external for many hours and been satisfied with its performance. What's the "right" way to do it? And "leave it alone and run 250 volts" is not an answer. It's 100 volts if I have to do it with batteries. So, all you smarty-pants engineer types ;-), Get'er Done! ------------------------------ Message-ID: <000701c75af9$94079570$6500a8c0@study> From: "Joe Watson" To: Old Tube Radios Subject: Looking for SX-28 parts Date: Tue, 27 Feb 2007 23:30:34 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0004_01C75AC7.47A361F0" This is a multi-part message in MIME format. ------=_NextPart_000_0004_01C75AC7.47A361F0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable For a current restoration, I need the following SX-28 parts: S-meter Top (RF) cover Bottom chassis cover Dial lock Audio output transformer Let me know if you have any of this stuff you would part with. Thanks. Joe W5WBR ------=_NextPart_000_0004_01C75AC7.47A361F0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ---REMAINDER OF MESSAGE TRUNCATED--- * * This post contains a forbidden message format * * (such as an attached file, a v-card, HTML formatting) * * Mail Lists at theporch.com only accept PLAIN TEXT * * If your postings display this message your mail program * * is not set to send PLAIN TEXT ONLY and needs adjusting * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ------=_NextPart_000_0004_01C75AC7.47A361F0-- ------------------------------ Message-Id: <7.0.1.0.1.20070227215121.01f05fe8@jlkolb.cts.com> Date: Tue, 27 Feb 2007 22:09:12 -0800 To: Old Tube Radios From: John Kolb Subject: Re: ARRL - end of code / duct tape Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed At 10:11 AM 2/20/2007, you wrote: > The military stopped using code because they switched to digital >transmission thru communication satellites. I think that the military >recently had cold shivers when the Chinese demonstrated that they could >shoot down communication satellites. Perhaps code will come back for >military communications. I'd say the military stopped using code because the volume of messages grew too high to be distributed through CW. 100 WPM teletype is much more efficent and accurate than 20 WPM CW. When I was a radioman for Commander 7th Fleet in 1964, we received up to 1500 messages a day addressed to us, which we handled with 25 RM's on watch at a time. Only 2 or 3 were actually receiving the msgs on the tty machines, the rest, were transfering them to mimeograph masters, making mimeograph copies, running around the ship geting officers sigunatures on hot msgs, etc. How many more would it have taken to receive that volume by CW? Spent 3 months in RM school learning 22 WPM CW, and sent 1 (only one) msg via CW in the next 3 1/2 years. The Navy was using teletype transmissions via HF transmissions long before satellites with either single channel RATT broadcasts or MUX (up to 16 tty channels on a single signal - 85 Hz shift per channel). John KK6IL ------------------------------ Mime-Version: 1.0 Message-Id: Date: Wed, 28 Feb 2007 01:40:40 -0500 To: Old Tube Radios From: Richard Post Subject: Re: Lowering power supply output voltage. Cc: Old Tube Radios Content-Type: text/plain; charset="us-ascii" ; format="flowed" I have tested several receivers at reduced voltages. Most work reasonably well. No big trick to reduce to 100. You can start by using choke input. That should drop the voltage to about 0.707 as much. Follow up with a new resistor or two for the modified pi filter (re-using the cap) after the choke to reduce it some more. Using choke input rather than cap input with a center-tapped-return power transformer can provide about 54% more current than capacitor input according to Hammond Transformer. Since reduced B+ voltage in a receiver results in significantly reduced current consumption, the power transformer will likely just loaf along and your electrolytics should also last a lot longer. I modified a regulated external supply used with my Commander transmitter. The supply was rated at 100mA and I needed more. And I only wanted regulated voltage for the oscillator and part of the modulator stage. Changing to choke input cut the voltage to the regulator pass tubes. That limited the current draw for a given regulated voltage. But a new tap to the unregulated voltage was used to feed the final. Total current draw for both regulated and unregulated could now be 150mA. If you add a choke to a receiver that does not have already one, an option is to put it in series with the center tap return. Same effect. 73, Rich At 9:32 PM -0600 2/27/07, David Stinson wrote: >OK; we've heard a basket of "it won't work." > >I have a BA receiver with standard +250 VDC B+, >full-wave rect. center tap grounded, >pi-type cap input/output filter, >...I want to run the B+ at 100 volts, not 250. >I will change nothing whatsoever in the receiver except >the power supply, having run it on 100 volts external >for many hours and been satisfied with its performance. > >What's the "right" way to do it? >And "leave it alone and run 250 volts" is not an answer. >It's 100 volts if I have to do it with batteries. > ------------------------------ From: W7QHO@aol.com Message-ID: Date: Wed, 28 Feb 2007 02:32:17 EST Subject: Re: Lowering power supply output voltage. To: Old Tube Radios MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_c23.121fc624.33168a01_boundary" --part1_c23.121fc624.33168a01_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 2/27/07 7:33:40 PM, arc5@ix.netcom.com writes: > OK; we've heard a basket of "it won't work." > > Here's the deal: > I have a BA receiver with standard +250 VDC B+, > full-wave rect. center tap grounded, > pi-type cap input/output filter, > 5 and 6 volt AC for fils > just like a bi-zillion radios out there. > I want to run the B+ at 100 volts, not 250. > I will change nothing whatsoever in the receiver except > the power supply, having run it on 100 volts external > for many hours and been satisfied with its performance. > Presume 6.3 vac heaters in the BA. Replace the original power xformer with a couple of 6.3 volt filament units of appropriate current ratings. Connect the secondaries of the two trannys in parallel. Run 120 vac into one primary and rectify the 120 vac coming off the primary of the second unit with a full wave bridge. With a choke input filter the DC output should be close to 100 volts. Feed the set's heaters off the 6.3 line, of course. Dennis D. W7QHO Glendale, CA Idiot message follows. (Live with it Hank.) ************************************** AOL now offers free email to everyone. Find out more about what's free from AOL at http://www.aol.com. --part1_c23.121fc624.33168a01_boundary Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * ---REMAINDER OF MESSAGE TRUNCATED--- * * This post contains a forbidden message format * * (such as an attached file, a v-card, HTML formatting) * * Mail Lists at theporch.com only accept PLAIN TEXT * * If your postings display this message your mail program * * is not set to send PLAIN TEXT ONLY and needs adjusting * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * --part1_c23.121fc624.33168a01_boundary-- ------------------------------ Mime-Version: 1.0 Message-Id: Date: Tue, 27 Feb 2007 23:45:28 -0800 To: Old Tube Radios From: Scott Robinson Subject: Re: Lowering power supply output voltage. Cc: Old Tube Radios Content-Type: text/plain; charset="us-ascii" ; format="flowed" Folks, In case any of you have been converted to the joys of choke input filters by recent postings, let me review how to calculate the minimum inductance needed for the filter to work correctly, in particular to give the predicted DC output voltage. Minimum L = load resistance in ohms/1100 This equation assumes a 60 Hz input single phase full-wave rectifier. Either CT or bridge requires the same inductance. For 50 Hz, multiply the inductance by 1.2. For example, supposing you have a receiver that draws 100 mA at 150V. The load resistance the DC supply sees is R = E/I = 150/0.1 = 1500 ohms You can now calculate the required minimum inductance: L min = 1500/ 1100 = 1.36 Henrys. More inductance does no harm and makes less ripple, but less won't work. Yours for smoke- and hum-free listening, Scott ------------------------------ Message-ID: <002401c75b20$d4293560$fa01fea9@Default> From: "David Stinson" To: Old Tube Radios Subject: Re: ARRL - end of code / duct tape Date: Wed, 28 Feb 2007 04:11:34 -0600 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit ----- Original Message ----- From: "John Kolb" Subject: Re: ARRL - end of code / duct tape >.... When I was a radioman for > Commander 7th Fleet in 1964, we received up to 1500 messages a day > .... How many more would it have taken to receive that volume by CW? I think a good question would be: "How many of those 1500 messages were unnecessary crap?" Many people believe that, just because we *can* do a thing, we *must* do it. Ain't so. Just because we *can* send 1500 a day, we dream up reasons to send 1500 a day. Just as "work expands to fill the available time" and "junk expands to fill the available space," information/data expands to fill the available throughput, even though, like the two cases above, most of the addition is make-work and unwarranted redundancy. It's like people getting "computer-itis;" going to the trouble to set up and work with a computer program over a task that would be easier and simpler done with a pencil and a piece of paper. This sets you squarely in the "failure mode" trap I've been talking about. Adding unwarranted complexity to a system adds ways for it to fail. If running a ship- or even the 7th Fleet- depends on 1500 messages a day, then you have another sort of problem and God help you if the teletype goes down (or the balloon goes up). ------------------------------ Message-ID: <032201c75b23$be2cf9b0$640fa8c0@radioroom> From: "Tom Rauch" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Wed, 28 Feb 2007 05:32:18 -0500 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=original Content-Transfer-Encoding: 7bit > I have a BA receiver with standard +250 VDC B+, > full-wave rect. center tap grounded, > pi-type cap input/output filter, > 5 and 6 volt AC for fils > just like a bi-zillion radios out there. > I want to run the B+ at 100 volts, not 250. > I will change nothing whatsoever in the receiver except > the power supply, having run it on 100 volts external > for many hours and been satisfied with its performance. > > What's the "right" way to do it? > And "leave it alone and run 250 volts" is not an answer. > It's 100 volts if I have to do it with batteries. When you have a cap input voltage is 1.4 14 times RMS transformer voltage. When you go to a choke input that is beyond critical inductance it becomes .9 times transformer RMS. So your 250 V would become 158 volts by going to a choke. Two things screw that up. One is the choke has to be huge in reactance value or you need a big bleeder. The critical inductance depends on load current and supply ripple frequency. Otherwise the light load voltage will rise too high. The other thing is the vacuum rectifier and transformer now become much more efficient because you corrected the load power factor on the HV secondary. This moves the HV back up again because the losses (causing heat) in the rectifier and transformer go way down. Depending on the quality of the original tranny and tube you might not see much of a voltage reduction at all, just a big drop in heat. If I wanted to run a receiver on half HV, I'd solid state the rectifier and run the power tranny at reduced primary voltage. I'd feed the tube heaters from a separate supply and only use the power tranny for HV. Of course I don't do that since too many things can fall apart performance wise. I just make sure the caps are good and run it like it was created and intended it to be...but that's just me. I figure if a 600V cap fails at 250V, I needed to change it anyway. Too many of these tricks work because the system tolerates additional stress, not because we made life easy. 73 Tom ------------------------------ Message-ID: <002901c75afd$7e4930a0$6b9c1f45@rtconline.com> From: "Ken Hickman" To: Old Tube Radios Subject: Re: Lowering power supply output voltage. Date: Wed, 28 Feb 2007 05:58:38 -0000 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Hi Scott, Not being well versed in those calculations, one thought occured to me - What would the calculations be for a "swinging choke" input? Just curious. Ken N5CM ----- Original Message ----- From: "Scott Robinson" To: "Old Tube Radios" Cc: "Old Tube Radios" Sent: Wednesday, February 28, 2007 7:45 AM Subject: Re: Lowering power supply output voltage. > Folks, > > In case any of you have been converted to the joys of choke input > filters by recent postings, let me review how to calculate the > minimum inductance needed for the filter to work correctly, in > particular to give the predicted DC output voltage. > > Minimum L = load resistance in ohms/1100 > > This equation assumes a 60 Hz input single phase full-wave rectifier. > Either CT or bridge requires the same inductance. For 50 Hz, multiply > the inductance by 1.2. > > For example, supposing you have a receiver that draws 100 mA at 150V. > The load resistance the DC supply sees is > > R = E/I = 150/0.1 = 1500 ohms > > You can now calculate the required minimum inductance: > > L min = 1500/ 1100 = 1.36 Henrys. > > More inductance does no harm and makes less ripple, but less won't work. > > Yours for smoke- and hum-free listening, > > Scott > > > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.446 / Virus Database: 268.18.4/705 - Release Date: 2/27/2007 3:24 PM > > ------------------------------ End of BOATANCHORS Digest 4021 ******************************