Mid-Atlantic Antique Radio Club - MAARC

09/03/2026

More MAARC Catchup for today, Thursday, 3 September.

On 31 July we had a post about 'Movies with Radios' to which David Nance commented: "I can't recall the name of the movie, but it is a late 1940's film noir where raspy-voiced Percy Helton is a timid proprietor of an Army-Navy surplus store filled with all kinds of radio surplus, including several Hallicrafters BC-610 transmitters. During the film's climax, much of the action takes place in and around his store, where he is caught in the middle of the gunfight and gets killed. You can usually count on seeing at least a Hallicrafters SX-42 or SX-43 in many film noir movies of that era. According to Chat GPT, the movie is "Kansas City Confidential" but that is not correct."

Tom Bryan also commented that we should check out "The Crooked Way" from 1949. He stated that the full movie is on YouTube at this link: https://www.youtube.com/watch?v=ZceZFGTGiZE

Thank you for those inputs David and Tom.

Jumping ahead to 5 August, our post for that day was on the huge Philco radio, to which a number of folks commented about their favorite Philcos. John C Wise commented "How about a restored vintage Philco 32 VDC farm radio model 642B?" Turns out we had a presentation on 32 volt farm radios. Here is the link to that video on our YouTube channel: https://www.youtube.com/watch?v=VH3gDMfudd4&t=903s&pp=0gcJCRoMAYcqIYzv

Charlie Scarborough commented about the Philco 37-116. "With the pair of 6B4s, and continuously-variable selectivity, it really competes with Scott's AW23 and the quad of 2A3s. Then both went and spoiled things by adopting those mushy-sounding 6L6s!"

Geoff Shearer stated "My favorite is the Philco PT-61," to which Ed Lyon responded
"That’s as close to a Fada as you can get." Ed went on to comment that "Michael Prosise, MAARC’s initial librarian was an avid Philco collector. He had a complete set of the hand-painted Philco cabinet sets, all in mint condition." He additionally pointed out "A weird thing about Philco was that they manufactured every part of their radios (except parts they could not make, like tubes. This included screws, nuts , bolts, washers, chasses, tube sockets, shield cans, etc., and substantially all of the cabinets. This left them independent of all the Depression-affected suppliers and any of Roosevelt’s efforts to spread the buying around so not so many companies would succumb to the poor sales levels prevalent at the time. I often wondered if Philco’s nut-and-bolt hardware differed in some small way from standard hardware so that fastidious collectors might be able to tell if a set was 100% absolutely genuine Philco-made or had been repaired casually in some small way by collectors/repairmen. I think Philco never used metal tubes, and might have been cavalier about the use of Pin 1 on Octal sockets, like use it for a handy junction involving B+, to the surprise of the inquisitive tube-swap owner or repairman."

Thank you all for those Philco comments.

On 7 August we kicked off a series on what makes a vintage radio function. It addresses my early involvement in vintage electronics, Specifically the Lafayette KT-135 EXPLOR-AIR radio kit I built when in Middle School. That got some comments of note. Peter Kay stated "That one always caught my eye when thumbing through Lafayette catalogs year after year back in the day." Mike Schlein stated "That was my first kit too!" Neill Carey added "I built an Allied Radio Space Spanner as a teenager. It was a later vintage than this one, using 12AT7, 50C5, and 35W5 miniature tubes, but looked very similar. I played it for many hours. It was my first soldering project, and the wiring and soldering were nowhere near as nice as this one. It got lost over the years; so, I bought one at the auction at an AWA Charlotte meeting 10-15 years ago. It belonged to John Dilks, who wrote a column on boatanchors for QST. I enjoyed his column, but was let go at some point. The radio still works great." Thanks for those comments.

On 8 August we had a post about the revival of Radio Shack stores in the U.S. Jim Massucco commented "Bring back p-boxes, the little kits you built on a red plastic base... Loved those things and would build them again..." Gregory Holliday commented "More Minimus speakers, less cell phones!" John C Wise stated "We have a hobby shop near Camp Hill Pa, that was selling RS parts. I stopped in last month and they no longer had any RS stuff. I sure do miss Radio Shack local stores, we used to have one only three miles from where I live in Etters PA. When they were selling out, I bought a bunch of parts, should have gotten much more. We still have a couple of boxes of new & nos RS electronic parts on hand yet. Nice to have a brick store nearby instead of mail order." Stan Modjesky commented "I don't miss Radio Shack nearly as much as I miss the locally owned electronic parts stores that Tandy Corporation put out of business with predatory pricing." David Dodgen, when we pointed out stores near the Mid-Atlantic region said "OMG, I can't believe I read this. I’m from Pennsville, NJ." Joe Sousa had this to say: "The nearest Radio Shack to me now is part of a store in Cape Ann MA, about 45 minutes from me in Billerica MA. The Radio Shacks that were part of a larger store had a better chance of survival. I worked part-time at Radio Shack during college from 78 to 82. I was studying to be an electrical engineer at U-Mass-Dartmouth. That was my second job after McDonald's when I emigrated in 1976 from Lisbon Portugal with my family to Fall River MA. Radio Shack and Lafayette were present as dream catalogs while growing up in Lisbon. I have an 80-in-One from Lafayette from circa 1973 and a 150-in-One from Radio Shack, circa 1975. We had discounted prices as employees plus first dibs on clearance items. I still have Radio Shack items I bought then, like my STA-52B receiver from 1982. I paid $99 back then as a loss-leader in the new Dartmouth mall store where I worked. I see that they are actually selling for a little more than that now. It has one weakness: oxidized push-button contacts that need a steady diet of DeOxit plus a trim pot that sets the 38kHz stereo decoder frequency that tends to go open. The 40-year old caps are still good enough to not affect performance in any way that I can tell. Another Radio Shack related tidbit: I first tasted an iced coffee while delivering and installing a high-end stereo system for Radio Shack on a hot summer day. The lady of the house offered it and, with me being an adventurous eater, I accepted and it has been my favorite form of coffee, exotic as it was to me then. When my office (Linear Technology) moved about 10 miles from Burlington MA to North Chelmsford MA in 1999, the first order of business was to find the nearest Radio Shack. It turned out to be within walking distance of the new location. Awesome! BTW, the full radio shack catalog history is somewhere on-line." Finally, Alan McChesney had this to say: "I used to shop at Radio Shack especially if I needed something that I didn't want to wait for. Their prices were a bit higher than others but it was the convenience. I did buy several items at their close out sales as my local stores shut down. I have ordered from them on-line within the last couple years. My closest store now is 100 miles away. I do have their first ever catalog printed in 1939 and the letter that came with it announcing that fact. Attached is a scan of the catalog cover and the letter (see photos). Thanks for all those comments. We will continue our Catchup next Tuesday.

09/02/2026

The MAARC Facebook post for 2 September will do a little Catchup (actually, it will start a Catch Series), but first we must acknowledge our winners from last Sunday's Ganged Switching Quiz. Both Ed Lyon and David Dodgen win Honorable Mention for their perfect scores. Congratulations Ed and David. I would also like to mention that Serge Moisan felt that the quiz was "A complicated way for a portable heating device."

As for the Catchup, we last did that just over a month ago. Addressing the AN/PSM-6 multimeter, Donald Gudmundsson commented "Got to laugh, its feature was "Only using a battery for the resistance scales"!!! That is true of pretty much every portable non-line powered VOM and also true of 99% of the line powered VTVM units. They had tubes AND a battery for resistance measurements. My old Triplett VOM has two batteries, a 1.5v D cell and a now rare 22.5v battery for the high resistance scales." True true Donald.

Additionally, Donald commented relative to our Catchup on HiFi amplifiers: "Love the audio comments about solid state amps being fatiguing. Blind studies show that audiophools prefer poorly designed class B push pull tube amps with measurable even harmonic distortion over the best of the best amplifiers of any design tube, transistor or class D, G or H with distortions in the .1 to .01 range. And never forget 'They' can hear a difference between your speaker cables laying on the floor OR placed up on little wooden spacers to eliminate the capacitive loading of the floor on the cables!!!"

On the subject of "listener fatigue", Paul Hart, who participated in the Hi-Fi Audio Panel Discussion we had at RadioActivity 2026 had this to say:

"I must offer comments on the discussion about "listener fatigue" being discussed. It may be real, but just short of my 89th birthday, I confess that I don't have that problem - at least not using a Hafler DH220 amplifier and a Crown IC-150 preamp. Those drive a pair of Altec 416 drivers in back loaded folded horns of a design which is a variation on the Jensen Imperial which we settled on in 1958. The HF drivers are Altec 802Ds, crossed over at 800 Hz using a variation of the original Imperial architecture to eliminate some wild swings at the crossover point. These speakers are very efficient and the Hafler amp has a damping factor of about 300. You are lucky to get a damping factor of 15 from a vacuum tube amp.

If you can hear a difference between solid state and vacuum tube systems, I cannot argue with that perception. But I do not believe the difference can be explained by distortion characteristics. If you do distortion measurements on good amplifiers at the program levels we use to drive our speakers in routine listening, they are so low that it is hard to believe you can be hearing differences for that reason. Something else is going on. On the other hand, less efficient speakers require more drive power, but if you are listening for a long time you should still be way below the point where any measurable distortion should be involved.

Recently, I had the opportunity to "regun" a couple of large power amps that originally had 4 EL 156 amp tubes - in PP parallel, those tubes were Shuguang and aren't available anymore. I regunned the amps with Russian KT-120s which required changes in the bias circuit and elimination of an undesirable rise in HF response at 80 kHz. The feedback amount was only 4 dB. These amps were used in a studio operation driving large speakers. Before and after, these amps showed about 1% distortion, even at 1 watt. All the way up to 150W output, the distortion was low. Driving my Altec speakers, the amps sounded great. After all the modifications I had made, the owner was overjoyed because he said the amps "had retained their previous character". Even so, he and all the witnesses agreed that the Hafler 220 had noticeably better LF capabilities.

I have heard many comments about "vacuum tube sound" and I do not argue with that. We have had many "hi-fi parties" here and I can easily substitute any amp for the DH220. After connecting a Dynaco ST-70, one of the people exclaimed "ah, vacuum tube sound". I could hear a difference as well, but I was hard pressed to identify it as better rather than different compared with the Hafler. The one difference that was clear to everyone was that the Hafler had much better definition and bass level when processing very low frequency material - organ, Enya! But the Hafler is power flat all the way down to 10Hz. In my youth, we had endless discussions about the differences in vacuum tube amps using pentodes or triodes!

My belief is that the difference between the harmonic structure of distortion is not the simple measurement of distortion at various frequencies into a fixed resistive load, but is largely influenced by the varying amount of impedance load from the loudspeaker with varying frequency. Maybe that is why so many people prefer single ended, feedbackless amps. That doesn't square with my experience, but the customer is always right, and has the right to listen to an amp he likes. The effective output impedance of the Hafler DH220 is very low. In my system, I can be driving my speakers at high level at 30Hz, rattling the windows - put your hand on the cone and feel only a small amount of movement. That is one element, and I don't know if that has any influence on the HF response, but if you look at most speakers at any high level, you will see lots of cone movement. Spurious cone movement will make an EMF generator out of the voice coil that will be presented to the amp through the feedback loop as a spurious element. The amp now has to try to correct that, working to correct spurious components it didn't create. I believe that much of the difference in perceived amp sound is the result of attempts of the amp to correct spurious signals it wasn't responsible for. Maybe that explains the reaction of many that amps without any feedback sound better, or at least "more neutral".

This discussion could go on forever, and we are endlessly confronted with subjective reactions to various combinations of amps and speakers. In the back loaded horns, the Altecs are extremely well damped at low frequencies - the only issue is that below their cutoff at about 23 Hz, they are no longer loaded to the air column in the room. My observations are that most amps sound very well when connected to these speakers. Many listeners have to really focus to see if they hear differences. My favorite tube amps are the AcroSound II and the Marantz 8B. But on one point, practically everyone agrees that at the low end, the Hafler provides better clarity and "presence". Maybe if we listen to audio material for longer, we could determine if we all experience "listener fatigue".

The frustration and attraction of this discussion will continue regardless. All of us have major variations in how we hear the same material, especially because so many of us are older - much of this is responsible for personal preference. My attitude is that anyone spending money on audio reproduction is entitled to hear what they want to hear. That is what I want for myself. Why should I question anyone with different perspectives?"

Thank you for that Paul, and that concludes today's Catchup.

09/01/2026

A quick post for this Tuesday, the 1st of September. Do you live in the Mid-Atlantic or Northeast region? Do you like vintage electronics? You need to attend the Kutztown Antique Radio & Vintage Electronics Show, September 18th and 19th, 2026. Sponsored by the Delaware Valley Historic Radio Club, this two day event features 60,000+ sq. ft. outdoor and under roof vending. Here is the schedule:
• Hours: Friday 10am-5pm, Saturday 8am-3pm
• Radio Auction 5:30pm Friday night in air-conditioned comfort
• Buy-it-now table open Friday & Saturday
• Capacitor & Tube sales at the Club Table Fri & Saturday
• Free admission
(Dealer Tag Required for 8am Friday entrance)
• Free parking & onsite camping
• Hot showers available
• Food available onsite & at nearby Farmer’s Market
Dealer spaces:
- 10’ x 10’ spaces are $55.00 (includes 1 table and electricity –bring your
own extension cords.) All spots are under roof. Extra tables are $10.
- To reserve a table contact Renninger’s. www.renningers.com or by
phone: Mon-Thurs (570)385-0104, Fri-Sat (610) 683-6848.
Friday:
-Friday is open for vendor setup after 8am. General public allowed at
10am. Vendors should expect to show their Renningers space tag upon
entry. Early buyers will not be permitted without a dealer tag.
Friday Night Auction 5:30PM:
-20% commission for consignors & 15% buyer’s premium. General
consignments are accepted starting at 2:00pm on Friday afternoon.
Preview is from 4:30-5:30.
-At the discretion of the DVHRC, items can be excluded (for unsold
items, the consignor can donate item to Buy-it-now or keep item.)
-Seller/bidder cards are required to sell or buy. All auction transactions
are cash only. NO credit or debit cards. (ATMs located on-site)
Saturday:
-Show open from 8am-3pm.
Buy-it-Now:
-The BIN table is the sale of donated items “as is” on a cash-and-carry
basis. Buy-it-Now is located at the DVHRC Club table in the Main
Pavilion and runs Friday & Saturday. DVHRC reserves the right to refuse
items to BIN.

Whether you are looking for that bargain piece of test gear at the low end, or a Zenith Stratosphere or McIntosh Amp at the high end, the odds are good you will find something you will cherish.

Here is the link for more information: https://www.dvhrc.com/

08/31/2026

The Monday, 31 August MAARC Facebook post provides the answers to yesterday's Ganged Switching Quiz, coming to us from the April 1972 edition of "Popular Electronics" and creator Robert Balin. It challenged your ability to trace out connections without getting confused by crossovers - which is easy to do. Each of the six-position switches illuminated a different combination of lamps. Your job was to figure out which lamps light for positions 1 through 6. Non-nodal crossing lines are not typically shown broken as they are here, so don't misinterpret them as open circuits.

On to the quiz: Electronics hobbyists, especially troubleshooters, can always use some practice in tracing out circuits that include ganged switches. Unless you are careful and systematic, it is easy to get confused, lose your way or overlook a component. Here's a chance to practice this important skill.

The schematic contains a 6-position, 3-pole switch, six 6-volt lamps and 6- and 12-volt batteries. As the switch is rotated, determine what combinations of lamps will light - each to full brightness.

Note that although the switching function which this circuit performs can be done by a much simpler circuit (a single 6-volt battery can do the job) such a circuit would be too simple to be challenging and only unnecessary schematic zig-zagging could make it look more complicated. Since this quiz is intended to be a training problem, practical considerations have been ignored.

For the answers, see photo # 2.

Did you get Honorable Mention?

08/30/2026

Is it really Sunday? Indeed! Quiz time.

The Sunday, 30 August MAARC Facebook post quiz is called the Ganged Switching Quiz. It challenges your ability to trace out connections without getting confused by crossovers - which is easy to do. Each of the six-position switches illuminate a different combination of lamps. Your job, if you accept it, is to figure out which lamps light for positions 1 through 6. Non-nodal crossing lines are not typically shown broken as they are here, so don't misinterpret them as open circuits.

On to the quiz: Electronics hobbyists, especially troubleshooters, can always use some practice in tracing out circuits that include ganged switches. Unless you are careful and systematic, it is easy to get confused, lose your way or overlook a component. Here's a chance to practice this important skill.

The schematic contains a 6-position, 3-pole switch, six 6-volt lamps and 6- and 12-volt batteries. As the switch is rotated, determine what combinations of lamps will light - each to full brightness.

Note that although the switching function which this circuit performs can be done by a much simpler circuit (a single 6-volt battery can do the job) such a circuit would be too simple to be challenging and only unnecessary schematic zig-zagging could make it look more complicated. Since this quiz is intended to be a training problem, practical considerations have been ignored.

Remember, you can only receive Honorable Mention if you provide us your answers (or guesses).

08/29/2026

A brief MAARC Facebook post for Saturday, 29 August. It comes to us curtesy the "At The Controls" page and author Michel Talbot. It provides us a little history behind electronics space technology pioneer Virginia Tower Norwood.

"MIT Physicist Virginia Tower Norwood¹ "The Mother of Landsat"² field testing a prototype Storm Detector Radar Set³ at Camp Evans Army Signal Corps Laboratories, New Jersey (1949). The Evans Signal Laboratory (ESL) was developing their first reflectivity weather radar which measures the position and intensity of precipitation displayed as echoes on a cathode ray tube.

A year after graduating at age 20 from the Massachusetts Institute of Technology with a degree in mathematical physics, and taking engineering classes through a Rutgers University extension program, she began working on weather radar and designed a radar reflector for weather balloons that discovered previously untrackable winds at 300 meters altitude before progressing to work on microwave antenna design, eventually patenting a folded sigma-shaped dipole antenna.

In 1953 she joined the Hughes Aircraft Company and designed a "Multispectral Scanner" (MSS)⁴ for use on the first Landsat mission², the first time a remote-sensing⁵ satellite carried such a scanner, simultaneously imaging the earth in four different bands of the electromagnetic spectrum from visible light to near-infrared (500 nm - 1.1 µm). Since then, MSS instruments on Landsat satellites have acquired millions of images effectively mapping our entire planet from space. At Hughes she also designed the microwave transmitter that NASA's lunar lander⁶ Surveyor-1 used to transmit the very first images from the lunar surface back to earth.

Footnotes:
1- https://en.wikipedia.org/wiki/Virginia_Norwood
2- https://en.wikipedia.org/wiki/Landsat_1
3- https://en.wikipedia.org/wiki/Weather_radar
4- https://en.wikipedia.org/wiki/Multispectral_Scanner
5- https://en.wikipedia.org/wiki/Remote_sensing
6- https://en.wikipedia.org/wiki/Surveyor_1

References
The woman who brought us the world by Alice Dragoon, MIT Technology Review, June 29, 2021 https://www.technologyreview.com/.../the-woman-who...
Virginia T. Norwood: The Mother of Landsat by Laura E.P. Rocchio, August 7, 2020 https://science.nasa.gov/.../virginia-t-norwood-the.../

Virginia Tower Norwood (January 8, 1927 – March 26, 2023) was an American aerospace engineer, inventor, and physicist.[1] She was best known for her contribution to the Landsat program,[2] having designed the Multispectral Scanner[3][4] which was first used on Landsat 1. She has been called "The M...

08/28/2026

Continuing with our series on what makes a vintage radio function, the Friday, 28 August MAARC Facebook post focuses on the making your AC/DC radio, or other similar device using series fed tubes, safer. Long-time MAARC member Ed Lyon addressed this in part in his "Radio Age" article from September 2014 entitled "A HOT-CHASSIS RADIO DĖJÀ VU ALL OVER AGAIN." Here are some extracts from Ed's article:

"In the repair shops (Sears and Panek’s) we ran across some ac-dc radios, but most of the repair jobs involved older sets with their heavy power transformers and paper filter capacitors. The ac-dc sets intrigued me and I went over the schematics again and again, marveling at the simplicity and cheapness of the whole power system in these radios.

Some magazine articles mentioned the need for “isolation transformers” when servicing these sets. Sears did not have an isolation transformer on the bench, but Panek did, and when I asked him about it he showed me how to use one to separate the radio power circuit from the “earthed” Duquesne Light Company grid. He brought up a small Emerson radio that had a “hot chassis,” and he pointed out the direct connection from one of the power line wires to the radio chassis when the radio was switched ON. He then gave me a vivid demonstration of the way the power line was “earthed,” his term for “earth-referenced.” Here he took a single piece of insulated wire about 20 feet long, soldered one end to a brass rod he had stapled to a stick of 2X2 lumber, and connected the other end of the wire to one blade of a regular power plug. He took the wooden stick with the brass spike on the end out the back door, strung the wire back through the doorway and plugged it into the wall receptacle. We went outside again and he carefully picked up the wood stick and jabbed the brass rod end into the ground in the tiny patch of lawn he called his back-yard. Nothing happened. He told me to turn the plug over and plug it in again so the wire would be connected to the opposite receptacle contact. After that he again stuck the brass electrode into the ground in the lawn, and immediately ten or fifteen huge night-crawler earthworms came up out of the lawn moving at breakneck speed to get away from the electrified zone he had created.

The lesson here was simple: one wire of the power line provides a nasty high voltage with respect to the earth, and that could mean that in a hot-chassis radio the chassis might be at that same high voltage with respect to my radio workshop (cellar) floor, which was earth. Panek took his trusty Weston volt-ohm-milliameter and stuck its black probe into the ground and touched the red probe to the brass spike on the 2X2 stick and the meter read 115volts a-c. That little experiment and several accidental shocks over the next year and I learned to respect the power line, and from then onward I had very little regard for the design of radios and test equipment that had “hot chassis” construction.

Today, when restoring ac-dc radios, I occasionally run across a hot chassis type, but most ac-dc sets use the “hot bus” method in which they tie all the B-connections (and, of course, one side of the power line, via the on-off switch) to a separate wire that is insulated from the chassis, and then connect that wire, by way of a modest-sized capacitor (and sometimes a resistor in parallel with the capacitor), to the chassis. Most “hot-bus” radios use a capacitor of about 0.047 to 0.1 µF at 400 volts rating (or higher) and sometimes a shunt resistor of about 220K ohms. The sizes of the capacitor (and resistor, if used) are such that the maximum current a person would conduct through his or her body, if touching both the chassis and Panek’s back-yard (or our cellar floor) at the same time, would be about 1 to 3 milliamperes, which might tingle, but will not hurt.

But those ac-dc sets with the hot chassis – they are a real problem for restorers. You hate to have to go through the circuit and lift every ground lead from the chassis and re-wire it to a B-minus-bus and then add the capacitor and resistor, but you really hate to return the set to its original lethal condition, because you never know who will someday own the set and try it out.

It would not be until the second world war that nearly every radio made had been relieved of the hot chassis syndrome, yet many magazine articles continued to show the budding radio enthusiast how to make little test instruments, phono oscillators, and other experimental breadboards using the most dangerous of hot chassis hookups, those where the entire ac-dc-powered device is in a metal cabinet tied to the hot chassis.

It may seem tempting to simply be careful always to insert the radio power plug into the wall receptacle with an orientation that results in the power line “neutral” (which is always securely connected to earth at the power entry point in the home) being connected to the radio chassis at switch-on. In fact, most power extension cords and appliance cords have one blade of the plug made much wider than the other, to identify which is the “neutral” (the wide blade) and which is “hot” (the narrow blade). The receptacles throughout the modern home are also polarized in this way. But an insidious problem persists as most hot-chassis radios are wired. The power on-off switch in these radios connects and disconnects a power-line wire to and from the chassis. By forcing that power-line wire to be the neutral, then when the radio switch is ON, the chassis is safely at ground or earth potential, and the radio is safe. But when the radio switch is OFF, the power-line hot wire, connected to the “high” end of the radio’s string of vacuum tube heaters (wired in series), the last tube in the string then having its heater terminal connected to chassis. This makes the chassis “somewhat hot” at switch-off, but safe at switch-on.

What is “somewhat hot,” you ask? Well, depending on the tube complement of the radio, the maximum current your body would carry if you grabbed the chassis with one hand and a water faucet or other grounded thing with the other hand, would be 150 or 300 milliamperes. The insidious thing here is that the level of current through the human chest that causes ventricular fibrillation in the heart is about 70
to 200 milliamperes. If defibrillation is not administered within a minute or two, the result is usually fatal. So forcing the chassis to be connected to the neutral wire at switch-on is about as bad as forcing it to be connected to the hot wire.

The only real fix is to re-wire the radio’s on-off switch so it interrupts the hot wire, and not the chassis connection, and then use a polarized plug. Now the only drawback is that the radio will probably trip a GFCI circuit breaker (like you have on the patio, near the bathroom sink, in the garage, and in many other places in the modern home) if the chassis finds a path to earth, like through your body (but it may just tingle)."

Let's look at our generic AC/DC radio schematic, this time annotated showing the potential of the "hot" (in red) being on the unswitched side of standard non-polarized plug. Note how the "hot", feeds throughout the radio via the tube string. And this is with the radio turned off. Note C9 and R4 that are connected to the chassis. Ed described theses as the "capacitor of about 0.047 to 0.1 µF at 400 volts rating (or higher) and sometimes a shunt resistor of about 220K ohms." These comprise the line filter that filters-out/remove RF (radio frequency) line disturbance and interference picked up by your home power lines. We will talk more about that next week. If, as can happen, the C9 capacitor fails in such a way as to conduct AC directly to the chassis, we have now made the entire chassis "hot".

A better solution (see second photo) would be to replace the power cord with a polarized plug, and to re-wire the switch to ensure the narrow blade "hot" is the line being switched. This stops the "hot" right as the power line enters the radio. The entire radio is now "neutral" (depicted in yellow). This is the better, safer solution.

Comments? Let's hear them.