Like a Phoenix rising from the ashes...Cool386 is back with its own domain!
So, what happened? On the 31st August 2020 the site was deleted by its
host. The site had been hosted by iinet for the past seven years, but was
deleted in the enforced change from ADSL to the NBN (Australia's fibre
optic network). Over this time, the site's hyperlinks have appeared around
the internet and published in magazines. It's unfortunate that these will
no longer work, and I can only hope that the followers of the site will
simply search for "cool386" again.
At this point in time, there are 177 pages, with a total size of 430Mb. It can be imagained what a huge job it was to go through every article and change the hyperlinks, and then upload to the new server.
If you find an old link to one of the previous domains, you'll need to change it to www.cool386.com. For example http://members.iinet.net.au/~cool386/AWA_221C/awa_221c.html is now https://www.cool386.com/AWA_221C/awa_221c.html
Some of the latest articles:
Mains Operated TDA7000 Van Ruyten 40W Inverter 2007 Giant Reign 1 Gold Phone for the NBN
For further pics and information
about my projects see also here http://www.flickr.com/photos/13469158@N05/
my You Tube channel here https://www.youtube.com/channel/UCB8qCNGTrXO1nanG0yDFxeA/
About this site:
All the pages are written using Netscape Composer 4.8 which keeps things simple, fast, and Windows 3.1 compatible (still in 2020!). It was intially hosted by Bigpond (an Australian ISP) who provided 10Mb. Once that was used up, I started putting pages on Geocities. In 2009, Bigpond terminated their webhosting, and Geocities closed down. So, I had to move the entire site to Tripod (another free host) where all seemed well for the next four years, until everything was deleted with no warning. I then changed my ISP to iinet who provided 1Gb of space.
At the end of August 2020, iinet deleted the site, as mentioned above. It is now hosted independently and I own the cool386.com domain name. The lesson here is, if you have a serious website, get a domain name and get it hosted independently. Free hosts and ISP's are good to begin with, but cannot be relied on for the long term.
The site's name comes from a 386DX40
computer still in use.
Articles are updated from time to time as required and time permits. The quality of circuit diagrams is largely because of lack of a drawing program which is as quick to use as is hand drawing them. Until 2010, photos were taken with a Sony Mavica FD-75, and with such a small server space, the already low resolution photos were reduced even further. Hence, the low quality of photos in the earlier articles.
Here is the 386...
Homepage shown in Netscape 2.0 operating under Windows For Workgroups 3.11. (Yes, that's an IBM XT next to it).
A bit about me:
An enthusiast for vintage technology and electronics. My technological
interests are based around all the things you see on this site.
I am from the Blue Mountains, about 80km west of Sydney on the east coast of Australia. Learn more here.
A Warning about eBay. Do Not Use Global Shipping! If you purchase vintage electronics from the U.S. ebay, watch out!
G.E. Monitor Top Refrigerators
CA-2-B15 restoration - (Parts 1,2,3, 4, & 5). Background to the General Electric Monitor Top refrigerator and restoration of a 1934 CA-2-B15.
Monitor Top thermal imaging. See what the human eye cannot see with these thermal images of my CA-2 Monitor Top fridge.
Monitor Top manuals. For 1927 DR machines, 1933-1934 CA machines, Canadian AK models, and 1934-1942 CK/CG/CE/CF/CH/CJ/DK/FBA/LK Monitor Tops, Globe Tops, Liftops, and Flatops. Also contains scans from Nickerson & Collins - Servicing Hermetically Sealed Units, covering DR rebuilding. 1934 Salesman's Bulletin. Other vintage refrigeration manuals relevant to the Monitor Top.
CA-1-B15 restoration. After the CA-2-B15, another Monitor Top came into my posession.
Capillary tube conversion for CA Monitor Top. Eliminates troublesome float valves. Also learn about operating on the unit fully charged, and how to extract methyl formate.
Notes on Super-Regen receivers. Please read before attempting to construct the following receivers.
12V Two Valve FM Receiver. New 6BL8 circuit operates from 12V supply and draws only 1.25A.
6BL8 Super-Regen Receiver. Excellent VHF performance using the common 6BL8/ECF80 valve.
Mains operated 12AT7 Super-Regen Receiver. Super-regenerative FM receiver with active filtering.
6 Transistor Super-Regen Receiver. Solid State Superregenerative Receiver. This separately quenched receiver far outperforms other solid state self quenched designs.
4 Transistor Super-Regen Receiver. Pocket size VHF receiver as simple as possible while still being practical.
One Tube FM Tuner. From August 1960 Popular Electronics, it uses a 6C4. I constructed this project as closely as I could to the original. Performance left a lot to be desired!
Improved One Tube FM Tuner. In view of the poor performance of the above receiver, I modified the design. Still using a 6C4, it is about the simplest valve receiver for FM.
12AT7 Super-Regen Receiver. One valve provides excellent sensitivity and drives headphones to an uncomfortably loud level. Includes vibrator power supply for portable battery operation.
New 12AT7 FM Tuner. An improvement on the Improved One Tube FM Tuner, this incorporates an RF stage.
One Valve FM Receiver with Loudspeaker. Using a single 6DX8, this receiver provides loudspeaker reception of FM stations.
Maxitronix MX801F FM Radio Kit. Three transistor FM receiver needed modifications. Also relevant to the MX901AF and MX901F kits.
Science Fair 28-234 AM/FM Radio Kit. The super regenerative FM receiver in this kit sold by Tandy/Radio Shack is of very poor design and needed modifications to work properly.
VHF receiver with 12V B+. This valve VHF receiver uses 12V for high tension.
Fremodyne Receiver (Parts 1,2, &3). Introduction to the single valve, low cost, FM receiver circuit developed by Hazeltine Laboratories in 1947. It uses a single 12AT7 in a super regenerative superhet circuit and was used in several commercially made AM/FM receivers and FM converters.
Servicing the Fremodyne Receiver. How to get your Fremodyne working at optimum performance. NEW for 2020
Four Valve FM Receiver. The "Simplified Fremodyne" from Radio News August 1951 is reconstructed.
Homemade Fremodyne. This is one of my attempts at building a Fremodyne receiver as an FM mantel radio. Sound quality turned out to be quite good with this set.
Solid State Fremodyne. Electronics Australia's article from May 1970 on making a solid state version of the Fremodyne. This is not the full article, but sufficient information is given for experienced constructiors to duplicate the design.
Simplified Fremodyne. How much further can the Hazeltine circuit be simplified? This receiver was the test.
Howard 474 (No.1). This was the first commercially made example of a Fremodyne receiver to enter my collection. UPDATED for 2020
Howard 474 (No.3). My third example of a Howard 474 AM/FM mantel radio with Fremodyne FM receiver. UPDATED for 2020
Meck FM Converter. Fremodyne tuner made to be used with the audio section of an existing AM receiver. The safety issues with this set were a bit of a surprise.
Gilfillan 68F. Another commercially made mantel radio using the Fremodyne circuit for FM reception.
Sentinel 315W. The third type of AM/FM mantel radio I've acquired with a Fremodyne circuit. This one had seen a rather careless attempt at restoration.
Heathkit FM Converter. The Heathkit FM1 was a kit version of the Fremodyne circuit.
Olympic 7-532W & 7-532V. Another mantel radio with Fremodyne FM receiver. UPDATED for 2020
Perco FM Tuner. Another kit version of the Fremodyne.
Pulse Counting Receiver. Hi Fi quality, high sensitivity, and only one tuned circuit. Popular in the UK but virtually unknown elsewhere.
Solid State Pulse Counting Receiver. Notes on building a transistor pulse counting receiver.
TDA7000 FM Receiver. Philips IC makes a simple FM receiver with no ceramic filters or IF transformers. Detailed application notes give an interesting insight into this excellent IC, and its offspring, the TDA7010T, TDA7021T and TDA7088T. As well as my own construction attempts, I also take a look at a commercially made receiver.
Future Kit FM Receiver. This TDA7000 FM receiver kit was of extremely poor design.
Armstrong Micro FM pulse counting receiver. Inspired by the Sinclair Micro FM, this is a modern pulse counting receiver kit.
Mains Operated TDA7000 FM Receiver. Hybrid FM receiver uses the TDA7000 and valves.
Rogers FM Tuner. English tuner from the 1950's.
Portable FET Regenerative Receiver. Superhet sensitivity and selectivity from the ETI-062 AM tuner circuit.
Reflex One. From Radio, Television & Hobbies, June 1963, this one transistor receiver needed modification. Two transistors were also added for speaker reception. NEW for 2021
Grand Opera Mantel Radio. Unusual three valve regenerative set from 1934. NEW for 2021
Future Kit AM Receiver. Practical use of the MK484 AM radio IC and discovering problems with the TA7642.
Transistor Reflex Receivers. Loudspeaker reception with no external aerial and only two transistors. Used in the "Boys Radio" circuit.
Tiny Tim II.My construction of this regenerative receiver from Radio & Hobbies, April 1943. An excellent little three valve set that drives a loudspeaker.
1J6 Receiver. A battery operated one valve regenerative receiver using a 1J6 or 19 twin triode.
Thames and Kosmos "Radio Ace". This reproduction valve radio isn't exactly a kit despite being sold thus. Performance was substandard and required modifications to turn it into something that was useable. Also see the Links further down the page for more on this set.
Automatic Regeneration Control. Make your regenerative receiver as easy to use a superhet! Ideal for non technical uses
Valve Receiver with Automatic Regeneration. Based on the Radio & Hobbies "Three Band Two" this receiver has automatic regeneration control.
ZN414 AM Receiver IC.Notes on this well known TRF receiver IC, and its clones; MK484, YS414, TA7642, LMF501T. Ideal for construction of miniature radios requiring only 1.5V to operate.
Four Valve TRF Receiver. This MW receiver uses four modern TV valves and provides hi-fi sound with its infinite impedance detector. Updated with cascode RF amplifier.
12V Superhet Receiver. This project was built to disprove the fact valves need high voltages. It uses ordinary mains type valves with 12V high tension. Performance is excellent.
Emerson CF255. Two valve TRF receiver from 1939 was said to be the world's smallest practical radio.
Gakken Vacuum Tube Radio kits. Modern valve radio kits from Japan using battery valves. One is a variometer tuned reflex receiver, the other is a 3 valve regenerative circuit.
Xmas Box Mantel. Three valve regenerative TRF receiver described in Radio & Hobbies, December 1950.
Minivox Mantel Receiver. From Radio & Hobbies, December 1947, was this three valve regenerative receiver project.
Detrola 6R Car Radio. Six valve 1935 model from the U.S.
5 Valve Car Radio. Home made car radio started as a student project back in 1985.
Detrola 297 Car Radio. Unusual U.S. made vibrator powered car radio from 1940. Very compact one unit construction.
Walbar 1255A. Two unit car radio with five valves.
Ferris M106. Portable radio designed for in car use with optional inverter.
AWA 930-A . Six valve single unit car radio made under the "Cruiser 6" name. Notes applicable to all the late 1950's-60's AWA car radios.
Motorola 66MF. Manufactured for 1956 Ford models in the U.S. Also known as FDR-18805-B1.
XP Falcon Car Radios. AWA radios fitted to Australian made XP Ford Falcons.
Ford "Auto Portable 8". AWA 982-A portable car radio for early Australian Falcons.
Falcon Car Radio. AWA 966-A hybrid car radio for the 1960
Paeansonic 210SP Kit Radio. Chinese AM-FM kit radio for under $10.
AM/FM Tuner/Amplifier. First use of my 6CM5 audio output stage design along with a superregenerative detector for VHF and regenerative detector for MW.
12V MW/VHF Receiver. This vibrator powered receiver operates from 12V and has Automatic Regeneration Control
Radio Television & Hobbies 5" TV Receiver. From the September 1957 issue, this set uses a 5BP1 / 1802-P1 electrostatic picture tube.
Sharp TRP-803. Japanese 8" transistor TV set from the early 1960's. Virtually identical to the TRP-804.
Sparton 4940TV. Mirror-In-The-Lid set from 1949.
AWA 221-C. One of the first Australian 110 degree sets from 1959.
Baird 812. This ex Radio Rentals set uses the Thorn R2M chassis, based on the British Thorn 1500.
2" TV set. This two inch set uses a 902-P1 cathode ray tube displaying pictures from a DVB-T receiver or other video source.
Ekco TCX-298. 21" 1957 model with doors.
Hiring out vintage TV sets. Unfortunate experiences in hiring out vintage TV sets. The golden rule is don't!
VHF-UHF Fan Aerial. This 1950's design also known as a "Conical" provides excellent results in the 21st century.
Ekco TX-287. 17" model from 1957.
Vertical Blocking Oscillator Transformer Replacement. Are you sick of unreliable blocking oscillator transformers and can never get good locking and linearity? Eliminate the nasty transformer forever with these circuits.
Digital TV and your Vintage Television. Do not worry about analog TV being turned off. You can still use your valve VHF black and white TV sets with the digital transmissions.
Philips PM5544 Test Pattern generator. Are you missing the test pattern that TV stations used to broadcast? Here's how I've regained it without paying $1000's. A digital box that plays .jpg files is the answer.
Airline 7" TV set.A rebadged Sentinel 400TV sold by Montgomery Ward under their in house brand. Read how I restored and converted this 1949 model electrostatic deflection American TV set for use in Australia.
Using foreign TV sets in Australia. Brought an American , UK, or European TV set into Australia? Here's how to modify it for the local standards.
Background to TV in the U.S. Brief description of the development of television in the U.S, with examples of first generation electronic TV sets.
History of Television in Australia. A talk and slideshow I presented at the HRSA.
Circuit diagrams and parts for vintage TV sets. I do not sell parts. Please go to High Country Service Data for diagrams and manuals.
The incandescent light bulb ban and how to defy it. Do you feel you shouldn't be dictated to as to what kind of light bulbs you use?
The origins of the Australian plug and other electrical trivia. Few would be aware the Australian plug is actually a U.S. design.
Browning Outdoorsman Porta-Lamp. 12V 15W fluorescent lamp uses vibrator inverter.
Jaycar AA-0474 Valve Amplifier (1). It looked nice and the price was right, but this Chinese vacuum tube amplifier turned out to be a fake. Please read this if you have any intention of buying a new valve amplifier, especially one made in China.
Jaycar AA-0474 Valve Amplifier (2). The Jaycar amplifier is rebuilt as a true valve amplifier.
The 6CM5 valve for Audio use. Australia's most popular TV line output pentode, also known as EL36, undergoes some experiments to test its viability for audio amplifiers, particularly in single ended class A. If the link doesn't work, go here.
6BM8 Amplifier. A simple but good quality audio amplifier using the 6BM8/ECL82 valve. Capable of a couple of watts. Information on using 100V PA line transformers as valve output transformers.
Simple Valve Amplifier circuits. A collection of economical low power amplifier designs using common low cost valves.
Valve Car Amplifier. Vibrator powered stereo valve amplifier for in car use.
40W Inverter. How to design a vibrator inverter for 12V to 240VAC with 40W output.
Heathkit GWA-12-1 Vibrator Power Supply. For 6 or 12V operation of the GW-12A CB transceiver. NEW for 2020
Heathkit GP-11 Vibrator Power Supply. Last of the modular vibrator power supplies, this was available as a kit.
Radiart 451 Vipower. Pre-built vibrator power supply from Radiart.
Electronic Laboratories 605 Vibrator Power Supply. Pre-built 6V vibrator power supply from Electronic Laboratories.
Mallory Elkon B Eliminator Type 6. The first commercially made vibrator power supply for car radio uses the Mallory Elkonode.
Mallory VP-401 Vibrapack. 6V to 250V pre-built power supply from Mallory.
Mallory VP-552 Vibrapack. Pre-built vibrator power supply made by Mallory.
Mallory VP-553 Vibrapack. New Old Stock vibrator power supply had never been opened and used.
Mallory G368 Vibrapack. An obscure 12 volt vibrator power supply from Mallory.
Battery Eliminator for Valve radios. Vibrator power supply provides A+, B+ and C- for battery valve sets.
Rohde & Schwarz NBU Inverter. 12V to 220V 35W vibrator inverter.
20W Transistor Inverter. Simple but practical, this self oscillating inverter provides 240V at 20W from 12V.
Inverter . Electronics Australia 12-240V 300W inverter
described in the September 1985 issue.
Vibrator Power Supply Design & Repair:
Ferrocart Vibrators. Some notes on the design of vibrator power supplies as used in car radios, inverters, etc. Includes Ferrocart type numbers. These were mostly used in Astor products.
The Mallory Elkonode. An introduction to how the vibrator power supply was developed, with details of the first widely used vibrator design.
Oak MSP Vibrator Notes. Information on the MSP/Oak/AWA vibrators used by AWA, Ferris and others.
Vibrator Life Expectancy. A guide to long-life vibrator operation, and what should be expected. A look at why vibrators have been unfairly maligned in the electronics world.
Communications Vibrators. A guide to the 7-pin dual-interrupter vibrators used in two way radio equipment. Used by Motorola and others.
Servicing Vibrator Power Supplies. A description of vibrator supplies and the associated waveforms.
Fundamentals of Vibrator Power Supply Design. Just about everything you wanted to know about vibrator power supplies, from the good folk at Mallory. This is a 13.6Mb pdf download.
Vibrator Test Panel. Simplifies testing and repair of vibrators.
VT-1 Vibrator Tester. Kit for testing vibrators made by Heathkit
in the mid 1950's.
Vintage Inverters - U.S. manufactured:
Terado Satellite 50-138-3 Inverter. 12V to 110W 75W vibrator inverter for portable TV use.
Terado Trav-electric SR Inverter. 6V to 110V 35W vibrator inverter.
Terado Super 50-127 Inverter. 12V to 110V 75W vibrator inverter.
Terado Electra 50-167 Inverter. 12V to 110V 42W vibrator inverter comes in a gift box.
All State Inverter. Sears rebadge of a Terado 12V to 110V 40W vibrator inverter.
DuMont 75W Inverter. DuMont Vibrator Power Pack model 2625 provides 115V at 75W from 6 or 12V DC.
Dubilier "Powercon" Inverter. This 115V vibrator inverter
Vintage Inverters - Australian manufactured:
Radar 12/100 and 12/300. 12V to 240V 100W and 300W solid state inverters from the early 1970's & 1980's.
Radar 12/40. 12V to 240V 40W solid state inverter.
Van Ruyten 32140. 12V to 230V 40W vibrator inverter.
Van Ruyten 58FF. 12V to 230V 100W vibrator inverter.
Van Ruyten 58TV. 32V to 230V 200W vibrator inverter.
Ferris 106 Inverter. 12V to 240V 30W vibrator inverter from the mid 1950's, intended for the model 106 radio.
Ironcore Shaver Converter. This uses a synchronous vibrator to provide 240V DC at 15W from 12V DC and was intended for motor driven shavers.
Robinson Motor Car Power Point. Simple 6V DC to 240V 10W vibrator inverter intended for shavers.
Bland Radio Shaver Inverter. Another 12V DC to 240V AC 15W shaver inverter uses interesting split reed vibrator circuit.
Smoothflo AC79/6. 6V to 240V 30W vibrator inverter.
Smoothflo AB13/6. 6V to 240V 15W vibrator inverter. The design fault with this was astounding.
Smoothflo AG88/12. 12V to 240V 175W vibrator inverter.
Glenradio "Champion" Shaver Inverter. This vibrator inverter was completely rebuilt with a new transformer and converted to 12V.
Glenradio 12100. 12V to 240V 100W vibrator inverter.
Breville AT21A. 32V to 240V 18W vibrator inverter.
AWA 1H60668. 12V to 240V 40W transistor inverter.
VB-32QA. 32V to 240V transistor inverter for television
sets. Notes also for model VC-32.
Low Power AM Transmitter. This "phono oscillator" design transmits over a suprising distance and uses only two valves.
Line Cord Resistor replacements. Relevant to equipment using series heater valves. Options for dropper replacements and how to calculate their value. Examines diode and capacitor dropper circuits.
Reproduction Line Cord Resistor. How to make a new line cord resistor for your American AC/DC radio that is completely authentic and requires no modifications.
Service Tips: An ever increasing list of faults and their repairs for various electronic items.
Electronics as a Hobby in the 21st Century. Reminiscing about the start of the hobby in Australia, and thoughts on where it is headed.
HD Holden Fuel Gauge Resistor. A common fault with HD and other model Holden fuel gauges is a burnt out resistor. Here's how to fix it.
Dyson DC05 Motorhead. Repairs to this Dyson vacuum cleaner were not helped with lack of spare parts.
Vane Electrical 453 Tester. Automotive coil & condenser tester.
Vintage phones and the NBN. How to use vintage phones with the NBN or other VOIP service. NEW for 2020
Using a Telecom Gold Phone on the NBN. How to interface a Gold Phone to a Dialgizmo and NBN modem. NEW for 2020
Ericofon installation notes. Information about this trendy Ericsson telephone.
Two line central battery telephone exchange. Allows two CB telephones to be used as an intercom.
Solar/Wind installation. Installation of a domestic 12V solar and wind powered lighting plant.
House Solar Supply Battery Regulator. This circuit prevents excessive rise in house voltage when batteries are under charge in solar electrical systems.
Solar Panel Charge Regulator. Provides cycle and float charging for 12V batteries.
Solar water heater. Installation and connection of an Evacuated Tube collector panel to an existing electric water heater.
Fun with the Model T, August 2015.
The Story of my Model T Ford. The acquisition of my Model T and some of the experiences I have had with it.
6V Turn Signal Flasher. 6 volt electronic flasher design with user adjustable flash rate, and low current wiring to the indicator switch. This design is not affected by supply voltage.
Car Radio for the Model T Ford. Three valve vibrator powered car radio for the Model T. This design uses the 12AT7 super-regenerative circuit.
Increased power for the Model T Radio. Push-pull output stage for the car radio provides greater audio output. NEW for 2020
Running coils without the magneto. Improve ignition system performance in cars where the 6V battery is the only power source.
Fun Projects Voltage Regulator. Ever wondered how this accessory voltage regulator works? Wonder no more as this article explains all.
Know Your Coils. Rebuilding and adjusting Model T Ford ignition coils.
6 to 12V converter. Powering 12V appliances in your 6V Model T.
6 or 12V? Examines the often asked questions about using 12V in a Model T.
Electronic Coil Tester. This allows Ford coils to be adjusted correctly without multiple sparking.
Model T thermal imaging. See what's really happening with your Model T.
The Model T Ford Battery and Charging System. Understanding the battery, generator, and cut out.
The ECCT. A performance review of the Electronically Cranked Coil Tester.
The E-Timer. Installation and testing of the electronic timer for the Model T. Also describes the new I-Timer.
Australian Model T Ford Parts List. Catalog of spare parts from Ford in Geelong 1927.
Trek Y bikes The Shrine of the Trek Y bike.
Trek Y5 (1997). The first Y bike in my collection. Top of the range 1997 alloy model.
Trek YSL200 (1999). The Y Superlite was the top of the range OCLV model.
Trek Y33 (1998). The fourth to be added to the collection.
Trek Y33 (1996). This is the bike featured in Popular Mechanics July 1996, and the fifth in my collection.
Trek Y22 (1995). This is probably the most common model, and also the earliest of the Y bikes.
Trek 3900 (2006). My first hardtail was a bargain I couldn't say no to.
Trek Y11 (1998). Base model in the carbon fibre OCLV series. NEW for 2021
Trek Y3 (1999). The last Y bike for my collection. NEW for 2021
Giant Reign 1 (2007). Something different to the Trek Y bikes. NEW for 2021
Use Google Translate where necessary.
Monitor Top Refrigerator Forum. All things to do with General Electric Monitor Top Refrigerators, including repair advice.
Model T Ford Club of America. This site has everything you need to know, and an excellent discussion forum.
Nostalgia Air. Source of circuit diagrams for US valve radios. PDF's of Riders manuals. Have found all known Fremodyne sets here.
Classic Radio Gallery. A good collection of U.S valve radios for sale. This is where my first Meck FM converter came from.
Phil's Valve Radio Site. Some interesting homemade receivers and amplifiers. For those wanting a solid state version of the Pulse Counting FM Receiver, this is worth a look.
Sams Photofacts. Known to most U.S technicians/restorers, this company is the place to go for circuits and service manuals for audio/radio/TV gear sold in the U.S. Expensive, but this is where you'll get them and they deal with vintage stuff.
Die Basteleke. This German site authored by Mr. B. Kainka is full of interesting projects, including those with valves operating at low voltage. Its author has written some excellent books, and has designed some of the Kosmos electronic kits (such as the Kosmos Radiomann / Radio Ace).
Children's science radio. For those who like building transistor radios, this Japanese site is full of interesting designs. Many are based around the popular 1960's reflex circuit. Good site if you're into germanium transistors.
Japanese links. A few days worth of browsing here. More Japanese designs using valves and solid state. Eventually, you'll stumble upon the guy who not only likes making pocket radios with valves, but modifies transistor radios to use valves instead of transistors.
American Radio History. If you like reading old electronics magazines, most issues of the well known U.S. and U.K. magazines have been scanned here. Also numerous other old electronics publications.