Hello All,

Got this radio in a "package deal" and was originally going to "pass it on" to someone else since I'm not much into the leatherette ( thin vinyl on cardboard ) sets---but the curiousity bug bit & decided to try & get it goin'...

The front trim panel & knob bright were off ( but present ) and battery contacts & springs rusted way beyond repair as well as the case being "rough" in areas...

So disassembled & cleaned, polished & re-glued knob bright in place, glued front nameplate back onto speaker grille, & attached new power wiring to PCB...

Connected new wiring to external battery holders, turned on, and WOW ! Radio worked
excellent with original caps---very good performance for a non-TRF stage set ( guess it's those excellent Philco Surface-Barrier transistors ) & plenty of good sounding audio...

It's passing my "standard" WSM 650 test as this is typed... May be a "keeper" now...

Here are a few pics:

Nice pickup, John. The dial is the same as the coat pocket size Philco T-45, except that their inserts are gold colored. Those four-Transistor sets can easily match a six Transistor radio in performance, so the one you have should be quite a DXer itself.

The early Philco Transistor sets overall are really good performers, what with the metal cased Transistors and generous sized loop sticks.

There have been sets I myself was going to part with, and after getting them going, they worked so well I decided to keep them (that's one contributing factor as to why I have so damn many, lol).

Richard

The case cleaned up pretty good and that circuit board couldn't be any simpler.
Looks like the leatherette snaps/ears are gone, but I'd bet you could recreate them.

Four transistors? - I'd be curious to see the schematic.

~ Mitch ~

Thanks guys...

Fifties---this IS a keeper... Like you, just couldn't get rid of something that performs & sounds so good !

Mitch---the 4-transistor set Fifties mentioned is the Philco T45... I had one of those many years ago as a kid, but never got it working ( probably needed electrolytics ). It was white with a pink back cover & disk under tuning knob... This T802-124 is an 8-transistor set. Yes, the snap tabs are long gone---but notice the Made in U.S. sticker survived !

John

Here ya go; drove me nuts until I figured out that "T-4" meant "T-45" with Sams. I have 3 of 'em.

Note the "cute" reflex circuit on the T-45 where the detected audio is reflexed through the 2nd IF to provide additional audio gain. That provides 5 transistor performance (more like 4.5) with 4 transistors. The audio out runs class A saving another transistor. That costs some current drain so power output suffers, still adequate for the speaker size.

Four double A cells deliver longer life and comply with Philco's policy of avoiding 9 volt batteries in domestic designs.

Overall it is a good performer for the component count.

The T-802 is a much more conventional design.

Now this is interesting; can you elaborate a bit more about it? I had no idea...What was their reasoning?

[quote ]Now this is interesting; can you elaborate a bit more about it? I had no idea...What was their reasoning? [/quote]

There were a few things going on at the time.

Philco invented the Surface Barrier transistor around 1955. It operated on low supply voltages and current and had excellent high frequency response. Designers quickly saw the benefits and incorporated them into all kinds of products like computers, weapon systems, satellites, commercial radios and consumer products. Philco’s expertise was the ability to turn out millions of them quickly, at low cost.

Philco’s first commercial transistor radio was the T-7 introduced in ’57. It operated on 3 volts from 2 “D” cells and sold for $69.95, pricy at the time. The first ones were warranted for 5 years. The original warranty did not exclude the battery so a few customers returned to the dealer for replacements. Smart dealers quickly figured out that $0.20 was cheap to get a customer into the store so they handed out batteries and showed them TVs and appliances. The warranty was soon rewritten.

Nine volts is too much for Surface Barrier transistors and 9V batteries did not last long. Application notes from Lansdale suggested 3-6 volts. Like everything else, there are trade offs in distortion, current drain, size and performance.

The T-7 IF and audio circuitry was used in a few other top line radios like the T-9. It added an RF stage and band switching to get the extended coverage.

Manufacturers understood that transistor radios would quickly ride down the price curve. Philco’s strategy was to offer tiered product lines so dealers could “sell up”. Each step up provided additional benefits at additional cost.

By mid 1958, there was a load of follow on transistor radios. Most ran on 3-6 volts and used 3-9 transistors. Some had tuned RF stages and most all had P/P output for low current drain and high audio output from low supply voltage.

My personal favorites are the T-805, T-901/903 and the T-7.

what is the difference between TRF and RF amplifier ? I hear TRF used a lot in transistor land but what I see is a single RF amplifier. TRF used widely describing early tube sets that amplified RF several times then detect into AF amplifier and finally power output amplifier. several RF stages tuned at the same time with separate tuners ganged together. the technology pre-heterodyne

TRF means Tuned Radio Frequency, i.e. tuned at the received frequency. A TRF receiver has one or more stages tuned at the station frequency and is detected at that frequency. TRF receivers preceded superhets.

A TRF stage in a superhet receiver has one or more RF stages preceding the mixer. The incoming signal is amplified by the RF stage before converting to an IF frequency. A 3 gang tuning cap in a superhet usually indicates a tuned RF stage. Those are more scarce and better performers than the typical design that feeds the antenna directly into the mixer.

A superhet receiver may have an untuned RF stage. An untuned RF stage is of marginal benefit because it provides very little useable gain and increases the noise floor. That will have a 2 gang tuning cap.