Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
I have been scanning and posting Radio Service Data
Sheets like this one featuring the ERLA Model 4500, dual-wave, T.R.F., 4-tube, A.C. receiver for many
years now. There are still many people who restore and service these vintage radios, and often it can
be difficult or impossible to find schematics and/or tuning information. I usually attempt to find somewhere
on the Internet of an actual existing example of the radios, but could not for the ERLA Model 4500.
ERLA Model 4500 Dual-Wave T.R.F. 4-Tube A.C. Receiver Radio Service Data Sheet
Band-Selector Switch: This receiver is de-signed for operation
on two different frequency bands. The frequency ranges of these bands are : 1,720 to 540 kc., and 4,200
to 1,500 kc. Selection of the desired frequency band is made with the band-selector switch knob which
is located on the lower right-front of the cabinet. When the band-selector switch is placed in the maximum
left-hand position the receiver is operating on the 4,500 to 1,500 kc. band. For operation on the 1,720
to 540 kc. band place the band-selector switch knob in the maximum- right-hand position. To Align the
Variable Condenser: It is important when aligning to follow the procedure carefully, otherwise the receiver
will lack sensitivity and the dial calibration will be incorrect. (1) Connect the high output side of
the oscillator to the receiver antenna lead and the ground to the chassis. (2) Place the band-selector
switch for operation on the broadcast band; tune the re-ceiver to exactly 1,400 kc. on the dial and
set the service oscillator frequency to 1,400 kc. Then bring in the 1,400 kc. signal to maximum output
by adjusting the trimmer condensers located on top of the gang condensers. Note: Generally the rear
gang condenser section trimmer bas to be adjusted to minimum capacity.
Posted February 2, 2017
Radio Service Data Sheets
These schematics, tuning instructions, and other data are reproduced from my
collection of vintage radio and electronics magazines. As back in the era, similar
schematic and service info was available for purchase from sources such as
SAMS Photofacts, but these printings
were a no-cost bonus for readers. There are 227 Radio Service Data Sheets as of
December 28, 2020.
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling
2 MB. Its primary purpose was to provide me with ready access to commonly needed
formulas and reference material while performing my work as an RF system and circuit
design engineer. The World Wide Web (Internet) was largely an unknown entity at
the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps
while typing up your telephone line, and a nice lady's voice announced "You've Got
Mail" when a new message arrived...
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and text used on the RF Cafe website are hereby acknowledged.