Equipment information:

PYE R25-1A Radio
Manufacturer:
PYE
Model: R25-1A
Date:
Category: Audio, Video, TV, Multimedia
Group: Radio
Description:
Information:
                                    The radio section is a high sensitivity superheterodyne ,
using a larpe diameter loopstick aerial for increased signal
pickup and incorporating two I.F . amplifiers 1'nr high
sensitivity.
Drift transistors áre used throughout for high gain and s
tab ility .
The loop3ticl: winding is matched to the se lf oscillating
mixer for optimum signal to noise ratio and the I.F . signal
is fed
to the I.F . amplifier by means of a bottom capacitively coupled
bandpass circuit consisting of L3, L4 and the coupling capacitor
C8. The base circuit of both I.F . amplifiers is matched to the
I.F . coils by means of a capacitive tap to ensure high transfer
efficiency. The diode detector D2 is arranged to give positive
output voltage, and A.V.C. io applied to the f ir s t I.F .
amplifier
and to the converter via the damping diode Dl. The f i r s t
I.F .
amplifier also acts as D.C. amplifier for the damping diode and
enables the audio output to be held constant over widely varying
input signals.
A high resistance volume control is connected across the
diode load R14 to make low listening levels possible and to give
the correct volume control law. A bass boost network, consisting
of R16 and C21, is connected to the tap on the volume control to
give loudness compensation at low volumes.
The 8'jdio preamplifier and driver are a D.C. coupled pair,
with D.C. feed-back applied by means of R18, R22 and R21, giving
good thermal stab ility . The output stage is connected in
series
push pull, so that the output transformer may be omitted, thus
eliminating any power loss and giving greater battery
economy, as
well as extending the frequency range. The transistors are
adjusted for B class operation and quiescent current is set
by the
base divider networks. Each transistor has an unbypassed emitter
resistor to equalise their characteristics and they are
thermally
compensated by the N.T.C. resistors R27, R28, and the shunt
resistors R25, R26. Negative feedback is also applied via the
bias resistors R29, R30 and by C26, G27, allowing the output
stage
to run with very low distortion. To further reduce the
distortion
and to minimise gain variations, negative feedback is applied
overall by R24 and the unbypassed emitter resistor R20.
Because of the large D.C. feedback and thermal compensation
the receiver may be run at temperatures as high as 120° F.

These manuals are available for the above equipment:

PYE -- R25-1A -- Service Manual
File name: PYE-7259-Manual-Page-1-Picture
Manual Type: Service Manual
Pages: 2
Size: 396.45 Kbytes (405966 Bytes)
Language: english
Revision: Issue 1
Manual-ID/Number:
Date:
Quality: Scanned document, reading partly badly, partly not readable.
Upload date:
MD5: 9dd8c3b4c0313362e93fd813617d3b8d
ed2kID: 36dd6dada503014d71fb05929238e24a
Downloads: 33 since 03 October 2015
Information:
PYE-7259-Manual-Page-1-Picture
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