Decca pt ml b service manual

Page 1

SIIIYIVIIHHII/ m 71w IIiII'I .
Iml 'Ir'gadc'l November]

TRADER " SERVICE SHEET

366$

DECCA

PT/ ML/ B

(OR PT/ B)

coupling to the l\\ tuning coil L3 and
as an aerial loading circuit lhe aerial
circuit is tuned by (123 (manual) (7! one
o[ the trimmer units 032 to C39, selec tiou
being etlected by s itches mounted on the
auto tuning unit and controlled by the
III buttons Ll,01 COIIIiCCttIl across
aerial circuit is an ll filter

lhe action of the switches can be
Iolloued [Iom the circuit diagram uheu it
is explained that the sIIitIIIIs are
nnIIIheroIl in the same SLIIILIILO III the
(liagIanI as they appear in the accum-
pauying illustIatiou of the auto unit and
an: nuniheIed In pairs as attached to each

the button controlling 86, S7 or 58 H
depressed, all x5 ' [mm 81 to S5 \Iili
be closed IonIIcIting 031 bctIIch the
junction of L3 and L4, and club 5 III
this condition the mm or will be
operating an I..\\', 56!, 57x or 38x being
open

It a button controlling snitch pairs
5]. to $5 is depressed, the associated
x " will open the ' Close 56x. 57x
and 88x \Iill slmrt- Lircnit L3 and the
19L or will operate on M
st \(ll\C (V1, Mazda metallised TPZS)
is n triodc pentode operating as trequenI V
changer with internal couplinq. TrinIIe

button, each snitch bearing a lettered oscillator gIIIJ coils L6 (II) and L5 (L\\)
It §.BUITON tuning of the sullix to indicate- its action. are tuned by 024 (manual) or one of the
PtI-immor type is included in the 813 and 81x are associated with the trimmer units 040 to 047 \ia Stlcctor
Decca IljML/B 5,Va|\ye battery MW manual button on the extreme left switches 310a to 8158. (auto) I'IIrIIIILI
Z-lfllltl superhet and caters for rm. of the unit, while 88a and 88x are trimming by 050 (\l) and C48, 049
IIII~<1IIIIII and tun long wave stations. associated with the LVV manual button, (I \I): series tracking by 052 UH) :IIIII
l|t'<\'rl)|l{[0|)$ are also incorporated (0,» Situated at the opposite end of the unit, 051(l II) ReIILtIon by Loil L7
mo changing he manual tuning is so that 81 and SB form the manual lt will be seen that as in the aerial
Irving employed waveband sztchIng. circuit, MW and [\I oscillator circuits me
While (1; C] of the receiver bears Throughout the diagram the suffix connected in series and the x " switches

:I plate caIry g the model number " n indi1tIs that the switch \\ II are connected between the tut) extreme
|>'|',I,\n,y/p, the 1-way itself is catm which it associated closes when its ends of the coils The junction of the tun
Iognedasllllli, button is depr sed, while an x coils is connected to the junction of

indicates that it snitch opens when the S13x and 814x and, as nIIly one of the
button is depressed \Vhen the button " x " seIics can be open at a time. one of
is released by the depression of another the tuning coils is short cirLIIiterl so
button the position is reversed, so that that \Iaveband selection is -IntoInI1tII 'Illv
the " sIIitLh openwmdthe x closes cllccterl \\|IiLIIeIer button is (lplfbttl

At any time, them-lore, sail x"s but Second \alic (V2, Tungsram metallised
one are closed and all but one are VPZB) is a \ariIIblo- mu RF peutmle
open, from uhich it nill he seen that it operating: as intermediate Irequeuiy

In i R!
C7

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IIII/mse (tam : July, 1933i

CIRCUIT DESCRIPTION
(IIIIpIiIIg between the aerial and MW
tuning; coil L4 is Via coupling condenser
02 and coupling coil L2. 0n LW, however,
031 is connected by s\ tching across L4,
the tun together operating as an aerial

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