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29

29; Invicta Radio Ltd.; (ID = 576077) Radio
 
29; Invicta Radio Ltd.; (ID = 576078) Radio
 
29; Invicta Radio Ltd.; (ID = 576079) Radio
29; Invicta Radio Ltd.; (ID = 1062343) Radio 29; Invicta Radio Ltd.; (ID = 1062332) Radio
29; Invicta Radio Ltd.; (ID = 1062335) Radio 29; Invicta Radio Ltd.; (ID = 1062336) Radio
29; Invicta Radio Ltd.; (ID = 1062349) Radio 29; Invicta Radio Ltd.; (ID = 1062351) Radio
29; Invicta Radio Ltd.; (ID = 1063472) Radio 29; Invicta Radio Ltd.; (ID = 1064938) Radio
29; Invicta Radio Ltd.; (ID = 1243060) Radio
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29; Invicta Radio Ltd.; (ID = 1062343) Radio
Invicta Radio Ltd.;: 29 [Radio] ID = 1062343 754x908
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For model 29, Invicta Radio Ltd.; Cambridge, London
 
Country:  Great Britain (UK)
Manufacturer / Brand:  Invicta Radio Ltd.; Cambridge, London
Year: 1957 Category: Broadcast Receiver - or past WW2 Tuner
Valves / Tubes 4: DK96 DF96 DAF96 DL96
Main principle Super-Heterodyne (Super in general); ZF/IF 470 kHz; 2 AF stage(s)
Tuned circuits 6 AM circuit(s)
Wave bands Broadcast (MW) and Long Wave.
Details
Power type and voltage Line / Batteries (any type) / 200-250 / 1.5 & 90 Volt
Loudspeaker Permanent Magnet Dynamic (PDyn) Loudspeaker (moving coil) / Ø 4.5 inch = 11.4 cm
Power out
from Radiomuseum.org Model: 29 - Invicta Radio Ltd.; Cambridge,
Material Leather / canvas / plastic - over other material
Shape Portable set > 8 inch (also usable without mains)
Dimensions (WHD) 10.5 x 5 x 8 inch / 267 x 127 x 203 mm
Notes Attache style radio same chassis as model 28. Similar to Pam models 712 & 716, also Pye model P114BQ.
Price in first year of sale 17.00 GBP
Source of data -- Schematic
Circuit diagram reference Radio and TV Servicing books (R&TVS) book
Mentioned in Attache Radios. By Mark Johnson.

Model page created by Keith Staines. See "Data change" for further contributors.



All listed radios etc. from Invicta Radio Ltd.; Cambridge, London
Here you find 113 models, 60 with images and 81 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.



 


Forum contributions about this model
Invicta Radio Ltd.;: 29
Threads: 1 | Posts: 5
Hits: 2645     Replies: 4
invicta: Invicta29 and all sets with DAF96, DL96
Michael Watterson
04.Oct.11
  1

I recently restored an Invicta 29 (A Pye Chassis same as Invicta 28, PAM 712, PAM716 and Pye Jewel Case with PCB version).

The question I asked people was where should the sceen can be?

I have seen both photographs

Pye Jewel case on RMorg

Screen on DAF96 (possibly wrong)
(RMorg Pye Jewel Case 1955)

and also

screen on DL96 (Invicta 29)

Screen on DL96 (probably right)
(Invicta29, also Pye)

Notice the 1955 and 1957 chassis are identical. Also I have seen in various photographs of the similar chassis the screen on DL96 or DAF96.

Well the DAF96 is sensitive and renowned for "Microphony", so I thought also since the RMorg photo showed it, that the DAF96 was correct location.

But I noticed that for a about 1/3rd of the mid range of the volume the Radio would often "squeal", always when "cold" and less so after an hour or two.

So I swapped screen shield (which has a soldered earth wire) to the DL96 output pentode and from cold the problem of "feedback squeal" at certain volume levels is cured.

 

 

Howard Craven
05.Oct.11
  2

 

Hello Michael,

It isn't clear from the documentation for this and the similar PYE models which valve was originally fitted with a screen can.  All B7G miniature battery valves tend to be microphonic but in my experience with valve portables with this series of valves it is the DAF96 which is most likely to squeal and was fitted with a screen can, indeed I tried three of them in a PYE portable recently and they were all microphonic. However I suggest that you fit the screen can on whichever valve squeals first !

Regards ....... Howard

Michael Watterson
05.Oct.11
  3

Thanks for the comment. My money too would have been on the DAF96, I had moved it to the DAF96 when fixing the radio and moving it back cured the problem. Really it's capacitive pickup I think, not microphonic as at higher volume it was OK.

Perhaps all the valves should have had shields and as a cost reduction they only put it on DAF96 or DL96 depending which worked better!

On my model the c22 had been replaced by RS part maybe in 1970s but only a small part of band worked due to damage of the tuning capacitor. I used very broad tweezers and meter for resistance with the unit removed from chassis. I was surprised that I was able to fix it. I also loosened the tension grub at rear and used that to move the plates back and forth too and eventually locking it in best compromise of position and stiffness to turn.

All the remaining paper waxed capacitors were definately faulty. Gain was very erratic as one is on AGC line till I replaced them.

 

Joe Sousa
06.Oct.11
  4

One possible explanation for the squeal with the volume near a central position and for the useful shielding effect on the DL96, is that there is stray feedback from the DL96 plate to the volume control wiper and it's wiring, including the coupling capacitor C20, the grid bias resistor R8 and the control grid of the DAF96.

The inductive load of the DL96 and the two stages of amplification agravate the conditions for instability between the DL96 plate and the DAF96 grid.

At mid-volume, the wiper impedance is highest, thus it is the most sensitive position for stray feedback.

In a volume type of potentiometer, the resistance characteristic has a logarithmic taper. The highest impedance point should not correspond with a 50% knob position.

Dressing the volume control wiper wiring close to grounded metal parts may also cure the problem.

A common trick to shield the wiper wire is to wrap solid wire around it in spiral and ground one end of this wire as a shield.

-Joe

Bruce Cohen
03.Aug.18
  5

Look at mine, probaly never tempered with, 

PYE P114BQ

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