Pye 838 TV-radiogram.

[FERNSEH]

The attachment shows the appearance of the Pye 838 TV-radiogram which was made in 1938. When I acquired the set in 1988 it was fitted with a BSR UA8 record deck which had been fitted sometime in the 1950s to replace the original Garrard RC4 78 rpm autochanger. The UA8 was subsequently replaced by a post-war Garrard RC60 with the belief that this is a more suitable record deck, at least in terms of appearance.
But I've been having second thoughts about the BSR UA8. Talking to a fellow forum member yesterday he believes the BSR record deck should be refitted because it is part of the history of the set. The RC60 is a record deck made between 1946 to 1950. It's very unlikely that the owner of the set would have replaced the original Garrard RC4 record player with something like an RC60.

DFWB.

[unitaudio]

I suppose in the context of an old replacement, the UA8 makes sense because it would play microgroove records and that could've been enough to convince the owner it was time for a new deck. Said owner would most likely have been hugely relieved to get away with replacing the deck instead of the whole thing.

Also, when the UA8 was fitted, if it was new, the radiogram would be around 20 years old. More chance of the original deck being worn out (whatever that's supposed to mean...) and being replaced.

I'd say go with the UA8. It gives a nice continuity to it's history and it's more usable. Someone else might care more about originality than I would but if that was you then you'd be looking for a Garrard RC4 to fit.

Regards,
Paul

[FERNSEH]

Found it, the BSR autochanger the set came with. It even has a Pye badge on the tone arm.

DFWB.

[Nickthedentist]

...almost as if it's been robbed from a Black Box!

I wonder whether it was really new in the early-mid 1950s, or whether it was a secondhand unit fitted even later in the machine's life.

N.

[wd40addict]

That's the original version of the UA6 (not UA8). As Nick says probably pinched from a Black Box.

Does the TV side work?

[FERNSEH]

I'll fire up the TV chassis later today and post up my findings. As mentioned in an earlier post it is a mildly modified 815 chassis. The main difference from the table receiver is in the sound output stage. In the 838 the EL3N pentode becomes a focus stabiliser valve and the sound output from the detector load resistor is transferred to the audio stages in the radio receiver.
The radio receiver is a modified 802 chassis. The valves employed in this unit are: 6A8G frequency changer. 6K7G IF amp. 6Q7G detector, AVC and amplifier.
The odd one out in this chassis is an EL3 for the output, strange they should chose an European valve considering all the others are American types from the Mullard Amerty range.
The power supply is assembled on a separate unit. 5Y3G HT rectifier.

I reckon you are right about the record deck, most likely been taken from a scrapped Black Box.

DFWB.

[Edward Huggins]

The Pye badged BSR UA6 started life late 1954/early 1955. The UA8 came out in the Summer of 1956. Edward

[FERNSEH]

The Garrard RC60 installed in the Pye 838. Note the curious bent spindle.

DFWB.

[wd40addict]

Is the CRT behind the metal grille?

[FERNSEH]

The grill on the right can be moved away to the right to expose the CRT screen by using the brightness control knob. The CRT is a Mullard MW22-1 and is a 9" magnetic deflection and focus type. The tube was actually made in Holland. Video drive to the control grid is direct from the full wave video detector which consists of two Mullard T6D diodes. Later recoded as EA50.
Rather like the Emiscope 6/6 tube the Mullard MW22-1 has a high slope characteristic. Needs only 15volts P - P video drive for a well contrasted picture.

DFWB.

[FERNSEH]

A couple of pictures of the TV chassis. It's surprisingly compact for a pre-war design, also very heavy.

DFWB.

[Panrock]

What a rare set and it couldn't be in better hands. The chassis looks strangely modern and 'before its time'.

Can't wait to see what happens when you (gently) fire it up.

Steve

[unitaudio]

I bet it weighs as much as a Mini when it's in one piece!

Regards,
Paul

[FERNSEH]

It's a heavy set but nothing like the HMV 900 and thankfully it does have castors so it's easy to push around.
Yesterday evening the TV chassis was connected up to the variac. The supply voltage turned up in well spaced stages. Even with 220 volts a smallish bright raster was apparent on the screen. Finally the full 240 volts was supplied to the set. Really bright raster displayed but not for long, then all of a sudden flashing and sparks in the Mazda UU5 HT rectifier followed by blown fuses.
I borrowed another UU5 from the Murphy A58V and fitted it in the Pye.
Again with caution the variac was used to bring the bring the mains. This time success and the results can seen in the attached picture. Note the bad line linearity this has always been a problem with the set.

DFWB.

[Panrock]

A pre-war tube with no ion burn! Is there an online source of data on the MW22-1 ?

Steve

[peter_scott]

https://frank.pocnet.net/sheets/101/m/MW22-1.pdf

[FERNSEH]

The CRT is amazing, no ion burn and is capable of displaying a very bright picture. As the data tells us the tube has a complex hexode gun assembly designed to give good contrast with a low video drive. All this means great care must be exercised to take care of this unique tube. There is no direct replacement for the MW22-1 and if later CRTs such as the MW22-7 or the MW22-16 were to be used as replacements it is doubtful fully contrasted picture would be displayed.
Also, the MW22-1 has a 4 volt heater, the MW22-2 is 6.3 volts. Some 815 receivers were fitted with the 6.3 volt CRT.
With regard to the Pye 838, the only fault that needs attention is the bad non linearity of the line scan.

DFWB.

[FERNSEH]

The oscilloscope trace shows the video drive to the control grid of the CRT, it's slightly less than 15 volts P - P which in real terms is only 10 volts of active video. Yet even with this low level of video a well contrasted picture is possible.
The second picture shows the underside of the chassis. Note the huge mains transformer. No separate EHT transformer in this set.

In 1939 the 815 chassis was replaced by the 915, this new chassis was installed in the models 9C and 12C. The same hexode CRT was employed but this time the video was supplied by the newly introduced EF50 pentode. No diode video demodulator and the EF50 operated as an anode bend detector.
All the RF pentodes were also EF50s, RF pentodes in the 838 are the EF6.
The timebases were very similar to the 815 except the line output valve was an EL50 instead of the Mazda AC6/PEN.
Only one Pye 12C is known to exist.

DFWB.

[Nuvistor]

The video waveform looks really good, nice sharp rise times of the sync pulses etc.

[Edward Huggins]

Ah yes, this early association with then then new (and very advanced) EF50 led to the long assocation with Pye and its famous EF50 based IF strip. The source of many valves for home constructors using surplus strip components after WW11. Edward