1948/1949 Philips type 520A television and radio

[grahamperrin]

I can't remember where I got this set, probably in the 1980s, but it was the closest I came to a 'project'.



The radio worked, and I could hear the sound of TV channels. As far as I recall, it had symptoms of a failed frame output transformer.

In the service manual I see a frame output choke (S57 on a diagram, replacement part MK.511.88) but not a frame output transformer. Does that make sense? Or am I missing something?

Long ago I kidded myself that the 520A was a rare and valuable secondhand set, because it was originally more than twice as costly as the relatively commonplace Bush TV22. I'm almost certain that the 520A was priced at 112 or 115 guineas.

Back to reality it's not valuable, one was auctioned for £48 in 2009.

Mullard equivalent

At http://www.thevalvepage.com/tvmanu/mullard/mullard.htm I see –

…MTS501 is a repackaged Philips 520A and the MTS684 the Philips 683U. They even cost the same…

– but there, the (1950/1951) price of the MTS501 is £79-16-0, and this Jonz Valve Page photograph of a (pre-October 1949) MTS521 (£102-18-0) – – appears to be an almost perfect match for my 520A:

The fabrics that cover the loudspeaker grille may be different. And if you wonder how the fabric of mine became so tattered, it's thanks to cats. In the first photograph above there's Pickle, emerging from a brief expedition into the shockingly dusty interior.

More on the Mullard MTS 521/521A:

• Mullard radio/television receiver, 1949 | Museu.MS
• http://www.tvhistory.tv/1949-UK-Ads.htm
• http://www.radiomuseum.org/r/mullard_mts521.html

Postscript: http://www.thevalvepage.com/tvmanu/philips/philips.htm confirms that the 520A was also released as the Mullard MTS521.

Distinction

1934/1945 Philips 520A radio pictured at http://www.jllacer.com/Euro_Radios/philips520A.htm

[thermionic]

Hello Graham.

I have the Mullard MTS 521 on my 'project pile'. Do you intend to restore yours? I shall follow your progress with interest if you do.

Good luck with it. You will find plenty of excellent advice from experienced TV engineers here to guide you to, hopefully, bring your project to a successful conclusion.

SimonT.

[grahamperrin]

Thanks Simon

I imagine it becoming a project after I retire, if circumstances allow …

[FERNSEH]

Long ago I kidded myself that the 520A was a rare and valuable secondhand set, because it was originally more than twice as costly as the relatively commonplace Bush TV22. I'm almost certain that the 520A was priced at 112 or 115 guineas.
Back to reality it's not valuable, one was auctioned for £48 in 2009.


But surely it's not what it's worth in an auction but the fact it is one of the most technically interesting TV sets to be made in late forties.
I'm of the opinion that the 520 was designed in Mitcham rather than Eindhoven.

DFWB.

[grahamperrin]

Originally Posted by FERNSEH

… one of the most technically interesting TV sets to be made in late forties. …

Please: can you (or Simon, or anyone with relevant technical knowledge) explain what makes a set such as this so interesting, compared to other sets from the same era? I don't doubt what you say, I'm just curious.

Around five years ago I might have given it away – half-expecting the donation to be either declined, or politely discarded by a new owner. So now, it's a pleasant surprise to find other people interested.

Thanks

[Heatercathodeshort]

It is a vintage television restorers delight. Very quirky, typical Philips design with an strange chassis with some odd valves even for 1949. It's all about the pleasure of restoring these old receivers. Value and cost on the whole plays no part of it.
These give an excellent picture in their day and would still be capable of very good results today given a good overhaul.
I would agree with David, I'm also of the opinion that this is a Mitcham design, probably the first one after the difficulties with the design of television receivers at Mitcham and the clash with Eindhoven. I hope we see a picture on it one day. Regards, John.

[grahamperrin]

In retrospect, the opening post probably gave an impression that I'm overly interested in the monetary value, that's not the case. I was initially puzzled by the difference in original costs between the 520A and the Mullard MTS501. Then realised that the corresponding Mullard is truly the MTS521.

More than anything I'd love to, some day, see sets such as this go to a good home (better than mine, with attention from expert restorers). I'm aware of Sets, Parts and Service Information Offered, but that's not why I joined; for now it's far more enjoyable to read people's stories and opinions.

Thanks again

[Jac]

The Philips 520A has a circuitry quite similar to other Philips sets of around that time, like the 563A and 663A.
A big difference is that is has no mains transformer, hence the special valves to make a 0.2A heater chain.

Indeed it would be nice to see a picture on it!

Jac

[FERNSEH]

Good morning Jac,
Just like the 563A there are some quite adventurous circuits in the 520A and 521A. The sound circuits in particular. Switched to radio operation the set performs just like a conventional receiver using 0.2amp heater chain valves, CCH35, EF39, EBC33 and CL33, Just to add to the confusion the radio HT rectifier is a 0.1amp heater type UY21. Radio IF is 470Khz.
On television all the 0.2amp radio valves remain in the circuit, the CCH35 performs as the sound frequency changer, The television sound IF is 9.8Mhz.
When switched to television an additional sound IF amplifier stage is introduced using an EF50.
Most of the television circuits resemble the 563A, however because no mains transformer is employed for the higher HT voltage required by the line timebase a voltage doubler circuit is used by employing a PZ30 double diode.
Thus the set cannot be used on DC mains.
Information for the Mullard version, the MT521 can be found in pages 592 to 601 of volume II Radio and Television Servicing by Molloy and Poole.

DFWB

[stevehertz]

The world of collectable vintage TVs has its own rules and trends when it comes to the value of sets.

1) Being rare does not necessarily make a vintage TV valuable.
2) TV sets are generally quite large and most collectors only have so much room to keep them, so often - pre war sets excepted - console sets are less sought after.
3) Like any aspect of vintage wireless and TV, appearance plays an important part in desirability, and often console sets can be quite ugly and bulky looking. Others are cute or handsome.
4) All pre-war TV sets are rare and sought after and hence are valued highly.
5) Trends and fads are as prevalent in vintage TVs as they are in most other collectable hobbies. Bush TV22s always used to be sought after and would fetch a comparatively high price. These days you can now pick up a Bush TV22 at the same kind of prices - or less - than you could in the 70s or 80s. However, I think this is partly due to their greater availability as a result of auction sites and the expanded supply chain that they bring.

[HamishBoxer]

Totally agree re Bush TV22s as I remember the days they were £250 plus,now possibly £150 max.

[Maarten]

A Mitcham design seems plausible, but can easily be confirmed by looking at an actual set and its documentation.

Code numbers of significant parts depend on the place where a set was designed, so one would expect to see code numbers starting with MK instead of A3 for more than a few components in the documentation and in the actual set as far as code numbers can be found there.

Also, the place where a set was manufactured depends loosely (more or less so depending on the era and the kind of equipment) on where it was designed. If the serial number starts with M for manufacture in Mitcham rather than E, chances are it was at least partially designed in Mitcham as well.

Last but not least the presence of an execution/destination suffix behind the type number. This doesn't say anything about where a set was designed, but it can give an indirect clue. If a suffix /15 is present, the set was intended for the UK but might have existed in versions for other countries as well. The chance it was designed in one of the destination countries instead of centrally, is a bit lower in that case.

[Jac]

Maarten,

There is a big chance that the serial number has no letter in front.
Perhaps grahamperrin is willing to post a picture of the type plate of his 520A?
The 383A/15 in my collection is of about the same era and just has a 4-digit number.
The service manuals issued by Philips for this generation of sets state Croydon as the service department, which does not inform us of the development or manufacturing location.

Later sets, like the 385U/15, have M in front of a 4-digit number.

All these sets have some Eindhoven components, but certainly a majority of part references start with MK or MS.

Jac

[Duke_Nukem]

Thanks to Graham I've now fixed the wee typo on the Mullard Page.

BTW if anyone has the Mullard version of the set getting in their way, I know of a good home

TTFN,
Jon

[grahamperrin]

Thanks folks

I'm nursing a cold at the moment, I'll get to the serial number maybe tomorrow.

[Maarten]

From Jac's statement that most part numbers start with MK and MS, it is at this point quite likely to have no letter or an M in front of the serial number as it makes sense that British designs were manufactured locally with only some parts imported from Eindhoven.

[grahamperrin]

https://goo.gl/photos/DU76Ep5h3qZh4xbY9

520A/15
MM 2884

Also on the plate:

• no voltage, AC, 230 W (I guess that's a mistake)
• A1872 (I guess that's a generic reference for the plate itself).

Originally Posted by Jac

…a majority of part references start with MK or MS.

I see many MK but (at a glance) no MS.

If it helps to date my service manual: eight notes under ADDITIONS AND CORRECTIONS on page 19 and when I flip that page, there's 'PR1789'.

[Jac]

That's interesting!

I hadn't expected this. Even 2x M on the plate!
The 230 W will be correct - these sets draw about 1 A.

Jac

[FERNSEH]

Circuit diagrams of the Philips 520A and Mullard MTS521.
V1 (CCH35) functions as the mixer-oscillator on radio and TV sound, the triode oscillator section is common to radio and television. V8 is the vision and sound RF amplifier. V9 is the vision frequency changer. It's likely because of all this complication in the signal circuits none of these receivers were converted to Band 3.

DFWB.

[Maarten]

The double M on the plate is something I've never seen before and may indicate another factory than a single M (or it was a simple error - by any chance, is the first M printed and the second M stamped?) but it is at this point extremely likely the set was both designed and manufactured in Great Britain.

Interestingly, the type plate itself was designed in the Netherlands as A1 872 is a Dutch issued part number missing the last 2 or 3 digits (it would be nice if you could decipher them).

Edit: I only see now, that you linked some (very nice and sharp) pictures. The second M is indeed stamped. The stamping machine was probably adjusted to non-pre printed type plates so for practical intents and purposes I would consider this a single M. Also the last (5 even) characters of the type plate's article code A1 872 23.0/A are visible, quite interesting for my archives. The voltage not being stamped wasn't a mistake but rather usual practice for sets with adjustable mains voltage.