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 Mullard 98
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 Return to top of page · Post #: 1 · Written at 1:14:26 PM on 10 February 2023.
Rogermark's Gravatar
 Location: Eleebana, NSW
 Member since 17 February 2016
 Member #: 1876
 Postcount: 15

Hello everyone,
I recently acquired this lovely old Mullard console radio. It was working after a fashion but in need of lots of TLC. Starting on the chassis and searching the Internet I found that it is a re-badged Philips 4462. I was able to find a service manual for the Philips but no luck with finding a schematic for the Mullard version. I am carefully going through the process of changing all paper and electrolytic capacitors and checking resistors as I go.
I have noticed some deviations from the Philips schematic in the value of components.
For example
The anode load resistor for the triode audio amp (6B6G )in the set is 470K where the Philips value is 220k.
The Mixer/Osc ( ECH33A in the set) has its screen grid feed via a Radio/Phono switch having a 50k resistor from B+ and there is a 220k from the screen to earth. The Philips schematic has no resistor from the mixer screen to earth ( 6J8G in Philips schematic).
Hopefully I can contact Members with knowledge of this radio and maybe get a Mullard schematic.
Looking forward to discussions on this topic.
Rogermark
PS I am posting some questions in the Cabinet Repair section with some cabinet pictures.


 
 Return to top of page · Post #: 2 · Written at 3:37:49 PM on 10 February 2023.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 558

There were always changes in the production runs.
So even if you had the right schematic the chances are there would be some differences.
Particularity with models that were continued for many years.
I would go with changing the components as marked or colour coded.
And if not easily done then refer to possible correct schematics.
Models for example that had phono inputs may have had more elaborate muting of RF, or power saving.
And don't forget the bean counters, often changes were for improvement not of performance but profit.
JJ


 
 Return to top of page · Post #: 3 · Written at 11:14:16 AM on 12 February 2023.
Rogermark's Gravatar
 Location: Eleebana, NSW
 Member since 17 February 2016
 Member #: 1876
 Postcount: 15

Hi JJ.
Thanks for your reply. I agree that changes are made during production runs and none of the changes I've found are outside what you would find in similar applications. Thanks again, Rogermark.


 
 Return to top of page · Post #: 4 · Written at 9:45:44 PM on 12 February 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

......


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 5 · Written at 9:50:37 PM on 12 February 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

A tutorial on model life cycles and the changes that can take place during the run is here. This article only deals with physical changes made on cabinets though but is an interesting read. It was not uncommon for circuits to change several times for a given model. At times, valves were in short supply or old stocks of certain valves needed to be used up before moving fully to the latest types would occur.

I own two four-valve AWA Radiola Champions. One is all-octal and the other has two octals and two baseless valves. The cabinets of both these radios feature in the linked article.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 6 · Written at 10:11:19 PM on 14 February 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5303

Mullard & Philips are basically the same thing and as with Cadet M5 there are two circuits and they are very different. Sets made during the War often chopped & changed tubes & circuit due to parts limitations. Due to the War many sets reverted to pre octal tubes. Based on supply & demand.

Check the wiring you cannot have a screen going to ground (pin 4) normally 100V with 0.1mfd decouple

Plate triode pin 6 ).02 meg to B+

Plate Heptode B+ Via IFT primary. 250V

Cathode 300Ohms to ground

G1 triode 0.05 meg to cathode pin 8


 
 Return to top of page · Post #: 7 · Written at 3:15:25 PM on 17 February 2023.
Rogermark's Gravatar
 Location: Eleebana, NSW
 Member since 17 February 2016
 Member #: 1876
 Postcount: 15

Thanks for your comments, Marc.
The wiring seems OK and when I get my dim bulb setup going I will be able to check all voltages etc.
Meanwhile I have managed to re-string the drum and dial drive chord and found what seems strange to me...
When you turn the tuning knob clockwise the pointer chord moves to the left...
This seems very counter intuitive
I will send Brad some photos of the diagram in the Philips manual and my re-stringing efforts.
There is a crossover at the drive spindle but if I change it over then the cord will rub on the spindle bracket.
Looking forward to comments from members
Roger

Mullard 98 valve radio
Mullard 98 valve radio
Mullard 98 valve radio


 
 Return to top of page · Post #: 8 · Written at 3:32:06 PM on 17 February 2023.
Redxm's avatar
 Location: Tamworth, NSW
 Member since 6 April 2012
 Member #: 1126
 Postcount: 466

Philips seem to make the most complex dial cord arrangement possible


 
 Return to top of page · Post #: 9 · Written at 5:52:40 PM on 17 February 2023.
Johnny's avatar
 Location: Hobart, TAS
 Member since 31 July 2016
 Member #: 1959
 Postcount: 558

Turn tuning knob clockwise then dial pointer should move to the right.
Unfortunately you need to study the problem more closely, to end up with the desired effect.
And some can be a pain.
JJ


 
 Return to top of page · Post #: 10 · Written at 11:46:40 PM on 17 February 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5303

The fault normally resides in the winding direction. It says "x" turns on it. But if you wind it Z instead of S, or vise versa it will go the wrong way.


 
 Return to top of page · Post #: 11 · Written at 9:01:26 PM on 19 February 2023.
Brad's avatar
 Administrator
 Location: Naremburn, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 7342

Photos uploaded to Post 7.


‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾
A valve a day keeps the transistor away...

 
 Return to top of page · Post #: 12 · Written at 10:28:56 PM on 19 February 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5303

Keep an eye on the Philips transformers. I have had a few where the windings are exiting the wrap from the sides. Do not put your dirty fingers on the copper wire to tease it back in.


 
 Return to top of page · Post #: 13 · Written at 7:11:07 AM on 20 February 2023.
Fred Lever's Gravatar
 Location: Toongabbie, NSW
 Member since 19 November 2015
 Member #: 1828
 Postcount: 1267

Roger,
The string should go around the tuning spindle the way you want to put it.
Take that silly bracket off and cut the side out so the string does not scrape on it!
I would sink a round file down until you have enough clearance and it will still look factory made.
Thats how it should have been punched in the first place!
There is nothing worse than a pointer that goes the opposite way to the knob.

Fred.


 
 Return to top of page · Post #: 14 · Written at 9:37:13 AM on 20 February 2023.
Marcc's avatar
 Location: Wangaratta, VIC
 Member since 21 February 2009
 Member #: 438
 Postcount: 5303

Having serviced a few dozen Philips sets, the bracket is inclined so the cordage does not scrape on it. If the cordage is scraping it is likely coming off the bottom of the driver instead of off the top.

If those are wooden pulleys, I give them a light coating of Araldite (High strength). They become brittle over time and that saves me making replacements.

Marc


 
 Return to top of page · Post #: 15 · Written at 1:49:16 PM on 20 February 2023.
STC830's Gravatar
 Location: NSW
 Member since 10 June 2010
 Member #: 681
 Postcount: 1284

Are the top right pulleys at the same level to their mounting? If not maybe these could be swapped.
Or else add another pulley near the spindle to allow a bottom rung cord to clear the bracket.


 
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