Mullard MAS1764 - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

ukcol · 20th Feb 2018, 5:24 pm

To expand on what Bill said in post 2 and what dazzlevision has just said. The audio amplifier in the Philips 643A is quite a lot more complicated than your average set. Instead of "that" capacitor" (one component) there are no less than 4 capacitors (C59, C60, C62 and C63) that could cause damage if leaky.

See snip below.

The munufacturer's manual is available here.

https://www.service-data.com/section.php/5896/1/643a

petergamston · 1st Mar 2018, 1:21 am

Belatedly many thanks for that - I was struggling. I have the "Trader" Service sheet 1208. https://www.************************...ILIPS/543A.PDF

and I will certainly get those you list.

I fear I am still a little confused. Are those Cap numbers (59, 60, 62 & 63) on your 'snip' taken from the manufacturers circuit diagram - unless I'm being particularly obtuse (a distinct possibility) they don't seem to tally with my 'Trader' service sheet numbers where C59, for example, is only one of a set of four Neg feed-back tone correctors (1500pF).

ukcol · 1st Mar 2018, 1:32 am

Quote:

Originally Posted by petergamston

Are those Cap numbers (59, 60, 62 & 63) on your 'snip' taken from the manufacturers circuit diagram...............

Yes Peter, the snip is from the manufacturer's service data and not the Trader sheet.

The manufacturer's data is available here:

https://www.service-data.com/product...05/5896/m14605

Boater Sam · 1st Mar 2018, 3:10 am

Trader sheets rarely agree with the component numbers on other sheets as they reverse engineered their own off an actual set.

boxdoctor · 2nd Mar 2018, 6:29 pm

I might be missing something, but the R34/35 network on the shown circuit seems rather odd. Is it the same on the other diagrams? Tony.

ms660 · 2nd Mar 2018, 7:36 pm

So far as I can make out it's drawn correctly, either side of center is treble cut by equal amounts but only on side of center gives treble cut and bass boost, the bass boost switches are ganged to the tone control. There's a brief description in the Trader for the 543a which shows a similar circuit although there appears to be a discrepancy with S25, S26 in the description....So far as I can make out.

Lawrence.

20th Feb 2018, 5:24 pm	#21
ukcol Rest in Peace Join Date: May 2003 Location: Harlaxton, Lincolnshire, UK. Posts: 3,944	Re: Mullard MAS1764 To expand on what Bill said in post 2 and what dazzlevision has just said. The audio amplifier in the Philips 643A is quite a lot more complicated than your average set. Instead of "that" capacitor" (one component) there are no less than 4 capacitors (C59, C60, C62 and C63) that could cause damage if leaky. See snip below. The munufacturer's manual is available here. https://www.service-data.com/section.php/5896/1/643a Attached Thumbnails

1st Mar 2018, 1:21 am	#22
petergamston Retired Dormant Member Join Date: Feb 2018 Location: Farnborough, Hampshire, UK. Posts: 10	Re: Mullard MAS1764 Belatedly many thanks for that - I was struggling. I have the "Trader" Service sheet 1208. https://www.************************...ILIPS/543A.PDF and I will certainly get those you list. I fear I am still a little confused. Are those Cap numbers (59, 60, 62 & 63) on your 'snip' taken from the manufacturers circuit diagram - unless I'm being particularly obtuse (a distinct possibility) they don't seem to tally with my 'Trader' service sheet numbers where C59, for example, is only one of a set of four Neg feed-back tone correctors (1500pF).

1st Mar 2018, 3:10 am	#24
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Mullard MAS1764 Trader sheets rarely agree with the component numbers on other sheets as they reverse engineered their own off an actual set.

2nd Mar 2018, 6:29 pm	#25
boxdoctor Rest in Peace Join Date: Sep 2010 Location: Ripley, Derbyshire, UK. Posts: 785	Re: Mullard MAS1764 I might be missing something, but the R34/35 network on the shown circuit seems rather odd. Is it the same on the other diagrams? Tony.

2nd Mar 2018, 7:36 pm	#26
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Mullard MAS1764 So far as I can make out it's drawn correctly, either side of center is treble cut by equal amounts but only on side of center gives treble cut and bass boost, the bass boost switches are ganged to the tone control. There's a brief description in the Trader for the 543a which shows a similar circuit although there appears to be a discrepancy with S25, S26 in the description....So far as I can make out. Lawrence.