Mullard radio MAS231 (Algemeen)

door Pandu Rajan @, 09.04.2018, 09:32 (347 dagen geleden)

Dear friends
I have completed the restoration of the radio set Mullard MAS231. The photos shows the condition of the set before and after restoration. It is one of the most difficult sets I have come across during restoration. Lots of work was done to restore the set and I have given the jobs done in detail. Also I have attaching many photos which will highlight the progress of the restoration of the set. The details of the restoration are as follows:

1. The set was received in a very bad condition. It was first thoroughly cleaned before starting the restoration.
2. The chasis was thoroughly cleaned.
3. The band switch gear assembly was dismantled cleaned and lubricated and fitted back.
4. The bottom of the audio amplifier around the valve B5 & B6 was badly carbonized may be due to some short circuit earlier. Thoroughly cleaned the chasis of the audio amplifier.
5. Changed all the black capacitors.
6. Removed all the wrong connections done and the wiring done as per the schematic including the wiring of R44. Removed all the defective wiring. Redone with fresh wires.
7. Replaced R42,R44,R34,R43 resistances.
8. Replace the screened cable around the volume control and P.U./Radio switch.
9. Then started the work on the top of the chasis.
10. Replaced the main transformer with a new one with original specification.
11. Replaced the filament transformer ( for the dial lamp and filament of EM34) with a new one as the same was missing.
12. Replaced both the filter capacitors C1 and C2 and rewired the same including R36 and C138 as per the schematic.
13. Replaced all the wires of EM34.
14. Replaced R89 and connected R63 which was missing.
15. Checked the O/P , Interphase transformer and the IF transformers and found them O.K.
16. Completed the top restoration of the chasis.
17. Painted the chasis with grey paint similar to the original.
18. Painted the dial cord mounting plate with silver paint.
19. Changed the cloth of the speaker baffle board and the wooden board behind the dial.
20. Replaced all the four springs of the band indication cord and put new cord.
21. Used the original steel cord for the pointer as the same was in good condition and fixed the pointer properly.
22. Changed the wiring of the dial lamps.
23. Repaired the speaker with new cone , coil and spider and provide a new dust cover.
24. The only modification done was providing fuses in the circuit for the protection of the transformer.


Mullard radio MAS231

door Pandu Rajan @, 09.04.2018, 09:39 (347 dagen geleden) @ Pandu Rajan

Dear friends
In continuation of my earlier message I am giving the other jobs done on the above set. As there were some limitation on the length of the msg I am giving the remaining jobs done in this msg.
25. Replaced 5Y3 with the original rectifier valve AZ31.
26. Switched ON the set and measured all the voltages and found them nearly O.K.
27.Replaced R53 and R54 which were out of tolerance.
28. MW , LW and SW3 bands Started working. SW2 and all the band spread bands were not working.
29. One of the connection of the coil S33 was open. Repaired the same and SW2 became O.K.
30. Volume control was defective. Replaced the same by value 200K + 650K as the original value of 500K was not available.
31. Tone Control found O.K.
32. Somebody had put Valve 6K8 in place of ECH35 in position B2. Replaced with a new ECH35.
33. All the band spread bands were not working. Checked thoroughly and found the ferrite cores of all the 8 oscillator coils damaged. I am attaching a photo which shows the different types of damages to the cores.

a. The ferrite core was cut. It was Glued with super glue. This was for the bands 16m,19m and 31m.
b. The core was cut and the remaining part of the core attached to the brass screw was damaged and not repairable. Fixed a small Brass/Nylon tube to the core with super glue and inserted the brass screw into the tube and fixed with the super glue. This was for bands 25m, 41m and 49m.
c. the third type of damage was that the core itself was missing and only the brass screw was there. Luckily I had spare cores and adopted the same procedure as in ā€˜cā€™ and was able to repair the core of 13m band and the coil S107/S108.
e. I was unable to repair the coil for the 11m band as no further cores were available.
34. Aligned all the bands of the set as per the service manual except the 11m band.
35. All the 11 bands working correctly.
36. Band indication pulley was broken and was repaired.
37. As the separator plate between the transformer and the output valves EL33 was missing, provided a new one.
38. Made a new Dial. I am very thankful to Mr. John Pearson who was kind enough to provide the original scan of the dial and also the clear photo of the four clamps which keep the dial in position. As all the four clamps were missing it had to be made new.
39. The cabinet was completely restored.
40. Fitted the chasis into the cabinet and completed the restoration.


Mullard radio MAS231

door Sietze Osinga @, Koekange, 09.04.2018, 13:19 (347 dagen geleden) @ Pandu Rajan

Hello Pandu Rajan.My greatest compliments for your restoration of this radio.I wish you very much pleasure with your Mullard radio.
Sietze Osinga.

Mullard radio MAS231

door Leo Snoeren āŒ‚ @, Dongen, 09.04.2018, 09:52 (347 dagen geleden) @ Pandu Rajan

Very nice job and a lot of work, the radio looks like new! :OK: :OK: :OK:

Met vriendelijke groet,

Leo Snoeren


Mullard radio MAS231

door S.Leunissen @, regio Kerkrade, 09.04.2018, 17:52 (347 dagen geleden) @ Pandu Rajan

Well done my compliments !:OK:

groet Sander

Mullard radio MAS231

door thijs bouma āŒ‚ @, Haarlem, 09.04.2018, 19:04 (347 dagen geleden) @ S.Leunissen

Well done. You made a great job.


Mullard radio MAS231

door Pandu Rajan @, 11.04.2018, 14:21 (345 dagen geleden) @ thijs bouma

Dear friends

Thanks to all.


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