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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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23rd Mar 2018, 7:54 am | #1 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Mullard Radio set MAS231 Restoration
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. 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 ācā 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. Regards P.Rajan |
23rd Mar 2018, 7:58 am | #2 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Mullard Radio set MAS231 Restoration
Dear Friends
I have many photos to upload so i am doing the same in separate threads as a max of 5 files can be uploaded regards P.Rajan |
23rd Mar 2018, 8:01 am | #3 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Mullard Radio set MAS231 Restoration
Some more photos
P.Rajan |
23rd Mar 2018, 8:06 am | #4 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Mullard Radio set MAS231 Restoration
Some more photos. These are last set of photos.
Regards P.Rajan |
23rd Mar 2018, 8:13 am | #5 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Mullard Radio set MAS231 Restoration
Dear friends
I think that one set of photos were not uploaded which I am doing again. Regards P.Rajan |
23rd Mar 2018, 9:21 am | #6 |
Moderator
Join Date: Jan 2003
Location: Ipswich, Suffolk, IP4, UK.
Posts: 21,192
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Re: Mullard Radio set MAS231 Restoration
Five threads on the same subject merged.
The limit is five pictures per post, not five pictures per thread.
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Graham. Forum Moderator Reach for your meter before you reach for your soldering iron. |
23rd Mar 2018, 10:02 am | #7 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Mullard Radio set MAS231 Restoration
Fantastic piece of restoration- that's a most impressive, thorough and painstaking piece of work on a top-class radio. It shows just what can be achieved even on something that's been long neglected. Well done, I hope it continues to give many years of service,
Colin |
23rd Mar 2018, 10:18 am | #8 |
Heptode
Join Date: May 2011
Location: Letchworth Garden City, Hertfordshire, UK.
Posts: 690
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Re: Mullard Radio set MAS231 Restoration
That's a great piece of work - a job well done, surely a success story.
I'd be interested to know more about the tuning dial reconstruction - that must be worth a thread in itself. Regards SR |
23rd Mar 2018, 4:35 pm | #9 |
Heptode
Join Date: Sep 2007
Location: Brentwood, Essex, UK.
Posts: 687
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Re: Mullard Radio set MAS231 Restoration
Fantastic work, I bet some hours have been spent on that restoration! The dial looks excellent, I would be interested in how the case was restored as well, the finish looks very good.
Steve. |
25th Mar 2018, 12:36 am | #10 |
Hexode
Join Date: Mar 2012
Location: London, UK.
Posts: 347
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Re: Mullard Radio set MAS231 Restoration
I must admit you've done very nice job on the restoration. I too would be interested to know how you got the cabinet looking that good. You also mention that you replaced the mains transformer. Was the original beyond repair?
Thanks, Peter |
25th Mar 2018, 5:22 am | #11 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Re: Mullard Radio set MAS231 Restoration
Dear mr. Pete.
I think the the original maims transformer was damaged along with AZ31. Some body had fitted a much bigger transformer which was only fixed on two screws and the rectifier valve also changed to 5Y3. I wanted to make it original. So I got a transformer made similar to the original and fixed it on all the four screws and changed the valve 5y3 to the original valve AZ31. Even the filament transformer for the dial lamp and the valve EM34 was missing. This transformer also was made new and all the connections made as per the schematic. The basic idea was to make it original as far as possible. Regards P.rajan |
25th Mar 2018, 7:49 am | #12 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Re: Mullard Radio set MAS231 Restoration
Dear Friends
During the restoration I found some of the things missing which made my task more difficult. The worst was, the person from whom I got the set had removed the dial and misplaced all the four clamps which are used to fix the dial in position. Since the clamps were missing it was very difficult for me to find out as to how the dial would be fixed in position as the pointer has to move behind the dial. Mr. John Pearson who had earlier sent the scan of the dial sent me the photo of the clamps which helped me to make new clamps. It is very difficult to remove the chasis from the cabinet and I do not know how Mullard designed it. You can not remove the chasis straight. First the right side of the chasis has to be pulled out and then only the chasis comes out at an angle. To get to the dial holding clamps first the chasis has to be removed from the cabinet and then the dial has to be removed to unscrew the clamps and then only the photo could be taken. I once again thank Mr. John Pearson who took all the pains to help me out. Regards P.Rajan |
25th Mar 2018, 7:55 am | #13 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Re: Mullard Radio set MAS231 Restoration
Dear Mr. Pete.
Regarding the cabinet all the old lamination was removed by a good carpenter on the top and two sides. New lamination was fixed on all the three sides. The front of the cabinet was polished and inside the cabinet was painted with black paint so that it gave a clean appearance. Also the back cover was painted properly which I am yet to fix. Repairing of the cores of all the band spread oscillator coils, which were damaged, was also a big job. Regards P.Rajan |
25th Mar 2018, 10:35 am | #14 |
Octode
Join Date: Jun 2004
Location: Hampton Vale, Peterborough, UK.
Posts: 1,698
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Re: Mullard Radio set MAS231 Restoration
A very successful project. Philips chassis are not the easiest to work on, generally speaking, so you have done very well indeed to have restored this set so effectively.
Well done! Tony |
25th Mar 2018, 12:09 pm | #15 |
Dekatron
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
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Re: Mullard Radio set MAS231 Restoration
There were quite a few "export" sets with multi-band/bandspread SW coverage, but this set is interesting and unusual as a double-conversion circuit on SW, I think 3.1MHz first conversion? It must have been a pricey set when new and there can't have been too many of these in the first place, so all the more worth saving, and the state of this set as found makes the restoration effort all the more commendable.
I wondered why a separate transformer was used for lights/EM34 heater? Perhaps the overall VA with a single transformer would have been pushing standard size stacks towards one that would have been less easy to accommodate, assuming 0.3A bulbs makes around 10VA for this supplementary transformer. If only the scale bulbs were powered, the primary-side switching could have been arranged as a night-light with that large glass scale! The inclusion of the magic eye suggests production convenience re. wiring loom. |
25th Mar 2018, 1:14 pm | #16 |
Heptode
Join Date: Sep 2007
Location: Brentwood, Essex, UK.
Posts: 687
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Re: Mullard Radio set MAS231 Restoration
Yes, excellent work all round, what did you use as a finish on the cabinet after it was re-veneered? it looks very good.
It's something I have never been able to do very successfully! Regards, Steve. |
25th Mar 2018, 2:15 pm | #17 |
Pentode
Join Date: Jul 2006
Location: Bangalore, India
Posts: 104
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Re: Mullard Radio set MAS231 Restoration
Dear Friends
Thank you very much for the encouraging comments. The front of the cabinet is curved so it was not possible to fix lamination so I requested a person who was very good at polishing and he did the polish work to the front frame of the cabinet. Alignment of the set is also difficult. As the service manual of this set was not available I took the help of the service manual for the Philips set 681A which is nearly identical to the Mullard set. Getting the dial image made and finally the printing took lot of time. The sensitivity is so good that even without connecting the antenna I get SW stations. Regards P.Rajan |
25th Mar 2018, 3:47 pm | #18 |
Dekatron
Join Date: May 2008
Location: Derby, UK.
Posts: 7,735
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Re: Mullard Radio set MAS231 Restoration
Well done, that's truly a stunning restoration job on a magnificent set Nice to see that all your hard work has come to fruition!
__________________
If I have seen further than others, it is because I was standing on a pile of failed experiments. |
26th Mar 2018, 10:01 am | #19 |
Pentode
Join Date: Nov 2011
Location: Wigan, Greater Manchester, UK.
Posts: 147
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Re: Mullard Radio set MAS231 Restoration
Fantastic piece of work - well done.
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26th Mar 2018, 10:24 am | #20 |
Heptode
Join Date: Dec 2014
Location: Lincoln, Lincolnshire, UK.
Posts: 583
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Re: Mullard Radio set MAS231 Restoration
Very good work! It is nice to see something restored to such good condition.
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