Friday, 24 June 2011

Majestic TV4A 23" Console TV

This Majestic TV4A deluxe 23 inch console was made in 1964 by the Dominion TV & Radio Company, Auckland NZ.  Fortunately it has the date stamped inside the cabinet so rather than guessing how old, the age of it is correct.

I have fully repaired/overhauled the electronics, it did require some work to bring it back to life properly again.

This set was given to me by a friend who bought it but never did anything with it and the thing was taking up space in his garage, he said it did work but not very well.

Upon removing the back cover the first thing I noticed was a broken EF85 video/if valve, upon replacement of that a quick visual of the chassis and power was then applied via a variac. After a gradual increase in mains there were noises and a rustle of EHT and then a washed out but cramped raster appeared on the screen so this looked promising so far.

I fed an aerial signal in and was greeted with a washed out picture and no horizontal sync, adjusting the hold control made it go berserk to the point where the horizontal oscillator started to shut down! I adjusted the oscillator coil and managed to get a locked picture but it wasn't very stable.

Eventually after checking voltages and a replacement line oscillator valve ECF80 and checking/changing various components around the horizontal area I tracked the fault down to the sync discriminator diodes one was leaky and the other was open circuit. After replacing the diodes I now had a nice stable picture and the oscillator was then readjusted back to its original position.

Now onto the vertical...The lack of height was due to the ECL85 vertical output valve, then I found the height pot had a dead spot right where it needed to be and the linearity pot did nothing at all as it was open circuit. Replaced the two pots and now I could adjust the picture geometry.

Some work has been done in vertical section in the past as there were some 'extra' capacitors tacked around the cathode section of the valve, have no idea why this way done, I'm guessing maybe some quick fix '1970's hack-job' to compensate for the faulty pots? Putting it back to original made the geometry adjustments easier in the end so my guess was probably right.

Now the picture filled the screen and looked ok but still was quite weak looking, this turned out be the other EF85 2nd IF valve was low emission, with that replaced the picture improved dramatically and now it had contrast.

The rest of the restoration progress was pretty straight forward, I went through and changed all the electrolytic capacitors and the coupling/bypass caps and rectifier diodes with 1N4007's. Checked all resistors and replaced any that were way out, there a few but the majority checked ok, I mainly concentrated on the resistors that were sitting on the B+ rails and in the supply lines to various valves etc.

At some point in this sets life one of the original filter caps must have exploded as there was paper and tar splattered inside the cabinet and there were bits of all around the bottom on the chassis too....Must have given the owner a good fright when it blew!

After some final adjustments and a full valve check with the trusty AVO VCM Mk4 and a good clean out inside of dust and capacitor innards, it's been in regular use and I've been watching it occasionally for the past year on and off.

Although one evening I was watching it and noticed the picture getting larger and blooming... then I heard something arc and the picture faded away... My initial thought after leaping at the volume control to turn to set off was the line output transformer had decided to keel over, but luckily it was only the EY88 boost valve which had failed while in use and went gassy. A new EY88 brought the picture back again. Used this again last week and still going fine.

Majestic in operation

Better picture shot

Back cover removed


Chassis underneath

Faulty capacitors/resistors/trimpots/diodes/valves that were removed

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