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Old 6th Nov 2011, 9:11 pm   #1
mark pirate
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Default Kolster Brandes 510 (1935)

Continuing from this thread https://www.vintage-radio.net/forum/...ad.php?t=73481 the story continues....

This set was a real challenge, it looked to have been badly stored in a coalshed for decades, just handling it made my hands black!

The kindest thing I could say about it, was it was complete

I will start with the chassis, on removal, it was in a real state. All the aluminium parts were corroded, the steel chassis and tuning cap were rusty, underneath was not much better, the speaker and o/p transformer were also rusty.

There were signs of some ancient repairs and it was truly filthy with black coal dust and over 75 years of muck. A friend who was round at the time said " there is no way you will get that working!"

Well, I took that as a challenge, "give me a week" I replied.

I printed off a copy of 'The broadcaster service man's manual' from 1936, and started work. The chassis was given a clean with a hoover and paintbrush, then thoroughly wiped down with rags and white spirit. Then I settled down with a coffee and had a good read of the service sheet.

I was fearful that both the mains and output transformer may have suffered in storage, so they were both checked on a meter and appeared to be ok. I replaced the tatters of the original mains lead and checked the mains switch, it showed as being ok. So I powered up the chassis on my variac with no valves fitted. As I wound up the volts, the scale lamp came on, so I brought it up to full mains and checked the output to the rectifier and the two heater circuits, this set uses 2 x 4V and 2 x 13V valves. Thankfully, all voltages were spot on.

I refitted the valves and slowly wound up the variac, but no valve heaters lit, and the set was drawing very little current. So all valve pins and holders were thoroughly cleaned, and on this attempt, three out of the four were glowing, and I had mains hum from the speaker, so at least the audio output stage showed promise!

After checking the offending valve, I found the heaters to be open circuit. I tried the old trick of resoldering the pins, but no luck. The valve was a Brimar 4D1. The service sheet listed a metalised Mullard HL13C as the valve in this position (All valves fitted to the set were Brimar).

Thanks to forum members, I now had a list of equivalents and I gave this list to a pal of mine to check his stocks, but no joy. He kindly contacted a pal of his who had a NOS HL13C, thanks Trevor

While I was waiting for the valve I got to work below chassis. At first I thought just one cap had been replaced, until I removed the cardboard box that contained the electrolytics. All three had been bypassed with replacements that looked like large waxies.

The original contained 2 x 8uF and 1 x 2uF so I dug out the old contents and fitted new replacements, then resealed the box using some of the old wax.

I removed the original replacements, noting that one had a date of Aug 1946.

Now I was getting audio with no hum so I fitted the new valve, plugged in an aerial and was greeted with music, albeit both quiet and distorted. Replacement of three more caps later and it was now working much better. This was improved by cleaning the wavechange switch and remaking of some dodgy solder joints. Volume increased even more when I tried my long wire aerial.

To my amazement, all resistors were still within tolerance, so the only other electrical work was to replace some rotten wiring.

As the chassis was now clean, I decided to tackle the cosmetics, the entire chassis was painted using grey Hammerite and an artists brush, the same treatment was given to the speaker.

The dial lamp was fitted using a grommet, this turned to dust when disturbed so I fitted with a new one. The dial was removed and cleaned and the light tray was given the same treatment.

The cabinet was next, the finish was totally shot on both top and sides. The front was almost saveable but I decided to bite the bullet and attempt my first full cabinet restoration .

I started with the top, using a scraper to remove the old brown lacquer, this was a slow job, but it all came off without damaging the wood. I then did both sides, finishing by carefully rubbing down with fine sandpaper.

The veneer on the front looked a bit fragile, so I removed the old finish with very fine emery paper on a wood block, taking extreme care at the edges and thin strips forming the speaker bars.

I then cleaned the entire cabinet with white spirit. The front of the cabinet is a dark mahogany veneer, while the top and sides were a much lighter wood and not veneered. This was hidden by the original dark brown lacquer.

A quick look in the garage revealed a tin of medium oak stain. This was applied in two coats and I now liked the contrast with the front. After hearing many good things on the forum about Danish oil, this was chosen as the finish.

The first application was done using a cloth. The end result looked promising, but as it dried, it became clear that it would need quite a few coats!

Over the next few days, it had six coats in total, with a bit of flatting down in between with fine wire wool, the biggest problem I had was dust settling on the top when drying. This was a real pain but I came up with a solution; when drying I put a clean plastic dustbin over the cabinet while it dried, this certainly worked!

In between coats I carefully removed the speaker cloth and gently washed it using biological liquid and cold water, then dried it with an iron. I thought it would disintegrate but it survived this ordeal, despite being almost black with dust on the inside. This was carefully reattached to the baffle with contact adhesive.

To finish the cabinet, I used an artist brush and black enamel paint. I painted the speaker fret bars on the inside edges and the two central bars. The plinth/feet were also painted, as were the screws that go through the front of the cabinet to secure the baffle.

The knobs and dial surround were cleaned and polished using T-Cut. I also gave the plywood back a couple of coats of Danish oil and painted the back edge of the cabinet. After a couple of days I refitted the speaker and chassis and gave the cabinet another buffing.

The set sounds much better for being back in its cabinet. While coming nowhere close to Col's (retired) efforts, I am quite happy with the finish and I learnt a few lessons on the way. It has given me the confidence to tackle another and, after all, this whole set was a wreck when I started, so I could have hardly made it worse!


Mark

I think the pictures tell the story....
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Last edited by Darren-UK; 19th Nov 2011 at 6:47 pm. Reason: Proper punctuation added to avoid the need for oxygen after reading.
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Old 6th Nov 2011, 9:13 pm   #2
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Default Re: Kolster Brandes 510 (1935)

And some more....
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Old 6th Nov 2011, 9:18 pm   #3
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Default Re: Kolster Brandes 510 (1935)

And the last few....
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Old 6th Nov 2011, 10:01 pm   #4
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Default Re: Kolster Brandes 510 (1935)

Hi Mark. Again you have done an excellent job of turning a tatty wreck into a lovely radio . cheers neil.
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Old 12th Nov 2011, 12:43 am   #5
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Default Re: Kolster Brandes 510 (1935)

An excellent restoration Mark. Much better that it is loved and used than languishing in a coal shed.
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Old 12th Nov 2011, 10:33 am   #6
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Default Re: Kolster Brandes 510 (1935)

Nice one Mark I hope your friend bought you that pint
another radio saved well done, Mick.
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Old 18th Nov 2011, 11:30 pm   #7
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Default Re: Kolster Brandes 510 (1935)

Thanks for the comments chaps.

Quote:
Nice one Mark I hope your friend bought you that pint
Not yet, but he was amazed how well it turned out, especially the cabinet!
I have been using it a fair bit this week, it stays nicely on tune and sounds pretty good for a 76 year old.

I have got two more cabinets to have a go at, the main one is a Bush console TV. This is in a real bad way, no worm, but it is coming apart at the seams. I will do another radio cabinet first, to improve on my skills.

I would like to recommend Danish Oil to anyone thinking of re-finishing a cabinet. I am quite impressed with the results, after six coats, it has a lovely deep shine, and has given me the confidence to tackle another.

Mark
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