my first real restoration - UK Vintage Radio Repair and Restoration Discussion Forum

radio edgar · 9th Aug 2008, 9:11 pm

Hi everyone,
have been tinkering about for a bit but I got a dac90a and thought about time I did a proper job.
The cabinet was very dull but did not have any scratches, when I took the back off it had about 50 years of dust and a couple of dead spiders and plenty of cobwebs.
I fired it up with my lamp limiter the dial lamps glowed as did the valves.
rather bravely I pluged it direct to the mains and it started playing music with lots of mains hum then smoke started to emit from it so I quickly unplugged it.
I stripped it down and found the mains capacitor had blown itself in half, not a good sign.
Anyway I stripped the chassis down and cleaned it up it now looks like a new one.
I replaced all the suspect caps and of course the ul41 valve .
I used brasso for the cabinet and it shines like a new pin The deflector for the dial lamps was yellow and very dirty It cleaned up a bit but not as well as I had hoped.
The speaker grill was a lovely shade of yellow/brown but some soapy water brought it back to golden.
Anyway put it all back together and after initial tests plugged it in and to my amazement worked fine.
I know the dac90a is an easy machine to work on but it has given me the confidence to tackle another.
Hope I have not bored you
Regards
Paul

Steve_P · 9th Aug 2008, 9:22 pm

Well done as always! How about a picture?

Are you sure the UL41 was faulty?

Cheers,

Steve P.

radio edgar · 9th Aug 2008, 9:33 pm

Hi Steve I will try and put some pictures on tomorrow
As for the valve I was told it was the most likely suspect for mains hum which this set had, so I replaced it anyway and now no mains hum,could it have been the bad caps giving it mains hum?
Paul

radio edgar · 9th Aug 2008, 9:43 pm

Sorry forgot to say the only thing anyone had done to it was to remove the mains plug in the chassis and poked the wires through with no restraint, so I wired it up directly to the on/off switch properly.
Thought about replacing the plug but then decided this was the safest way, not strictly original but much safer.
Paul

Paul_RK · 10th Aug 2008, 12:24 pm

Very likely the UL41 needed replacing, but there's an issue with the DAC90A which as I recall kept at least one of my UL41s in service. Pins 3 and 4 of the valve base shouldn't connect to anything inside the valve, but with some examples they do: the 90A uses one or both of the valve socket tags as connection posts. Removing wires from these (whilst of course keeping their connectedness to one another

) is sometimes all it takes to cure mains hum.

Paul

radio edgar · 10th Aug 2008, 8:19 pm

Hi Paul,
thats a good tip to try as the price of ul41s keeps going up, I have kept the old one from my set just in case
Regards
Paul

9th Aug 2008, 9:11 pm	#1
radio edgar Pentode Join Date: Jun 2005 Location: Grimsby, Lincolnshire, UK. Posts: 133	my first real restoration Hi everyone, have been tinkering about for a bit but I got a dac90a and thought about time I did a proper job. The cabinet was very dull but did not have any scratches, when I took the back off it had about 50 years of dust and a couple of dead spiders and plenty of cobwebs. I fired it up with my lamp limiter the dial lamps glowed as did the valves. rather bravely I pluged it direct to the mains and it started playing music with lots of mains hum then smoke started to emit from it so I quickly unplugged it. I stripped it down and found the mains capacitor had blown itself in half, not a good sign. Anyway I stripped the chassis down and cleaned it up it now looks like a new one. I replaced all the suspect caps and of course the ul41 valve . I used brasso for the cabinet and it shines like a new pin The deflector for the dial lamps was yellow and very dirty It cleaned up a bit but not as well as I had hoped. The speaker grill was a lovely shade of yellow/brown but some soapy water brought it back to golden. Anyway put it all back together and after initial tests plugged it in and to my amazement worked fine. I know the dac90a is an easy machine to work on but it has given me the confidence to tackle another. Hope I have not bored you Regards Paul

9th Aug 2008, 9:22 pm	#2
Steve_P Dekatron Join Date: Sep 2003 Location: Bolton, Greater Manchester, UK. Posts: 6,644	Re: my first real restoration Well done as always! How about a picture? Are you sure the UL41 was faulty? Cheers, Steve P. __________________ If we've always had it, why is the Car Boot open? You're not sneaking another Old TV in are you...?

9th Aug 2008, 9:33 pm	#3
radio edgar Pentode Join Date: Jun 2005 Location: Grimsby, Lincolnshire, UK. Posts: 133	Re: my first real restoration Hi Steve I will try and put some pictures on tomorrow As for the valve I was told it was the most likely suspect for mains hum which this set had, so I replaced it anyway and now no mains hum,could it have been the bad caps giving it mains hum? Paul

9th Aug 2008, 9:43 pm	#4
radio edgar Pentode Join Date: Jun 2005 Location: Grimsby, Lincolnshire, UK. Posts: 133	Re: my first real restoration Sorry forgot to say the only thing anyone had done to it was to remove the mains plug in the chassis and poked the wires through with no restraint, so I wired it up directly to the on/off switch properly. Thought about replacing the plug but then decided this was the safest way, not strictly original but much safer. Paul

10th Aug 2008, 12:24 pm	#5
Paul_RK Dekatron Join Date: Nov 2003 Location: Fakenham, Norfolk, UK. Posts: 4,256	Re: my first real restoration Very likely the UL41 needed replacing, but there's an issue with the DAC90A which as I recall kept at least one of my UL41s in service. Pins 3 and 4 of the valve base shouldn't connect to anything inside the valve, but with some examples they do: the 90A uses one or both of the valve socket tags as connection posts. Removing wires from these (whilst of course keeping their connectedness to one another ) is sometimes all it takes to cure mains hum. Paul

10th Aug 2008, 8:19 pm	#6
radio edgar Pentode Join Date: Jun 2005 Location: Grimsby, Lincolnshire, UK. Posts: 133	Re: my first real restoration Hi Paul, thats a good tip to try as the price of ul41s keeps going up, I have kept the old one from my set just in case Regards Paul