Blaupunkt Barcelona 2342 - UK Vintage Radio Repair and Restoration Discussion Forum

Ferguson 2000 · 29th Jul 2021, 11:56 am

I was asked to repair this along with a Ferguson 421 UXL ( see earlier posting) now it has been many years, perhaps decades since I last repaired a domestic valve radio. My last two valve repairs have been a Top Band Direction Finding receiver with D series valves, used very successfully by Eric Mollart the winner of countless DF events and a Marconi Q meter with it's LF/MF/HF oscillator.

The set came with a photocopy of a badly damaged service sheet so onto the bench with it, I was concerned that unlike my work workbench of years ago this one is not earth free and does not have an isolating transformer, the mains voltage adjuster looked very easy to brush against. No way was I going to use my True RMS many digit meter on 2-300 volts so out came my Avo 8 which I prefer for fault finding with it's large analogue scale.

As demonstrated it came on with background noise but no stations on any band except VHF. Frequency changer perhaps? Applying a test probe to the grid brought noise from the loudspeaker so onto the voltages helped by a Mullard 1964/5 wall chart for the ECH81 pin out, low anode volts on the triode oscillator and positive volts on the grid, onto cold circuit checks and L714 feedback from anode to grid is o/c. Very fine, difficult to solder wire and even harder to find where it should connect to but eventually I switch on and have negative volts on the grid but the anode is about 15 volts low and still no AM signals.

Do what I should have done in the beginning and measure the HT at the smoothing capacitors, it is about 50 volts low, on another hunch (experience related inspired guess) I find a duster and remove the EL84 audio output valve, the HT goes up to 300 volts.

Onto the grid with my Avo 8 and there are positive volts there, two possible candidates, both difficult to get at, C763 and C765 an in circuit check suggests C765 5000 pF @ 500 volts is leaky so I cut one end of it and measure again, yes about 3 Meg ohms, but what to replace it with? A series parallel combination of 1 uF surface mounts? After much searching I find a RS polyester .0033 at 500 volts, in it goes and I still have positive volts on the grid so cut the end of C763 25,000 pF @ 350 volts and measure, the leak is about 10 M ohms, where am I going to find one of those? Eventually it is a choice between 0.22 uF @ a 1,000 volts or 0.033 uF @ 1,000 so in goes the 0.33 uF and negative volts on the grid.

Even better there is a programme on Long Wave and after cleaning the wave change switches Medium Wave as well. I set the mains selector to 240 volts rather than the 220 volts it is on and go and make a cup of coffee.

Half an hour later selectivity seems to have improved, probably moisture in the IF transformers drying out and the heaters are correct at 6.3 volts. The owner thinks that he has some capacitors of the right value so I will return it and recommend replacement of the overrun ECH81 and EL84 as well.

The moral of this tale is always check the HT first, just as you would for a City & Guilds Final practical examination, but then you only had one fault at a time in those examinations.

Best wishes,

Geoffrey.

TonyDuell · 29th Jul 2021, 5:35 pm

Quote:

Originally Posted by Ferguson 2000

The moral of this tale is always check the HT first, just as you would for a City & Guilds Final practical examination, but then you only had one fault at a time in those examinations.

One of the first things I learned when I started collecting/restoring vintage computers was 'check the power rails first for voltage and ripple'. No electronic device works properly if it's not getting the right voltages.

Ferguson 2000 · 5th Aug 2021, 3:58 pm

Hi Tony,

How vintage? I started with a NASCOM, it had an extra 1 K of RAM, from my memory.

Voltage rails are much more critical in equipment containing processors etc, I remember changing about 20 electrolytics in a power supply after which it worked, even though all the capacitors read OK on my ESR meter.

In the Blaupunkt an early selenium rectifier was used, had it been a valve or silicon rectifier then I do not think that the HT line wold have dropped more than a volt or two. That a 15 volt drop on the oscillator anode stopped it from oscillating suggests that there is another fault, perhaps the valve losing emission but there is only so much that I can do on a get it working basis.

Fifty years a go I would have changed the output and oscillator valves but they are a scarce resource nowadays, not to be replaced unless essential. The set will probably end up as a display item, I don't know how many the owner has but several per room.

Are the early Amstrads collectable? I have one in the loft in original box.

29th Jul 2021, 11:56 am	#1
Ferguson 2000 Tetrode Join Date: Jun 2008 Location: Stratford upon Avon, Warwickshire, UK. Posts: 80	Blaupunkt Barcelona 2342 I was asked to repair this along with a Ferguson 421 UXL ( see earlier posting) now it has been many years, perhaps decades since I last repaired a domestic valve radio. My last two valve repairs have been a Top Band Direction Finding receiver with D series valves, used very successfully by Eric Mollart the winner of countless DF events and a Marconi Q meter with it's LF/MF/HF oscillator. The set came with a photocopy of a badly damaged service sheet so onto the bench with it, I was concerned that unlike my work workbench of years ago this one is not earth free and does not have an isolating transformer, the mains voltage adjuster looked very easy to brush against. No way was I going to use my True RMS many digit meter on 2-300 volts so out came my Avo 8 which I prefer for fault finding with it's large analogue scale. As demonstrated it came on with background noise but no stations on any band except VHF. Frequency changer perhaps? Applying a test probe to the grid brought noise from the loudspeaker so onto the voltages helped by a Mullard 1964/5 wall chart for the ECH81 pin out, low anode volts on the triode oscillator and positive volts on the grid, onto cold circuit checks and L714 feedback from anode to grid is o/c. Very fine, difficult to solder wire and even harder to find where it should connect to but eventually I switch on and have negative volts on the grid but the anode is about 15 volts low and still no AM signals. Do what I should have done in the beginning and measure the HT at the smoothing capacitors, it is about 50 volts low, on another hunch (experience related inspired guess) I find a duster and remove the EL84 audio output valve, the HT goes up to 300 volts. Onto the grid with my Avo 8 and there are positive volts there, two possible candidates, both difficult to get at, C763 and C765 an in circuit check suggests C765 5000 pF @ 500 volts is leaky so I cut one end of it and measure again, yes about 3 Meg ohms, but what to replace it with? A series parallel combination of 1 uF surface mounts? After much searching I find a RS polyester .0033 at 500 volts, in it goes and I still have positive volts on the grid so cut the end of C763 25,000 pF @ 350 volts and measure, the leak is about 10 M ohms, where am I going to find one of those? Eventually it is a choice between 0.22 uF @ a 1,000 volts or 0.033 uF @ 1,000 so in goes the 0.33 uF and negative volts on the grid. Even better there is a programme on Long Wave and after cleaning the wave change switches Medium Wave as well. I set the mains selector to 240 volts rather than the 220 volts it is on and go and make a cup of coffee. Half an hour later selectivity seems to have improved, probably moisture in the IF transformers drying out and the heaters are correct at 6.3 volts. The owner thinks that he has some capacitors of the right value so I will return it and recommend replacement of the overrun ECH81 and EL84 as well. The moral of this tale is always check the HT first, just as you would for a City & Guilds Final practical examination, but then you only had one fault at a time in those examinations. Best wishes, Geoffrey. __________________ Best wishes, Geoffrey.

5th Aug 2021, 3:58 pm	#3
Ferguson 2000 Tetrode Join Date: Jun 2008 Location: Stratford upon Avon, Warwickshire, UK. Posts: 80	Re: Blaupunkt Barcelona 2342 Hi Tony, How vintage? I started with a NASCOM, it had an extra 1 K of RAM, from my memory. Voltage rails are much more critical in equipment containing processors etc, I remember changing about 20 electrolytics in a power supply after which it worked, even though all the capacitors read OK on my ESR meter. In the Blaupunkt an early selenium rectifier was used, had it been a valve or silicon rectifier then I do not think that the HT line wold have dropped more than a volt or two. That a 15 volt drop on the oscillator anode stopped it from oscillating suggests that there is another fault, perhaps the valve losing emission but there is only so much that I can do on a get it working basis. Fifty years a go I would have changed the output and oscillator valves but they are a scarce resource nowadays, not to be replaced unless essential. The set will probably end up as a display item, I don't know how many the owner has but several per room. Are the early Amstrads collectable? I have one in the loft in original box. __________________ Best wishes, Geoffrey.