Alba 3112: completely disoriented

[aechopan]

Hello!

Sorry for the radio silence for the last month... overdose of Christmas.
I managed to replace every component in the way you all recommended me and this seems to be looking good... but I still have an issue to solve: the selection of voltage, because i find the instructions in the manual quite vague, so not sure how to do it. In order to set the device on 240V, "both ends of the link should be connected to A", when for 110V it should be A and C. Thats why I connected the yellow end in A, even though I it was attached to C.

Before I changed the settings, this was the configuration:

____ A black (i guess one of the both ends)
¦ ¦
¦ ¦
----- B green ring cable, self connected
¦ ¦
¦ ¦
----- C black to C31, red and yellow

I wonder if the code color is related with the other yellow and red cables visible in the picture coming out from what i guess is the rectifier of voltage.
I am quite excited!

[Ed_Dinning]

Hi, as a general rule of thumb, the green lead in this case is the "selector cable".
If it is looped back on itself it is not linking out any resistance, so the set is on the highest available voltage i.e. 240V.

Set like this and then power up using a lamp limiter. It should work and will not be damaged. It will probably be low in voltage and any voltage readings you take will be lower than service sheet values as would be expected.
You can then try running without the lamp limiter and it should work fine with voltages nearer service sheet values.

Ed

[aechopan]

Thanks, Ed!

I still don't understand why the selector have both ends in B, when the service sheet says both in A...

[ms660]

Don't panic...It should be easy to sort out, the Trader sheet schematic is drawn correctly and the voltage tappings are explained correctly so far as I can make out, so working from that, there should be three points that connect to the bottom tag in the photo which is tag C on the schematic and the layout drawing, so start from there, 1) and follow through to 2) and 3)

Mark each stage on the schematic/drawing as you progress.

1) Connected to tag C: One needs to be from the live side of the mains bypass capacitor (C31) One needs to be from the AC input side of the rectifiers surge limiter (R23) and one needs to be from the switched live output on the mains on/off switch.

2) Remove completely the green wire link that's connected to the next tag up, that's tag B, that should result in nothing being connected to that tag.

3) The top tag is Tag A, connect the wire that leads back to the heater tag of the rectifiers valve holder to Tag A, also connect both ends of the previously removed green link to that same tag.

The mains voltage setting arrangement for the receiver should, all being well, be set to 225 to 250 volts as per the manual which should be ok for your location.

EDIT: Post crossed.

Lawrence.

[aechopan]

This is emitting a veeeery exciting buzz!!
After connecting the device on power, I wait about a minute and then the valves start to buzz and eventually the speaker emits some cracks.

Sadly, that is it for the moment, since the capacitor I replaced (the lamp shunt, R24) produces such an insane amount of heat (note that i used a 100 Ohm/ 3W resistor) that the soldering tin melts... how can I fix that?

This is looking very well, I am very thankful for the support, guys!

[Ed_Dinning]

Hi I suggest you use the lamp limiter as the lamp shunt should not get that hot, so you appear to have a problem in the heater circuit.
A lamp limiter (say 60w max INCANDESCENT type bulb) should keep things under control to allow you to take voltage readings without any expensive damage taking place.

Ed

[crackle]

I assume you have no working dial bulbs fitted. Can you measure the AC voltage across R24, and the DC voltage across R23, from those we can see what sort of current is passing through.

Mike

[aechopan]

Dear all,

I have spent some time on it after building a lamp limiter.

The AC current measured in R24 is approx. 0.1A, and the voltage 18V. I guess the reason why the soldering tin melts is the high amperage.

On the other hand, I measured voltages in V5, and the potential difference between the pin in the centre and the rest is around 80V, which is quite different from what I read in the specification: 182V/200V.

[Al (astral highway)]

Hello,

I just read Graham's post no 19 encouraging you to use a suitably rated resistor (2W).


The advice is spot on but you say you tried a 3W device and the solder melted. This must be a fault condition.

Can you hand draw the relevant part of the circuit with your amendments?

[Station X]

0.1A flowing in a 100R resistor is only 1 watt. ie 0.1 * 0.1 * 100.

On the other hand 19V across a 100R resistor is 3.61 watts ie 18 * 18/100.

Something doesn't add up.