The Workbench

Re: None functining tuning meter and S lamps Beocenter 3500 / Beomaster 3000

Dillen — Sat, 20 Mar 2010 18:00:02 GMT

Well done !

There's nothing like finding faults that were introduced by a previous "repairer".

Martin

Re: None functining tuning meter and S lamps Beocenter 3500 / Beomaster 3000

Ben — Sat, 20 Mar 2010 11:48:40 GMT

Well, the fault was two different ones,

The tuning meter problem was to do with the trimpots controlling the zero offset and gain. The one that controls the gain must have a bad area on the track, when adjusted outside this bad area, the meter works great, although probably a little inaccurate - I will aim to change this pot when I order some parts next week.

Next, the 'S' lamps - Transistor TR9 did test as good, but it had been installed wrongly. If you look at the circuit diagram, the configuration of the pads on the PCB is E B C, but the transistors legs are E C B!

It had been installed incorrectly, probably in a previous repair attempt. Upon swapping the legs of the base and collector, the lamps functioned perfectly.

Re: None functining tuning meter and S lamps Beocenter 3500 / Beomaster 3000

Dillen — Thu, 18 Mar 2010 15:05:12 GMT

Too low antenna signal or a tuner sensitivity fault.
You can test the meter, they are sometimes mechanically seized.
The signal meter will normally give a reaction if you put an ohm-meter across it.

Martin

None functioning tuning meter and S lamps Beocenter 3500 / Beomaster 3000

Ben — Thu, 18 Mar 2010 13:48:31 GMT

I'm trying to figure out why neither the tuning meter or S lamps work in this Beocenter 3500 I have.

Both transistor TR9 and TR16 on the IF board are good. I shorted the collecter and emmiter of TR9, and the lamps function as they should. The voltages I have on TR9 and 16 are similar to what the manual says.

Are there any common problem points I should be looking at?