ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hey all!
I am trying to fix a Beomaster 5500 that has right channel a bit quieter than left. I did already install new relay and also setup the no load current on both channels to 0.11mV on test points (I did not replace trimmers as they function properly).
Relay was bad so I had to replace it anyhow, but this difference in channels comes through on headphones too (so it was not relay issue).
I now quickly went through all the transistors on each channel with diode test and compared them, but I did not find any difference (IC200,201,205, TR 201-201 and 4xx respectively).
I also noticed that when I set volume to 24 left channel (louder one) did actually show more mV on the test points for idle current...Left was around 60mV where right was around 30mV.
Any other tips?
Update: I traced the signal through channels and the difference is visible on E and C on TR205 - BF423. The good channel has voltage level of 11.2V on C, bad one 3.6V. I ordered the transistor and let's see...
What about the emitter voltages?Has R215 or R216 burned?
Martin
All measure OK, also other resistors.
After switching over all transistors between left/right channel I saw that well....it was NOT transistor :)
I then started to take off the capacitors and measure them one by one and VOILA...it was C206! Instead of 100uF measured cap. was in nF.
Both channels now OK!
I am a bit worried about heat though...no load current is set to 11mV and still afer playing radio for 5 min heatsink gets to 50C (measured with laser thermometer). Is that that normal?
I measured all components with laser thermometer and it does not seem to be any different on right or left channel.
The output stages heatsink is shared with the voltage regulators. The heatsink willbe a little more than handwarm after 5-10 minutes. That's normal.
Thnx dillen, it got too warm then....I found bad caps in voltage part C8, C9...Replaced all and now it seems to run as it should - warm not HOT.