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
Normal 0
I have two Beocenter 3500s and two problems. I’m a newbie with no useful knowledge of electronics but as an ex-jeweller I am used to fiddling with intricate things rather carefully. I can solder and use a test meter, although I do not always understand what it is telling me.
1) Unit 1 works fine except that when it is switched on there is a rumbling, rather like distant thunder, from the base output on one of the speakers. This dies away after a few seconds. The problem has developed over the last month or two and seems to be getting worse. The speakers are Beovox 3800s that I’ve recapped (thanks Dillon). The base is also distorted on one speaker when playing some LPs with emphasis on low notes. Think symphonic or organ music. The only thing that I’ve done to the Beomaster 3500 since I bought it a couple of years ago is dig all the way down to the switches and treat them and the pots with Deoxit, which made a huge difference. I’ve done the following tests using the Beovox 3800s: Swapped the speakers round on No 1 speaker connections. The speaker connected to LH1 is affected both ways round, so I assume that the problem is not with the speakers. Connected the same speakers to RH2 and LH2. No rumbling or distortion problem other than slight hum at volumes over about 4 on the slider noticeable only when nothing playing. Connecting a pair of CX150s to LH1 & RH1 the problem is far less noticeable but still there. So rightly or wrongly, I’m assuming the problem is confined to the 3500’s LH1 output and everything else is OK. Is there any chance that there is a simple answer?
2) Unit 2 kind of came free with the Beovox 3800s when I bought them on Ebay. It seems to have had a hard life but it had a reasonable stylus although the turntable isn’t working. The tuner works, so I’m just using it for radio and iPod output in my office. The problem is that I am only getting output to speakers on the RH1 and RH2. Swapping the speakers round makes no difference. I assume that this is likely to be much more difficult to sort.
Any suggestions will be greatly appreciated.
1, Could be bad capacitors. Could also be a bad transistor. Both can get noisy. Grab a service kit with capacitors, trimmers etc. and replace the lot.
2. Not necessarily more difficult. Could be anything from a simple bad capacitor to a completely burned output stage. Look for DC on the speaker output.
Martin
Many thanks Martin and apologies for the mis-spelling in my post.
1. Not really.Having said that, it could be that the problem is just capacitors, as mentioned earlier, but replacing trimmers does requiresome alignment involving tools, instruments and some experience and knowledge.But it could also be, that something more "complicated" is wrong and servicing complementary DC-coupled amplifiers canoccasionally cause headaches even for trained tech guys.It's rarely safe to diagnose a problem like this from a distance
2. Not really.DC on speaker outputs is a no-go. It typically tells that a more "structural" failure has occured in the output stage.One or more output stage transistors, drivers etc. could be at fault if the center rail is pulled up or down.
Sorry Martin, and thanks for that. UK politics has rather claimed my attention over the last couple of days for obvious reasons.
I’m having a long hard think about what you say and assume that the issue of adjusting trimmers can’t be dodged as replacing caps and transistors will require different settings on these. I’ve been looking for some kind of basic guidance on how to approach this but at the moment can’t find any at Beoworld.