Fixing a Bel Canto Evo 4 Gen II

Bought @bixby s broken unit, to try and fix myself.
First step, get replacement parts. The tripath chips are probably what failed. They are found in the Motorola dcp501 as @dBel84 told me, and I found a brand new one for just about $100 on ebay. Here it is

This is a cable receiver, av receiver, DVD player, 5 channel Amp. Pretty cool for 2003. Brand new, time to take it apart.
Still plastic on screen and batterys with remote!

Apparently sold for $900 originally, and while it does feel pretty hefty, the front looks and feels cheap. Doesn't matter, all I'm after is the tripath chips.

 

Oh yeah and the actual bel Canto unit should be here in a few days. The Motorola is 39lb for 5 channel Amp/receiver while the bel Canto is 60lb for 4 channel only amp.

 

First minor problem: the tripath chips are soldered in the motorola, and socketed in the bel canto. SShould be easy enough to work around, probably just solder them into the bel canto. And ill have an extra chip from the motorola.

 

You know I dont know why I didnt think of this but I could have just bought the chips alone... would have been cheaper and easier...
https://www.ebay.com/sch/i.html?_from=R40&_trksid=p2047675.m570.l1313&_nkw=Tripath+TA3020&_sacat=0

Honestly still might do that because getting these chips out is kinda hard. Lots of desoldering... well there is $100 wasted maybe. Too late to put the motorola back together.

 

as long as they are not fakes . Not sure why the forum chatter didn't discuss buying the chips directly. I should have looked too

 

Yeah, the one listing seems pretty sketchy "PARTS ARE NEW BUT SOME BONEHEAD SCRATCHED OUT THE LABEL - I HAVE SOLD TONS OF THESE 100% GUARANTEED TO WORK"
But others seem alright. For now ill see if I can desolder these existing chips, if not, then Ill go just get the chips.
I did harvest the transformer from the Motorola unit though, its a pretty beefy toroidal transformer. Probably get some of my money back selling that, or save it for any later project.

 

All the old tripath stuff is long out of production now right?

 

Yes, only stuff you will find is NOS. I have a stash of the "100W" chips but no 3020s unfortunately.

 

Wow that's a big transformer compared to the Motorola...

 

Also an interesting note, in the motorola unit the tripath chips had heatsinks, here they dont. I wonder if that is related to the failure

 

I ordered some new tripath chips, just received and installed them. Maybe the amp works now, but I don't have any speakers to test it. Time to finish my speakers I guess.

 

So it was fixed for a bit, but now idk what to do. Have been troubleshooting a while.
Here is what I found:

All voltages at test points on both channels are good.
The left channel is the only one that works, regardless of if I switch around the wires or not.
The relay clicks over and over again on the power/protection board: regardless of whether the amplifier boards or the transformer is connected to it or not. Sometimes it takes a bit to click, sometimes it's right away. Both relays seem to click.
The protection light doesn't come on though.

I'm out of ideas. Close to giving up, but not there yet.

Thoughts?

 

Do you have a circuit diagram for it?

I know this is risky but have you tried changing the chips from one side to the other?

If the relay is dc sensing, it would be good to see where it is coming from.

 

Nope, could not find a circuit diagram. I was going to change the chips but couldn't find my chip puller. I'll have to keep looking for it and try.

 

I've switched the chips around- same channel not working.

I don't know what it could be now...

 

if you like, and are not in a major rush, I could pick it up when I grab the Aegir and take a look.

 

Yeah, I'm not in a rush, as long as I have a working amp. I'll continue to see if I can figure anything out but don't have too many ideas.

 

Update:

well @spwath entrusted this to me quite some time ago and I have been working on it intermittently as I had time.

The first thing I noticed was some "capacitor juice" leak on the underside of one of the boards




It was agreed that we would do a full amp recap and I got to removing the caps



one side complete



both sides done



sadly still no joy - this was the first time I had tried to power up the amp but it kept shutting itself down and rapid cycling. This is not good for amp amp, so I disconnected the transformer and determined that the behavior was in the power up relay circuit.



After much searching, I could not find a replacement for the transformer and decided a little ingenuity ( or rough hacking ) was in order. I dug through my parts bin and found a 12V SMPS that I could rig up to supply the 12V needed by the circuit to trigger the relays. This did the trick and I was able to get stable power to both amp boards. I wish I could tell you that was the end and the amp was fully functional but we were only half way.

One board powered up and played music as it should, the other did not. After some investigation I determined that the amp itself was working as it should but the output DC sensing / relay was not. The small SMD transistors were only identified by 1A and 2A = after some web searching I found a document that listed some manufacturer demarcations for NPN and PNP transistors for the 1A and 2A parts. I duly ordered up 5 pairs of various BJTs as well as the mosfet driver and set about systematically removing the transistors, soldering in new ones , testing .... repeat x 5 without any success. the voltages without the relays in place matched the other board , replacing the relays did not solve the problem. Ultimately I decided to bypass the relay and although the start up thump was enough to startle any sleeping babe, I figured it was better than no music at all.

After closing it all up and putting the amp back in the box to get back to its patient owner, it dawned on me that I could just use an external relay board which I knew I had picked up for a project that got waylaid

and here you have the functional end result - clearly hacked but ready for many more years of happy function.



I am glad that I do not have to move this beast around anymore - it weighs a ton.
..dB

 

Super @dBel84 saves the day again!

 

I think I pulled a muscle just looking at that transformer