One of mine stopped working recently and I was hoping to fix it...
I've checked the trafo an it appears to be ok, it's giving 18V ac on the secondaries.
There are 2 heatsinked chips say LM3886 on them, so I guess this makes it's amplifier similar to the infamous gainclone?
There are also 2 what appear to be op-amp type chips, which I assume are the crossover/pre-amp part of the circuit...
Where would be the best place to start in finding what is wrong with this circuit?
I've checked the trafo an it appears to be ok, it's giving 18V ac on the secondaries.
There are 2 heatsinked chips say LM3886 on them, so I guess this makes it's amplifier similar to the infamous gainclone?
There are also 2 what appear to be op-amp type chips, which I assume are the crossover/pre-amp part of the circuit...
Where would be the best place to start in finding what is wrong with this circuit?
If you could post (or e-mail me) the schematic of the TR6 board that would be great. My e-mail address is mike_hunt_79uk at yahoo.co.uk (change the at to @).wxn said:
I'm getting around +-25V on the legs of the large smoothing caps. I cannot see any voltage regulators on the board tho, so I'm assuming the op-amps are running of +-25V?
The LM3886's do get warm tho, so I'm assuming they are ok... I'm assuming the switch is ok as the LED lights up and I get quiet hiss thru the speakers... but if it's a dual gang switch then I guess one of the gangs could not be working.
One more thing, if I do have a signal going into the board, I can hear it very faintly thru the speakers if I put my ear up to it... So I'm thinking the signal isn't quite making it to the LM3886's.
I haven't tried tracing the signal with a a scope yet, but I will do once I get more free time later on tonight with any luck.
I managed to grab a few pics, I'll post them up in case I'm missing anything obvious?
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Thanks for send the schematic, it makes fixing things much easier.
It turns out the on/off switch wasn't switching the MUTE pin on the LM3886's, yet it was switching the LED on and off ok. They're on separate gangs so I guess one of the gangs in the switch has gone.
I'll try switching the MUTE pin with an external switch to see if this fixes things...
It turns out the on/off switch wasn't switching the MUTE pin on the LM3886's, yet it was switching the LED on and off ok. They're on separate gangs so I guess one of the gangs in the switch has gone.
I'll try switching the MUTE pin with an external switch to see if this fixes things...
Good idea, the treble definitely sounds like it could be improved (, I found this out today - see my mod )...
After shorting the mute pin switch gang to the LED gang, the amp is now giving out sound, but it's still pretty quiet, and reaches clipping very early... My zeners are giving out +-15v ok also, so once I get hold of a scope I'll have to trace my signal. I guess the LM3886's could have burned out, I've found the backplate and transformer can get pretty hot...
I figured it wouldn't hurt to remove the working PCB from the other speaker, as I'll be able to compare them and it would really help finding the problem with the non-working pcb.
I still wanted to listen to the speakers however, so I've gone for some external amplification. I made my own replacement backplates out of 4mm perspex and hot glued some 4 pole speakon jacks, then connected up the woofer and tweeter.
I used a 41Hz.com Amp9 amp which is 4 channels and a DCX2496 as a crossover I can still keep it bi-amped...
The sound quality has definitely improved, the treble or a lot more refined, but I still am going to try and fix the LM3886 PCB's tho, plus change the caps to see if I can get them to match the Amp9 for sound quality.
)... After shorting the mute pin switch gang to the LED gang, the amp is now giving out sound, but it's still pretty quiet, and reaches clipping very early... My zeners are giving out +-15v ok also, so once I get hold of a scope I'll have to trace my signal. I guess the LM3886's could have burned out, I've found the backplate and transformer can get pretty hot...
I figured it wouldn't hurt to remove the working PCB from the other speaker, as I'll be able to compare them and it would really help finding the problem with the non-working pcb.
I still wanted to listen to the speakers however, so I've gone for some external amplification.
I made my own replacement backplates out of 4mm perspex and hot glued some 4 pole speakon jacks, then connected up the woofer and tweeter.I used a 41Hz.com Amp9 amp which is 4 channels and a DCX2496 as a crossover I can still keep it bi-amped...
The sound quality has definitely improved, the treble or a lot more refined, but I still am going to try and fix the LM3886 PCB's tho, plus change the caps to see if I can get them to match the Amp9 for sound quality.
You're right, I guess the accountants must have stuck their oar in and tried to cut costs wherever they can...wxn said:
Usually pro stuff is built a little better...It is a shame really as I'm always worried something might melt if I crank the volume... Still, at least with my current setup I can crank it all I want and the amp is ClassD so it carely gets warm...
Event did also make a TR8 XL which was basically the same as a TR8 with a more powerful amp and a toroid trafo. I've seen a photo of the back and it does have a bigger Alu plate but not anything resembling a proper heatsink...
Yeah well I'm in the process of redoing these speakers. I had a pair of 200W trafos, nice heatsinks, some spare LM3886 and willingness to redo everything from scratch, including filters and input section. I'll post pictures later
Nice, some pics would be great once it's finished.
I'm tempted to do something similar, maybe using some sort of Tripath chip amp as they need very little power and heatsinking...
The LM3886's seem to have a lower noise floor tho, but I guess having very short speaker cables helps this a little in the active setup.
Nice, some pics would be great once it's finished.
I'm tempted to do something similar, maybe using some sort of Tripath chip amp as they need very little power and heatsinking...
The LM3886's seem to have a lower noise floor tho, but I guess having very short speaker cables helps this a little in the active setup.
HEY Whats up guys im having the same problem, low volume and everything seems fine nothing noticeable as burnt and the lm3866 are getting warm, i have the same tr8 but my heatsink is the whole back plate......... i get sound but its very low and the input sensitivity noob makes it louder but its still barely hearable any ideas hey maybe i can get that schematic for the tr6... email is ramseycontreras@gmail.com
Apologies for not replying sooner, I've not been on this forum for ages!
Hi, thanks, I eventually replaced the whole lot of electronics with a digital XO and class D amplifiers, I gave up with the original electronics in the end.
Mine was +-24Vac I think, I still have them, you could probably use a toroid type which may give better results.
A bit late post I know, sorry for that. Attached one picture of the new crossover and a pre-rebuilding photo of what I wanted it to look like in the end. It turned out just like in the photo with some additional screws here and there and the trafo inside. I only did one speaker this way because after listening to them both I came to a conclusion that the original sounds better - somewhat more clear, more "airy". So what my oversized heatsink barely gets warm even when blasting away.. They actually sound pretty much the same, even the stereo image doesn't get messed up (I'm listening to them both right now) but one ear always gets that extra bit of detail in highs.
So I was thinking about leaving the same sink, same trafo but instead of active xo, put a passive one inside. Just to test if all the cheapo capacitors in the active path were to blame.
So I was thinking about leaving the same sink, same trafo but instead of active xo, put a passive one inside. Just to test if all the cheapo capacitors in the active path were to blame.
Attachments
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.