Classe DR-25/25 repair

[Ketje]

I found this, hope not to many mistakes, transistor nr wrong too.
Made some mod's
Mona

 

[ungie]

I found this, hope not to many mistakes, transistor nr wrong too.
Made some mod's
Mona

Thank you, but that schematic is for later Model 25s and does not match my PCB.

 

[ungie]

And that is why everyone moved on from this thread. The first step is ALWAYS to check the power supply. You were way past that point right from the beginning.

You will note above that I DID check the power supplies first. What I did not do was to check them with a scope, only a meter. A mistake and one that I will not make again when diagnosing failed equipment.

Doesn't surprise me a bit. As I said, what you get with Classe is styling and innovation at the expense of, well, reliable and tested designs.

Your opinion. I'm not aware that Classe has any massive failure issues over the decades...probably no more than any other audio electronics company. I'm not defending their circuit design capabilities, but they have managed to stay in business longer than most in the higher-end audio industry, and that has to say something.

Most designs REQUIRE that the cover be on the unit to achieve the designed air flow past the heat sinks. This design may still be lacking, but just understand that running it with the cabinet off will almost always mean higher heat.

Noted. I will make more measurements of these device temperatures once I have the unit knit back up.

Well that's certainly a tall order unless you have nothing better to do. Replace your incorrectly specified main filters and re-assess. There is really no need to start replacing everything in sight. I wouldn't stress over the Q6/Q9 problem. Why start re-designing the unit? Put in a cooling fan and maybe a vent and you are done. Popping in different transistors won't make it produce less heat. You simply need to remove the heat more efficiently.

This amplifier is over 20 years old and runs warm/hot. My SOP is to replace all electrolytics if the unit is something you are going to hang on to and keep in service, so replacing less than 15 parts is not a big deal. The amplifier is also apart right now and all PCBs are easily accessible. As to changing the circuit, sgrossklass has suggested that this design "error" could pose a reliability issue. This amp was already back at Classe for service over a decade ago for a dead channel. Maybe that error was the cause of the failure?

Regardless, thank you and everyone else in this thread that has contributed their input. It is much appreciated.

 

[Ketje]

Thank you, but that schematic is for later Model 25s and does not match my PCB.

Still another Classé
I changed the schematic you posted at #16 the same way.
Hope this helps.
Mona