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T1 amp have gone silent

T1 amp have gone silent

I have been using T1 for more than 1/2 year, then recently I detected burning smell and a few seconds later the amp went silent. I immediately switch it off and open up the casing to check for any burnt parts but could not detect any. The burnt smell I noticed came from T1 and not from the smps board. An hour later I switch it on again and found that green LED is lighted but red LED is not, but still no sound.



But from hifimediy manual mention: I quote " The red light means that there is power connected, the green light means that the relays have turned on and the amp is functional. Normally both lights should come on. If the green light does not come one, either the voltage is too low or a technical problem has occured "



But in my case there is no red LED on but green LED is off !!

I am at a loss on how to proceed further from here to diagnose the problem.



For info I am using ConnexElectronic smps300R 36V with no modifications on my T1 sta510a in a well-ventilated metal casing.
When I switch on the amp, red led off, green led on; If I switch it off, the green led will turn off after 5 secs with a click sound.
I did some basic checks with a multimeter when the amp is on:
1) T1 amp is still getting about 35V from the smps ( but red led is off, so which component is out........anyone can help? )
2) Left output channel - 1.2mV, Right output channel - 0mV

That's about all I can think off to do some basic diagnostics, as I am a complete novice at electronics.
Hopefully someone can point out to me on what to do next..............anyone?.....Nick perhaps!
Hi, pls check the voltage of input of 78M05 regulator. about 10~20V is normal. And the output of 78M05 should be 5V to ground.
@yubing

Input / output voltage of 78M05 regulator is 0.14 / 0.04V.

So if this regulator is damaged, will it cause other components to fail also? Or the burning smell that I detected comes from the regulator only.
Hello,

I have the exact same problem with my T1. Green but no red LED. I've used the T1 STA510 with a SMPS300R 38V (230V) for months with no problems. But suddenly when I tried my amp on a different set of speakers (16 ohm) I got no sound. I didn't notice any burning smell. From the 78M05 regulator I measure input/output voltage to ~0.19/0.05V.

What has happened and more importantly, can it be fixed? :)

Thanks,
Soren
Hello,



I have the exact same problem with my T1. Green but no red LED. I've used the T1 STA510 with a SMPS300R 38V (230V) for months with no problems. But suddenly when I tried my amp on a different set of speakers (16 ohm) I got no sound. I didn't notice any burning smell. From the 78M05 regulator I measure input/output voltage to ~0.19/0.05V.



What has happened and more importantly, can it be fixed? :)



Thanks,

Soren



Hi, yes it can be fixed and quite easy.

33

Follow the sch, remove the Q4 (BC639) and add a 200~330ohm 1W resistor. Also repalce C32 with a 50V rating one. A 100uF 50V caps should be ok.
Hi, yes it can be fixed and quite easy.

33

Follow the sch, remove the Q4 (BC639) and add a 200~330ohm 1W resistor. Also repalce C32 with a 50V rating one. A 100uF 50V caps should be ok.



Your reply came just a little bit too late. Thanks anyway. Earlier, I tried to replace the damaged 78M05 with a new one, but due to my inexperience and haste, the output trace of the 78M05 on the board became detached and I have no way to solder back my new 78M05. In this case, can your above solution still work?



Anyway I have already ordered a replacement board but I think it has got stuck in the Christmas traffic.
Your reply came just a little bit too late. Thanks anyway. Earlier, I tried to replace the damaged 78M05 with a new one, but due to my inexperience and haste, the output trace of the 78M05 on the board became detached and I have no way to solder back my new 78M05. In this case, can your above solution still work?

Anyway I have already ordered a replacement board but I think it has got stuck in the Christmas traffic.

Hi, sorry. yes just do the repairement and you can use a wire to jump the output of 78M05 to board.
This is the top layer of pcb.
34
You can find the 5V on C34 positive pin.
Hi, sorry. yes just do the repairement and you can use a wire to jump the output of 78M05 to board.

This is the top layer of pcb.

34

You can find the 5V on C34 positive pin.



Thanks for the reply.

I do not have a chance to try out the fixed yet because my new T1 with mcap arrive and I use that instead.



There is one problem though.

Both the left and right speakers emit quite a loud hissing and cracking sound when I place me ear about 1 foot away when there is no music.

I switch off the connected dac but the hissing/cracking sound loudess remains the same level.



By the way I have adjusted both the left and right channel to as close as possible to 0mV. ( it came with +160mV right, -150mV left)



I did not detect any hissing sound with my previous T1 (version 1.2)

Is this normal with this new T1 (ver 1.3)?
Hi, yes it can be fixed and quite easy.
33
Follow the sch, remove the Q4 (BC639) and add a 200~330ohm 1W resistor. Also repalce C32 with a 50V rating one. A 100uF 50V caps should be ok.

Hello,

I have this same problem. Unfortunately in my haste, I lifted both solder pads to the C32. Is there a way to use jumper wires from the new capacitor leads? Where would you connect the new resistor when replacing the BC639? I have no music at home, so I would be really appreciative, if you could find a solution for me.

Thanks
Can anyone help?
Hi, look at the attached drawing for where to connect the resistor.

64
Hi, look at the attached drawing for where to connect the resistor.



64



Thanks for the answer Nick. Really appreciate it. What can I do about the lifted solder pads for the C32? Is there a way to use jumper wires. If so, where do they need to be connected to?



Thanks
Hi, you can use the input of 75M05 (pin1) to "+", and ground as "-".

There is also a free pad marked +9V, which can be used.

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