SR technology jam 150 plus (Schertler) keep burning resistor R2

Thread Starter

Cesco77

Joined May 23, 2022
269
Hi everybody I'm new to the forum so thank you for having me! I did sign in with the hope that someone can help me on this! I have this amp from a friend who ask me if I can fix it for him.
The problem with this is that I get power from the power supply but the relay doesn't click I did check all the part, resistor, capacitor, etc all the obvious but I can't find anything wrong! I really need help as my knowledge is limited! If someone could address me on the right direction will be great, thank you in advance
 

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sghioto

Joined Dec 31, 2017
3,271
Check the voltage on the collector of Q1 when first powered ON. It should rise and when above 6 volts the relay should turn ON.
 

Thread Starter

Cesco77

Joined May 23, 2022
269
Thank you for reply, I did remove and check Q1 today, but I haven't check the voltage when installed, should I do that even if I know that Q1 is good?
 

Thread Starter

Cesco77

Joined May 23, 2022
269
Ok I will do, give me 30-40 min! The problem start after changing the TDA7294 I change it because it was emitting noise, cracking noise intermittently, I read that TDA7294 could be the problem so I change it, it was ok for 10 min after replace it, than it stop working and it blow up cap C3 and C4 which I replaced, but now it does not power up...
 

Thread Starter

Cesco77

Joined May 23, 2022
269
I have 4-5 up and down, never 6 but I can't understand! Sorry for late reply but something happen, I replace tda7294 again and is working!!! I take it of from old bose broken amp! Thank you very much for your help really appreciate, at the moment is working, hope it will
 

Thread Starter

Cesco77

Joined May 23, 2022
269
If it's 4 to 5 volts then that's normal.
You're welcome, good luck.
Bro, I didn't test it properly, now I found out that the guitar input does't work! it work with the normal line in (hifi input) but not the guitar input and it's make noise at low volume...Any suggestion? I'm going to bed now, please if tomorrow you can help with this other issue I will appreciate! Thank you
 
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Thread Starter

Cesco77

Joined May 23, 2022
269
If you can post the complete schematic that would certainly help?
Thank you so much, but unfortunately I haven't got the mixer part that is all I could get from the factory, what part do you need? Prior to change the tda7294 (a part from the noisy) it was ok, I didn't touch anything on the mixer side...Anyway if you need I can ask if they could send me the missing parts. Good night bro, tomorrow I got up early..Thank you again
 

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Thread Starter

Cesco77

Joined May 23, 2022
269
Hi, could anyone please help me on this? I have this amp which I have change the TDA7294, after i start it up it was worked 10 min then it blow up 2 resistor and capacitor 2 cap R1 R2 C3 C4 I change them and it power up, but it has noise and the input for guitar does not work, I can connect my stereo on the "line in input", a part for the noise at low volume, at highest volume is more or less ok! I don't know what to do, I have checked many component and I'm running out of idee, I'm stuck, I need more expertise, I'm not an expert on power amp please help! Thank you in advance
 

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Thread Starter

Cesco77

Joined May 23, 2022
269
Hi
The amp make high and low humming noise at the start, than those noise decrease a little when worn up but always there, the 3 guitar input are not working, no one! The only working one is the entry "line in" what could it be? as I mentioning the only thing I have done is replace TDA7294 and 2 cap and 2 resistor that blow up after I replace this transistor as suggest to eliminate intermittent cracking noise..I can't get the schematic at the moment, I email them but not answer yet
 

Thread Starter

Cesco77

Joined May 23, 2022
269
What part of it do you need? they don't wont to send all the schematic (don't asking me why) but they can send the required parts only. Please let me know
 

Thread Starter

Cesco77

Joined May 23, 2022
269
Thank you for reply! So the mixer one? The mixer is connected with a ribbon cable to this board, I didn't touch it at all....Anyway I did contact the factory already and I hope they will send it to me soon! This is a very good amp and it is very expensive to buy! It deserve to work again! The sound was amazing......
 

Thread Starter

Cesco77

Joined May 23, 2022
269
Could you please tell me (if you know) if all the TDA7294 are the same? I did replace it with one that I got from ebay, after install it the problem start! It blow 2 resistor and 2capacitor (104 capacitor) so a replace the burned component and it happen again! Than I replace the TDA7294 with one that was on a old Bose amp! With this chip the cap and resistor didn't burn but now I have this other problem (no input working) as explain to you! Is it possibile that the TDA7294 is not the same of the original and it made all the problem that I got now?
 
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