As if one power supply mystery wasnt enough I have another one which I cant figure out.
This is my first Hifonics amp. Looks very good, compared to the budget stuff I fix most of the time
At first I powered the amp up, it did not draw current, did not go into protection only the sound was distorted on both channels. Dont have a scope so I can only tell what I hear. Seems that there is no noise, higer frequencies sound right but bass is bad on both channels. Sounds like when I use a current limiter and turn the volume so far up that limiter starts to actually limit and lower frequencies get "clipped".
So I measured voltages between ground and:
Output transistors: 0V, 12V, 0V or 0V, -15V, 0V.
PS FETs: 1,8V, 10,6V, 0V
Rectifiers: 22V, -15V, 19V or 19V, 12V, 22V
I assume that rail voltage is not supposed to be 12 to 15V?
PS Chip is KA7500 BD, so I dont know if 1,8V is correct on gates of FETs.
Datasheet says that Common Collector output Vcc is 1,5 to 2,5V. Is Vcc what is sent to gates of FETs?.
10,6V on drain is also low. Same voltage between GND and + terminals
Without remote I got 0V, 12,5V, 0V on FETs
Arent rectifiers supposed to have 0V on two of their legs?
What I tried:
Removed rectifiers to see if voltage between + and GND still drops to 10, yes it does. Rectifiers test out OK. Highest voltage on drain I got when I left in only T1 side FETs. Then drain had 11V on it.
PS FETs: two gave funny readings, I measured and measured again out of the board and finally one gave out the secrets of its soul and shorted. I swear it was not shorted before. Again I replaced all temporarily with IRFZ44Ns. Before source resistors got quite hot, now R72 gets hot (see pictures).
Voltages on rectifiers changed a bit after replacing FETs, now they have: 8V, 12V(-15V), 9V on their legs.
Can not measure voltages on PS chip because I cant get my probe there, transformer is in the way.
Can I remove the driver board and run wires from pins to main pcb?
This is my first Hifonics amp. Looks very good, compared to the budget stuff I fix most of the time
At first I powered the amp up, it did not draw current, did not go into protection only the sound was distorted on both channels. Dont have a scope so I can only tell what I hear. Seems that there is no noise, higer frequencies sound right but bass is bad on both channels. Sounds like when I use a current limiter and turn the volume so far up that limiter starts to actually limit and lower frequencies get "clipped".
So I measured voltages between ground and:
Output transistors: 0V, 12V, 0V or 0V, -15V, 0V.
PS FETs: 1,8V, 10,6V, 0V
Rectifiers: 22V, -15V, 19V or 19V, 12V, 22V
I assume that rail voltage is not supposed to be 12 to 15V?
PS Chip is KA7500 BD, so I dont know if 1,8V is correct on gates of FETs.
Datasheet says that Common Collector output Vcc is 1,5 to 2,5V. Is Vcc what is sent to gates of FETs?.
10,6V on drain is also low. Same voltage between GND and + terminals
Without remote I got 0V, 12,5V, 0V on FETs
Arent rectifiers supposed to have 0V on two of their legs?
What I tried:
Removed rectifiers to see if voltage between + and GND still drops to 10, yes it does. Rectifiers test out OK. Highest voltage on drain I got when I left in only T1 side FETs. Then drain had 11V on it.
PS FETs: two gave funny readings, I measured and measured again out of the board and finally one gave out the secrets of its soul and shorted. I swear it was not shorted before. Again I replaced all temporarily with IRFZ44Ns. Before source resistors got quite hot, now R72 gets hot (see pictures).
Voltages on rectifiers changed a bit after replacing FETs, now they have: 8V, 12V(-15V), 9V on their legs.
Can not measure voltages on PS chip because I cant get my probe there, transformer is in the way.
Can I remove the driver board and run wires from pins to main pcb?
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.
An externally hosted image should be here but it was not working when we last tested it.
New results on FETs. Black probe on non-bridging speaker terminal.
2,25V
10,33V
0,3V
or
2,6V
10,33V
0,3V
Rectifiers, black probe on non-bridging speaker terminal:
1,6V
-15V
1,8V
1,9V
14,5V
1,3V
2,2V
14,3V
2,2V
2,2V
-13,9V
2,2V
All outputs are out, amp powers up, does not draw current.
I heard some faint sizzling noise coming from T2 transformer, after twisting and turning it I got 0V, -17V, 0V on one of the rectifiers.
After some more twisting amp started to draw some current. Twisted transformer back and current draw went to minimum.
2,25V
10,33V
0,3V
or
2,6V
10,33V
0,3V
Rectifiers, black probe on non-bridging speaker terminal:
1,6V
-15V
1,8V
1,9V
14,5V
1,3V
2,2V
14,3V
2,2V
2,2V
-13,9V
2,2V
All outputs are out, amp powers up, does not draw current.
I heard some faint sizzling noise coming from T2 transformer, after twisting and turning it I got 0V, -17V, 0V on one of the rectifiers.
After some more twisting amp started to draw some current. Twisted transformer back and current draw went to minimum.
By terminal windings you mean on the terminals side, yes?
Because I removed both of them and added insulation to the other side. :S
That did not help. At first it seemed it did because there was 0, -17 and 0V on diodes, but afterwards it had again 2, -16 and 2.
Do find the exact spot i have to set MM to continuity test, one probe to the end of winding and with the other I have to search where the insulation is bad?
-17 and 17 is correct rail voltage for this amp?
Because I removed both of them and added insulation to the other side. :S
That did not help. At first it seemed it did because there was 0, -17 and 0V on diodes, but afterwards it had again 2, -16 and 2.
Do find the exact spot i have to set MM to continuity test, one probe to the end of winding and with the other I have to search where the insulation is bad?
-17 and 17 is correct rail voltage for this amp?
I have this lacquer for fixing leaks on transformers but I am not quite sure how to use it.
Writing on the can in german is:
Klarer Schutzlack zum versiegeln und isolieren von gedruckten schaltungen, spulen und sonstigen elektronischen bauelementen, elektrischen anlagen wie verteilern, batterien, motoren. Verhindert kriechströme, beseitigt feinschlüsse an spulen und transformatoren.
Google translate:
Clear protective lacquer to seal and isolate them from printed circuits, coils and other electronic components plants, such as electrical distribution boards, batteries, motors. Prevent leakage, eliminates fine connections to coils and transformers.
I understand that the lacquer is exactly for this purpose?
Do I remove the transformer, find the leaking spot and spray that spot?
Or can I just go nuts and spray the entire transformer and hope that does the trick?
Writing on the can in german is:
Klarer Schutzlack zum versiegeln und isolieren von gedruckten schaltungen, spulen und sonstigen elektronischen bauelementen, elektrischen anlagen wie verteilern, batterien, motoren. Verhindert kriechströme, beseitigt feinschlüsse an spulen und transformatoren.
Google translate:
Clear protective lacquer to seal and isolate them from printed circuits, coils and other electronic components plants, such as electrical distribution boards, batteries, motors. Prevent leakage, eliminates fine connections to coils and transformers.
I understand that the lacquer is exactly for this purpose?
Do I remove the transformer, find the leaking spot and spray that spot?
Or can I just go nuts and spray the entire transformer and hope that does the trick?
You don't want to blindly apply anything because that may make it unrepairable.
With no remote voltage applied (only B+ and ground connected), place the black probe on the amp ground and the red probe on any of the secondary windings. Twist the transformer back and forth while pushing and pulling on it. At any time do you read anything near 12v? Ideally, you should never see any voltage on the secondary windings when doing this.
With no remote voltage applied (only B+ and ground connected), place the black probe on the amp ground and the red probe on any of the secondary windings. Twist the transformer back and forth while pushing and pulling on it. At any time do you read anything near 12v? Ideally, you should never see any voltage on the secondary windings when doing this.
After insulating the transformers terminal windins I get no noise from transformers any more.
With no remote voltage I get 0 ohms from all the secondary windings.
I replaced temporarily installed IRFZ44Ns with original replacements: 50N06
On Q43 FET I have 0.08V on first leg. Other three PS FETs have 0V on their first leg and -0.03V and 0.06 on center legs of D11 and D12 rectifiers.
That is still without remote voltage.
With remote voltage applied I stll get 2.1-2.8 V on rectifiers 1st and 3rd leg.
When I removed T1 for closer inspection and powered amp up without it, it had 0V on 1st and 3rd leg of rectifiers. T1 in place and T2s secondary windings disconnected from board it still had 2V on rectifiers 1st and 3rd leg.
I dont understand, is it the transformer or not?
With no remote voltage I get 0 ohms from all the secondary windings.
I replaced temporarily installed IRFZ44Ns with original replacements: 50N06
On Q43 FET I have 0.08V on first leg. Other three PS FETs have 0V on their first leg and -0.03V and 0.06 on center legs of D11 and D12 rectifiers.
That is still without remote voltage.
With remote voltage applied I stll get 2.1-2.8 V on rectifiers 1st and 3rd leg.
When I removed T1 for closer inspection and powered amp up without it, it had 0V on 1st and 3rd leg of rectifiers. T1 in place and T2s secondary windings disconnected from board it still had 2V on rectifiers 1st and 3rd leg.
I dont understand, is it the transformer or not?
Got some funny readings from one of the rail caps and replaced them with new ones.
Now the rail voltage is up to 21V. 12.5V between FETs center leg and non-bridging speaker terminal. There is still 1,4 to 1,6V between non-bridging speaker terminal and rectifiers 1st and 3rd leg.
New symptom.
With speaker connected (bridged), no input, amp switch to LP mode. After switching amp on, protection LED goes off, power LED comes on, then speaker makes low frequency boom and power LED turns off. Then power LED comes on again and the process keeps repeating itself once every 1-2 seconds.
With amp switched to HP or Full mode it plays music and power LED comes on and stays on.
Now the rail voltage is up to 21V. 12.5V between FETs center leg and non-bridging speaker terminal. There is still 1,4 to 1,6V between non-bridging speaker terminal and rectifiers 1st and 3rd leg.
New symptom.
With speaker connected (bridged), no input, amp switch to LP mode. After switching amp on, protection LED goes off, power LED comes on, then speaker makes low frequency boom and power LED turns off. Then power LED comes on again and the process keeps repeating itself once every 1-2 seconds.
With amp switched to HP or Full mode it plays music and power LED comes on and stays on.
Yes if they're both used for the ±15v regulators. Before you replace it, find the defective op-amp. It could be that the defective op-amp is causing excessive current draw and pulling the voltage down. If that's the case, the defective op-amp should be considerably warmer than the others.
I don't know.
Probe from the bottom of the board.
I don't know.
Probe from the bottom of the board.
Voltages on the opamps IC3, IC4, IC5 and IC6:
01:0
02:0
03:0
04: fluctuates between -5 to -8
05: 0
06: 0
07: 0
08: fluctuates between 4 to 6
Voltages on IC2
01:0
02:0
03:0
04: fluctuates between -5 to -8
05: fluctuates between 0,004 to 0,048V
06: fluctuates between 0,004 to 0,048V
07: fluctuates between 0,030 to 0,120V
08: fluctuates between 4 to 6
When I was touching leg 3 on IC2, leg 3, leg5 on IC3 the switching got faster, like the tempo of heartbeat.
I missed IC701 and removed at first IC02 to see if voltage on the other opamps supply legs rises, it did not. But turning on and off stopped. I removed other opamps which I measured but voltage on their supply pads did not rise.
Voltage on zeners is 9 and 6V. (Earlier I stated incorrectly that one of them had 15V on it, it did not, it had 10V. 15V I measured near IC701 on a zener.) They seem to be fine or if they are defective then they failed exactly the same way. I get similar readings on them with my DMM with one leg of each zener lifted.
Voltages on IC701 after zeners are reinstalled and all the other opamps are still out:
01: -9,23
02: 0,7
03: 0,04
04: 0,04
05: -0,43
06: -10,83
07: -0,41
08: -1,62
09: -3,68
10: -0,01
11: 9,5
12: 0
13: -0,91
14: -0,94
15: -0,95
16: -9,73
Legs 3, 4 and 5 seem a bit weird, 0,04 on inputs but -0,43 on output. Legs 12, 13 and 14 are also weird to me. 0 on ouput but -0.9 on inputs.
During testing rail voltage got down to 12-13V again.
With no remote voltage I have -0,5V on D12s center leg and about 0,1V on D11s center leg and Q32 has 0,2V on its first leg. These numbers differ a bit every time I switxh the amp on and off.
I get weird resistance readings between FETs 2nd and 3rd leg on the board. With continuity test DMM beeps and ohms start to climb down near zero and then to -0,04 so resistance is 4 ohms. I removed two of them and out of the board they check out OK.
I will remove the other two as well to be sure.
Also I get 0,3V on 3rd leg of two of the Q32 and Q33 FETs.
01:0
02:0
03:0
04: fluctuates between -5 to -8
05: 0
06: 0
07: 0
08: fluctuates between 4 to 6
Voltages on IC2
01:0
02:0
03:0
04: fluctuates between -5 to -8
05: fluctuates between 0,004 to 0,048V
06: fluctuates between 0,004 to 0,048V
07: fluctuates between 0,030 to 0,120V
08: fluctuates between 4 to 6
When I was touching leg 3 on IC2, leg 3, leg5 on IC3 the switching got faster, like the tempo of heartbeat.
I missed IC701 and removed at first IC02 to see if voltage on the other opamps supply legs rises, it did not. But turning on and off stopped. I removed other opamps which I measured but voltage on their supply pads did not rise.
Voltage on zeners is 9 and 6V. (Earlier I stated incorrectly that one of them had 15V on it, it did not, it had 10V. 15V I measured near IC701 on a zener.) They seem to be fine or if they are defective then they failed exactly the same way. I get similar readings on them with my DMM with one leg of each zener lifted.
Voltages on IC701 after zeners are reinstalled and all the other opamps are still out:
01: -9,23
02: 0,7
03: 0,04
04: 0,04
05: -0,43
06: -10,83
07: -0,41
08: -1,62
09: -3,68
10: -0,01
11: 9,5
12: 0
13: -0,91
14: -0,94
15: -0,95
16: -9,73
Legs 3, 4 and 5 seem a bit weird, 0,04 on inputs but -0,43 on output. Legs 12, 13 and 14 are also weird to me. 0 on ouput but -0.9 on inputs.
During testing rail voltage got down to 12-13V again.
With no remote voltage I have -0,5V on D12s center leg and about 0,1V on D11s center leg and Q32 has 0,2V on its first leg. These numbers differ a bit every time I switxh the amp on and off.
I get weird resistance readings between FETs 2nd and 3rd leg on the board. With continuity test DMM beeps and ohms start to climb down near zero and then to -0,04 so resistance is 4 ohms. I removed two of them and out of the board they check out OK.
I will remove the other two as well to be sure.
Also I get 0,3V on 3rd leg of two of the Q32 and Q33 FETs.
FETs are OK.
After testing with op amps etc amp started to draw some current, current limiting lamp glows just a little bit.
FETs are all OK, removed them and checked. I measured resistance between + and GND terminals, I got the same result as in FETs 2nd and 3rd leg. 4 ohms. If I remove C31 resistance is bigger between + and GND. Tried to trace the small resistance. I get this down climbing 4 ohms between 3rd leg of Q33 and primary windings of T2, between 2nd and 3rd leg of Q33, between Q33s 3rd leg and R26s one leg. Between Q33s 3rd leg and 4th pin of PS driver board.
At first I thought it was still the transformer acting up. I removed T2. Then this small resistance went to the other side on Q42 and Q43s 2nd and 3rd leg. With T2 in place resistance between Q42s and Q43s 2nd and 3rd leg were much bigger.
Without T2 I get rail voltage up to 19V and one of the Zeners up to 15V which measured 9V earlier.
After testing with op amps etc amp started to draw some current, current limiting lamp glows just a little bit.
FETs are all OK, removed them and checked. I measured resistance between + and GND terminals, I got the same result as in FETs 2nd and 3rd leg. 4 ohms. If I remove C31 resistance is bigger between + and GND. Tried to trace the small resistance. I get this down climbing 4 ohms between 3rd leg of Q33 and primary windings of T2, between 2nd and 3rd leg of Q33, between Q33s 3rd leg and R26s one leg. Between Q33s 3rd leg and 4th pin of PS driver board.
At first I thought it was still the transformer acting up. I removed T2. Then this small resistance went to the other side on Q42 and Q43s 2nd and 3rd leg. With T2 in place resistance between Q42s and Q43s 2nd and 3rd leg were much bigger.
Without T2 I get rail voltage up to 19V and one of the Zeners up to 15V which measured 9V earlier.
I dont really know what to check next.
What can cause the resistance between FETs 2nd and 3rd leg to drop to just a few ohms?
Decided to give this amp some rest and started to work on next one, completely different amp, some symptoms differ but sound is very distorted and there is only few ohms of resistance between FETs 2nd and 3rd leg.
Have you seen this before? What caused it?
What can cause the resistance between FETs 2nd and 3rd leg to drop to just a few ohms?
Decided to give this amp some rest and started to work on next one, completely different amp, some symptoms differ but sound is very distorted and there is only few ohms of resistance between FETs 2nd and 3rd leg.
Have you seen this before? What caused it?
I will start the thread for another amp later, if I wont be able to figure that one out by myself.
FETs on Nemesis are OK.
4 ohms between 2nd and 3rd leg was at first on T2-s side FETs and on the other side there was big resistance. After removing T2 resistance got smaller between legs 2 and 3 on the FETs on T1s side of the board.
FETs on Nemesis are OK.
4 ohms between 2nd and 3rd leg was at first on T2-s side FETs and on the other side there was big resistance. After removing T2 resistance got smaller between legs 2 and 3 on the FETs on T1s side of the board.
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