Aleph 30 problem - half of power supply voltage on speakers output

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hi all
I believe that someone before me have this kind of problem but the search option didn't come up with result.

I manage to burn one chanell of Aleph30 ;-)

So does any one have some idea what could cose that I have half of power supply voltage on speakers output ?
When I measure voltage on source resistors ( 0.5/5W) on side with Q9/Q11/Q13 I have 0.45V but on the other side I have around 0.1V across source resistors resistors.

What should I check ?

Thanks

(p.s. I'm not an expert, this is my hoby and I only have one multimeter ;-))
 
MEGA-amp said:
I've got two meters, and managed to let out plenty of the magic smoke. Looking at the A30 service manual, I don't see any Q13. Which schematic are you using? Maybe a close up pic if possible.

-john

sorry for misunderstanding.
I was reading from PCB markings so I state Q13 and so. The PCB that I'm using is from BrianGT GB and there was shematic with it but I have reinstall windows and didn't have time to transfer old files on new one, so at this moment I don't have original shematic for those PCB.
A friend diyer have send me original Alwph30 service manual and the mosfets that I'm talking about are Q6-Q8

Could someone please send me shematic that have come with Brians Mini and Aleph 30 PCB since there is difference in markings betwin original and Brians.
And it's hard for me to track diferences by looking on PCB

(email josip.katalinic at gmail.com)

Thanks
 
it seams that Brian's schematic is close to the original;
I have masure voltage over
- R11 - 5V - o.k.
- Q3 Dpin to 0 - 4V o.k
- Q5 - 4.5V - I think o.k.
- R14 - I have 3.1V not o.k.

and I have notice something strange at least visualy...bacause I don't think that I solder this bad ;-) but the PCB under Capacitor ( I think it's C11 ) looks burned ?

not shure is C1 on this pcb the C11 on original shematic ?
http://www.diyaudio.com/forums/showthread.php?postid=585816#post585816
 

Attachments

  • clipboard01.jpg
    clipboard01.jpg
    65.3 KB · Views: 476
Here it is again with red cloud ;-)

one more thing...
this amp was working fine, for some time, until I conect wrong output of 7.1 preamp (NAD S170) to onother amp which couse one Alpeh 30 amp to make some duuulllll/tuuull sound and after couple sec it start to smell bad ;-)

I don't know how conecting wrong preamp output to other amp can make some amp which is conected to another output to burn ? but !
...complicated story...it would be much easyer to draw it then to describe it with words...

(sorry for bad english)
 

Attachments

  • clipboard02.jpg
    clipboard02.jpg
    62.7 KB · Views: 430
Zen Mod said:
OK - seems that you have problems with biasing of output , not with burned output mosfets

check zenners for short , especially one in input CCS ( 9V1)

I'll send you Algar_emi's A30 pdf , with all measuring points , so you can compare ... and write here what's difference


I have recive pdf ... thanks Choky ;-)
will play a litlle and post results...
 
For now...
Colegue diyer advised me to mesure voltage on ZTX base.

I have conect one side of multimeter to the ground and with the other I mesure voltage on Q4 base which is like 21V and on the Q5 is like 13V.

( I mesured resistance betwin ZTX leegs , they are not shorted so I think thay are not broken )
 
O.K.
top view ( o represents pins )

Q5 o 4.62V o
3.9V o 0.64V

Q4 o 5V o
4V o 0.6V


not shure but this should be like when woching from component side

c e
b


whell it looks diferent when I post, so if I'm right bouth have around 0.6V betwin b and e, and 5 or 4.6 be twin c and e.
 
Official Court Jester
Joined 2003
Paid Member
yoke , it's useless ( at least to me ) to post without known nomenclature ;

use this schematic , and just disregard part names on pcb ;

I know ( and have in my PC ) too much Aleph schematics , to even remotely be sure what you're talking about , without exact schematic ...

I hope it will help
 

Attachments

  • a30.jpg
    a30.jpg
    50.9 KB · Views: 390
Zen Mod said:
yoke , it's useless ( at least to me ) to post without known nomenclature ;

use this schematic , and just disregard part names on pcb ;

I know ( and have in my PC ) too much Aleph schematics , to even remotely be sure what you're talking about , without exact schematic ...

I hope it will help

you are rigth
there are several schematic of Aleph30 with diferent markings...
and it's been a while since I build this ;-)


lets resume
power is +/-22V

I have around 13V on the output
R11 - 5V
R14 - 2,5V
Z5 - 9V
Q5 - from c to e 4.6V from b to e 0.6V
Q4 - from c to e 5V from b to e 0.6V
Q 6-8 source resistors 0.5V
Q 9-11 source resistors 1V
 
Official Court Jester
Joined 2003
Paid Member
in my xperience ( lifetime as repair techie ....... lousy one :clown: ) - fastest and most convenient way of repair - for simple circs as A30 is - is simply to pull out ( ONE BY ONE , to ensure possible mixing ) all semis

desolder it , pull out , measure
if good - solder it back , if suspicious - replace , if broken - replace


check input LTP ( both IRF9610) , for start ;

what WAS initial current through outputs - when you made amps ?

to me - seems that even 0V5 across each source resistor is on highish side ...... not to mention 1V ..........
 
Yes it seams that would do the trick...resolder everything...

The thing is that I can't keep amp on for a more than a fiew sec since the side with 1V on source resistors start to smell ;-)

so I have to turn it on and off...

About voltage on source resistors, 0.5V is normal....I think it drops to 0.45 once the amp heat's up. I think that this 0.25V on original shematic is wrong. It should be like 0.5V.

1V is to much and I have to find out what is cosing it.

will try to mesure some voltage over input pair of mosfets.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.