[WireNut]

 I have a Hafler 9505 power amp that I use for bass duty in my bi-amp system.
The Halfer has developed a random popping sound after about 5 minutes from turn on.
I’m not a Tech, so I’m hoping I can get some feedback on what the problem may be before I send it to a repair shop that I know nothing about.
The amp is about 20 years old.  It pops with or without music thru the system.

I appreciate any help from AC members.

Thanks,
WireNut.

[Folsom]

Hmm can you check DC on the output? How random is it? How loud?

Check solder/contact areas. (wiggle stuff but not vigorously; careful of voltages on big caps and such, it's fine to do it when it's been off for quiet awhile/after draining caps)

If there's no one in your area, you can PM me.

[paul79]

Checking the DC Output is a good idea. I see input jacks mounted on a circuit board... One may have a bad solder connection. Not knowing allot about the amp, but if the basic checks reveal nothing, it is most likely the input differential pair transistors showing ugly...

[Folsom]

Checking the DC Output is a good idea. I see input jacks mounted on a circuit board... One may have a bad solder connection. Not knowing allot about the amp, but if the basic checks reveal nothing, it is most likely the input differential pair transistors showing ugly...

Transistors typically turn off (or blow up the amp). But IC's go nutty. However if power going to transistors on the front end are intermittent, you can get on/off behavior. The thing is with these particular potentials is the random pattern doesn't fit overly well except with IC's.

The input soldered RCA's is a great suggestion to look at if they're not also chassis mounted.

[Davey]

If it's input board related you might try swapping the gray cables.  If that moves your problem to the other channel you'll have narrowed down the problem to the input board and/or connectors.  (I worked on a 9505 many years ago and the cables were just long enough to support swapping.)

Whatever you do, be very careful poking around in there if the power is on or has recently been turned off.

Dave.

[G Georgopoulos]

power supply or power transistor bad solder joints...

[WireNut]

If a capacitor is going bad could that cause the popping sound in the right channel ?
I did talk briefly with a tech over the phone and he said it might be the power supply. That's all the info I got from him. He didn't comment any farther.

[Davey]

If a capacitor is going bad could that cause the popping sound in the right channel ?
I did talk briefly with a tech over the phone and he said it might be the power supply. That's all the info I got from him. He didn't comment any farther.

A capacitor certainly could be the issue.
However, if it's a power supply problem, likely you would experience the issue in both channels.  So, probably not the PS.
In this case you have a dual secondary for the big voltages, but a common supply for the low voltages.  So, you can't rule it out completely.
Be careful.

Dave.

[randytsuch]

A capacitor certainly could be the issue.
However, if it's a power supply problem, likely you would experience the issue in both channels.  So, probably not the PS.
In this case you have a dual secondary for the big voltages, but a common supply for the low voltages.  So, you can't rule it out completely.
Be careful.

Dave.

I also think it may be old caps.  There are 4 big lytic caps, and 20 year old lytics could certainly be a problem, they do fail over time.
You may want to replace them anyway at this point.

But, like others said, be careful, they may be charged.  I'd measure for dc voltage across the caps before touching them.

[G Georgopoulos]

If a capacitor is going bad could that cause the popping sound in the right channel ?
I did talk briefly with a tech over the phone and he said it might be the power supply. That's all the info I got from him. He didn't comment any farther.

no, it would not cause random popping,only a bad joint at its leads
from what you describe the popping is random right?then it is a single bad connection
usually a joint,better leave the ps caps as is if there is no hum,this indicates they still
have life in them,from what i've seen the amps use separate ps's if it were common and the
fault was in the ps it would appear on both channels

it's not a serious fualt this i can tell you for sure,a good technician would not charge you much

good luck