Hartke HA5500

Carlosraj

Member
2010-01-17 11:12 am
Hi


I need some help with this amp. I plugged in the power supply, plugged in a signal and turned the amp ON, There is power going in to the amp, but no sound. I did not hear the relay "click". I then plugged the amp thru a Variac, turned on the power switch, and starting from 240V, I slowly brought the voltage down in steps. At about 160V, the relay clicked on and there was sound as normal. At 160V AC, when I turn the amp on and off, the relay kicks in within 2 secs without any problem. If I increase the voltage back to 240V with the amp turn ON, the relay does not click off, but when I turn the amp off, plug in direct to 240V, the relay does not kick in. I have checked all the transistors and diodes on the power amp board, and they test OK. Can the problem be due to a leaking cap or transistor. Pls assist.


Thanks
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> You want us to guess and suggest without a schematic?

https://elektrotanya.com/hartke_ha5500_sch.pdf/download.html

Searching, filtering, and passing that robot-check and wait-wait-wait is SO tedious, and then I see "2003" date, and fuggit. (But Carlosraj could have posted the plan here...) I'd rather go out and play in the freezing rain than work-work for someone else's old bass amp.
 

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Carlosraj

Member
2010-01-17 11:12 am
ANy chance the amp is expecting 120v and the 240v overvoltage is making it malfunction?

Right above the power cord jack is a small hatch. It pulls off, and the orientation switches mains voltage.




The voltage setting is correct. It is set at 230V. Yesterday, when I set the voltage at around 160V AC, the amp had no problem and the relay was kicking in as normal, but today it is not. I tried adjusting the voltage above and below 160V, but the relay is not responding. I have stripped off all the caps and transistor and checked them off the circuit board and they all tested good. I will put back all the components and check whether there is any voltage present at the speaker output terminal before the relay.


Thanks
 

Carlosraj

Member
2010-01-17 11:12 am
be aware that the grounding in these is weird/problematic one needs to use star type lockwashers on the corner location where the PCB should see case ground otherwise they break into severe oscillation.




I have changed all caps and small transistors on the power amp board. No change. This is what happens. if I set the mains voltage at 160V, the relay turns on as normal within approx 2secs, as I increase the mains voltage, the relay turns on but takes a longer time, the higher the voltage, the longer it takes. Connecting direct to mains 240V, the relay took about 15mins to turn on. Once turned on,when I turn the amp off and on it back immediately, it takes about 2 mins to turn on again. To me it seems like a problem with the power supply. Can it be.


Thanks
 
I have stripped off all the caps and transistor
Ouch!!
I will put back all the components and check whether there is any voltage present at the speaker output terminal before the relay.
You should have started by doing that.
I have changed all caps and small transistors on the power amp board. No change.
I am not surprised.
In fact I am surprised it still works after the unwarranted messing.
You must troubleshoot it (start by checking no signal voltages) instead of throwing parts at it.
To me it seems like a problem with the power supply. Can it be.
Like a Statistician would say, "with 95% confidence": no.
Please measure and report.
Considering that said voltage might not be a static value but change with time.
Maybe you have "x" volts at turn on and it drifts to "y" volts after some time, making relay click ON or OFF in the process.
 

Carlosraj

Member
2010-01-17 11:12 am
Ouch!!

You should have started by doing that.

I am not surprised.
In fact I am surprised it still works after the unwarranted messing.
You must troubleshoot it (start by checking no signal voltages) instead of throwing parts at it.

Like a Statistician would say, "with 95% confidence": no.
Please measure and report.
Considering that said voltage might not be a static value but change with time.
Maybe you have "x" volts at turn on and it drifts to "y" volts after some time, making relay click ON or OFF in the process.




I have replaced TA7317 as well with the C3198, A1266 and C3200 transistors. Voltage at output before the relay reads 200mv. The +B and -B read +95V and -95V before the relays turns on and drop to +88 and -88 after turn on.
 

Carlosraj

Member
2010-01-17 11:12 am
200 mV of DC offset might be just enough to trigger protection. Does it stay like that regardless of AC input voltage?

Not sure why supplies would be dropping that much after the relay clicks in. Maybe oscillation? Identify and check the Zobel network components.




I replaced the bias pot since the top plastic piece was broken (and I think it is damaged). I replaced with a 470 ohms trimpot and set it fully counterclockwise for the time being. I tried adjusting VR302 to null the 200mv offset but adjusting VR302 does nothing to the offset voltage, but by adjusting VR301(bias), the offset voltage is adjustable so I manage to bring the offset voltage to almost zero. But still no change. It still takes the relay about 15mins at 240V to kick in. The DC offset voltage does change according to change in mains voltage. I have an old CRT scope, I will try to check for oscillation. I am not sure which are the components which make up the zobel network. Pls assist.



Thanks
 

turk 182

Member
2012-10-26 3:03 pm
eek! don't cut the trace lifting one end of R336 should do the trick!
as to relay operation i don't know(never been this deep into the protection circuit of a Hartke!) i'm hoping it would help determine if the fault is from the amp's operational condition or whether it's with the protection circuit itself.
i've spent a little time looking at the data sheet for the 7317 it seems to be a comparator of sorts and i'm unclear as to how turn on delay is acheived??


have you had a chance to check for oscillations?
 
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