Could the detached back panel be under rail voltage due to output transistor (or its connection) isolation falure?
The back panel houses the left and right channel main amp boards along with the mosfet output transistors. Right now its reconnected back to the main body. I powered it up and the dbt light goes dim but no relay engagement. If I push or ever sp lightly touch either main board the dbt light will start pulsating.
At one point in time Mooly and I had the amp working beautifully until I started to button it back up then it all went south.,
I can power this thing up and have a dim bulb with the relay engaged. Power it down and connect my preanp and power up to a bright bulb on the dbt and no relay engagement. Strangest thing i have ever encountered. I feel there is a bad solder joint or a cap that is failingbecause of the pulsating light on the dbt.some cap is charging and discharging I could be wrong, Im no expert by antneabs.
At one point in time Mooly and I had the amp working beautifully until I started to button it back up then it all went south.,
I can power this thing up and have a dim bulb with the relay engaged. Power it down and connect my preanp and power up to a bright bulb on the dbt and no relay engagement. Strangest thing i have ever encountered. I feel there is a bad solder joint or a cap that is failingbecause of the pulsating light on the dbt.some cap is charging and discharging I could be wrong, Im no expert by antneabs.
Can you power it up with the relay engaging with the back panel detached from the chassis?
Sorry for the delay in response. I had to make a trip to Texas to help with my father in law..
Yes with the back panel detached the relay would engage and everything appeared to work. The last I worked on it the relay had stopped engaging and left channel was not working. I swear this amp will be the death of me. I'm just getting settled back home and I plan on taking voltage measurements on the regulator board to ensure I have proper voltages going to the main amp boards.
Phil
Yes with the back panel detached the relay would engage and everything appeared to work. The last I worked on it the relay had stopped engaging and left channel was not working. I swear this amp will be the death of me. I'm just getting settled back home and I plan on taking voltage measurements on the regulator board to ensure I have proper voltages going to the main amp boards.
Phil
Well, the first thing to find out is whether the problem is mechanical or electrical.
Try poking the boards with a wooden stick, then with a (disconnected from DMM) lead wire and then connect via that lead wire the heat sink to the chassis.
Try poking the boards with a wooden stick, then with a (disconnected from DMM) lead wire and then connect via that lead wire the heat sink to the chassis.
Connecting to the heat sink and connecting to the chassis i get the blinking DBT. Without connecting it stays nice and dim but no relay enagagement. At this point im less worried about no relay and more concerned with the blinking DBT or is it possible they are in fact related?
These things are probably related - DBT indicates excess draw of current which most probably results in DC in output.
It seems that your heatsink is under voltage - most probably an insulation of an output transistor has failed.
You should measure voltage between chassis and heatsink.
I'm still following...
Off the wall idea, could you connect a resistor between heatsink and chassis to get an idea of what is happening. Try a 1k and see if any voltage of any sort is across it. Go higher or lower as needed. Does real current flow in that resistor or does it provoke some unwanted behaviour such as oscillation.
Off the wall idea, could you connect a resistor between heatsink and chassis to get an idea of what is happening. Try a 1k and see if any voltage of any sort is across it. Go higher or lower as needed. Does real current flow in that resistor or does it provoke some unwanted behaviour such as oscillation.
Im still here. I was just playing around with it, poking proding. still nothing. Ive never encountered anything like this. To go from putting out some nice music just a few weeks ago Mooly and I thought we had this until I started to put it all back together and now were here. It's #am here in Nebraska and still reeling from a turkey overload. I will definately try the resistor and voltage measurements tomorrow and report back my results. I truly thanks you for all the help. In the other table I have another Nikko Alpha II that needs help as well but for another day. One channel is putting out 20vdc on the dc offset. but another day
Until tomorrow I bid you a good morning
Phil
Until tomorrow I bid you a good morning
Phil
I measured voltage real quick, VDC, between heat sink and chassis and get a good 10mv with light on and .1 when it dims.
What about the current?
Could the output transistors be turned on by defective feed resistors in some circumstances?
hi all, just getting up, not a good morning tummy wise but I will head into the work room and connect that resistor and see what we get
edit: 587mv across the resistor with the dbt dim. drops to .1 when the blub is brightest. The positive lead is on the heat sink side of the resistor
I believe I fixed it. Flipped it over to inspect the power supply board and there was a small wire fray on one solder pin barely touching a ground wire solder pin. Snipped the fray and seperated the solder pins just a bit and now no more pulstaing dbt whe the heat sinks touch the chassis but I still dont have a relay engage