Ok, you are almost there and everything is 100%.
So blowing your fuses is probably because they are rated too low.
What I can find tells me they should be 10 Amp slow, but maybe you have the original manual telling something different.
When you have finalised BR300 and BR301 we go back to the Right channel with the confidence that everything else is in perfect state.
Hans
So let's resume where we were in getting the Right Channel working properly.
With the lamps again in the Vcc lines, turn R124 to a position where you have ca 50 Volt over the lamps.
1) After having connected the OL-2 board in #133, there was a short circuit that caused a hum and blew a fuse.
So now with the much safer 50Volt over the lamps, connect OL-2 again and see whether the voltage over the lamps changes.
And BTW, have you already checked the line carrying the opto coupler signal from OL-2 board P210 to P332 on the power board and are you sure it is not connected or short circuiting to anything else ?
2) Now if the voltage on the lamps is still 50Volt, disconnect P211-3 from the OL-2 that comes from the thermal sensors.
The amp should switch off almost immediately, correct ?
3) And can you still repond to my question in #154. This circuit if existing in your amp should also be investigated.
Waiting for your answers.
Hans
With the lamps again in the Vcc lines, turn R124 to a position where you have ca 50 Volt over the lamps.
1) After having connected the OL-2 board in #133, there was a short circuit that caused a hum and blew a fuse.
So now with the much safer 50Volt over the lamps, connect OL-2 again and see whether the voltage over the lamps changes.
And BTW, have you already checked the line carrying the opto coupler signal from OL-2 board P210 to P332 on the power board and are you sure it is not connected or short circuiting to anything else ?
2) Now if the voltage on the lamps is still 50Volt, disconnect P211-3 from the OL-2 that comes from the thermal sensors.
The amp should switch off almost immediately, correct ?
3) And can you still repond to my question in #154. This circuit if existing in your amp should also be investigated.
Waiting for your answers.
Hans
Once again, you are amazing. Thank you so much for the help so far, not only the instructions but also theory behind. That part I need to read a few times to understand. Now I understand that this is not only amplifier but there is so much other circuits to prevent accidents. I really admire people who have designed this.
I checked your post number #154 and downloaded same schematic. It cannot be from this amp because there is for example only 8 output transistors and this has 12. Maybe ML 27 or something...
Everything have matched so far with my amp and the schematic that I have. So no such cirquit in this amp.
Everything have matched so far with my amp and the schematic that I have. So no such cirquit in this amp.
I did investigation for the P210 to P332 cable. Cable seems to be ok. There is 0.2 ohm resistance between and around 250Mohm to the ground. I also measured the resistance between the ground and the OL-2 connector(P210) and that is only 500kohm as the the front board connector(P332) measures over 300Mohn.
Is that alarming?
Is that alarming?
Now I do not get this, I disconnected the OL-2 board and also the optocoupler cable. Amp stays nicely on, but I cannot get any more 50V between the lamps, I have turned the pot all the way to the end(safest position) There is always 84V between the lamps. Short somewhere? Or am I still missing something?
This is exactly what I was hoping for, because now you have the short circuit effect we are searching, great.
Keep it that way and don't switch the Amp off.
Are you sure you still have this situation ??
That both lamps are showing now 84 Volt instead of the previous 50 Volt means that the short circuit current is flowing through the complementary output transistors, that's already one piece of very important information.
Now please measure the following voltages:
1) The voltage over R50, and the voltage on both side of R50 with respect to ground (so 3 voltages)
2) The voltage between WH.1 and WH.5 and their voltage with respect to gnd (again 3 voltages)
Hans
It would be nice when you had 110 V lamps, then you could see them go on and off. Now you have to measure all the time whether you have correct 50 V or the wrong 80 Volt.
Everything now points in the direction of an intermittent contact, like a bad soldering or a pcb trace with a problem.
Hans
Everything now points in the direction of an intermittent contact, like a bad soldering or a pcb trace with a problem.
Hans
That is completely wrong.
When R50 has 1.2V, WH.1 to WH.5 should be 3.6 Volt and not 2 Volt.
The Negative voltages on WH.5 and R50 are O.K, so we will have to concentrate on the positive halve. and make sure the lamp voltages are still 85V all the time.
1) Now please measure the 3 voltages over R45 and with respect to gnd.
2) Measure the voltages with respect gnd of R35, R25 R28, R26 and R27 all on both sides.
Hans
That means that q40 and q52 are probably working properly.
The problem seems to be around q29 and q30.
Plse go on.
Hans