ARCHIVED FORUM -- March 2012 to February 2022READ ONLY FORUM
This is the second Archived Forum which was active between 1st March 2012 and 23rd February 2022
Hello again,
BM2200 is now recapped and reassembled with a new operator panel and sounds really good..
I have a question about setting the no signal current (presumably the same as idle current). The service manual gives two methods for doing this: either adjust with 8R24 the current in the collector of 01C1 to 30mA, or adjust the voltage across 8R26 to 12mV by the same means.
As the first method presumably involves unsoldering one transistor leg, I measured the voltage across the emitter resistor. The manual says the receiver must be cold, volume down and speakers disconnected.
On first switch on, the measurements on each channel were approximately 11mV, but rising over a period of a few minutes to 15 or 16mV. If I had left it on, they would have risen further.
So my question is, at what point after switch on should I determine the voltage and how do I adjust it if it's increasing?
The set is not running hot and it's been on for twelve hours. My feeling is that it's probably ok as is (I don't like fiddling with old trimmers) but I would be grateful for any comments.
Many thanks (again),
Adjust when cold.
Check and readjust after 5 minutes. A small rise at this point is not unusual.
Check again after another 5 minutes.
If it still rises, the idle circuit must be repaired.
Martin
Thanks, Martin.
Just to clarify, do I leave the set turned on between measurements?
Regards,
Yes.It needs to warm up the components to "normal working temperature".
Thank you.