Hi Bill
It sounds as if you have a lot of work ahead if you are going to fix both the BM8000 and 6000. They are fairly complex units but I have also been able to take non working units and get them functioning brilliantly once again so it can be done. I have recently finished my BM8000 and it now takes centre stage in my collection. See photo taken last week.
For such a complex topic, your questions are a bit vague but I can try and help as follows:
Do you need a scope and signal generator? The answer is sometimes and depends on what is wrong. In many cases, you can get away without but you must have access to a fairly good multimeter. I have access to both the scope and the sig gen and for me, they have been worth their weight in gold.
With regard to what fails, Craig has already mentioned that a capacitor replacement is probably inevitable but again, it has its limits. I have just replaced about 60 in the 8000 and the improvement has not really been noticeable. However, that doesn’t mean to say that the electronics aren’t performing better and they probably are. Thereafter, the problems can be related to faulty trimpots and even burnt out resistors and transistors.
In order to get everything functioning properly once again, you will probably have to dismantle and reassembly the unit several times. If you are comfortable with all of that and you have good soldering skills then you might have some fun with this project. As I mentioned, I dismantled mine almost completely, and I have many photos, notes and assembly points that might help you. Even the removal of the layers of dust and muck can go a long way towards getting it to function again. I gave mine a thorough clean and even spray painted some of the more rusty and grotty looking items. I think my unit was taken apart and reassembled about four times and in the end you do become very quick and proficient.
Before you start dismantling, you will need to understand the present condition of the unit. I am not sure in what condition your unit is, and presumably it is fully assembled and ready for startup. If it is, I would first disconnect the speakers and everything from the socket panel before powering up and then switch in using Tape 1. Listen for the two relay clicks and note the volume setting that is indicated on the panel. If it comes in high, quickly turn the volume down to zero and see if the unit does or doesn’t trip. Which lights are on and does the clipping indication still show if the volume setting is low? If the unit is able to power up without tripping, leave it for a while and sniff around for burning smells and hot spots. If anything is getting too hot, switch off immediately. This would be a good starting points and the next step would be to repeat the same operation while the box is open and everything is in service mode.
That is all that I can suggest at the moment. If you can clarify what happens under these conditions, it would be a great help and then you would be in a better position to sort out the real problems that you are dealing with.
Regards
Geoff