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XForce 1KW supply voltage.
- Thread starter BJ radionut
- Start date
So initially as soon as the power was turned on the transistors that turn on the fans would smoke. Once I lifted the leg of those transistors my short went away. And the amp powers up fine now. I think those transistors for the fans are just switching transistors. I’m going to try and order the transistors and capacitors that’s attached to them. I think this was my issue. Your thoughts and opinions are greatly appreciated. Let me know your thoughts. Thanks again.
They are 7812 regulators. The problem is they are being asked to sink alot of power without a heatsink. Remove them. Power the fans from The switch.
Roger that. Thanks. They are 12 volt fans. The 21 volts I have access to in the amp will over power the fans right?
I forgot to add on my last reply that they had the heat sinks on them I just removed the while I was working on them.
Another option, one i used to do, is use an ac fan. It will be powered by the wall current off the main switch. They will not slow down.
Awesome. I thought about adding a 110vac relay and triggering it from the main power switch to turn them on. However I would like to keep all the components original. Again y’all have been super helpful. Thanks again.
One last question. You can see it’s a straight 10 pill SC2879 Toshiba red dot. What is a good safe amount of wattage to drive it with?
A 1 or a 2 pill.
That box will produce 2-2500 pep easily. Use as much drive as it takes to get there. Likely 10% of its output. Probably 100-200 watts
High quality double ball AC fans is what my tech installed in my box on a rebuild. Run lots quieter than the DC fans ever did, and push a good amount more air. It did have the DC fans, but they were annoying loud, and that up and down DC fan speed as the amp was keyed was annoying too.
Only bad thing is high quality double ball AC 120mm fans are not cheap. Get what you pay for I reckon.
before I put the cover back on, I tested the fans with a12 volt power source. All 6 fans are toast. So it looks like it will be getting 115 ac fans. And that’s not all the collateral damage. I have 1 of the 2879 transistors that isn’t balanced. I’m sure they have been replaced already once with all Chinese knock offs. I’m having trouble finding 1 with the same date code. How critical is the date code?
Shadetree Mechanic
Delaware Base Station 808
How do you know that one is not "balanced"? Date code doesn't make much difference. The big thing is the gain or hfe. If the gain is matched for all transistors, then the load will be spread evenly amongst them. A transistor tester can measure this, but you will need to unsolider the tabs to check.