Hmm. I guess I can just run the sub using only the good voice coil? I assume it'd halve the power the sub can take, but it'll be running at 4 ohms instead of 2 ohms then so it'll kind of take care of itself.
I was able to get some desoldering braid to work in place of the tinsel lead, but there wasn't much left coming from the cone to get a connection I can trust with it. This sub has seen better days anyway, maybe I should just save up for a new one. 🙂
I was able to get some desoldering braid to work in place of the tinsel lead, but there wasn't much left coming from the cone to get a connection I can trust with it. This sub has seen better days anyway, maybe I should just save up for a new one. 🙂
Ugh. Another dead IRF540. It went 20 minutes and then fried.
Upon further inspection, I see that the original IRF540 took a nice thin chunk of copper with it. Solder just flowed and visibly bridged the gap on the MESHA board so I never saw it. I did observe that it was more difficult to get the replacement IRF540(s) to stick than the IRF9540 beside it.
I had the gains all the way down, the bias pots midway between the original settings and zero, and the bass remote detached. Ran the stereo maybe 3/4 volume of what I usually do. Amp heatsink was a little warm, dead IRF540 was very hot.
Any way to deal with a messed up MESHA board like this? Or am I screwed now?
Upon further inspection, I see that the original IRF540 took a nice thin chunk of copper with it. Solder just flowed and visibly bridged the gap on the MESHA board so I never saw it. I did observe that it was more difficult to get the replacement IRF540(s) to stick than the IRF9540 beside it.
I had the gains all the way down, the bias pots midway between the original settings and zero, and the bass remote detached. Ran the stereo maybe 3/4 volume of what I usually do. Amp heatsink was a little warm, dead IRF540 was very hot.
Any way to deal with a messed up MESHA board like this? Or am I screwed now?
Someone may have a donor insulator. Seankane, possibly.
If not, you can repair it but it may not be worth the effort.
If the MEHSA insulator delaminated, the output had no chance to survive.
If not, you can repair it but it may not be worth the effort.
If the MEHSA insulator delaminated, the output had no chance to survive.
Hmm. If I can't find a replacement insulator, is there any chance I can cut the insulator between the output transistors and the other three transistors, and then mount the output transistors directly to the heatsink with (insulated) thermal pads and screws?
I've decided I'm going to buy a new amp for the car, I think a R500X1D should be just dandy.
I'm not giving up on the 300S, but with all the time I spend in my car it's been annoying not having the sub for the last month now. I think the 300S would make an excellent garage stereo, my dad always talk about building one... I've even got a couple 6x9 boxes that were his. 🙂
You can cut the MEHSA insulator and clamp them to the heatsink. You may need to sand the heatsink and you'll need to use new transistors so the back is perfectly flat.
Well just an update on this, I did manage to get the amp going. I ripped out the entire bad MEHSA insulator and replaced all the transistors on that side, as my attempt at cutting it in half didn't go very well. Also replaced Q5 with an IRF3205 to match the new Q6 in case that mattered, plus changed their gate resistors to 47 ohms. I'm kind of surprised nothing else on the board was fried throughout this ordeal.
Currently got the amp hooked up to a couple 4 ohm 6x9s in the garage, no heat issues. I think I'm going to stay away from 2 ohm speakers on the amp now though, a clean 75W per channel is plenty for the garage.
Currently got the amp hooked up to a couple 4 ohm 6x9s in the garage, no heat issues. I think I'm going to stay away from 2 ohm speakers on the amp now though, a clean 75W per channel is plenty for the garage.
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