No. It was a tiny small dot when fuse blew. Almost imperceptible, like a tiny static dot. No smoke or smell. OK, all tabs are quiet when tested. BUT. now, the ground outs buzz with continuity to ground on PS outs, which makes perfect sense as a ground wire is attached! The other two outs are all quiet. Problem is the inputs A/C 0 A/C pads all have continuity to ground. All 6 pads on input buzz. I guess I killed something?
Oh, I thought I fried something. I guess it's time for fire up #2. Whew!!!. I really thought I fried them. I've got extra MOSFETs if necessary.
Apparently, I was WAY over tightening them.
Bubba
Apparently, I was WAY over tightening them.
Bubba
Last edited:
The space was minimal, solder iron at a cute angle, once pad was melting solder, I added some to cover pad, it sort of built up on legs a bit.
Headway! Fuses arrived on schedule and replace the fried one. Successful fireup! Well, everything lit up and nothing smoked or acted up.
I put the multimeter set to DC on the pre output and ground, about 280 mV on each side. I did not have the outputs shorted, it seemed
fairly stable. I did not attempt to reduce it, just powered down and thought best to check in.
If all sounds as it should be, I will refire up and twiddle the pots. does this all sound as it should?
Russellc
I put the multimeter set to DC on the pre output and ground, about 280 mV on each side. I did not have the outputs shorted, it seemed
fairly stable. I did not attempt to reduce it, just powered down and thought best to check in.
If all sounds as it should be, I will refire up and twiddle the pots. does this all sound as it should?
Russellc
It checks high mV at first because the offset trimmers are midpoint factory set. Which is high for where they need to be in this preamp.
Turn them towards 0mV and dancing around there. Don't short any outputs! To short inputs is only permissible.
Turn them towards 0mV and dancing around there. Don't short any outputs! To short inputs is only permissible.
Im sorry, thats what I meant. I will refire and turn them a bit. One thing I was a bit unclear on, after it is set as low as possible, and the 8 leg device is installed, is there further adjustment of the pots, or is that as good as it gets? I have not done this yet...
Russellc
Russellc
Check the DC power rails once more, now that everything is connected. They should still be around +/- 17V and fairly symmetrical.
If I remember right, I used standard gain, but higher bias. This huge heatsink is unphased...
If .936ishv is normal, I will let it burn a while, reset offset. I will then switch it off and install 8 leg. I assume as usual, this should NOT be done with pre switched on, right?
Russellc
Russellc