Daan Jacobs amp project

[u235]

Swapped valves, no difference.

Then I bridged somthing with a screwdriver and the capacitor discharged, blowing to transistors. Rudi kindly offered to replace them for me. Off to his place where he did just that (v. patient man). He connected and tested the power and preamp board, and told me to reinstall them AS IS, no fiddling. This is did, after blowing the whole affair off with an air duster on the compressor. Checked it all v. carefully. Switched the power on, and BANG! A VERY fat little electrical explosion. How, I have no idea.

So its off to Waverley tomorrow to buy new transistors again - electronics123 are the only people who have all 3 transistors in stock.

Pic of the damage to the board attached.

[Heinrich]

Swapped valves, no difference.

Then I bridged somthing with a screwdriver and the capacitor discharged, blowing to transistors. Rudi kindly offered to replace them for me. Off to his place where he did just that (v. patient man). He connected and tested the power and preamp board, and told me to reinstall them AS IS, no fiddling. This is did, after blowing the whole affair off with an air duster on the compressor. Checked it all v. carefully. Switched the power on, and BANG! A VERY fat little electrical explosion. How, I have no idea.

So its off to Waverley tomorrow to buy new transistors again - electronics123 are the only people who have all 3 transistors in stock.

Pic of the damage to the board attached.

just check for yourself that they give you the correct parts,they usually get it wrong.

[chipwelder]

^^^ +1!!! 

[u235]

I wonder how long I can push my luck. Got a call from Rudi yesterday offering to help (again!) and he fixed the board for me this morning. He's a great guy, didn't even look at me skeef when I showed him the board. Thanks Rudi, you're a gentleman!

So now to try again.

(It looks like when I disassembled the board, and put the little rubber risers on my workbench, one got some metal stuck on it. When I put the board down I didn't screw it down because I wanted to test it first, I just put the risers in place and rested the board on them. So the rubber riser wasn't in it's place at the corner of the board, it sat in the middle, I think with a strand of copper wire on its head.)

Rudi also spotted that I'd soldered the one earth on the preamp in the wrong place, and fixed it. I'm holding thumbs that this fixes the buzz!

I see I didn't post the pic last time.

[u235]

This is now thoroughly tedious.

I decided to test the power amps before connecting the preamp. Put a signal straight from the CD walkman into the signal input to the power amp. ie No channel selector, no volume pot, no preamp, preamp power supply not connected. Preamp and power supply are still in the box from Rudi. I disconnected one amp by taking out the fuse in the power cable.

It buzzes. Swapped them around. Buzzes.

Neither buzzed when the poweramps were individual units AND connected up to the preamp on Rudi's lounge floor. No accident has befallen either poweramp since then.

I am not having fun.

I will not post on this thread again until this f*cking project is done and dusted.

[Shonver]

Neither buzzed when the poweramps were individual units AND connected up to the preamp on Rudi's lounge floor.

Can't you connect it that way now (in the enclosure)?
Do you have separate power supplies for each channel?
Did my suggestion not help?

[soundadv]

And how is the enclosure coming?

[u235]

Sorry about the no news - I've delivered the paltes to a company in the south to do the rolling. They've given me a reasonable price but have said that I shouldn't be in a hurry as they will squeeze it in.

I'm sailing to the Caribbean as a crewmember on a 40ft yacht in a couple of weeks time, probably only back in April, so I'll pick up the threads then!

[Atjan]

That sounds fantastic! The cruise more so than the amp, at this stage.