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What is Don Up To? — June 14, 2016

The Ampeg SVTCL is the re-issue of the SVT300. The most common fault with this unit is the protection circuit comes on...which is good, in that these amps never go up in flames. It is bad because a slight mismatch in your output tubes and the amp shuts down. This one just got a new set of output tubes and it was still shutting down. I had to test the tubes in my old SVT100 and verify that they were indeed working and matched. I couldn't do this test in the SVTCL because it kept shutting down. The tubes were all good. So I took the amp apart and searched for a reason for the protection circuit to turn on. The filament wires to the output PC-board was badly heat-stressed. The protection circuit does monitor filament voltages. I fixed that. The grid resistors to the the output tubes were out of spec. I replaced the grid resistors as they could cause mismatched currents in the output tubes. Then I found the foils on the output tubes socket were lifting off the PCB. These loose foils could easily tear causing intermittent tube performance. Jumpered all of these foils on each output tube socket with 600V wire. Put it all back together and it worked. I ran it with a bass thumping GOOD. Ran it with a test tone into a dummy load to clipping 300+Watts GOOD.

What is Don Up To? — June 2, 2016

This is a $250.00 baby monitor. The battery charges through the USB port. The USB port is surface-soldered to a cheap Chinese PC-board. Guess what? Over time, the foils rip off the PC-board and then you have no way to charge the battery anymore. Spend another $250 on a new one? Not this time! I found a power supply that had a similar rating as the battery. I soldered the power supply to the battery wires, dumped the battery, turned it on and it works again! No more battery charging. The owner said the batteries died way too fast anyway.

What is Don Up To? — May 29, 2016

Just finished chopping this Yamaha D80. We had to make the power supply external as it would induce hum if we put it into the top half of the unit. We could have replaced the power supply with digital switching modules, but we were on a budget for this project. I think it turned out really well.

Click on the image to toggle between the before and after pictures.

What is Don Up To? — April 29, 2016

Before I was an ugly ***** hiding in someone's garage for 20 years. Now I have had a complete makeover. See me on the right. I have an effects loop and I have both a 122 and 147 Leslie ports. I sound so sweet.

This makeover was 6 months or more in the making. Isn't she lovely!

Click on the image to toggle between the before and after pictures.

What is Don Up To? — April 11, 2016

Fixed this hand-wired Marshall under warranty. Yes, Marshall still makes some really sexy handmade amps. This unit had output tube failure. Another shop replaced the tube and gave it back to the customer. He tried it and it hummed like a banshee! So he brought it to me. As I have said before, I love kicking technical ass. This was a hard problem. I searched for an open or burned ground: nothing. All grounds were fine. I found the effects loop circuit seemed to contribute to the hum a bit, but this was not the main problem. It turned out the problem was with the hum balance control. It has a dead spot in it. This likely happened when the output tube failed. I measured the pot and it was definitely burned inside but it look perfectly OK from the outside. Replaced the pot and adjusted out the hum. Fantastic! Everything was good. Don fixed what someone else missed.

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