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Genz Benz Streamliner, Part 10

#907
ImageUploadedByTalkBass1417484467.487635.jpg
Self made rack kit, cost.... $30 thanks to eBay and Ace Hardware.
 
#908
Be sure those screws are short enough that there's no chance of contact with the circuitry. 3 of the 4 screws are under PCBs, including the DI section where there's not much clearance. There's >300 volts all over the preamp PCB.
 
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#909
agedhorse said:
Be sure those screws are short enough that there's no chance of contact with the circuitry. 3 of the 4 screws are under PCBs, including the DI section where there's not much clearance. There's >300 volts all over the preamp PCB.
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That was something I considered when I bought the screws. So I bought 2 different lengths. The longer ones did not seem to contact anything (by feel), but I will switch to the shorter ones tomorrow and add washers to get the depth exactly the same as the stock feet screws.

Thanks a million for the advice! Glad I didn't power it up!
 
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#910
By feel isn't good enough with high voltage circuitry. A hard short to the HV supply could easily cause failure of a very expensive component.

By the way, this is the reason ALL of our products are manufactured with grounded AC supply cables. If the chassis was ungrounded and a screw made contact with the HV supply, the entire chassis would rise to the same high voltage relative to everything else around the amp, creating a very dangerous condition. This is why I am so against designs that use ungrounded AC cables, even if they use double-insulated construction methods.
 
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#911
agedhorse said:
By feel isn't good enough with high voltage circuitry. A hard short to the HV supply could easily cause failure of a very expensive component.

By the way, this is the reason ALL of our products are manufactured with grounded AC supply cables. If the chassis was ungrounded and a screw made contact with the HV supply, the entire chassis would rise to the same high voltage relative to everything else around the amp, creating a very dangerous condition. This is why I am so against designs that use ungrounded AC cables, even if they use double-insulated construction methods.
Click to expand...
I understand. I've got electricians in the family. I started to disassemble the underside to check the screw length and possible contact points. Looks like I should've done that or just asked you first. I'm meticulous, a scientist by trade, I'll get it right tomorrow.
 
#912
Just warningothers who may try the same thing.

The screw length will be a function of space between the rack shelf and the underside of the chassis, if you removed the feet than you would add about 0.060" for the thickness of a typical rack shelf metal. In fact, removing the feet, the original screws might be the same length as the recess in the feet are about 0.080". Double-check!
 
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#913
I'll check. I plan on leaving the feet, as it leaves the amp sitting right even with the curved up lip of the shelf. I also didn't want metal on metal (chassis to shelf) contact since the rack will be sitting on speaker cabs, vibrating at high volume. I've heard that can shorten tube life?
 
#915
What I did with the longer screws was slip them through the shelf holes and through the rubber feet and marked the remaining protruding screw thread with a black sharpie. I then pulled the screws out and carefully threaded them into the chassis until the sharpie mark just disappeared. When I didn't feel resistance/contact, I thought I was ok. But tomorrow, I'll use the shorter screws and (with washers as spacers) I'll get the same length of thread going into the chassis as the stock screws did (with the feet in place).
 

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