[tomb]

Quote:

Originally Posted by smrtby123 /img/forum/go_quote.gif Here is my Beezar SSH kit fresh from this morn. Sounds amazing so far, definitely a step up from my hacked together Cmoy. Kudos to TomB, Dsavitsk and Pete Millett for such a great little amp.

Thanks so much!

Your amp looks great - love those LED's. I sure don't want to be discouraging, but I'm forced to tell you that the endplates/bezels are in the wrong order. The metal plate goes on outside of the bezel. The endplates are supposed to fit on top of the bezel recesses and on top of the bezel screw holes.

 

[tomb]

Quote:

Originally Posted by nkk /img/forum/go_quote.gif Ok, I think I got it. Where would one buy more of the Berquist pads? I think one of mine is shorting. I just put the upper part of the box back on the PCB, and it is not even powering on again. That would make sense if the transistor were shorted to ground, right? -Nkk

Before we jump to conclusions, let's back up and ask some questions, first.

1. Can you see the Bergquist pad and are you certain that it's cut? Unless you've torqued the MOSFET down so hard that the tab has cut into both the Bergquist pad and the case anodizing, conceivably the case anodizing is enough to insulate the MOSFET.

2. Did you install the shoulder washer correctly - in the right position and in the correct orientation? I finally finished some more of the SSMH website. Refer to the heat sink mounting diagram here:
SSMH Heat Sink

Confirm that your assembly is in the same orientation and sequence - especially the shoulder washer. If the shoulder washer is not correctly insulating the MOSFET tab, then it could very well cause a short. This is because the mounting hole is most definitely NOT anodized. However, the shoulder washer provides all the needed insulation from this hole - if installed correctly.

3. Is it possible that the standoff hardware is contacting the LED resistor and/or pad? If you did not install the lock washer on the PCB side of the standoff kit, it's possible that the hex standoff would turn when assembled to the lid. This might allow a hex corner to contact the resistor lead and/or pad.

In short, there may be a number of issues going on besides the Bergquist pad. It's not automatic that the MOSFET would short without the Bergquist pad - the case anodizing must be damaged as well.

 

[Fishline]

I've (almost) finished building my second p2p SSMH. The problem is that I can measure 48v at the power jack, but as soon as I turn on the power switch, it drops to basically 0v. Can someone give me some hint on diagnosis?

 

[Llama16]

wrong wiring if the power jack perhaps? Just guessing

 

[tomb]

Quote:

Originally Posted by Fishline /img/forum/go_quote.gif I've (almost) finished building my second p2p SSMH. The problem is that I can measure 48v at the power jack, but as soon as I turn on the power switch, it drops to basically 0v. Can someone give me some hint on diagnosis?

This is classic and has come up at least three times in the last week in this thread and others. You have a short. The Cisco power supply has a VERY good circuit breaker and will instantly cut off the power supply in face of a short. So, it appears everything is fine until you throw the switch - exposing the Cisco to whatever short exists in your circuit - and the voltage instantly drops to zero.

Go over your build carefully - check for exposed wire, lack of heat shrink, parts that can be binding against the case, and/or a MOSFET that's not isolated.

 

[Juaquin]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif The Cisco power supply has a VERY good circuit breaker and will instantly cut off the power supply in face of a short.

Just can't say this enough

 

[smrtby123]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif Thanks so much! Your amp looks great - love those LED's. I sure don't want to be discouraging, but I'm forced to tell you that the endplates/bezels are in the wrong order. The metal plate goes on outside of the bezel. The endplates are supposed to fit on top of the bezel recesses and on top of the bezel screw holes.

Haha wow. That makes a lot more sense than the way I hacked them on there. I think I was so excited that I actually got it to work I didn't even notice.

 

[nkk]

Tomb, you are truly amazing. Thank you. I now have a working SSMH.

Although, I get a really loud crack/pop at power up if my phones are plugged in. It also happens sometimes at power down. Is this normal?

-Nkk

 

[tomb]

Quote:

Originally Posted by nkk /img/forum/go_quote.gif Tomb, you are truly amazing. Thank you. I now have a working SSMH. Although, I get a really loud crack/pop at power up if my phones are plugged in. It also happens sometimes at power down. Is this normal? -Nkk

Oops! Never have your headphones plugged in before the amp is already turned on! The Starving Student's music output is referenced at 19VDC. That means "zero" sound is actually 19VDC. (The actual sine wave of music is able to vary from +48VDC down to zero, but 19VDC is the center.) This works because we have the output coupling caps at C3 and C5, which block the DC voltage. However, capacitors take time to charge - perhaps 10 to 20 seconds. While this is happening when you turn the amp on, that 19VDC is gradually reducing down to zero on the headphone jack.

If you have your headphones connected during those first few seconds, they're exposed to all of that voltage.

Turn-off is similar, but not as bad. It depends more on how slow the capacitors discharge.

Best advice to protect your headphones? Keep them unplugged unless the amp is up and running.

 

[tomb]

Quote:

Originally Posted by smrtby123 /img/forum/go_quote.gif Haha wow. That makes a lot more sense than the way I hacked them on there. I think I was so excited that I actually got it to work I didn't even notice.

's OK - you're not the first one to do it. Looks great, anyway!!

 

[CaptHowie]

tomb, is there still chance of more kits before Christmas?

-CaptHowie

 

[nkk]

That is what I figured was happening. That would be really helpful as a sort of post build note in your step by step build thread.

Anyway, thanks for all the help. I am thinking of building the second PCB I have, although I do not have the time now. Maybe spring break.

Thanks again,
Nkk

 

[tomb]

Quote:

Originally Posted by CaptHowie /img/forum/go_quote.gif tomb, is there still chance of more kits before Christmas? -CaptHowie

I'm sorry - it will be after the new year. There's just too little time for Hammond to produce the cases again and after talking with them, I felt it was best to wait instead of rushing everything and ruining everyone's holiday.

 

[CaptHowie]

Quote:

Originally Posted by tomb /img/forum/go_quote.gif I'm sorry - it will be after the new year. There's just too little time for Hammond to produce the cases again and after talking with them, I felt it was best to wait instead of rushing everything and ruining everyone's holiday.

Understood. Better decision I guess. It's only a few more weeks.

-CaptHowie

 

[GeckoSlayer]

I apologize for not wanting to read through all 284 pages of this thread, but a question to someone who has followed this thread, can you use alternate tubes? Namely ones off this page? (And preferably the cheaper ones off that page..?)

Thanks.