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August 20, 2019, 11:43:24 AM

Author Topic: Smash build with a few wonky resistance measurements (resolved)  (Read 651 times)

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Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #15 on: February 17, 2019, 11:52:09 AM »
When I removed the PCB from the chassis, the mica insulator pad looked well positioned to prevent the L-200 touching the chassis. I have reinstalled this, with the mica covering the full length and width of the L-200 metal tab. The shoulder washer is properly set.
I still have the same issue. The screw and the nut show OL, the L-200 tab shows 360 Ohms. Shall I insulate the mica from the cassis with electrical tape underneath, and another piece of electrical tape over the shoulder washer?

Offline Paul Birkeland

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Re: Smash build with a few wonky resistance measurements
« Reply #16 on: February 17, 2019, 03:49:10 PM »
Pull it back off an check again.

I'll reiterate that the solder tab, screws, and L-bracket touch the chassis, and terminal 6 touches the chassis, ergo the solder tab should show 0 ohms.  Do the L-brackets themselves show 0 ohms?  What is the DC resistance between the L-200 metal tab and the chassis when it's mounted?

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #17 on: February 18, 2019, 05:20:35 PM »
Pulled it off and mounted it again. The mica sits perfectly under the L-200 body, and the shoulder washer is properly set. The screw and nut holding the L-200 showed OL at first, so I tightened them to make proper contact. It not shows a reading of 0 Ohms. The resistance between the L-200 when mounted and the chassis is 360 Ohms. The solder tab at the PCB shows 0 Ohms. The L-brackets also show 0 Ohms against ground/chassis.


Offline Paul Birkeland

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Re: Smash build with a few wonky resistance measurements
« Reply #18 on: February 18, 2019, 07:13:11 PM »
Let's see some closeup photos of the L-200 where it's mounted.  The metal tab of the L-200 is internally connected to the ground reference of the regulator (the solid black wires coming in and out of the board).  If these measure properly when the L-200 isn't mounted to the chassis, then we have to conclude that there's something weird going on with the mounting. 

-PB
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline 2wo

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Re: Smash build with a few wonky resistance measurements
« Reply #19 on: February 19, 2019, 08:46:41 AM »
 In the last pic you posted of the back of the Reg board, is the solder connection at the lower left,  closest to the screw perhaps touching the top plate?...John
John Scanlon

Offline Natural Sound

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Re: Smash build with a few wonky resistance measurements
« Reply #20 on: February 19, 2019, 10:04:08 AM »
In the last pic you posted of the back of the Reg board, is the solder connection at the lower left,  closest to the screw perhaps touching the top plate?...John

Good catch John.

Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #21 on: February 19, 2019, 05:29:38 PM »
Hey guys,

Alright. It did not seem to me that the solder touched the chassis plate, but I trimmed a little more, and re-soldered here and there. Just to be on the safe side, I have also put a bit of Kapton tape underneath the PCB where it touches the chassis.
Redid my resistance measurements, and they are all spot on now. You guys were right! Thanks to eagle eyes 2wo and Natural sound, I can go ahead and do my voltage checks tomorrow! And a big Thank you! to PB for all the troubleshooting and leading me to the PCB board with his patience and awesome response times! And thanks also to Oguinn for the suggestion with the Dremel tool. Cheers, FS

Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #22 on: February 23, 2019, 10:35:26 AM »
After the resistance measurements checked out, I moved on to the voltage measurements. Everything came out to be within 5% of the listed values. I hooked it up to the Seductor. It sounds very different from the SS pre-amp. I can't explain the signature very well. It sounds both blurry yet detailed. It is easy to get the Orcas to show distortion or clipping, something I did not get from the Seductor when driven with the Pre V630. When I hooked it up to the Crack, I heard the same kind of distortion when turning up the volume on the Smash. I have the smash-up ready for installation. It seems that people observe even more tube microphonics with the upgrade, so I am wondering if it will be worth it.

Offline Paul Birkeland

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Re: Smash build with a few wonky resistance measurements
« Reply #23 on: February 23, 2019, 10:42:06 AM »
The Smash-up makes an enormous difference, perhaps more than any upgrade other than the iron upgrade for SEX 2.0.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #24 on: February 23, 2019, 10:55:15 AM »
Thanks! That is what I needed to hear :) How much more in improvement would be there to be gained from the additional SmashQuiet upgrade?

Offline Paul Birkeland

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Re: Smash build with a few wonky resistance measurements
« Reply #25 on: February 23, 2019, 11:43:58 AM »
The SmashQuiet will have perfect channel balance and some qualitative improvements that are also substantial, but not as substantial as what the Smash-up provides.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline FS

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Re: Smash build with a few wonky resistance measurements
« Reply #26 on: February 23, 2019, 06:08:56 PM »
I have installed the Smash-Up. All voltage measurements were spot on. I have put the pre-amp back in front of the Seductor. The sound is now completely different from what it sounded before.  :o It sounds awesome.  :) I am not good at describing sound signatures. I just feel that it sounds right to me. Also, the clipping with the Orcas is gone. Now I understand why BH later folded this upgrade into the base kit. I would not want to have to go back to the stock version. The only thing I am missing is the awesome purple glow from the poor tube that had to make way for the 6SN7. I am seriously considering the SmashQuiet now. However, I may not be able to hear a difference if it is too subtle  :) While the 6SN7 tube seems now as microphonic as the 4P1L tubes (the OD3 was quite), it does not really bother me. Thank you, Bottlehead! This was a very satisfying build. FS

Offline FS

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Re: Smash build with a few wonky resistance measurements (resolved)
« Reply #27 on: April 21, 2019, 05:51:34 PM »
I have now completed the SmashQuiet installation. To be on the safe side, I started with the resistance checks as outlined in the basic Smash manual. Everything checks out as it is supposed to, except fo B2, which shows a value of OL instead of 0. I have re-soldered all taps on the B socket, and the red wire from 4 to B2. Does the SmashUp change any of the resistance values on the B socket? I was assuming that none of the resistance checks changed from basic Smash to SmashUp, correct? Thanks!
FS

Offline Paul Birkeland

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Re: Smash build with a few wonky resistance measurements (resolved)
« Reply #28 on: April 21, 2019, 07:27:56 PM »
Does the SmashUp change any of the resistance values on the B socket?
Yes, all of them, especially the 4 pins on the octal socket that have no connections in the stock Smash but get connected for use with the 6SN7 in the Smash-up.
Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man