Issue with Crack Voltage [solved]

lwhitit · 7901

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Online Paul Birkeland

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Reply #15 on: January 16, 2015, 01:39:04 PM
Quote from: lwhitit on January 15, 2015, 08:27:19 PM
When checking the voltage touching the middle and either end leg causes the leds to light up bright. What should I try next?
That would tend to suggest a flaky solder joint on the MJE-350.

Do a slow 3 second count once your tip is on each solder joint, that ought to give the solder enough time to work into the through hole and make a good connection.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #16 on: January 16, 2015, 01:41:19 PM
Quote from: Caucasian Blackplate on January 16, 2015, 01:39:04 PM
That would tend to suggest a flaky solder joint on the MJE-350.

Do a slow 3 second count once your tip is on each solder joint, that ought to give the solder enough time to work into the through hole and make a good connection.

As always thanks for the reply PB! I tried this last night but I will give it another whirl tonight and report back the results.


Offline lwhitit

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Reply #17 on: January 16, 2015, 07:09:00 PM
No Change. Should I try swapping some parts or moving things around?


Offline Strikkflypilot

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Reply #18 on: January 16, 2015, 07:19:18 PM
Any chance of a closeup?
When I had this problem, reheating that joint took a couple of tries because rosin had solidified between the pad and leg, what helped me was desoldering with a braid before redoing the joint.

Home system:
Sources: Ibasso DX90, Google Chromecast Audio optical out
DAC: Schiit Gumby
Amp: Bottlehead Mainline
http://bottlehead.com/smf/index.php?topic=7463.0
Phones: HD800S

Office:
Sources: Iphone/ Ipod
DAC: Dragonfly Red+Jtrbug
Amp: Crack/Speedball heavily modded
Phones: HD580,HD600 grilles

Offline lwhitit

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Reply #19 on: January 16, 2015, 07:23:40 PM
Quote from: Strikkflypilot on January 16, 2015, 07:19:18 PM
Any chance of a closeup?
When I had this problem, reheating that joint took a couple of tries because rosin had solidified between the pad and leg, what helped me was desoldering with a braid before redoing the joint.

Best I can do. Thanks for the quick reply.


Online Paul Birkeland

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Reply #20 on: January 17, 2015, 09:39:59 AM
On your last photo, have a look at the solder joints on R2.  One of them looks very inadequately heated.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #21 on: January 21, 2015, 08:57:27 PM
Quote from: Caucasian Blackplate on January 17, 2015, 09:39:59 AM
On your last photo, have a look at the solder joints on R2.  One of them looks very inadequately heated.

I removed the old solder and cleaned everything up again but still no change. Not sure what else to do.


Online Paul Birkeland

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Reply #22 on: January 27, 2015, 08:11:22 AM
You might want to try running the amp with no 6080 and with the large Speedball board removed.  This will isolate the 12AU7 and the small PC boards that feed it, and may bring your voltages at T1 and T5 back into check.

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #23 on: January 27, 2015, 12:17:10 PM
Quote from: Caucasian Blackplate on January 27, 2015, 08:11:22 AM
You might want to try running the amp with no 6080 and with the large Speedball board removed.  This will isolate the 12AU7 and the small PC boards that feed it, and may bring your voltages at T1 and T5 back into check.

-PB
Thanks for the response

Just to confirm I remove the 6080 and disconnect the large SB board (with the heatsinks). After that do I leave the originally connecting wire unconnected or how should I orientate everything after removing the big board?


Online Paul Birkeland

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Reply #24 on: January 27, 2015, 03:46:16 PM
Leave the wires that went to the big board poking up in the air, away from anything else.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #25 on: February 04, 2015, 07:14:34 PM
Quote from: Caucasian Blackplate on January 27, 2015, 03:46:16 PM
Leave the wires that went to the big board poking up in the air, away from anything else.

Real life got in the way but I was finally able to test this out. Removing all wires to the middle pcb did regulate the voltage for #1 (75) but #5 jumped all the way to 211.


Online Paul Birkeland

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Reply #26 on: February 04, 2015, 07:24:19 PM
Now swap the small boards.  This will either isolate the issue to one of the C4S boards, or half the circuit under them.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #27 on: February 04, 2015, 07:49:17 PM
Quote from: Caucasian Blackplate on February 04, 2015, 07:24:19 PM
Now swap the small boards.  This will either isolate the issue to one of the C4S boards, or half the circuit under them.

Swapping the boards: B is the bad one 211 on #1. A jumped up a bit when I swapped it 83 on #5.


Online Paul Birkeland

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Reply #28 on: February 05, 2015, 07:23:58 AM
Try again to reheat the center leg on the MJE-350 on the bad board.  Also be 100% sure that you have the correct R1 resistor installed, as swapping one of the big board R1 resistors onto a small board will leave you with high plate voltage.

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline lwhitit

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Reply #29 on: February 09, 2015, 08:37:33 PM
Quote from: Caucasian Blackplate on February 05, 2015, 07:23:58 AM
Try again to reheat the center leg on the MJE-350 on the bad board.  Also be 100% sure that you have the correct R1 resistor installed, as swapping one of the big board R1 resistors onto a small board will leave you with high plate voltage.

You were right I swapped the resistors :o I triple checked this thing but sure enough. I now have 80 on #1 (bad one) and 82 on #2.

Putting it back together and powering up now I am back to where i started but with different readings. I am going to get there.

3/4 LEDS on big board lit other 4 leds are lit but very low.
Terminal Voltage
1 75-90 (67)
2 170 (76)
3 0 (0)
4 170 (75)
5 75-90 (36)
6 0
7 100 (66)
8 0
9 100 (33)
10 0
11 0
12 0
13 170 (75)
14 0
15 185 (129)
20 0
21 206 (189)

So the issue is now on the big board?
« Last Edit: February 09, 2015, 09:03:55 PM by lwhitit »


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