Can't get Speedball to stay stable.

danosol · 6654

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Offline Paul Birkeland

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Reply #15 on: June 04, 2013, 07:39:50 PM
It is probably worth rolling in a different 12AU7 if you have one.

You should also have a look at the 12AU7 itself, to see if one half of it goes dim when you're having your issue (half of the heater could be getting crusty once it's warmed up).

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline danosol

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Reply #16 on: June 04, 2013, 07:44:35 PM
Just reheated the LED again and It's working, but for how long.  If you're looking from the back it seems to be the LED on the left cause when they are out the one the right is lit but very very dimly.


Offline Doc B.

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Reply #17 on: June 04, 2013, 07:50:39 PM
Ajay, if you could leave it with us for a day I'm sure we can carve out some bench time to go over it more rigorously and sort it out for you. Maybe the 2N2907 or an LED was stressed when the MJE350 was in backwards and is having some kind of intermittent issue or something. If that is the issue we can build up a new board and install it for you.

Dan "Doc B." Schmalle
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Bottlehead Corp.

Offline danosol

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Reply #18 on: June 04, 2013, 08:02:07 PM
I'll see how this goes.  It's a bit expensive taking the ferry over.  You guys have been very generous however, and I appreciate that.  I think it may be the LED's but why would it work for a full day and all of a sudden stop.  I don't think it's the 12AU7 I tried another 12AU7 prior to this and it made no difference.  I also metered the transistors and they all tested OK.  I'm currently about a half an hour into the re-flow of solder on the LED that I think is the culprit so I'll be a bit more patient.
« Last Edit: June 04, 2013, 08:05:53 PM by danosol »


Offline Doc B.

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Reply #19 on: June 05, 2013, 05:24:30 AM
My hunch is that it may be a thermal issue. It might be that when the amp goes through a warm up and cool down cycle that a solder joint that looks good shifts ever so slightly and a connection is opened. Reflowing the joints on the C4S is indeed a good place to attack the problem. Luckily the components on the board are all pretty heat proof so you don't need to worry about reflowing the pads if necessary.


Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline Paul Birkeland

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Reply #20 on: June 05, 2013, 06:18:09 AM
I agree with Doc, I have yet to see an LED that sometimes works, either they conduct and function, or they are 100% broken (generally from being overheated).

If you had an MJE-350 in backwards, then the 2N2907 is probably also toasted. 

What part of town are you in?  I'd be happy to host you over the weekend and look over your amp (I'm in SE King County).

-PB

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline danosol

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Reply #21 on: June 05, 2013, 06:24:14 AM
Fired it up this morning and It seems to be working.  I didn't flip it over to check to see if the LED's were lit up, but I asume it was.


Offline danosol

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Reply #22 on: June 05, 2013, 06:29:04 AM
PB that would be awesome!  I live in North Edmonds.  Let me know what works for you and I'll be there.  I will in the interim keep tabs on it during the rest of the week and see what happens. 

I do notice that it gets pretty hot, both the chassis plate and the transformer after about an hour plus.  If I try and grab the transformer by it's sides I can't hold it for long cause it's so hot.  I'm s that's normal but not sure.


Offline Doc B.

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Reply #23 on: June 05, 2013, 07:27:35 AM
Yes, it will get pretty hot. That's normal.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline danosol

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Reply #24 on: June 07, 2013, 06:52:23 AM
Seems to have stabilized.  I put in 5 hours last night with the amp being on and i fired it up this morning and no problems.  Been running it a bit the last few days.


Offline danosol

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Reply #25 on: June 12, 2013, 03:27:43 PM
Got home from work today, put in my Bendix 6080 and after a few minutes the right channel went out and practically took out my right eardrum.  LED's out again on board B.  This is rediculous.  I am done flowing solder!  It should either work or not.  There has to be more robust components to use.


Offline Doc B.

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Reply #26 on: June 12, 2013, 03:45:43 PM
I will suggest one more time that you let us do the repair for you.

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.

Offline danosol

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Reply #27 on: June 12, 2013, 04:04:58 PM
How do I measure the components to find the problem?  Im sure it's the LED's.  where can I buy a surplus of them.   What is the point of diy if you do it for me.


Offline Paul Birkeland

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Reply #28 on: June 12, 2013, 05:10:45 PM
Quote from: danosol on June 12, 2013, 04:04:58 PM
Im sure it's the LED's.

I'm 99% sure that your issue is not the LED's. 

Paul "PB" Birkeland

Bottlehead Grunt & The Repro Man

Offline danosol

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Reply #29 on: June 12, 2013, 05:18:57 PM
PB when are you able to look at the amp with me?


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