Beta 22 needs repair...Can anyone out there please help me?

beta22

Beta 22 needs repair...Can anyone out there please help me?

Postby daltonlanny » February 23rd, 2016, 11:18 pm

Hello all,
I am a new poster on this forum? Great to be here!
I cannot find anyone willing to repair my Beta22 on any other forums, or locally, at all.
I really don't want to scrap it, or even the bad board, cause it has high quality parts, and hard to find black gate caps in it.
A new board, if needed, would be ok, as long as it matched the other 3 boards, sonically.
A couple of weeks ago I bought a nice used fully balanced 4 board Beta22 amp with a separate dual power supply, single-ended and balanced inputs and outputs, high quality parts such as Black Gate caps, Goldpoint attenuator, etc.
It sounded wonderful until night before last.
I was listening to headphones with the single-ended 1/4" trs output jack, and I changed them out for another set of headphones that also were single-ended, and forgot to turn the volume all the way down, or the unit off.
I started smelling smoke and saw smoke come out of the top cover, and immediately turned it off.
It was still playing normally as far as the sound goes.
I took the top cover off, and on one of the boards, R32 was basically fried, so I figure that R32, some mosfets, maybe some other resistors, and possible diodes may have to be replaced.
If a new board has to be assembled, I would like the existing black gate caps and Nichicon Muse caps to be removed from the bad board to the new board. That way it would still match sonically with the other 3 boards too.
The other 3 boards inside the amp appeared normal, however.
I am no where near good enough at soldering, desoldering, or installing small parts to attempt a self repair, and my vision isn't what it used to be.
Ti at AMB suggested I try to find help on this forum, so I am asking for help.
Any help at all would be sincerely appreciated.
Thanks alot.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby lundervold » February 24th, 2016, 5:11 am

I'm located in Huntsville AL which is about 1.5 hour drive from Chattanooga so you most likely an additional hour from there. If you are willing to drive to Huntsville, I would be glad to help. I have most of my equipment here, Hakko 937 solder station, Hakko 972D de-solder station, Hakko 808 de-solder gun, yada yada. Have many spare parts for the B22 but don't remember off hand what I have. I have with me, a second 3 board B22 that hasn't been cased yet we could steal parts from if needed. I've built many of Ti's projects.

The down side is I'm negotiating a new contract in VA and not sure how long I'll be here but I suspect they will not be successful in making the changes I requested. Which means I could be here a while longer. I've been here for a year and it's time to get closer to home in PA

Anyway, give it some thought. If you find someone closer that would be awesome and save you a 2.5 hour drive.

BTW, If we couldn't get it complete in one day (parts etc, and no new contract) I'll be driving home March 11, we could meet at a place on 75 to drop it off.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby hagak » February 24th, 2016, 5:42 am

Clear detailed photos of the damaged area of the board would be very helpful for people assisting to get an idea of if the PCB is damaged or not.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby daltonlanny » February 24th, 2016, 7:19 am

There is really nothing to see except the burnt R32 resistor on that one board. Everything else looks perfectly normal on both that board as well as on the other 3 boards.
I have thoroughly looked at everything with a flashlight.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby amb » February 24th, 2016, 10:17 am

At the very minimum R32 and Q23 need to be replaced. There may be other damage but it will be hard to tell from photos. I would check the other MOSFETs for shorts, the values of R33, R34, R35, and do a diode check on D9 and D10. To prevent this from happening again, I recommend replacing R34 and R35 with 2.2Ω 2W metal oxide resistors and re-adjust the output stage bias on all boards.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby daltonlanny » February 24th, 2016, 1:38 pm

Thanks for the info, Ti. Much appreciated.
I still need someone to check it out and repair it for me.
I am basically a buyer and not a builder. Lol.
I'm not good at soldering, desoldering, replacing parts, or testing parts. I would probably wind up screwing it up even worse, to be honest.
I'm still waiting to hear from someone out there who might be willing to help me out.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby daltonlanny » February 27th, 2016, 9:41 pm

Update.
I'm sending my balanced Beta 22 and companion sigma 22 power supply to hagak for repairs, and possible mods next week.
He has kindly agreed to work on it for me.
Thanks a million hagak!
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Re: Beta 22 needs repair...Can anyone out there please help

Postby daltonlanny » March 12th, 2016, 1:09 pm

Update:
Still waiting on Jeffrey (hagak) to repair the board on my balanced Beta 22 amp, increase the gain to 8x on all boards, change out the twin toroidal transformers, and replace with 100 va ones, and a few other minor mods.
He still has it, and is waiting on parts.
Can't wait to get it back!
Will keep everyone posted.
Thanks again, hagak.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby daltonlanny » April 26th, 2016, 8:06 am

Hate to revive this thread, but I need repair help...Again.
Hagak got my amp repaired a few weeks ago and did a great job on it.
Unfortunately, I loaned my B22 to a friend last weekend and specifically told him not to unplug 1/4" trs plugs while the amp was on.
Well, he did and another board is damaged.
Hagak and Mister X said they were too busy to help me right now.
So if anyone else out there can help me out here, and repair this board for me, please let me know.
Thanks for your help.
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Re: Beta 22 needs repair...Can anyone out there please help

Postby cfcubed » April 27th, 2016, 4:23 am

This is always disappointing to see because its so avoidable. Besides lowering volume whenever inserting/removing cans & following proper pwr-on/pwr-off order there's something else that should be done & should be well-known to those working on TRS jack β22s.
Only my 1st β22 had 0.47Ω R34s & R35s. Early on in all the hubbub WRT β22s & TRS jacks decided any β22s that passed through my hands would have ≥ 1R R34s & R35s. This must work because brought TRS 2-channel β22 to a meet once & some guy removed my headphones as slowly as physically possible & with volume up. As if he was trying to burn the amp. Was too far away to stop him but let him know about it. Amp was fine. Wondering what values your β22 has.

Some Ti quotes (β22 parts page + post @ other forum):

Notes about R34 and R35:
The default value for these resistors is 0.47Ω. If you have TRS headphone output jacks, the value may be increased to 1Ω to 2.2Ω for added protection. This is because TRS plugs create momentary short circuits while being inserted or removed, and could potentially damage the output MOSFETs.


Originally Posted by amb
Note that increasing the value of R34/R35 will impact your output stage bias adjustment. Ohm's Law says V = I * R, so if you want 120mA of quiescent current, and R is 1 ohm, then you need to adjust VR2 to get 120mV across R34 (and R35).


IMO β22 w/TRS jack builders / repairers should not consider using default value 0.47Ω R34s & R35s & should retrofit any that pass their way to ≥ 1R.
Doing that may prevent us seeing any more of these sorts of posts:) BTW I'm waaayyy back-logged w/work or I'd help this guy out.
Last edited by cfcubed on April 27th, 2016, 4:38 am, edited 1 time in total.
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