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SUPPORT FORUMS FOR CURRENT DECWARE GEAR >> MINI TORII   >> OA 3 tube fluctuating brightness.
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Message started by roggae on 01/28/13 at 22:40:06

Title: OA 3 tube fluctuating brightness.
Post by roggae on 01/28/13 at 22:40:06

Left channel tube is fluctuating in brightness while playing. Not slowly. It looks like it is losing a little juice then it comes back. Should I be concerned?

http://youtu.be/XQFnJosGKMs

Edit for video

Title: Re: OA 3 tube fluctuating brightness.
Post by Rivieraranch on 01/28/13 at 23:36:56

Switch it with the other one and see if that behaves like the tube that is flickering.  

Title: Re: OA 3 tube fluctuating brightness.
Post by roggae on 01/28/13 at 23:42:05

That's the first thing I did. The fluctuation stayed in that tube.  

Title: Re: OA 3 tube fluctuating brightness.
Post by Rivieraranch on 01/29/13 at 00:24:58

Maybe you should call Steve.

Title: Re: OA 3 tube fluctuating brightness.
Post by roggae on 01/29/13 at 00:35:24

Does that mean you think it could be something more troublesome? A replacement is like $8. Thanks for the responses!

Title: Re: OA 3 tube fluctuating brightness.
Post by Fireblade on 01/29/13 at 01:02:36

These are not expensive.  Just by yourself a pair of new ones.  These NOS tubes are generally very sturdy (Sylvania, RCA, etc.).

If you were to experience the same issue with one of the new ones, then call Steve.

Title: Re: OA 3 tube fluctuating brightness.
Post by Rivieraranch on 01/29/13 at 01:46:55

These tubes are all vintage. They are not in current production. You can find military and industrial types out there that are NOS.

Title: Re: OA 3 tube fluctuating brightness.
Post by roggae on 01/29/13 at 01:55:58

I guess my main concern was "is this going to hurt my amp?"

Title: Re: OA 3 tube fluctuating brightness.
Post by Fireblade on 01/29/13 at 01:57:20

http://www.ebay.com/itm/One-1970s-Sylvania-OA3-tube-New-Old-Stock-New-Box-/360436804890


http://www.ebay.com/itm/0A3-Tube-RCA-NOS-GE-Voltage-Regulater-VT-260-OA3-/200876160289?pt=Vintage_Electronics_R2&hash=item2ec526f521

'New ones' referred to replacements bought from the market, RR.

Title: Re: OA 3 tube fluctuating brightness.
Post by Fireblade on 01/29/13 at 02:00:57

Roggae,

If the particular tube is faulty, I would stop using it altogether.  Just replace that pair and see if the problem goes away.  This would not make anything worse.  If the problem persists with the replacement, stop the amp and call Steve.

Title: Re: OA 3 tube fluctuating brightness.
Post by roggae on 01/29/13 at 02:03:16

You know, mine look nothing like those. Am I mistaken? Mine look like my stock 6v6s only smaller.

Title: Re: OA 3 tube fluctuating brightness.
Post by Fireblade on 01/29/13 at 02:10:41

It does not matter.  My stock ones are larger than any 6V6 tubes I've tried so far (Coke shaped, with wide shoulders).  

The important thing is to use the same spec tube.  These come in different shapes and sizes, but internally are all equivalent and should do the job.  

They may sound slightly different than your originals, in which case if you prefer that sound, just buy those same ones. Technically, there are no differences.

Title: Re: OA 3 tube fluctuating brightness.
Post by Rivieraranch on 01/29/13 at 02:23:21

Get a matching pair of old GE, Sylvania, RCA or CBS brand; not 70's stuff though.

http://www.ebay.com/itm/5-NOS-GE-0A3A-GREAT-BRITAIN-TUBES-TEST-GREAT-LOOK-VOLTAGE-REG-TUBES-/330858113922?pt=Vintage_Electronics_R2&hash=item4d08ae2b82 

http://www.ebay.com/itm/LOT-OF-5-0A3-OA3-CBS-RADIO-TUBES-/321052572645?pt=Vintage_Electronics_R2&hash=item4ac0397be5

Title: Re: OA 3 tube fluctuating brightness.
Post by Fireblade on 01/29/13 at 10:55:11

RR,

My point was that the Op could easily and inexpensibly replace them and find out what the real issue is with his amp.

It is well documented that, in general, these voltage regulator tube types last for a long time and are very robust.

Having said that, better reputed vintage NOS types 'may' even sound better and may last longer.  The Op will always have the prerogative of choice.

Thanks!


Title: Re: OA 3 tube fluctuating brightness.
Post by Rivieraranch on 01/29/13 at 12:14:51

My point was that the older ones might do better.

Title: Re: OA 3 tube fluctuating brightness.
Post by JD on 01/29/13 at 14:27:02

Roggae,

One of my Ob3a's does something similar just not as often or obvious.  Since I love them and it hasn't affected the sound negatively they've stayed in place.  Pick up a couple back up pairs and tube swap to see if there is an audible change.  I suggest NOS RCA's.

JD

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