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-   -   Bryston 3B Output Transistors (http://www.diyaudio.com/forums/solid-state/227839-bryston-3b-output-transistors.html)

jkuetemann 15th January 2013 02:48 AM

Bryston 3B Output Transistors
 
I have an older (circa 1988) Bryston 3B that has blown two output transistors on one channel.

They seem to have house part numbers on them, BR6521 and BR6522. They are of Motorola manufacture. The amp appears to have been repaired at some point as there are two newer transistors. They also appear to be house part numbers, SJ6521 and SJ6522, also from Motorola. The drivers are SJE1490 and SJE1491, again Motorola parts.

Does anyone know with reasonable certainty if these are simply selected standard devices and what the standard equivalents would be? Newer Versions of the 3B use MJL21193 and MJL21194 for outputs (yes, a different case style) and MJE15030 and MJE15031 for the drivers.

Any thoughts on using MJ21193/MJ21194, MJ21195/MJ21196, or MJ15003/MJ15004 pairs? I'll assume the selection criteria will be good match in hFE and Vbe. The MJ2119x have a little more SOA at higher voltages and a higher fT at the possible expense of hFE. The MJ1500x have similar SOA at the amplifier's operating voltage, but loose a little at higher voltages. Also fT is lower, but hFE could potentially be higher. Or should I simply see if Bryston will sell spares?

It seems there is no collateral damage, but if anyone is well versed in servicing these then I'm open to suggestions on what to look at before putting it back into service.

This was a freebie, but I'll spend some money on it if it is worth pursuing.

DUG 15th January 2013 03:35 AM

Read this thread:

Bryston 3B repair.. What should I do? - Gearslutz.com

Despite the naming in the link it is about a Bryston 3B. :)

The link is a US based situation...Try to call Bryston Canada and see if their policy and pricing is similar.

DUG 15th January 2013 03:43 AM

If you don't want to pursue repair, let me know...I might be interested in a drive to Paris for the right price.

:)

Darn, just found this link:

D 'n A Electronics Specifications | Bryston 3B Specs | Bryston 3B Repair | Bryston Repair | Bryston Stereo Repair | Vintage Stereo Repair

"Bryston 3B Restoration:
We restore 3B power amplifiers."

Let me know either way.

jkuetemann 15th January 2013 04:21 AM

I would really like to have a listen to this unit before I decide wether or not it will have a permanent home here or not. I have it stripped down and have it all cleaned up, I just need to fix the bad channel. These don't look like they are exceptionally complicated and I don't think it will be tough to set right. I comes down to parts selection / sourcing at the moment.

I have some other 'rescued' old pro amps, one all cleaned up and working (Yamaha PD2500) and another I also just got (HH V800) that doesn't seem to power up properly (I think the voltage selector switch is toast). That Yamaha is actually nice sounding, though the fan cooling is a bummer in a quiet setting. The HH has yet to sing, we'll see. It is a massive over-built british beast with a wiring loom that looks like a nightmare and also fan cooled. Comparatively the Bryston is nicely made and and convection cooled. I'm looking forward to hearing it.

jkuetemann 15th January 2013 04:24 AM

The company that is retiring some of their gear (and where my existing pieces were sourced from) apparently has more 3B and 4B available, but since they apparently work they aren't free. Something like $200 per 3B and $500 per 4B. I've no idea if that's reasonable for ex-sound reinforcement equipment. Any thoughts?

DUG 15th January 2013 04:34 AM

I've seen $150 up to $400 (in 2010 post) for a 3B

$150 for a 3B working would warrant a drive, $200 if it was in really good shape.

$500 for a 4B may be a good price but out of my range.

Do you know how clean the "working" ones are?

jkuetemann 15th January 2013 12:39 PM

If they are anything like the equipment I have already gotten from them then they will be well travelled with a smattering of abuse and inexpert repair / modification, oh, and dirty inside. I have stripped every piece I have ever gotten from them to the base plate and built it back up. But then, I also wait for the scraps to fall off the table, so to speak. Sounds like they want premium dollar.

DUG 15th January 2013 12:44 PM

I guess I will pass on this opportunity.

Good luck on your repairs.

:)

jkuetemann 15th January 2013 11:59 PM

No one has any information about replacing the 3B's transistors with industry standards?

I got a message back from Bryston to say they will sell the parts at $15 CAD plus tax and shipping. Any idea how many standard parts like the MJ21195 / MJ21196 would have to be ordered to achieve a suitable match?

It may be worth it to pay the premium to buy the OEM devices.

ticknpop 16th January 2013 12:30 AM

Better to buy the correct device and save your time - playing with subs for a few dollars less isn't worth it.


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