Hello
This is a nice project!
I am interested in hearing more about the solution .
Greg
Hi Greg,
I'm going to be replacing all 8 BJT output transistors along with the 4 BJT drivers.
(4,) OnSemi MJ21194G NPN)
(4,) OnSemi MJ21193G PNP)
(2,) OnSemi MJE15030 NPN)
(2,) OnSemi MJE15031 PNP)
Also replacing the four 220uf/6.3v capacitors and the two 470uf/16v caps.
Just a quick little background on my B3. I originally purchased this amp used in 1999 off of Audiogon for $250 shipped from NY to my home here in NJ. I've used this amp on and off with various speakers and even as a dedicated sub amp in bridged mode.
About two years ago I pulled the amp out my system to run a Anthem Amp 1 tube amp that I purchased off of Facebook for measly sum of $100. Only catch was that the amp was missing all the tubes. (every single one them were missing---> 4 x EL34, 1 x 12AX7 driver, 2 x 12AU7) So I took a chance that all it needed was a tube compliment. (bought a full tube compliment off of the TubeStore) Boy was I wrong. Unbeknownst to me it had a buggered up main circuit board with traces broken and some resistors missing. I hadn't realized this secondary problem when I purchased it, but none the less, I found out as soon as I powered it up through a dim-bulb tester and the two EL34 on the right channel showed no life. Spent the next two weeks sourcing a schematic and all the parts to fix it. Luckily I had a good Left channel to compare the dead right one with as I started my journey on fixing it. Got it fixed and I had been enjoying the tube amp ever since. (by the way Anthem is also another Canadian Co. like Bryston)
But to sum things up I purchased a MiniDSP 2 x4 HD and wanted to run my M&K Mx-125 (the M&K was purchased used off of Craigslist without its plate amp) sub in a 2.1 system with the Anthem and Bryston. When I pulled the B3 out of the closet and put it into my system I noticed that it wasn't sounding quite right. The B3 was the stereo amp that I had for many years and it exclusively powered both my JBL-L7's and McIntosh XR3 over the years and it made those two speaker systems sing. The 3B can produce detailed sound without the amplifier running out steam.
When I started looking into the B3 the first I noticed was that one of the stereo channels heat sink was getting way to hot when I tried powering it off the dim-bulb tester. Some quick testing revealed that one of the original 2N6609 transistors was kaput. Not sure as to why it failed, but then again I had a good working channel to compare the voltages and everything else too. Just to be clear I pulled all the output transistors from both channels when I was measuring things; and some of my measuring was done both in series with the dim-bulb tester, and without, along with a cheap DMM and a USB oscilloscope running through my Dell laptop.
I really don't have a lot of knowledge when it comes to this sort of repair stuff, but I have a ton of patience, commonsense and I don't rush into things without reading first. I'm always putting myself preservation first--- lol
So I decided that it would probably be best to replace all the transistors and capacitors as the only thing that I can think of that caused the channel to fail on its own after coming out of storage was most likely due to the age of the amps hardworking components.
And with all that said above I will stop back in a week or two and give an update after my replacement parts arrive and installed.
Kind regards,
B