Bryston 3B Amp

0 Members and 1 Guest are viewing this topic. Read 691 times.

Benjisan265265

  • Jr. Member
  • Posts: 9
Bryston 3B Amp
« on: 25 Nov 2022, 06:26 pm »
 I have an early 3B amp that needs some love. One channel gets hot real fast (140 F degrees within 30 to 40 seconds) but isnt blowing any fuses and still puts out music.

I removed all four of the BJT and tested them in a transistor tester and one of them is coming up faulty (No hFE).

I was told by a DIY forum member that Bryston could provide matched BJT replacements. So I opened up a ticket via their Help Desk Support portal on 2022-11-08. About one week later the ticket was assigned by James Tanner to Mike Pickett and now it's un-assigned.

Could someone from your company please advise me on whether getting matched Bjt's is a possibility.

Kind regards,

James Tanner

  • Facilitator
  • Posts: 19785
  • The Demo is Everything!
    • http://www.bryston.com
Re: Bryston 3B Amp
« Reply #1 on: 25 Nov 2022, 09:16 pm »
Email Mike - mpickett@bryston.com

james

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #2 on: 26 Nov 2022, 01:50 am »
Email Mike - mpickett@bryston.com

james

Will do; and thank you for following up, Mr. Tanner.

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #3 on: 5 Dec 2022, 07:16 pm »
Will do; and thank you for following up, Mr. Tanner.

Just wanted to say thank you Mr. Tanner as I have been in touch with Mr. Pickett and I'm starting to sort things out now for my 3B.

Kind regards,

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #4 on: 5 Dec 2022, 07:35 pm »


On a related note with the particular model 3B amp I own, I have a question for anyone here who is familiar with the early vintage 3B amps.

I want to also replace some of the aged capacitors on both of the amp boards.

The visual inspection of the capacitors shows two electrolytic values being used as noted below.

Two, 220uf/6.3v per channel that appear to be in series from what I can tell by looking at the component side of the board and one 470uf/16v capacitor.

Is the 470uf/16v capacitor a polarized or non-polarized capacitor.

My question is that from the schematics I was able to source it appears that it may be either a polarized or non-polarized capacitor. I'm not sure which capacitors (polarized or non-polarized) should be used.

I will upload a couple of pics of both schematics to illustrate this.

Any help here would be greatly appreciated.






 


Rocket

Re: Bryston 3B Amp
« Reply #5 on: 6 Dec 2022, 03:24 am »
Hi,

Why don't you send it back to Bryston for them to check the amplifier out for you? Bryston make rock solid audio gear so its worth investing money into it.

Cheers Rod

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #6 on: 6 Dec 2022, 05:11 am »
Hi,

Why don't you send it back to Bryston for them to check the amplifier out for you? Bryston make rock solid audio gear so its worth investing money into it.

Cheers Rod

Hi Rod,

This amp is to old for any warranty repair. And most likely any out of warranty repair would be in the range of at least $150 to $250 for the parts and labor. Then you have to factor in the extremely high cost shipping of this very heavy amp (both ways) would most likely be in the neighborhood of about $200.00 to have it professionally packaged and then shipped.

The value of this particular amp in full working condition, unfortunately, is only $300 to maybe $400. So that would be a foolish mistake on my end to spend more money on this amp then it's actually worth.

So I'm taking a stab at trying to fix this myself.

I just want to confirm a few things before I order some parts as I have never seen an axial polarized capacitor like the one that is pictured below with the arrow, plus sign, and that squiggly design that is after the plus sign. 



James Tanner

  • Facilitator
  • Posts: 19785
  • The Demo is Everything!
    • http://www.bryston.com
Re: Bryston 3B Amp
« Reply #7 on: 6 Dec 2022, 10:38 am »
Check with Mike - mpickett@bryston.com

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #8 on: 7 Dec 2022, 07:02 pm »
Okay, I spoke to Mr. Pickett and would like to share his expertise on this particular 3B circuit. 

His response was that the 220uF capacitor is a protection circuit timing capacitor. The 220uf/6.3v capacitors carries a small amount of DC voltage and you can use either a polarized or non-polarized capacitor when replacing it. 

The 470uF/16v are the feedback capacitors in this design and it sees no offset at all. That capacitor can also be polarized or non-polarized capacitor too. Mike also made it clear that if you use a polarized capacitor, its orientation is not critical.

According to Mr. Pickett, Bryston has tested non-polarized capacitors in both positions for the 3B amplifier and noticed no change in performance or behavior but they tend to use polarized for both circuit positions to this day.

Hats off to Mr. Mike Pickett and Mr. Tanner for supporting their products with such willingness and promptness in order to help out a fellow Bryston owner.

Kind regards,
« Last Edit: 8 Dec 2022, 02:03 am by Benjisan265265 »

wdizard

  • Jr. Member
  • Posts: 21
Re: Bryston 3B Amp
« Reply #9 on: 7 Dec 2022, 07:19 pm »
Hello
This is a nice project!
I am interested in hearing more about the solution .
Greg

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #10 on: 8 Dec 2022, 03:30 am »
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

         

 
« Last Edit: 8 Dec 2022, 05:33 am by Benjisan265265 »

Benjisan265265

  • Jr. Member
  • Posts: 9
Re: Bryston 3B Amp
« Reply #11 on: 17 Jan 2023, 01:52 am »
Hi all.

Well here's an update on my 3B amplifier.

My 40 year old 3B amplifier had a lot of things going on with it that was wrong. High DC offset and unstable bias. First problem addressed was a couple of bad output transistors. Bought a total of 16 Onsemi BJT power transistors (8-PNP and 8-NPN).

Replaced all 8 power transistors (4 for each channel) and matched each channel as close as possible using a TRL/LCR/ESR tester.  Powered up the 3B on a Dim-bulb tester and no problems were observed.

Next I tackled the high DC offset. I very carefully de-soldered and replaced the 8 small BJT transistors for 4 for each channel each channel. These transistors need to be very carefully matched and the TRL/LCR/ESR tester was not suitable for the task. I ended up buying about 20 pieces each for type needed to do a full replacement. So I sourced the various needed parts from Digi-key. I also replaced just about every other BJT transistors in this amp with the exception of just two. The majority ofthe BJT transistors were way out of spec. So I replaced them. I even did the 4 BJT's on the small input board too. I also replaced the two antique 10K bias trimmer pots with new ones from Bourns and all capacitors except the big AC mains filtering caps.

My next step was to figure out how I was going to match the critical pairs of BJT's correctly. I found a video on YouTube where some fellow made a transistor tester from a few parts and a dual 15 volt transformer. That seemed like the way to go, but as I was searching and researching things I inadvertently stumbled on a Ebay seller from Thailand.  The seller was offering fully assembled and DIY curve tracer kits that simply used an oscilloscope.

So I purchased the $28 kit plus shipping and 10 days later my kit arrived. I quickly assembled it (you need to have two 15 volt power supplies. I have an analog scope and a dual channel regulated power supply) and hooked it up to my oscilloscope and that little curve tracer kit worked fantastically in helping me get perfectly matched sets of differential pairs. 

So here's where I'm at right now.

The 3B is powered up but without the 8 power transistors installed. The DC offset is now perfect at 00.1 mv and 00.9 mv (see pics below) and I'm letting it burn in for a day or two to verify that everything is good. I will then install the power transistors and bring the amp back up on the Dim-bulb tester at first and if all is well then I will adjust the bias trimmers and reintroduce the amp into my system and report back on how things sound.