SANSUII BA-3000 PROBLEMS
- Thread starter pppoffice
- Start date
pppoffice
AudioBear
pppoffice
AudioBear
I will check out all the resistor values and report back, maybe this evening. Yes, I just recapped ALL of BOTH of my BA-3000 amps. And yes, I am very anal and will probably change out all of the resistors to Metal Film 1/2 watt resistors as soon as we are done with these fixes. WHAT DO YOU THINK OF ME POPPING MY OTHER POWER SUPPLY BOARD IN AFTER YOUR HAPPY WITH THIS ONE? Also, did you read that I have 4 complete sets of new Power Transistors. When we get to this point do you want me to match them up and use 2 sets in my amps?
pppoffice
AudioBear
I WANT you to be very OCD about everything. I don't know how much longer I have on this wonderful earth but I would like to listen to my Sansui's and not be working on them all of the time.
pppoffice
AudioBear
I will get all of these readings right now and report back before I quit for the night.
pppoffice
AudioBear
OK, here we go again. After setting the voltage to the amp at exactly 100 volts AC I took the following readings. The spots where B+- are read on the 2512 Board I get +85.1 VDC and -85.1 VDC. On the 2512 board where the +- 60 VDC is suppose to be I get +69.2 VDC and -69.2 VDC. On the 2512 board where the +-35 VDC is suppose to be I get +1.677 VDC and -0.320 VDC. lAfter checking R05 I got 560.2 Ohms and R06 I got 561.5 Ohms.
pppoffice
AudioBear
On the positive side of C17 I got 1.675 VDC. On the negative side of C18 I got -0.331 VDC. On the positive side of C15 I got +0.685 VDC and on the negative side of C16 I got -84.5 VDC. I think that was everything you asked for.
pppoffice
AudioBear
Oh, and I totally forgot that last year before I started working on these two amps of mine I had read a report about the use of Metal Film resistors in amplifiers. I got on Mouser and purchase enough Metal Film resistors to replace all of the 1/2 Watt resistors on the Power Supply board and the two Driver Boards TIMES 3. I just found all of them in an 85 drawer parts bin I bought just for storing these resistors in. I had planned on replacing all of the 1/2 Watt resistors like I changed all of the Electrolytic Caps after I got both amps working PERFECTLY. They are just sitting there waiting for me to use them.
vigman
SUBSCRIBER
Here is the resistor " trick " pix to fool protection.. Lets start in the AM with the measurements from the caps.. again something is a bit fishy. I like the idea of testing out the 2nd reg board next.
When your new On Semi transistors come in we will match those up, the closer you can get them the SLIGHTLY better, What you do not want is an HFE to 18 next one of 60 +/- 15 % is close enuf.
When your new On Semi transistors come in we will match those up, the closer you can get them the SLIGHTLY better, What you do not want is an HFE to 18 next one of 60 +/- 15 % is close enuf.
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pppoffice
AudioBear
I already have the 4 complete sets of On Semi transistors in my shop. They are still all wrapped up like Mouser Electronics sent them to me. I can make sets up in between feedback from you. I don't understand why I still don't have the +-35 VDC on the 2512 board. When I finally gave up and asked for help was because I couldn't get all the voltages where they belonged. The +-35 VDC has been the biggest problem as far as the power supply boards. I refused to go any further with my work on these amps until I got all the voltages where they should be and that is why I finally asked for help I am sure now that I have your help that you will figure it out. I will watch for your next post in the morning. I think that it makes sense to get the 2 power supply boards AND the 4 driver boards figured out and fixed while working on this first amp. I think it will be easier that way.
vigman
SUBSCRIBER
We cannot do any drivers till we get 1 good brick.... I would take your " best" OE transistors and get a right brick stuffed....& ready to rock
The HFE of the NPN vs the PNP will be a tad off just get your closest 3 NPN's and PNP's
That being said I think the fastest fix for the reg board is to print out the schematic, pull each transistor out & test it, mark what you have done.. and keep moving down the road/
Things to trust on the reg boards... NOTHING, these get COOKED over the years ( like the drivers ) ...
So lets get the +/- 35 going on the 2508 THEN worry about connectors & traces on the 2512.
The HFE of the NPN vs the PNP will be a tad off just get your closest 3 NPN's and PNP's
That being said I think the fastest fix for the reg board is to print out the schematic, pull each transistor out & test it, mark what you have done.. and keep moving down the road/
Things to trust on the reg boards... NOTHING, these get COOKED over the years ( like the drivers ) ...
So lets get the +/- 35 going on the 2508 THEN worry about connectors & traces on the 2512.
vigman
SUBSCRIBER
SO.. a bit of brain bend, in order for the regulator transistors to work the transistors need to be turned on ( or off ) The WORK happens from the collector to emitter
The BASE is the control and TYPICALLY .7 of a volts turns the device on.. and no voltage shuts down current flow.If we look at the positive +35 part of the regulator,TR-11
does that majority of the voltage drop by controlling the base but without 12 13 & 03 you are kinda up da creek...The emitter of TR-12 is a key player here because it controls the base of TR-11 we are trying to step down 85 volts down to 35... I'll stop there and see if you got all that .....
The BASE is the control and TYPICALLY .7 of a volts turns the device on.. and no voltage shuts down current flow.If we look at the positive +35 part of the regulator,TR-11
does that majority of the voltage drop by controlling the base but without 12 13 & 03 you are kinda up da creek...The emitter of TR-12 is a key player here because it controls the base of TR-11 we are trying to step down 85 volts down to 35... I'll stop there and see if you got all that .....
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pppoffice
AudioBear
Understood on all counts. I can be putting sets of new power transistors in between posts. I was just thinking out loud about getting both power supply boards and all the driver boards working properly on this amp as we go. I am not trying to get ahead of myself. Its just my old feeble brain trying to think.
pppoffice
AudioBear
I think that I got most of it Mike. When I was in electronics vocational school (9th thru 12th grade) everything being taught was TUBES. Transistors hadn't started being taught yet. It has only been the last few years that I have started trying to understand transistors. I may just be too old but I am still going to try and understand them. I do understand the turning on and off of a device though. I'm finally awake (I think) and have taken care of my lovely wife's concerns of the day and ready to get going.
pppoffice
AudioBear
And I did get the picture file of the resistor trick for on/off speaker protection. GOT IT.
vigman
SUBSCRIBER
All good... I would stuff the 1 "TEST BRICK " with the older transistors so in case of POOF no new transistors are wasted.
If your transistor " theory " is not up to scratch... the more you do .. the more you learn. and that will stick...
Remember a transistor ( like a tube ) needs current flow from the base ( think grid ) or it will not do any work.
It MIGHT be a bit faster just to pull the transistors test em, and BEFORE re install test surrounding resistors that are now out of circuit.
There was a good post on that style of reguator board ( AU 717 ) one of the members schooled me on....I'll see if I can dig that up....
But now I need those measurements off the caps to help...Keep it up Mike !!!
If your transistor " theory " is not up to scratch... the more you do .. the more you learn. and that will stick...
Remember a transistor ( like a tube ) needs current flow from the base ( think grid ) or it will not do any work.
It MIGHT be a bit faster just to pull the transistors test em, and BEFORE re install test surrounding resistors that are now out of circuit.
There was a good post on that style of reguator board ( AU 717 ) one of the members schooled me on....I'll see if I can dig that up....
But now I need those measurements off the caps to help...Keep it up Mike !!!
vigman
SUBSCRIBER
http://audiokarma.org/forums/index.php?threads/sansui-au-717-2663-board-issues.556401/
Hyperion helped me ALOT on getting my head around this design... it
's a LONG ASS thread, but if you need a snooze read away !
Hyperion helped me ALOT on getting my head around this design... it
's a LONG ASS thread, but if you need a snooze read away !
pppoffice
AudioBear
I must have missed a request for a measurement from you as I thought I had sent all the measurements you asked for last night. Also, I can't figure out if you are wanting me to put one of the bricks back in or not. I understand the reasoning for using the old power transistors it makes perfect sense. Why take a chance on blowing new transistors when I have old ones that have not been blown. Please look back at all the measurements I sent to you last night and if you don't see something you need, please ask again as I must have missed it. I plan on working late again tonight in hopes we can get some of the problems resolved.
pppoffice
AudioBear
And yes, you taking the time to work with me on this is going to help me a bunch understand more and more about transistors. That darn little transistor tester I bought off of ebay was like going from crawling to running. It helped me be sure that I was installing transistors correctly and figuring out if they were good or bad. Since I started working with the BA-3000 and other transistor pieces of equipment I have it has been a slow process of me learning on my own as I can figure it out. It has NOT been easy for me. A lot of what I have learned to date has been pure logical thinking.
pppoffice
AudioBear
Mike, are you wanting me to get the voltages off of these same caps again. This is the only thing that I can think of that you want. I will go get these voltages again but I doubt they have changed as nothing I can think of has been done to cause a change. I will get back to you in a short period of time.
