Page 2 of 2 FirstFirst 12
Results 36 to 60 of 60

Thread: Ampeg B200R Bass Amp

  1. #36
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    12,360
    Thumbs Up/Down
    Received: 2,031/24
    Given: 5,166/11
    Rep Power
    24
    Quote Originally Posted by robgrif View Post
    ok thanks here are the values that I got
    Q7 E=+.06 v C=+18v B=+3.16v
    Q6 E=-.06 v C=-18v B=-2.6v
    Quote Originally Posted by The Dude View Post
    It would appear from your measurements that Q6 and Q7 are open.
    If those measurements are correct (and the e,b, and c are not mixed up), then Q6 and Q7 must be bad.

    0 Not allowed! Not allowed!
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

  2. #37
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    thanks for all input lots of thought thanks
    anyway i think JAZZ p Bass is on to something about the limiter upsetting things. put new mosfets in 60 watt limiter glowing bright .Installed preamp board and tube module.
    light limiter went dim. put in 100 watt light bulb bulb went right down to faint glow.a bit later removed limiter and amp stayed on. tripped over myself and thoughtlessly hooked up speaker thinking this was it fixed at last. hooked up to input with signal nothing coming through and boom out go the lights. all four mosfets went down this time.
    plus fuse.wtf happened here ,. seemed so close to success. anyway inspection right after 10 w 330 power supply resistor very hot. the other one not and as i pulled on it one leg of cold resistor came out of board. so my question is if this solder joint was disconnected at power supply resistor would that unbalance things enough to short rails to a ground some how turning on all four mosfets? as to the other discussion about q6 and q7 i am not sure those measurements are correct for base value. may have taken measurement from wrong place on board hard to get to pins under heat sink took measurement at closest resistor so could be wrong however double checked each one with meter when board was out and they both tested fine forward and reverse. so used up all my parts will order more and try again . thanks again for your help here. also just before the mosfets blew the amp light went out it is connected to each side of rails .

    0 Not allowed! Not allowed!

  3. #38
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    The 330 ohm/ 10 watt resistor is used on the + or - 16 volt supplies.

    The proper function of the bias/ driver circuit relies on both supplies being present.

    0 Not allowed! Not allowed!

  4. #39
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    ok thanks will return as soon as new parts arrive
    happy thanksgiving to all those celebrating

    0 Not allowed! Not allowed!

  5. #40
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    Okay hi all parts arrived put in 4 new mosfets. The amp is working on limiter right now. Bulb is dim. Measuring 1.0 volts dc on speaker output. Preamp output working.touched. Small 8 ohmns speaker to speaker output. Light dim no hum just hiss of amp.Coming through.Put guitar signal through.it came through fine.on small speaker. limiter bulb glowing brighter and dim with signal.
    briefly hooked up ampeg cabinet speaker and limiter bulb went much brighter all controls at 0.disconnected immediately.speaker measures about 6.5 ohmns .retested with small 8 ohmn speaker bulb dim .what is happening here .is there still some problem with this amp. would it be ok to remove limiter .or is there some way to test non destructively.to
    verify operation. thanks for any suggestions.

    0 Not allowed! Not allowed!

  6. #41
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    I would suggest that you remove the speaker load.
    If there is a problem, that will only provide a path to ground for the output.

    Install the smallest value fuse that you have, remove the limiter & test the output for any Vdc.

    IF it is reading in the mv range, then you can install a speaker & try it with the proper fuse.

    Note: I cannot understand why a 6.8 ohm load, compared to an 8 ohm load, is pulling severely more current.
    Unless the 6.8 ohm speaker or the wiring is somehow shorted.

    0 Not allowed! Not allowed!
    Last edited by Jazz P Bass; 12-05-2014 at 02:19 PM.

  7. #42
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    12,360
    Thumbs Up/Down
    Received: 2,031/24
    Given: 5,166/11
    Rep Power
    24
    The speaker measures 6.5 ohms, but how about connecting cable,etc. Maybe a short that is only showing up with signal applied.
    Try another cab and cable.

    0 Not allowed! Not allowed!
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

  8. #43
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    Quote Originally Posted by Jazz P Bass View Post
    I would suggest that you remove the speaker load.
    If there is a problem, that will only provide a path to ground for the output.

    Install the smallest value fuse that you have, remove the limiter & test the output for any Vdc.

    IF it is reading in the mv range, then you can install a speaker & try it with the proper fuse.

    Note: I cannot understand why a 6.8 ohm load, compared to an 8 ohm load, is pulling severely more current.
    Unless the 6.8 ohm speaker or the wiring is somehow shorted.
    ok removed limiter 1 amp fuse no speaker 3.5 volts dc on output terminals this does not change with bias adjustment fuse blew while I was adjusting bias. installed new one amp fuse . still 3.5 volts dc on speaker output. any thoughts on possible cause or source of the dc ?

    0 Not allowed! Not allowed!

  9. #44
    Supporting Member The Dude's Avatar
    Join Date
    May 2010
    Location
    Sioux Falls, SD
    Posts
    6,697
    Thumbs Up/Down
    Received: 1,511/1
    Given: 1,119/1
    Rep Power
    17
    A couple of things:

    First, I'm still hung up on your post 23. The voltages were wrong on Q6 and Q7. Have you fixed this? At the risk of sounding harsh, you need to figure out the problem. The shotgun approach is counterproductive. You could be installing new problems.

    Second, the bias control won't change your DC offset problem. It adjusts idle current of the output stage. If you get DC on the output, you have a problem. No amount of adjusting will matter. There is no reason to mess with the bias control until the amp is fixed.

    So, let's back up. What are the current voltages on Q6 and Q7. Measure base to emitter voltages on both and report. Also report polarity of these voltages. In other words, for example, I got voltage "x" with my negative probe on the emitter and positive on the base. You said you checked those transistors. HOW did you check them? Only for shorts? Diode check function? Did you check for valid junctions? Unless your readings were wrong, you had a problem there. I see 3 possible scenarios. 1) The transistors are bad. 2) You replaced them and the basing diagram or cross reference is not correct. 3) Readings are incorrect.

    We know we had/have a problem there. Let's figure it out instead of snipping wires, randomly replacing parts, etc.

    0 Not allowed! Not allowed!
    Last edited by The Dude; 12-05-2014 at 11:06 PM.
    “Yeah, well, you know, that’s just, like, your opinion, man.”

  10. #45
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    Quote Originally Posted by The Dude View Post
    A couple of things:

    First, I'm still hung up on your post 23. The voltages were wrong on Q6 and Q7. Have you fixed this? At the risk of sounding harsh, you need to figure out the problem. The shotgun approach is counterproductive. You could be installing new problems.

    Second, the bias control won't change your DC offset problem. It adjusts idle current of the output stage. If you get DC on the output, you have a problem. No amount of adjusting will matter. There is no reason to mess with the bias control until the amp is fixed.

    So, let's back up. What are the current voltages on Q6 and Q7. Measure base to emitter voltages on both and report. Also report polarity of these voltages. In other words, for example, I got voltage "x" with my negative probe on the emitter and positive on the base. You said you checked those transistors. HOW did you check them? Only for shorts? Diode check function? Did you check for valid junctions? Unless your readings were wrong, you had a problem there. I see 3 possible scenarios. 1) The transistors are bad. 2) You replaced them and the basing diagram or cross reference is not correct. 3) Readings are incorrect.

    We know we had/have a problem there. Let's figure it out instead of snipping wires, randomly replacing parts, etc.
    ok thanks probe + on emitter - on base q6=+.6 v probe +on emitter - on base q7 = -.45 v

    0 Not allowed! Not allowed!

  11. #46
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    12,360
    Thumbs Up/Down
    Received: 2,031/24
    Given: 5,166/11
    Rep Power
    24
    Ok, those results are radically different than what you posted before.
    Should we trust the other measurements or do you think it would be wise to double check them all again?

    0 Not allowed! Not allowed!
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

  12. #47
    Member
    Join Date
    Jun 2010
    Posts
    200
    Thumbs Up/Down
    Received: 5/0
    Given: 1/0
    Rep Power
    10
    Find a local tech with a variac. I have loaned one of mine out a couple times. You can buy one with the $ you keep spending on parts. Bulb limiters are ok, but also can become an issue getting normal operation on some occasions. A variac you can run up slowly and check things before destroying new components.

    OP circuits are balanced as many have said. You should essentially have maybe 40mv or less on the output at idle.

    0 Not allowed! Not allowed!

  13. #48
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    ok the amp voltages are
    q6 B -04.2 V C -44.6 V E -3.5 V BE RANGING .9V TO 50V
    Q7 B +3.4 V C 45 V E 3.0 V BE RANGING .5 V TO 50 V
    Q4 G +45 V D -43 V S +48 V GD +88V GS -4V
    Q11 SAME AS Q4
    Q5 G -45V D -43V S -48V GD -1.8 GC +4
    Q8 SAME AS Q5
    AMP IS ON 100 WATT limiter dim bulb
    readings on q6 and q7 were inconsistent from one time to the next
    so do these readings give any clue to a fault source for this amp
    thanks for any thoughts you might have

    0 Not allowed! Not allowed!

  14. #49
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    Quote Originally Posted by robgrif View Post
    BE RANGING .9V TO 50V
    Q7 B +3.4 V C 45 V E 3.0 V BE RANGING .5 V TO 50 V
    I have no idea what this statement means. " BE RANGING .5 V TO 50 V"

    0 Not allowed! Not allowed!

  15. #50
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    Quote Originally Posted by Jazz P Bass View Post
    I have no idea what this statement means. " BE RANGING .5 V TO 50 V"
    sorry for confusion of that statement . the base emitter voltage on q6 and q7 is not static it is constantly changing
    from approx .9 v to approx 50v it is not staying at any particular voltage. thanks i hope this is clearer also -43 volts is appearing on drain of q4 and q11 making gate drain voltage 88 volts . just putting these numbers out there from circuit measurements to see if any of these values are expected or unexpected in this particular circuit
    thanks for response

    0 Not allowed! Not allowed!

  16. #51
    Don't forget the joker g1's Avatar
    Join Date
    Feb 2010
    Location
    Canada, somewhere north of Fargo
    Posts
    12,360
    Thumbs Up/Down
    Received: 2,031/24
    Given: 5,166/11
    Rep Power
    24
    Are you seeing any pulsing of the lamp? Are the supply voltages stable?
    I don't see how the BE voltages should be fluctuating when measured B to E, but not when referenced to ground.
    Maybe there is a board ground that is not connected because the board is out of the chassis?

    0 Not allowed! Not allowed!
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

  17. #52
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    Is the preamp hooked up?

    That header references the power supply chassis ground to the output board ground (Marked triangle 2)

    0 Not allowed! Not allowed!

  18. #53
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    no pulsing in light. board in chassis. preamp / tube circuit are not hooked up .I will re-connect those items.

    0 Not allowed! Not allowed!

  19. #54
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    ok preamp and tube section hooked up
    new measurements
    q5 and q8 g-52v d+3v s -52v
    q4 and q11 g+50v d+3v s +52v
    q6 be .6v
    q7 be .5v
    speaker output +3vdc

    0 Not allowed! Not allowed!

  20. #55
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    Get Rid Of The Limiter.

    0 Not allowed! Not allowed!

  21. #56
    Member
    Join Date
    Dec 2009
    Location
    Toronto Canada
    Posts
    50
    Thumbs Up/Down
    Received: 0/0
    Given: 0/0
    Rep Power
    11
    Quote Originally Posted by Jazz P Bass View Post
    Get Rid Of The Limiter.
    ok no limiter still 3vdc on speaker output

    0 Not allowed! Not allowed!

  22. #57
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    Without sounding malicious, cranky or a wiseass:
    Do you understand how this circuit functions?

    You cannot throw voltages around & expect someone else to fix this amp.

    Do a little more digging.
    Look at the mosfet gates & try to decide why one is turning on enough to output 3 volts.
    Is the polarity of the 3 volts +?
    That is a sure fire hint.
    End of rant.

    0 Not allowed! Not allowed!

  23. #58
    Supporting Member bsco's Avatar
    Join Date
    Jan 2012
    Location
    Eastern Canada
    Posts
    1,754
    Thumbs Up/Down
    Received: 138/0
    Given: 173/0
    Rep Power
    10
    There are lots of people here giving very good advice...reading through these posts should have narrowed down your problem...maybe you need to start fresh...it doesn't make any sense to keep installing parts and going around in circles.......what exactly is the state of the amp at this particular point??Are you still blowing mosfets??? if you are getting dc at the output there has to be something wrong in the output stage somewhere......either you have problems with the mosfets, the way they are mounted, etc....the drivers, or associated parts.....resistors, capacitors, diodes...you could even have problems with circuit traces.......so......what is the current condition of the amp at this moment....

    0 Not allowed! Not allowed!

  24. #59
    Supporting Member The Dude's Avatar
    Join Date
    May 2010
    Location
    Sioux Falls, SD
    Posts
    6,697
    Thumbs Up/Down
    Received: 1,511/1
    Given: 1,119/1
    Rep Power
    17
    Quote Originally Posted by robgrif View Post
    sorry for confusion of that statement . the base emitter voltage on q6 and q7 is not static it is constantly changing
    from approx .9 v to approx 50v it is not staying at any particular voltage. thanks i hope this is clearer also -43 volts is appearing on drain of q4 and q11 making gate drain voltage 88 volts . just putting these numbers out there from circuit measurements to see if any of these values are expected or unexpected in this particular circuit
    thanks for response
    To quote my previous post, "If the voltage is the correct polarity from b to e on a transistor, the only way it can be more than .7 or so volts on a standard transistor is if the transistor is open/bad/defective."

    When you made these measurements, was it with NO signal applied and volumes down? If not, try it again. These DC measurements should not change.

    0 Not allowed! Not allowed!
    “Yeah, well, you know, that’s just, like, your opinion, man.”

  25. #60
    Supporting Member Jazz P Bass's Avatar
    Join Date
    Dec 2008
    Location
    Wernersville, PA
    Posts
    13,068
    Thumbs Up/Down
    Received: 609/3
    Given: 314/0
    Rep Power
    28
    The amp was not fully hooked up.
    The last posting the OP hooked up the preamp & tube board.
    So these readings probably settled down as there is now 'only' 3 Vdc on the output.

    0 Not allowed! Not allowed!

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Ampeg B-100 Bass Amp rebuild
    By mcdemo49 in forum Music Electronics
    Replies: 2
    Last Post: 11-01-2011, 09:20 AM
  2. ampeg ba-115 bass amp.
    By Jose8a in forum Maintenance, Troubleshooting & Repair
    Replies: 4
    Last Post: 04-28-2010, 05:05 PM
  3. Ampeg BA-115 Bass amp
    By Cal57 in forum Maintenance, Troubleshooting & Repair
    Replies: 11
    Last Post: 03-30-2010, 11:22 PM
  4. ampeg ba210sp bass amp
    By donegone in forum Theory & Design
    Replies: 6
    Last Post: 10-02-2009, 03:23 AM
  5. Ampeg B2-RE bass amp DC on output
    By lespaul924 in forum Maintenance, Troubleshooting & Repair
    Replies: 12
    Last Post: 05-21-2009, 03:27 AM

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •