I am in the process of exchanging the Scourge FE to the Missouri FE. I have a question on wiring up the XLR input connections to the Missouri FE. I figure that pin #2 is wired to the “Pos In” on the board and pin # 3 is wired to the “Neg In” on the board. Pin #1 is the ground pin, do I wire it to the Chassis?.
Oh Oh…it’s probably bad when smoke is coming out of the amp. :-(
Looks like I mixed up the input wires on the XLR inputs. Reversed pins #1 and #3. Rewired them correctly but there is smoke coming off the Missouri board around C11 and U2 chip.
Hmm…. I will pull the FE boards out and inspect them. Reinstall the Scourge FE and check to see if the rest of the amp is Ok.
Looks like I mixed up the input wires on the XLR inputs. Reversed pins #1 and #3. Rewired them correctly but there is smoke coming off the Missouri board around C11 and U2 chip.
Hmm…. I will pull the FE boards out and inspect them. Reinstall the Scourge FE and check to see if the rest of the amp is Ok.
AMP Works great with the Scourge FE’s installed.
A close inspection of the Missouri boards doesn’t show any obvious damage, shorts or blacked areas. But one of the boards was smoking after I corrected the wiring. So something is damaged.
How do I trouble shoot this board? I thought I saw a thread about that earlier, but I will have to do a bit of searching. Maybe it wasn’t for these FEnds.
A close inspection of the Missouri boards doesn’t show any obvious damage, shorts or blacked areas. But one of the boards was smoking after I corrected the wiring. So something is damaged.
How do I trouble shoot this board? I thought I saw a thread about that earlier, but I will have to do a bit of searching. Maybe it wasn’t for these FEnds.
Good choice, Pequod is sparse and inexpensive and simple. And also, flexible. Pequod is aimed at people who build their own output stage cards from their own private stash of previously acquired SITs, and who certainly don't want to spend much money on Front Ends. Here it is, an opamp and a transformer and precious little else. Have a great day.
Parts in today for the Tuba, and Pequod - Tuba will get built next weekend - at the beach for holiday weekend. Awaiting the Pequod/BHR boards from PCBWay (might get in next week)
Question for Mark Johnson - I found a matched quad of 2SK170 from a guy in the Swap meet a few years ago. (digging through the parts bin, no clue what I originally bought those for) Does the circuit need refinement for any of the various transistors you have listed on the schematic? Or do they all work just fine with the existing R values? I am going to go through the bin to fill out the BHR BOM before ordering more stuff. I did get a pair of AD797 awhile back, while the getting was good.
Question for Mark Johnson - I found a matched quad of 2SK170 from a guy in the Swap meet a few years ago. (digging through the parts bin, no clue what I originally bought those for) Does the circuit need refinement for any of the various transistors you have listed on the schematic? Or do they all work just fine with the existing R values? I am going to go through the bin to fill out the BHR BOM before ordering more stuff. I did get a pair of AD797 awhile back, while the getting was good.
Hey Mark could you help me out a bit here….I have been trouble shooting my two Missouri FE boards that I missed wired. One board, smoked R6 and C15, (board #1). The other board seems to be OK as far as anything getting hot. So following the previous trouble shooting guide that you gave ElliotA around post #141, I have been checking the top half of the schematic
of the boards, ie the PSU in to IC componets. I find that on both boards, pins #7 of U2 and Pin # 8 of U1 both measure 14.2 volts. Pins #1 on both also have 14.2 volts. So I measured the voltage of the Resistors and Diodes as you suggested and find the following….everything seems to be OK until I measure the pins #8 and #7 on U1 and U2. I ordered new IC‘s and installed one pair onto board #2 so they should be good. Board #1 has a set of the original IC‘s. I replaced R6 on board #2, and need to order C15, but want to wait on ordering it until I find if I need other stuff. Seems that pin #8 on U1 and pin #7 on U2 are too low by half. any ideas?
of the boards, ie the PSU in to IC componets. I find that on both boards, pins #7 of U2 and Pin # 8 of U1 both measure 14.2 volts. Pins #1 on both also have 14.2 volts. So I measured the voltage of the Resistors and Diodes as you suggested and find the following….everything seems to be OK until I measure the pins #8 and #7 on U1 and U2. I ordered new IC‘s and installed one pair onto board #2 so they should be good. Board #1 has a set of the original IC‘s. I replaced R6 on board #2, and need to order C15, but want to wait on ordering it until I find if I need other stuff. Seems that pin #8 on U1 and pin #7 on U2 are too low by half. any ideas?
Make four copies of the attached image file. Using MacPaint or MSPaint or some other image editing software, put your own text labels in the bottom left corner
Since your first goal is to learn whether the power supply filtering circuitry (at the top of the Missouri schematic) is functioning correctly or not, you will test it WITHOUT the IC chips plugged in. Then you will test it again, WITH the ICs in place. With/Without testing helps you discover whether you're accidentally plugging the chips in backwards, or whether the chips themselves have problems with their positive power supplies, or whether your sockets are faulty, etc.
You will perform four sets of measurements. Two sets on Board #1 and two sets on Board #2. The sets are: without ICs, and with ICs. Be sure to attach a physical label to each Missouri board, so "Board 1" and "Board 2" mean the same thing in every experiment. Label the ICs too; you don't want to accidentally swap chips between boards, when you're not sure whether the chips are bad, the boards are bad, or perhaps both.
Measure the voltages at the four device pins labeled ATLANTA (pin 1 of Q2) , BOSTON (pin 7 of U2) , CHICAGO (pin 8 of U1) , and DENVER (flying wireloop of R13). It is important that you probe right on the device pins, because at the moment you don't know whether the solder joints and PCB traces are trustworthy. Your boards might have an accidental short (or open) somewhere.
Using your image editing software, attach text labels to each of the four image files. Next to "ATLANTA" , label the voltage you measured at test point ATLANTA. Continue onward with BOSTON, CHICAGO, DENVER. Four sets of measurements, four image files.
Now when you post these four image files including measured voltages, you'll be doing diyAudio members a big favor. They don't have to hunt up a Missouri schematic from elsewhere, nor carefully scrutinize that schematic in order to discover what in the world is "U1 pin 8" etc. It's all right there to see and ATLANTA ... DENVER are clearly marked. Make it easy for people to offer advice and opinions. Otherwise they'll decide not to put forth the effort and you get no replies.
_
- Board #1 : ICs removed from sockets
- Board #2 : ICs removed from sockets
- Board #1 : ICs plugged in
- Board #2 : ICs plugged in
Since your first goal is to learn whether the power supply filtering circuitry (at the top of the Missouri schematic) is functioning correctly or not, you will test it WITHOUT the IC chips plugged in. Then you will test it again, WITH the ICs in place. With/Without testing helps you discover whether you're accidentally plugging the chips in backwards, or whether the chips themselves have problems with their positive power supplies, or whether your sockets are faulty, etc.
You will perform four sets of measurements. Two sets on Board #1 and two sets on Board #2. The sets are: without ICs, and with ICs. Be sure to attach a physical label to each Missouri board, so "Board 1" and "Board 2" mean the same thing in every experiment. Label the ICs too; you don't want to accidentally swap chips between boards, when you're not sure whether the chips are bad, the boards are bad, or perhaps both.
Measure the voltages at the four device pins labeled ATLANTA (pin 1 of Q2) , BOSTON (pin 7 of U2) , CHICAGO (pin 8 of U1) , and DENVER (flying wireloop of R13). It is important that you probe right on the device pins, because at the moment you don't know whether the solder joints and PCB traces are trustworthy. Your boards might have an accidental short (or open) somewhere.
Using your image editing software, attach text labels to each of the four image files. Next to "ATLANTA" , label the voltage you measured at test point ATLANTA. Continue onward with BOSTON, CHICAGO, DENVER. Four sets of measurements, four image files.
Now when you post these four image files including measured voltages, you'll be doing diyAudio members a big favor. They don't have to hunt up a Missouri schematic from elsewhere, nor carefully scrutinize that schematic in order to discover what in the world is "U1 pin 8" etc. It's all right there to see and ATLANTA ... DENVER are clearly marked. Make it easy for people to offer advice and opinions. Otherwise they'll decide not to put forth the effort and you get no replies.
_
Attachments
Ok, I found my error. I had misidentified the pins on the IC‘s. So after researching how the pins on the IC’s were numbered I found that all is good. I have the correct voltages on both boards with and without ICl‘s attached as per Mark’s discussion on and around post 141 and post 196. So I am awaiting an oscilloscope and a signal generator that I have on order to have the tools to make sure that the two boards function properly before I install them into the amp.
Thanks Mark.
Learning lots because of this error.
Thanks Mark.
Learning lots because of this error.