Amp in question is a B&K AV5000 v.1 not II.
Not sure on the wattage as Ive seen reference to it being both a 100W x3/60W x2 AND 100W x5. The 60W x2 is also in the owners manual. Not sure if this was a running change or if there were some mistakes in the literature. Im going to go ahead and say its 100W x5 because I went through the entire amp after a lightning strike and every part on every channel was exactly the same.
I believe this is a '98 build date.
The problem:
Replaced a bunch of parts and Im going through and adjusting the bias and DC output. Im having trouble getting anywhere near the recommended current at the test location. According to a B&K tech sheet I obtained online, to adjust bias:
1. Monitor the (-) negative rail of each channel by removing the fuse and placing a current meter across the fuse clips.
Pulled the fuse on the negative rail and put one meter lead on one fuse holder clip and the other lead on the other. Left positive fuse in place. Im assuming that correct.
2. Connect an 8 Ω load to each channel. Supply an input signal of 100 mV RMS @ 20 Khz
I supplied a 100mV @ 17.5kHZ signal with an iPod with a test tone on repeat to only the channel Im testing. I adjusted the iPod volume to reach 100mV output. I dont imagine 2.5kHz is going to make any difference.
For the 8 Ohm load I put a 8Ohm/20W resistor across the speaker output leads of the channel being tested but I couldnt do it for all channels because I only had one resistor. Not sure if this is contributing to the problem. Theres no place locally for me to pickup 4 more resistors so I would have to order them online.
3. Slowly turn the variac up to operating voltage while monitoring the rails for excessive current draw. The meters should not read more than 400 mA DC. If one or both read more than 400 mA, turn the bias pots (P2) to minimum and retry.
I didnt have a variac so I just turned the P2 bias pot all the way down and crossed my fingers and powered up the amp from 120V residential power as normal.
4. Set bias of the amplifier by adjusting the bias pot (P2) mounted on the solder side of the board to achieve a reading of 200 mA on each channel for models ST 140, ST 140M, ST 202, and ST 202+. The bias for the Pro 600, EX 442 and M 200 amplifiers is 250 mA. Setting the bias higher than stated only causes the amplifier to run hotter and burn out faster. It does nothing for the sound quality of the amplifier.
This is where Im having issues.
First of all, my model isnt listed in this lineup. I think these are older models than the AV series. I think B&K offered some of these models concurrently with the AV series for a period of time but Im not sure if this test procedure or test specs apply to the AV series.
I looked at pics online of the internals of all of these and they are all look completely different from the AV series, internally. All except the M200. The M200 looks identical to the AV series.
Second of all, the spec of 200-250 mA is not remotely close. I set my DMM to mA, place my leads across the negative rail fuse clips, set my iPod to repeat for the input signal, connect my 8 Ohm resistor across the speaker leads and power the amp up. Even with the bias pot turned all the way up I cant get more than 48mA reading from my DMM. With the pot turned all the way down I get somewhere in the neighborhood of 10-15mA and it rises from there as I turn the pot up until I get about half way and then it levels off around 45-48mA. The second half of the adjustment range on the pot does nothing at all. At 48mA current the heat sink does get pretty hot (~105F measured right @ where the MOSFETS attach to the 'sink) but Im nowhere near the 200-250mA suggested by the tech sheet.
Am I supposed to divide that 200-250mA number by the number of MOSFETS or the number of MOSFET pairs per channel? There are 4 MOSFETS per channel or 2 pairs. That would give me a new target of 50-62.5mA or 100-125mA. I cant reach even the lowest of those numbers.
Any ideas?
Not sure on the wattage as Ive seen reference to it being both a 100W x3/60W x2 AND 100W x5. The 60W x2 is also in the owners manual. Not sure if this was a running change or if there were some mistakes in the literature. Im going to go ahead and say its 100W x5 because I went through the entire amp after a lightning strike and every part on every channel was exactly the same.
I believe this is a '98 build date.
The problem:
Replaced a bunch of parts and Im going through and adjusting the bias and DC output. Im having trouble getting anywhere near the recommended current at the test location. According to a B&K tech sheet I obtained online, to adjust bias:
1. Monitor the (-) negative rail of each channel by removing the fuse and placing a current meter across the fuse clips.
Pulled the fuse on the negative rail and put one meter lead on one fuse holder clip and the other lead on the other. Left positive fuse in place. Im assuming that correct.
2. Connect an 8 Ω load to each channel. Supply an input signal of 100 mV RMS @ 20 Khz
I supplied a 100mV @ 17.5kHZ signal with an iPod with a test tone on repeat to only the channel Im testing. I adjusted the iPod volume to reach 100mV output. I dont imagine 2.5kHz is going to make any difference.
For the 8 Ohm load I put a 8Ohm/20W resistor across the speaker output leads of the channel being tested but I couldnt do it for all channels because I only had one resistor. Not sure if this is contributing to the problem. Theres no place locally for me to pickup 4 more resistors so I would have to order them online.
3. Slowly turn the variac up to operating voltage while monitoring the rails for excessive current draw. The meters should not read more than 400 mA DC. If one or both read more than 400 mA, turn the bias pots (P2) to minimum and retry.
I didnt have a variac so I just turned the P2 bias pot all the way down and crossed my fingers and powered up the amp from 120V residential power as normal.
4. Set bias of the amplifier by adjusting the bias pot (P2) mounted on the solder side of the board to achieve a reading of 200 mA on each channel for models ST 140, ST 140M, ST 202, and ST 202+. The bias for the Pro 600, EX 442 and M 200 amplifiers is 250 mA. Setting the bias higher than stated only causes the amplifier to run hotter and burn out faster. It does nothing for the sound quality of the amplifier.
This is where Im having issues.
First of all, my model isnt listed in this lineup. I think these are older models than the AV series. I think B&K offered some of these models concurrently with the AV series for a period of time but Im not sure if this test procedure or test specs apply to the AV series.
I looked at pics online of the internals of all of these and they are all look completely different from the AV series, internally. All except the M200. The M200 looks identical to the AV series.
Second of all, the spec of 200-250 mA is not remotely close. I set my DMM to mA, place my leads across the negative rail fuse clips, set my iPod to repeat for the input signal, connect my 8 Ohm resistor across the speaker leads and power the amp up. Even with the bias pot turned all the way up I cant get more than 48mA reading from my DMM. With the pot turned all the way down I get somewhere in the neighborhood of 10-15mA and it rises from there as I turn the pot up until I get about half way and then it levels off around 45-48mA. The second half of the adjustment range on the pot does nothing at all. At 48mA current the heat sink does get pretty hot (~105F measured right @ where the MOSFETS attach to the 'sink) but Im nowhere near the 200-250mA suggested by the tech sheet.
Am I supposed to divide that 200-250mA number by the number of MOSFETS or the number of MOSFET pairs per channel? There are 4 MOSFETS per channel or 2 pairs. That would give me a new target of 50-62.5mA or 100-125mA. I cant reach even the lowest of those numbers.
Any ideas?
Last edited:
Hello nola000 by looking at the owners manual it looks like this is a 5 channel amp there doesnt seem to be much information information for this amp
On the B&K website it says for legacy support to contact Amplifier Technologies at (323) 278-0001 or sales@ati-amp.com.
SUPPORT — B & K
B&K AV6000/654 Owner's Manual (Page 10 of 12)
On the B&K website it says for legacy support to contact Amplifier Technologies at (323) 278-0001 or sales@ati-amp.com.
SUPPORT — B & K
B&K AV6000/654 Owner's Manual (Page 10 of 12)
Last edited:
Not sure I read it correctly, but if this is a multi-channel amp, you would need to turn up each channel separately to get to the total of 200 or 400mA. Assuming there is one fuse position for the whole amp.
So if this is a 5-channel amp, with 200mA target, start with all pots turn down, turn the 1st channel up to 40mA, then the next to 80mA, then the next to 120mA etc.
Does that make sense?
Jan
So if this is a 5-channel amp, with 200mA target, start with all pots turn down, turn the 1st channel up to 40mA, then the next to 80mA, then the next to 120mA etc.
Does that make sense?
Jan
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.