700B and speaker out DC protection?
- Thread starter BMWR75
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Joe,
I've not made any changes to the L/R inputs (other than the ground change, which I will now fix). The RCA inputs are still stock. No replacement RCA jacks were included in the kit I got from Watts Abundant.
Will read your prior post instructions closely. Make the needed changes and report back.
Thanks,
Scott
I've not made any changes to the L/R inputs (other than the ground change, which I will now fix). The RCA inputs are still stock. No replacement RCA jacks were included in the kit I got from Watts Abundant.
Will read your prior post instructions closely. Make the needed changes and report back.
Thanks,
Scott
You will usually see a wire connecting the copper ground plate to the selection switch body. This is not proper and PL should not have done it but they did. You should swap out the cheap electrolytic coupling caps to the 1uF polyester film type as shown in the photos. The 220K ohm resistors should be terminated directly to the small copper plate as shown in the photos.
You will achieve lower noise and hum with these changes.
You will achieve lower noise and hum with these changes.
Joe,
Please check my understanding on correcting the ground scheme.
1. New white wire from the filter cap copper bus plate to Pin 6 of the DC protection board
2. New white wired that was soldered to the RCA input ground plate should be removed and thrown away
3. The old white wire from the WO PCB 5R connection (you said 5L below, so I'm confused) should be going where? To the RCA input ground? It was formerly connected to the negative speaker posts, which where also tied to the RCA input ground via a bare silver wire.
Thanks,
Scott
Please check my understanding on correcting the ground scheme.
1. New white wire from the filter cap copper bus plate to Pin 6 of the DC protection board
2. New white wired that was soldered to the RCA input ground plate should be removed and thrown away
3. The old white wire from the WO PCB 5R connection (you said 5L below, so I'm confused) should be going where? To the RCA input ground? It was formerly connected to the negative speaker posts, which where also tied to the RCA input ground via a bare silver wire.
Thanks,
Scott
Your step 1 and 2 are correct Scott. Your step 3 is wrong.
Connect 5L to the filter cap bus plate (the single point ground)
No connection to 5R (that comes from the bus wire jumper on the backside of the PL14_20 board.
Here is a schematic of the way the ground scheme should be within the PL700B
View attachment PL700 Grounding.pdf
Connect 5L to the filter cap bus plate (the single point ground)
No connection to 5R (that comes from the bus wire jumper on the backside of the PL14_20 board.
Here is a schematic of the way the ground scheme should be within the PL700B
View attachment PL700 Grounding.pdf
Joe,
I am looking at the White Oak 700B PL14_20 PCB wiring diagram I used to install this board in my amp.
It says 5L is No Connection and 5R is Chassis Ground. 5R is a white wire and the other end was formerly connected to the Left negative speaker post.
You are saying 5L in your posts below.......so I am still confused.
I am looking at the White Oak 700B PL14_20 PCB wiring diagram I used to install this board in my amp.
It says 5L is No Connection and 5R is Chassis Ground. 5R is a white wire and the other end was formerly connected to the Left negative speaker post.
You are saying 5L in your posts below.......so I am still confused.
Correct, 5L and 5R are the same Scott because they are connected by a bus wire on the back. The 5L run is a shorter run to the bus bar single point ground which is why it is preferred for the OPTIMUM ground scheme.
The wiring charts are for those that just are looking to slap in a replacement board quickly. The original PL wiring brings it into the 5R connection because they had all the chassis wiring wrong. That is why the wiring charts are that way.
You are reworking to the improved single point ground thus will bring in the shorter wire to 5L.
Now clear??
The wiring charts are for those that just are looking to slap in a replacement board quickly. The original PL wiring brings it into the 5R connection because they had all the chassis wiring wrong. That is why the wiring charts are that way.
You are reworking to the improved single point ground thus will bring in the shorter wire to 5L.
Now clear??
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- Joined
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- Tagline
- Halfbiass...Electron Herder and Backass Woof
Actually the resistors are the right ones. They're 2.7 ohm, tied in series. I was using one 5.6 ohm/5W. They stood up to high and I had one break in shipping. I just changed to the new resistors last week.
Sorry for the confusion on the directions. When I first wrote them I wanted to minimize the changes needed to do the install, knowing full well that it did not solve the original ground issues. I need to revise the procedures. Given that so many people have successfully installed the White Oak board, I probably underestimated the average person's capability.
Even with an improved grounding scheme, that's not likely going to resolve the issues here. The question is did the amp work properly before the relay was installed? Second, is there anything connected to the output?
My guess is there is a load on the output terminals of the amp. Then there is either (1) DC offset on the output that is below the detection level of the relay circuit, (2) the amp is oscillating, (3) there is a signal on the input. Given the above, when the relay pulls in the DBT will do as it is intended to do which is limit the input current and the result is the bulb gets bright. The relay drops out and the cycle start over again.
Referring back to the instructions, step 2 has you measure the offset before beginning. What was the measurement in step 2? See below. Then refer to the first troubleshooting section in the instructions.
Check the DC offset voltage for each channel. To do this disconnect the inputs and speakers. With the amp turned on measure the voltage on the output terminals. If it’s more than 50mv (typical is less than 15), contact us...
Sorry for the confusion on the directions. When I first wrote them I wanted to minimize the changes needed to do the install, knowing full well that it did not solve the original ground issues. I need to revise the procedures. Given that so many people have successfully installed the White Oak board, I probably underestimated the average person's capability.
Even with an improved grounding scheme, that's not likely going to resolve the issues here. The question is did the amp work properly before the relay was installed? Second, is there anything connected to the output?
My guess is there is a load on the output terminals of the amp. Then there is either (1) DC offset on the output that is below the detection level of the relay circuit, (2) the amp is oscillating, (3) there is a signal on the input. Given the above, when the relay pulls in the DBT will do as it is intended to do which is limit the input current and the result is the bulb gets bright. The relay drops out and the cycle start over again.
Referring back to the instructions, step 2 has you measure the offset before beginning. What was the measurement in step 2? See below. Then refer to the first troubleshooting section in the instructions.
Check the DC offset voltage for each channel. To do this disconnect the inputs and speakers. With the amp turned on measure the voltage on the output terminals. If it’s more than 50mv (typical is less than 15), contact us...
Also, remove the 4 mounting nuts, lift the board and take a pic of the input jacks. The white wire going to the input ground bus can not make accidental contact to the bottom of the board.
I believe Joe has posted a drawing showing the proper grounding scheme which addresses this issue.
I believe Joe has posted a drawing showing the proper grounding scheme which addresses this issue.
Last edited:
Please allow me to recap how this amp was fixed and answer all the questions posed in the prior posts.
First, the amp is working fine now!! BIG THANKS TO GEPETTO!!!
This amp was working fine before I installed the Watts Abundant DC Protection board (and is now working fine again after fixing the grounding scheme problem). The DC offset and bias were as shown below before the DCP board installation:
I had previously installed the White Oak PCB14_20 board in this amp.
Followed Watts Abundants instructions on how to wire up the new DC Protection board. The instructions say connect three white ground wires to J6 (Pin 6) on the DCP board. When I did this, it caused me to get a bad dim bulb test. The dim bulb would burn bright, go about 1/2 dim and then cycle back to bright, then dim and just keep cycling (the DCP board relays were NOT clicking). As required in dim bulb testing, nothing was connected to the amp inputs or speaker outputs.
Followed Gepetto's instructions to only have one ground wire going into J6 on the DCP board. The J6 connection is the new white wire that is installed on the copper plate between the power supply filter capacitor posts. Next moved the white wire on 5R connection to the White Oak PCB14_20 to the 5L position on the same board (just to shorten the wire in keeping with good grounding protocol, 5L and 5R are jumpered together on the back of the board). Then removed the new white wire that was running from the L/R inputs on the amp to the DCP board (just snipped it off where it was soldered on the bare silver wire up near the inputs). The changes in this paragraph solved the dim bulb test failure problem.
Now when I put the amp on the dim bulb tester.....it burns bright initially, then dims down to nothing.....then the DCP board relays click. Watts Abundant's instructions say the DCP board relays won't click on the dim bulb, but they do for me.
Once again this amp is sounding great. On my test bench speakers it also has low background noise using pretty high sensitivity speakers.
First, the amp is working fine now!! BIG THANKS TO GEPETTO!!!
This amp was working fine before I installed the Watts Abundant DC Protection board (and is now working fine again after fixing the grounding scheme problem). The DC offset and bias were as shown below before the DCP board installation:
Left = 378 mV bias and -14.0 mV offset
Right = 379 mV bias and -14.8 mV offset
Right = 379 mV bias and -14.8 mV offset
I had previously installed the White Oak PCB14_20 board in this amp.
Followed Watts Abundants instructions on how to wire up the new DC Protection board. The instructions say connect three white ground wires to J6 (Pin 6) on the DCP board. When I did this, it caused me to get a bad dim bulb test. The dim bulb would burn bright, go about 1/2 dim and then cycle back to bright, then dim and just keep cycling (the DCP board relays were NOT clicking). As required in dim bulb testing, nothing was connected to the amp inputs or speaker outputs.
Followed Gepetto's instructions to only have one ground wire going into J6 on the DCP board. The J6 connection is the new white wire that is installed on the copper plate between the power supply filter capacitor posts. Next moved the white wire on 5R connection to the White Oak PCB14_20 to the 5L position on the same board (just to shorten the wire in keeping with good grounding protocol, 5L and 5R are jumpered together on the back of the board). Then removed the new white wire that was running from the L/R inputs on the amp to the DCP board (just snipped it off where it was soldered on the bare silver wire up near the inputs). The changes in this paragraph solved the dim bulb test failure problem.
Now when I put the amp on the dim bulb tester.....it burns bright initially, then dims down to nothing.....then the DCP board relays click. Watts Abundant's instructions say the DCP board relays won't click on the dim bulb, but they do for me.
Once again this amp is sounding great. On my test bench speakers it also has low background noise using pretty high sensitivity speakers.
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