WOPL pl14 board kit rev e
- Thread starter shinynickel4272
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- Halfbiass...Electron Herder and Backass Woof
- Joined
- Jan 14, 2011
- Messages
- 74,914
- Location
- Gillette, Wyo.
- Tagline
- Halfbiass...Electron Herder and Backass Woof
hi I,m new to kit building and trying to breath some life back into my 700sr2. I know that caps must be installed pole specific and diodes in direction of current impedance. Do resisters have a specific orientation are are they by directional?
Of your 3 posts, you say it's a 700 Series II WOPL. Post some pics so we can see what the hell you have. This post would not indicate that it is WOPL'd
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I took on this project. Where to start? Need to know the status of the driver board. Howe to test it? I've been wanting to build a test set for a long time. This is the right excuse.
Started hunting around the shop. Figured I'd mkae a single channel amp with one NPN and one PNP output. I have a box of complimentary outputs, 2N5631 (NPN) and 2N6031 (PNP) from the days of testing Dynaco 400 driver boards. Checked them on a curve tracer and they looked to be OK. Found a heatsink for 4 x TO3's. Not very big which is good as it won't run long enough to heat up. Found a 70VCT transformer. A couple snap in caps and Joe's adaptor board. Used a 10amp bridge rectifier. A piece of 3/4" plywood that didn't need to be cut down.![IMG_4061[1].JPG](/data/attachments/61/61973-cdd4c26e74b8402ff2a5c57741ef33db.jpg)
![IMG_4063[1].JPG](/data/attachments/61/61974-3b379989b95f77723e933126f648baaf.jpg)
Built the power supply first and got +/- 50 VDC at 120 VAC input. Mounted the board and made up the connections from the outputs and drivers to the to the right channel of the board. Used the same wiring color convention for the board as the back planes. Since it follows the resistor color code it doesn't require any thought once the brown wire is landed.
Issues found:
First off the Phoenix connectors for the bias transistor was mounted on the front of the board. They are supposed to be on the back. In this case it made it easy to temporarily connect a bias transistor that had been pulled from a working amp. The leads on the bias transistor were intact. Eventually the Phoenix bias transistor connectors will get moved to the back of the board.
Not to begin testing. Brought up the power supply through a 100W bulb. No +15V power supply. Found D83 installed backwards. Now +15V supply Ok but no -15VDc on pin 4 of the opamp. Found R40 missing. Installed resistor and got output but positive cycle truncated. Found R35 on both channels missing. This supplies + VDC to the collector of the positive predriver (Q6).
The channel then worked at no load but went into current limit and was unstable with load. For some reason I had picked the value for the output emitter resistor as 1.2 ohms. Changed them to 0.22 ohms. Negative half cycle was ok but positive unstable with high frequency oscillations. It was 3:00 AM at that point. Called it a night. On the way to bed realized I hadn't put in a zobel.
today I repurposed a zobel that had been removed removed during a relay board install.. That tamed the oscillations.
Moved all of the driver board wiring from the right channel to the left channel. Didn't have any +/- 15 VDC. Realized I had to jumper +/- 75VDC from left channel to the right channel to get +/-15 vdc. Left channel worked ok.
So now that I know the driver board works I can redo the back plane.
Throughout all of this, the amp has been on the back edge of the bench while I worked on the test set. A like minded friend looked at the chassis and noticed one of the fuse holder didn't look right. We assumed someone put in a 1.25" AGC fuse rather than the 1" AGX fuse that belongs there. Pulled it out and found a piece of sheet copper that had been fashioned as a fuse. I've seen foil wrapped around a fuse. Never a piece of copper. A new standard has been set.
Now to remove and reinstall the back plane mess.
![IMG_4057[1].JPG](/data/attachments/61/61976-4bd8b2af303ad18b510dace21e864179.jpg)
Started hunting around the shop. Figured I'd mkae a single channel amp with one NPN and one PNP output. I have a box of complimentary outputs, 2N5631 (NPN) and 2N6031 (PNP) from the days of testing Dynaco 400 driver boards. Checked them on a curve tracer and they looked to be OK. Found a heatsink for 4 x TO3's. Not very big which is good as it won't run long enough to heat up. Found a 70VCT transformer. A couple snap in caps and Joe's adaptor board. Used a 10amp bridge rectifier. A piece of 3/4" plywood that didn't need to be cut down.
Built the power supply first and got +/- 50 VDC at 120 VAC input. Mounted the board and made up the connections from the outputs and drivers to the to the right channel of the board. Used the same wiring color convention for the board as the back planes. Since it follows the resistor color code it doesn't require any thought once the brown wire is landed.
Issues found:
First off the Phoenix connectors for the bias transistor was mounted on the front of the board. They are supposed to be on the back. In this case it made it easy to temporarily connect a bias transistor that had been pulled from a working amp. The leads on the bias transistor were intact. Eventually the Phoenix bias transistor connectors will get moved to the back of the board.
Not to begin testing. Brought up the power supply through a 100W bulb. No +15V power supply. Found D83 installed backwards. Now +15V supply Ok but no -15VDc on pin 4 of the opamp. Found R40 missing. Installed resistor and got output but positive cycle truncated. Found R35 on both channels missing. This supplies + VDC to the collector of the positive predriver (Q6).
The channel then worked at no load but went into current limit and was unstable with load. For some reason I had picked the value for the output emitter resistor as 1.2 ohms. Changed them to 0.22 ohms. Negative half cycle was ok but positive unstable with high frequency oscillations. It was 3:00 AM at that point. Called it a night. On the way to bed realized I hadn't put in a zobel.
today I repurposed a zobel that had been removed removed during a relay board install.. That tamed the oscillations.
Moved all of the driver board wiring from the right channel to the left channel. Didn't have any +/- 15 VDC. Realized I had to jumper +/- 75VDC from left channel to the right channel to get +/-15 vdc. Left channel worked ok.
So now that I know the driver board works I can redo the back plane.
Throughout all of this, the amp has been on the back edge of the bench while I worked on the test set. A like minded friend looked at the chassis and noticed one of the fuse holder didn't look right. We assumed someone put in a 1.25" AGC fuse rather than the 1" AGX fuse that belongs there. Pulled it out and found a piece of sheet copper that had been fashioned as a fuse. I've seen foil wrapped around a fuse. Never a piece of copper. A new standard has been set.
Now to remove and reinstall the back plane mess.
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- Gillette, Wyo.
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- Halfbiass...Electron Herder and Backass Woof
Nice work Don, kinda like mine but I use one channel of a backplane board set instead.
You will have oscillations unless you get some bypass capacitors on the backplane very near the transistor loads. The wiring lead inductance will cause that. It is amazing how a little wire length will do that to you. That was a problem that the original PL point to point backwall wiring had too.
Get yourself some of those Molex KK headers I emailed you about and it will make it easy to swap a board in and out to test.
You will have oscillations unless you get some bypass capacitors on the backplane very near the transistor loads. The wiring lead inductance will cause that. It is amazing how a little wire length will do that to you. That was a problem that the original PL point to point backwall wiring had too.
Get yourself some of those Molex KK headers I emailed you about and it will make it easy to swap a board in and out to test.
Joe
working w a New board Rev G w a Phase liner 400II Full
At about 1250Hz it changes from solid line (Sine wave) to a not solid and has like dots in it (like a dotted line sine wave) What kind of problem is this?
and when I play music and turn the bass up at high Volume I get a ripping noise (like going thought the tweeter) and I turn the bass down and it disappears but it will come back if I turn the volume up
I need to test at lower volume w the bass up and see what happened.
The Good
I tested at 1k and it had a good sine wave and when I brought it up into clipping (I think 150v peak to peak watts? ) and everything looked good.
Is this a High-frequency oscillations and/or high frequency slewing at high output power?
History
1. I rewired it w new wires and after the fist test I made the wires shorter and also the Bias wires (critical?) a lot shorted
(It helped but did cure the problem)
Phase linear drawing 400II and 700II Npn side did not match drawing (I'm going to look into this)
First question is what wires are the most critical? and/or Backplane Components?
also do you know how many Full-comp w Original Backplanes been done or out there?
Thanks
Steve
working w a New board Rev G w a Phase liner 400II Full
At about 1250Hz it changes from solid line (Sine wave) to a not solid and has like dots in it (like a dotted line sine wave) What kind of problem is this?
and when I play music and turn the bass up at high Volume I get a ripping noise (like going thought the tweeter) and I turn the bass down and it disappears but it will come back if I turn the volume up
I need to test at lower volume w the bass up and see what happened.
The Good
I tested at 1k and it had a good sine wave and when I brought it up into clipping (I think 150v peak to peak watts? ) and everything looked good.
Is this a High-frequency oscillations and/or high frequency slewing at high output power?
History
1. I rewired it w new wires and after the fist test I made the wires shorter and also the Bias wires (critical?) a lot shorted
(It helped but did cure the problem)
Phase linear drawing 400II and 700II Npn side did not match drawing (I'm going to look into this)
First question is what wires are the most critical? and/or Backplane Components?
also do you know how many Full-comp w Original Backplanes been done or out there?
Thanks
Steve
Update
Check the location and value of the Mica Caps all OK
unhooked the Bias Transistor's and install temporary one a in its place w Short leads
still have problem at high volume and bass
It has Has one ferrite beads for each bank (4 total) The 400II was converged from Quad to Full if that mean anything.
Another factor is - The updated supply caps and voltage and the higher speed of the Output Transistor
all new MJ21195 and MJ21196
PL made a lot changes for the Full comp and for some reason the assemblers did not do all the updates.
What wires cause the most problem?
Next -back on the scope (see if anything changed)
Thanks
Steve
Check the location and value of the Mica Caps all OK
unhooked the Bias Transistor's and install temporary one a in its place w Short leads
still have problem at high volume and bass
It has Has one ferrite beads for each bank (4 total) The 400II was converged from Quad to Full if that mean anything.
Another factor is - The updated supply caps and voltage and the higher speed of the Output Transistor
all new MJ21195 and MJ21196
PL made a lot changes for the Full comp and for some reason the assemblers did not do all the updates.
What wires cause the most problem?
Next -back on the scope (see if anything changed)
Thanks
Steve
