nelsress begins his WOPL 400 project

[laatsch55]

The row closest to the transformer is for the MJ 21196's, the next the 21195's, then the 96's then the 95's...

 

[nelsress]

Excellent!!

The row closest to the transformer is for the MJ 21196's, the next the 21195's, then the 96's then the 95's...

Thanks Lee! Easy enough but didn't want to just wing it and hope I guessed right!! From previous reading I remember that I'm only supposed to install the transistors in four slots initially, I believe it was QX17 & QX18, on the left and right boards in order to more safely apply power for the first time. Do I understand that correctly? Thanks again.

Nelson

 

[laatsch55]

Yes, just the bottom row...

 

[Gepetto]

Thanks Lee! Easy enough but didn't want to just wing it and hope I guessed right!! From previous reading I remember that I'm only supposed to install the transistors in four slots initially, I believe it was QX17 & QX18, on the left and right boards in order to more safely apply power for the first time. Do I understand that correctly? Thanks again.

Nelson

Put in the bottom row only which is XQ11 and XQ12 locations on each backplane board. Do your power up with variac and DBT to check things out before installing the next row, then the next row etc.

 

[Gepetto]

Put in the bottom row only which is XQ11 and XQ12 locations on each backplane board. Do your power up with variac and DBT to check things out before installing the next row, then the next row etc.

Here is the recommended procedure Nelson. This was written for the quasi-comp with the RCA410 devices in the bottom row, you can substitute XQ11 and XQ12 for the RCA410 references and the remainder is relevant to bring up.

With this configuration (somewhat like safe mode), you should be able to power up the amp WITH NOTHING (except a DMM) CONNECTED TO THE OUTPUT AND NOTHING CONNECTED TO THE INPUT.
This will allow you to check everything out before doing any further work. The amp will work in every normal way except that it will not be able to power much of an output load without the 6 or 10 (depending on PL400 or PL700 amp) remaining output drivers per channel installed.
Step by step:
1. Check for any shorts or workmanship issues
2. Turn bias pots on control board to full CCW position (bias set to minimum, bias level setting is of no real concern during bring up unless Q6 is broken)
3. Install 1A fuses in the B+ and B- fuse holders
4. Attach DMM in voltage measurement mode, plus lead to the left channel speaker white output post and minus lead to left channel speaker black ground post.
5. With the Variac off and dial turned to minimum, plug in the amp to the Variac output.
6. Turn on Variac and slowly (over about a 30 second interval) bring the dial up to 60V input. Pause approximately at each 20V input interval along the way to 60V and ensure nothing is abnormal and your DMM voltage is behaving reasonably. Ensure no overheating, smoke, bad smells etc. Shut it down if you do!
7. If you made it this far and things are OK then check the output of your DMM. It should be very close to 0 V, typically less than 50 mV. Ensure no overheating, smoke, bad smells etc. Shut it down if you do.
8. Next slowly (over about a 30 second interval) bring the dial up to the full 120V input. Pause approximately at each 20V input interval along the way to 120V and ensure nothing is abnormal and your DMM voltage is behaving reasonably. Ensure no overheating, smoke, bad smells etc. Shut it down if you do!
9. If you made it this far and things are OK then check the output of your DMM. It should be very close to 0 V, typically less than 20 mV. Ensure no overheating, smoke, bad smells etc. Shut it down if you do.
10. Using your DMM plus lead (with the minus lead still connected to the left channel speaker black ground post) check each of the 2 bias test points on the control board. These should measure less than 0.400V (typically these will be at about half of this with the bias pots turned to minimum)
If all goes well in the above 10 steps, you are ready to install the next row up from the RCA410 pre-drivers. Allow the amp to discharge prior to the installation of each next row of devices. Unplug the amp and let it sit for 5 minutes before installing each row of additional driver devices. You do not want to damage output devices or yourself by working on a somewhat live amp. The rest of the tests are somewhat continuous with no discharge need involved. Carefully check each device installed using your DMM to ensure that they are good devices and then install the 4 drivers in this first row above the pre-drivers. After this step is completed:
1. Repeat step 1-10 from above.
If all goes well in the above 9 steps, you are ready to install the second row up from the RCA410 pre-drivers. Allow the amp to discharge prior to the installation of each next row of devices. Unplug the amp and let it sit for 5 minutes before installing each row of additional driver devices. You do not want to damage output devices or yourself by working on a somewhat live amp. The rest of the tests are somewhat continuous with no discharge need involved. Carefully check each device installed using your DMM to ensure that they are good devices and then install the 4 drivers in this second row above the pre-drivers. After this step is completed:
1. Repeat step 1-10 from above.
If all goes well in the above 9 steps, you are ready to install the third row up from the RCA410 pre-drivers. Allow the amp to discharge prior to the installation of each next row of devices. Unplug the amp and let it sit for 5 minutes before installing each row of additional driver devices. You do not want to damage output devices or yourself by working on a somewhat live amp. The rest of the tests are somewhat continuous with no discharge need involved. Carefully check each device installed using your DMM to ensure that they are good devices and then install the 4 drivers in this third row above the pre-drivers. After this step is completed:
1. Repeat step 1-10 from above.
After all the above and things are still looking good, turn on the amp at nominal AC line voltage and let it sit for 5 minutes and then adjust the bias per the procedure.
This is the procedure that I utilize for a new amplifier bring-up. It does not take as long as the procedure seems to indicate after you have done this a couple of times.

 

[nelsress]

Thanks Joe,

this is incredibly helpful. I went over the capacitor installation instructions quickly on the WO site but will go over it in earnest tomorrow when I print it out. It's easier for me to read on paper for some reason. I'm guessing that where the yellow wires go will be (hopefully) cleared up in that document. I'm positive they were attached somewhere in the old configuration, I'm sure I cut them leaving as long leads as I could, but I didn't pay attention where when I disconnected them, thinking it would be obvious later. I'll be taking more "before" pictures on my 700B project, to be sure!

Anyway, thanks again Joe, looking forward to these next steps and a successful power up. Wish me luck!

 

[Gepetto]

this is incredibly helpful. I went over the capacitor installation instructions quickly on the WO site but will go over it in earnest tomorrow when I print it out. It's easier for me to read on paper for some reason. I'm guessing that where the yellow wires go will be (hopefully) cleared up in that document. I'm positive they were attached somewhere in the old configuration, I'm sure I cut them leaving as long leads as I could, but I didn't pay attention where when I disconnected them, thinking it would be obvious later. I'll be taking more "before" pictures on my 700B project, to be sure!

Anyway, thanks again Joe, looking forward to these next steps and a successful power up. Wish me luck!

It appears you have the international transformer Nelson (120V/240V). For 120V wiring, the blue and brown get connected together and to one side of the AC line (you will see this connection at the fuseholder ring terminal. The Yellow/Brown and Yellow/Blue wires also get connected together and are routed to the other side of the AC line which in this case is the thermal cutout switch.

 

[Gepetto]

Thanks Joe and Lee, good advice for sure. The straight edge test showed everything to be good in that regard, so that's a good thing. I've attached a couple pics of the boards in the chassis.

Doug (fitz43) has some silpads in the mail on their way to me. Progress!


View attachment 19539View attachment 19540

Your AC wiring in this picture is NOT correct Nelson. Right now you have it wired such that the AC Neutral and Hot line are tied together through the fuse holder.

 

[Gepetto]

Your AC wiring in this picture is NOT correct Nelson. Right now you have it wired such that the AC Neutral and Hot line are tied together through the fuse holder.

AC wiring should be as follows:

AC In1 (short wire from line cord) to AC mains fuse TIP
AC mains fuse RING to transformer BLUE and BROWN wires connected together

AC In2 (long wire from line cord) to Thermal Cut out switch terminal 1
Transformer Yel/Blu and Yel/Brn to Thermal Cut out switch terminal 2

Let me know if you are clear on this?

 

[nelsress]

Okay, let's see if I've got this now...

AC wiring should be as follows:

AC In1 (short wire from line cord) to AC mains fuse TIP
AC mains fuse RING to transformer BLUE and BROWN wires connected together

AC In2 (long wire from line cord) to Thermal Cut out switch terminal 1
Transformer Yel/Blu and Yel/Brn to Thermal Cut out switch terminal 2

Let me know if you are clear on this?

So if I understand you correctly, I remove the white wire from the fuse AC mains fuse tip and the thermal cut out switch and put the yel/blu & yel/brn wires to the terminal on the cut out switch where the white wire is now. Would it be best to splice/extend these two wires and route them above the boards to avoid having them in between the backplane board and the control board or can I use them as is?

AC In1 is where it is supposed to be, on the AC mains fuse tip, as is AC In2 which is routed to the thermal cut out switch. I did remove the strain relief as suggested and feed an extra inch or so of the AC mains cord inside the amp.

The blue and brown wires are already where you say they should be, I believe, as they are currently attached to the AC mains fuse ring (side lug).

Does it sound like I've got it right now? If not hit me over the head with it again, it will sink in eventually!!

 

[Gepetto]

So if I understand you correctly, I remove the white wire from the fuse AC mains fuse tip and the thermal cut out switch and put the yel/blu & yel/brn wires to the terminal on the cut out switch where the white wire is now. Would it be best to splice/extend these two wires and route them above the boards to avoid having them in between the backplane board and the control board or can I use them as is?

AC In1 is where it is supposed to be, on the AC mains fuse tip, as is AC In2 which is routed to the thermal cut out switch. I did remove the strain relief as suggested and feed an extra inch or so of the AC mains cord inside the amp.

The blue and brown wires are already where you say they should be, I believe, as they are currently attached to the AC mains fuse ring (side lug).

Does it sound like I've got it right now? If not hit me over the head with it again, it will sink in eventually!!

Yes, get rid of that white wire you have routed to the thermal cut out switch and extend the joined yellow/brown, yellow/blue wires over the top and then L down to the thermal switch. You can use that white wire to extend the yellow/blue/brown wires to save having to solder that end again at the thermal switch.

DO NOT run the AC wires over the backplane boards.

 

[nelsress]

Sounds good

Yes, get rid of that white wire you have routed to the thermal cut out switch and extend the joined yellow/brown, yellow/blue wires over the top and then L down to the thermal switch. You can use that white wire to extend the yellow/blue/brown wires to save having to solder that end again at the thermal switch.

DO NOT run the AC wires over the backplane boards.

Will do, I'll splice the white wire to the two yellow striped wires and route them around the boards, not over them. Thanks Joe, much appreciated.

 

[nelsress]

After removing the glue residue from the cap cradle on the tranny that was missing the double faced tape and removing the old tape from the other side and cleaning it up I decided to change over the AC snafu I had. No sweat, I disconnected the white wire from the AC mains fuse tip, took the yellow striped wires and slid a piece of shrink tube over them, stripped the ends of both, untwisted each separately and twisted them all together. Then I fluxed and tinned those and bent a hook in them. Next I tinned the white wire and bent a hook in it, put the two hooks together, crimped them with my needle nose, soldered them together and let it cool for a couple minutes. Then I slid the shrink tube that I placed over the two yellow striped wires over the connection point, applied heat and that was that.

My next step was to remove the screw from the center of the bridge rectifier to insert the threaded rod for the capacitor hold down plate but I ran into a slight problem. I'm going to have to find a piece of threaded rod with a finer machine thread because the self-tapping screw that held down the bridge rectifier is finer. I figure this is the correct solution since the instructions warn not to go in too far or the transformer windings could be damaged so I assumed that re-tapping that hole is NOT a good idea-the last thing I need are metal shavings inside that hole!!! Right? Below is a photo showing the different threads. Minor road block, beats the hall out of a major road block!!

 

[laatsch55]

Sometimes the self-tapper leaves a rather crude thread. Double nut the threaded rod and try using a small wrench to turn the rod..

 

[Gepetto]

Sometimes the self-tapper leaves a rather crude thread. Double nut the threaded rod and try using a small wrench to turn the rod..

Or better yet, take a 10-24 tap and chase the threads. The stock PL units are 10-24, looks like a PO kludged in a alien bolt.

If you go carefully, you will know when the tap bottoms out, elsewise loosen the tranny bolts and separate the die cast from the laminations.

 

[laatsch55]

I have used a bottoming tap and my little 1-1/2 gallon shop vac.....

 

[fitz43]

Or better yet, take a 10-24 tap and chase the threads.

When we were adding full flow oil systems to VW air cooled aluminum/magnesium engine blocks we would coat the tap with wheel bearing grease to help catch the flakes being removed.

 

[nelsress]

Thanks guys

I appreciate the suggestions Joe, Lee and Doug, thanks. What I ended up doing was running the 10-24 tap about 3/4 of the way in and backed it out. It didn't seem like it was taking much of the aluminum out, it went so easily and when I backed out the tap, a couple little shavings came back out with the tap. Then I threaded the rod into the hole and when it stopped, well short of the distance the screw was in, I turned it with a nut driver over the two nuts and went the rest of the way, stopping 1/16" or so from the depth the screw had been in.

The instructions say to attach the two black wires with ring lugs coming from the transformer to the rearward cap screw. The black wires coming out of the transformer were attached to lugs on the bridge rectifier as were the green wires with the ring lugs so those are the ones I attached. Is that correct? I had to extend the white wire from the transformer to the copper bus so it would reach the end of the new, longer resistors without being bent fairly drastically in the middle.

The upper capacitor's rearward connection point is supposed to get the red wires with ring lugs and the photos on the instructions show the old point to point wiring on the back wall, not the backplane boards so I'm not sure what wires go to that spot yet.

I installed the bottom row of transistors with silpads starting from the transformer and going away from it in this order-95-96-95-96 and snugged them down. Now I may have missed it or perhaps it comes in a later step but I didn't see anything about soldering the transistor leads. Do these solder cups have some sort of contact inside them that eliminates the need to solder them or am I just getting ahead of myself and I'll be told to solder them farther along in the assembly?

Attached are some more photos so you can see what I've done up to this point. Thanks guys!

 

[laatsch55]

The row closest to the transformer gets the 96....the 95....then 96....then 95..

 

[nelsress]

You are correct sir!

The row closest to the transformer gets the 96....the 95....then 96....then 95..

That's what I did, but it's definitely NOT what I said I did!! Thanks for making me make sure though, Lee. That's why I'm bombarding you guys with photos, I figure it's the best way for you to catch my mistakes and why I'm narrating as well. In this case I wasn't even able to narrate correctly what I had done. Sometimes I get a little fuzzy!