Resurrected a Customized WOPL 400

[scottonnob]

Okay — I'll get at it tomorrow, when I'm fresh and patient.

 

[laatsch55]

Don't glue the standoff, solder it back in the hole...

 

[scottonnob]

Yeah, I'm going out to work on it for a couple hours today. And, yes, I'll solder it in, and also inspect all the other sockets for good solder jobs. I have to do something about making the boards fit, so I'm going to de-solder them and get them into a circuit board holder to make it easier to work on everything.

 

[laatsch55]

Don't alter the boards to fit the chassis, alter the chassis to fit theboards.....

 

[Gepetto]

Okay, well, I've figured the whole mess out. The socket pulled loose, even with only finger-tight screws because the board wasn't perfectly flat against the spacers. The reason, and now that I've checked, it's the same on the other board, is that neither board is right. This is an old, four sink amp. It's one of the first groups to have come off the line. Unfortunately, and I ran into this elsewhere, if you recall, the dimensions of the chassis are, apparently, just a bit off from later runs. I had to re-drill two holes a long time ago for this reason. Anyway, the screw that holds the transistor and board doesn't line up. When the top screw is in place and has a nut on it, the bottom hole is at least an 1/8" too low to line up with the screw hole in the chassis and heat sink. I wasn't able to see this because the transistor and clamp, which were soldered in long before the boards were installed, blocked my view. So when the nut on the bottom screw was put on top of the board, everything canted and the board never got all the way down to the spacers. Therefore, when I put the screw in, there was at least a 1/16" gap between the board and the spacer, which was enough room to put pressure on the socket and pull it away when the board couldn't bend enough to contact the spacer. Christ, I don't know exactly how to remedy this problem. It isn't realistic to re-drill both the heat sink and the chassis. The misalignment isn't sufficient to allow a new hole to be drilled, and the present hole is too small to allow reaming it out enough. The only solution I can see is to use a Dremel to elongate the holes in the boards. Either way, it seems like I'm going to need to de-solder the boards from the connecting wires so I can remove both completely away from the rest of the unit. Otherwise, there is so much to fix, there's just no way to do it all with the boards still attached to the wires. The only other thing I can possibly think of is to just drill much bigger holes into the heat sink and chassis big enough to allow alignment, and then use a small fender washer on the outside of the chassis. I'd probably have to go 3/16" to get enough room, but at least it's on the back. Any thoughts would be greatly appreciated.

Hi Scott
Just getting to your post, been away for a bit. I also notice that your component leads are not clipped short enough. This is emphasized a lot in the build instructions for the backplane (Step 18). The board has to be absolutely flat on all of the PEM standoffs when you are done which means every lead has to be clipped shorter than 1/16" on the backside of each backplane board. It also appears that you have excess solder on the tops of at least one of the PEM standoffs which will not allow the board to be flat to the chassis adding stress. When flat and aligned to all holes, these standoffs see very little to no stress in the bond between the board and each standoff. The short lead trimming is also required to prevent any inadvertent shorting to the chassis. Air is your friend here and preserving the nominal 1/8" gap to the extent possible is the best.

And yes, the earliest chassis were not precision built, agreed. PL got its act together when they started running the 8 fin versions of the chassis, still not great but much more consistent than the early units.

You should be able to complete your resurrection project however, all is not lost.

 

[scottonnob]

Okay, I spent quite a few hours correcting a whole bunch of stuff today. I soldered the socket back in, no problem. Since I had the boards out, I trimmed and cleaned up the backside of both. Afterward, I put a straight edge on them to make sure nothing was going to be a problem. As recommended, and because I had already decided I didn't want to take any chances messing with the boards, I altered the chassis holes using a transfer punch so that everything now lines up. I reinstalled and soldered the boards back in then made certain everything is as it should be now. The boards are now lying perfectly on the standoffs, and I even ran a tap through all the sockets, just to make sure the threads were okay. I didn't want to take a chance on any of the screws binding up in during installation. Tomorrow I'm going to reinstall the first row of transistors and get ready for the first run of power. Unfortunately, I will have to wait until Wednesday to do anything because I discovered I don't have any 5 AGX fuses. I have two boxes of 5 AGC, but only a single 5 AGX, so I ordered a bunch, and they'll be here Wednesday. I'm in rural Northern California and our last Radio Shack closed last year. The closest one is now 30 miles away, over in Mendocino County. So now I have to order even the most insignificant stuff. Oh yeah, and I rechecked all the continuity issues because I feared altering the chassis might somehow affect the ground on the transistor strap. Everything is as it should be, but I know I'm going to be freaked when I go to actually put power to the thing. I think I'll take an hour and just look at it before anything gets plugged in.

 

[laatsch55]

Just have the dim bulb in circuit, you'll be OK...

 

[scottonnob]

Yeah, fortunately, I'll have two dim bulbs in the circuit. I have the mechanism with the bulb and a Variac, and then there's me. So two for the price of one.

 

[scottonnob]

Everything is now together, taped off, and hooked up to my dim-bulb tester. Unfortunately, the fuses didn't come today, but I already expected that. They'll be here tomorrow, and then I will begin the ceremony and ritual. I just hoping it doesn't turn into a fire dance. I will definitely go slowly and only after double-NASA-checking everything involved.

 

[laatsch55]

Good luck Scott....

 

[VSAT88]

Everything is now together, taped off, and hooked up to my dim-bulb tester. Unfortunately, the fuses didn't come today, but I already expected that. They'll be here tomorrow, and then I will begin the ceremony and ritual. I just hoping it doesn't turn into a fire dance. I will definitely go slowly and only after double-NASA-checking everything involved.

View attachment 31198

It looks sweet. Very nice. Hope you get your fuses tomorrow so I can come back and have a peek.

 

[scottonnob]

Well, I'm stumped. Up to 60 volts without any problems, unless no voltage to the boards is an issue. I have power from the fuse holder, power to the caps, about 50 volts, power to the rectifier, but nothing to the boards at any of the check points. I stared at it for almost two hours, then figured my gaze was unlikely to resolve any electrical problems. While staring, I looked over everything I can think of, but nothing seems amiss. But at least there was no smoke or ozone. I'm not sure what the diagnostic procedure is, but I'm hoping you guys can help me out.

 

[grapplesaw]

Well, I'm stumped. Up to 60 volts without any problems, unless no voltage to the boards is an issue. I have power from the fuse holder, power to the caps, about 50 volts, power to the rectifier, but nothing to the boards at any of the check points. I stared at it for almost two hours, then figured my gaze was unlikely to resolve any electrical problems. While staring, I looked over everything I can think of, but nothing seems amiss. But at least there was no smoke or ozone. I'm not sure what the diagnostic procedure is, but I'm hoping you guys can help me out.

Check the four fuses soldered on the back plane. They are little fuse green in color 1/2 watt

 

[scottonnob]

All four test good. However, this is probably a REALLY stupid question, but what is the wiring of the + sides of the bulk capacitors supposed to look like? Mine have just one wire each, both of which go to the rectifier. Shouldn't they be connected to the boards somehow?

 

[grapplesaw]

All four test good. However, this is probably a REALLY stupid question, but what is the wiring of the + sides of the bulk capacitors supposed to look like? Mine have just one wire each, both of which go to the rectifier. Shouldn't they be connected to the boards somehow?

Yes you need pos and meg to the board from the caps. Here is a shot of a 700. In the middle are two red and two black wires one each come from the cap the other set powers the right channel back plate.

 

[grapplesaw]

Yes you need pos and meg to the board from the caps. Here is a shot of a 700. In the middle are two red and two black wires one each come from the cap the other set powers the right channel back plate.

This is in addition to main power supplied to board from the two fuse holders above the transformer

 

[scottonnob]

The grounds are in place, but there's nothing going anywhere, other than the rectifier, from the positive posts. The leads are in place from the fuse holders to the boards. And, obviously, there's power to the thermal cutoff.

 

[orange]

So, I'm late but what you were referring to were bipolar (nonpolar) capacitors?

https://www.google.com/search?q=bipolar+capacitor

Are they marked or listed as NP on the wrapper or packaging?

 

[scottonnob]

This is what I'm referring to. Of course, the copper ground bar is reinstalled. But, if you can see from the photo, the only leads coming off of the positive sides are those between the caps and the rectifier. I'm dead in the water until I figure out what I'm doing wrong.

 

[scottonnob]

This is a fairly good picture of the left board, obviously; although, with the ground lead in place. If I missed something on the boards, I can't find it.