700B blew one Right channel 5A supply fuse

[Gepetto]

My bad, the extra white wire is a ground on the right which is not on the left. Unsolder the purple , and white/green stripe on both channels...

9 is either a blue (sometimes looks grayish) on the left side of each connection bank and 3 is violet over more to the right side. Not the white/green stripe.

You have a schematic Gary. They are the wires that connect to the base of Q11 (blue) and Q12 (violet)

Try again.

 

[laatsch55]

Pulled my ass outta te fire again, thanks Sir Joe..

 

[Gepetto]

Pulled my ass outta te fire again, thanks Sir Joe..

I know you have been pulling long hours lately Lee...

 

[laatsch55]

Braindead goes with the territory, well, oilfield territory....

 

[62vauxhall]

9 is either a blue (sometimes looks grayish) on the left side of each connection bank and 3 is violet over more to the right side. Not the white/green stripe.

You have a schematic Gary. They are the wires that connect to the base of Q11 (blue) and Q12 (violet)

Try again.

Since I last posted, I detached from the back wall all the output transistor sockets, both thermoswithces and both terminal strips looking for the possible short. To accomplish this, I had to drill out all but two of the mounting bolts, they were torqued on too tight and the screw heads stripped. I also removed the faceplate completely so as to facilitate looking for the short.

Using the buss bar ground, I have not yet gotten a short circuit reading on the meter but on visual examination, I believe I found one on the third terminal strip on the side wall next to the big caps. It is the thin "V" shaped piece of wire soldered between the two upper terminals.



Regarding the PC board pads, when disconnected the first time in order to mount new components, I diagrammed the board pads indicating what color wire went in what hole. I also placed numbered tags on the wires as a second means of identification. After re-connection the board, the colored wires went to the proper pads according to this diagram from the manual.


Just to confirm, I am now to re-attach the wires I disconnected earlier, disconnect the blue and violet and do the dim bulb test again? If so, presumably I need to re-mount the transistor sockets, the termoswitches, insert the RCA 410's, install the resistors between speaker terminals and re-test with the dim bulb?

To do that, I'll need to hit a shop in the morning and get replacement machine screws to replace those I've drilled out.

 

[laatsch55]

That's exactly what we are proposing, It doesn't take a very latge piece of stuff to short out a socket. Make sure they are super clean where they mate to the backwall. That thin wire jumps the 6 volt AC for the lights and that is stock. When you put in the RCA 410's are they going easy or do you have to push hard? I'm asking because I've put them i n backwards and they'll go but things sure get weird on the board....

 

[62vauxhall]

OK, I'll get the mounting hardware at 9AM tomorrow and do a temporary re-assemble. Just in case they have to come off again, can I plug in the 410's without the heatsinks in place?

When I first mounted the 410's, they seemed to slip in OK, I did not have to force them. Doesn't the pins being offset from centre prevent incorrect installation?

 

[laatsch55]

To a normal person yes Gary, but I can be a wee bit pigreaded and that F*&^%$ was going to go regardless!!! Yes the heatsinks must go back on....

 

[NavLinear]

OK, I'll get the mounting hardware at 9AM tomorrow and do a temporary re-assemble. Just in case they have to come off again, can I plug in the 410's without the heatsinks in place?

When I first mounted the 410's, they seemed to slip in OK, I did not have to force them. Doesn't the pins being offset from centre prevent incorrect installation?

Don't forget that the heat sinks do two jobs - they provide a thermal path from the transistor to the chassis and they also isolate the transistor case electrically from the chassis. If you're using the Sil-Pad - http://www.bergquistcompany.com/thermal_materials/sil-pad.htm - you should replace them prior to a final assembly. They're kind of like a condom - you only want to use them once.

The pins are offset from center so the mounting fasteners will not line up but the pins will.

 

[62vauxhall]

It took me a while but I was able to find some of the right size machine screws so now the heatsinks are back in place and RCA 410 transistors installed. As I examined the transistpr sockets, looking for that short, I happened to to notice stray strands from the red wire in this photo that goes to the right channel Q11 Collector. Those strands look like they've been exposed (as in unsoldered) for some time, like maybe from the factory because they seem oxidized. So much so that they won't take solder. I pushed them out of the way for now but can cut the end from that red wire and make a new connection. I can't say whether those strands were in contact with Q11 Base but they might have been.



To prepare for another dim bulb test, I re-soldered the wires I disconnected from the PC board and looked for the wires as per Gepetto's post:

9 is either a blue (sometimes looks grayish) on the left side of each connection bank and 3 is violet over more to the right side. Not the white/green stripe.

You have a schematic Gary. They are the wires that connect to the base of Q11 (blue) and Q12 (violet)

Try again.

What I found was that the wires I just re-connected (white/green striped one and the purple one) are the wires going to Q11 base and Q12 base.

The grayish blue wire goes to Q11 Emitter and the viollet one to Q12 Collector.

This photo shows how the board is wired and exactly like it was was before I first disconnected it. Please advise which wires I am to remove prior to the dim bulb test.

If those wires are what go to Q11 Base and Q12 Base then they are the striped one and purple one, not blue/grey and violet.

 

[laatsch55]

Q11, Q12 are the RCA 410's drivers....and the wires do connect to them...Q11 being the positive side, Q12 being the negative side...

 

[Gepetto]

It took me a while but I was able to find some of the right size machine screws so now the heatsinks are back in place and RCA 410 transistors installed. As I examined the transistpr sockets, looking for that short, I happened to to notice stray strands from the red wire in this photo that goes to the right channel Q11 Collector. Those strands look like they've been exposed (as in unsoldered) for some time, like maybe from the factory because they seem oxidized. So much so that they won't take solder. I pushed them out of the way for now but can cut the end from that red wire and make a new connection. I can't say whether those strands were in contact with Q11 Base but they might have been.

View attachment 14459

To prepare for another dim bulb test, I re-soldered the wires I disconnected from the PC board and looked for the wires as per Gepetto's post:

9 is either a blue (sometimes looks grayish) on the left side of each connection bank and 3 is violet over more to the right side. Not the white/green stripe.

You have a schematic Gary. They are the wires that connect to the base of Q11 (blue) and Q12 (violet)

Try again.

What I found was that the wires I just re-connected (white/green striped one and the purple one) are the wires going to Q11 base and Q12 base.

The grayish blue wire goes to Q11 Emitter and the viollet one to Q12 Collector.

This photo shows how the board is wired and exactly like it was was before I first disconnected it. Please advise which wires I am to remove prior to the dim bulb test.

If those wires are what go to Q11 Base and Q12 Base then they are the striped one and purple one, not blue/grey and violet.

Your color code is all messed up. Someone has rewired some of this before you and the colors are not stock (and your camera probably is not rendering colors right either). If you flip down the board and take a photo of the bottom of the socket stacks we should be able to visually trace the wires.

Tie this off with the assembly drawing you posted a few posts back.

On the LEFT channel the wiring goes from left to right as Pin 12, skip, 10, 9, 8, 7, 6, skip, 4, 3, 2, 1 On the right channel the wiring goes from left to right Pin skip, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1

 

[Gepetto]

I think I just figured it out by you explaining Pads 1 & 2 is the shielded lead coming from the pots. As such, Left Channel Pad 3 is the purple wire and Left Channel Pad 9 is the multi color wire.

If that;s the case, Right Channel Pad 3 is also a purple wire but Right Channel Pad 9 is a blue wire. The Rich Channel multi color wire is on Pad 10.

View attachment 14431

BUMP, your left channel identification of pin 9 is not correct. Keep going until you find the wires to the base of Q11 and Q12.

Your right channel flags of pin 9 and pin 3 on the assembly drawing are correct.

 

[laatsch55]

And this might help Gary.....the diagram you are looking for is the 3rd post and when you open it the drawing you are looking for is the top left, the original PL14 bord wiring....http://forums.phxaudiotape.com/show...ams-for-the-White-Oak-PL14-20-replacement-PCB

So there is no confusion, the drivers, Q11, Q12 are the RCA 410's...the pins on those are reversed to those directly above them....


EDIT--4th post in that thread...

 

[laatsch55]

Also, I understand what i linked is for a 400, but it's the same for a 700 with a 14 board. The pl 020 bords had the bias tranny wires going to the bottom of the bpard, not the middle....

 

[laatsch55]

Gary, on your last pic, do you think the bus bar on the left goes to Q11's base? It doesn't , it goes to Q11's emitter, then it proceeds to q13's base and on up the line...

 

[62vauxhall]

Gary, on your last pic, do you think the bus bar on the left goes to Q11's base? It doesn't , it goes to Q11's emitter, then it proceeds to q13's base and on up the line...

Yes I see that now. The lugs on the backsides or those sockets are all identified E, B or C. Since all the sockets looked identical and identical in positions, I thought they were but the RCA sockets are turned 180 degrees.

Going strictly by the markings on each individual socket, the blue/grey wire does go to Q11 Base and purple goes to Q12 base.

Now with that bit of insight, I am to disconnect those and repeat the dim bulb test with resistors at the speaker terminals?

 

[laatsch55]

Yes...

 

[62vauxhall]

And this might help Gary.....the diagram you are looking for is the 3rd post and when you open it the drawing you are looking for is the top left, the original PL14 bord wiring....http://forums.phxaudiotape.com/show...ams-for-the-White-Oak-PL14-20-replacement-PCB

So there is no confusion, the drivers, Q11, Q12 are the RCA 410's...the pins on those are reversed to those directly above them....


EDIT--4th post in that thread...

Wire color on my board leaves something to be desired but seems to concur with what you sent in the link.

 

[laatsch55]

It was shitty wire to begin with and it did not fare well in the high heat enviroment...