Extended Foreplay 3 Help

[John EH]

Everything good up to terminal 12. 
All resistance readings ok.

No LED's anywhere with power.

Both A side and B side (all corresponding terminals).

12 - 180V supposed to be 150
15 - 1.5V  supposed to be 75

Just to aid in the troubleshooting I did foul up an HLMP-6000 and subbed it.  Left one on the A channel.  Same LED I subbed out in the old Foreplay 2 C4S.

I know it is the regulator.  I used the tube in the kit.  I'll swap it next just to make sure.

John

[John EH]

Just for clarity these voltages were taken at 100V mains input.

I went to 120 and got basically 220v on 9 and 10, both power supplies.  Seems the 220 is going straight to 12,21, and 32.

Terms 15 and 31 are 1.6 volts.

Term 22 - is now 40volts.

Gotta be the regulator but I swear it is together right.  I took a meter to the LED's and they seem to be installed correctly.  But I'm game for somebody telling me I'm wrong.

Maybe a stupid mis-wire?  I don't see it.

John

[John EH]

And one more note.  I have another operational Extended FP3.  The diodes on the regulator board match up with the operational one.  A channel red on left, black on right gets 1.8 v across with the fluke, same on the other bad one.  Swap the black and red and the B channel is the same as the other one as well. 

Good FP and Bad FP mirror in regards to the LED but something is letting B + pass unregulated.

Stupid wiring error?  Bad transistor?

John

[Paul Birkeland]

Yes, your regulator isn't working.  On the center board, what are the voltages at IA/IB, OA/OB, and KregA/KregB?

Triple check all those transistors!!!!

[John EH]

Yes, your regulator isn't working.  On the center board, what are the voltages at IA/IB, OA/OB, and KregA/KregB?

Triple check all those transistors!!!!

A and B

I  - 186
O - 185
K - 1.1

Next I'll take photos of the transistors so I can read them.

John

[John EH]

Measurements above taken at 100v mains and reflect voltages from my first post before I upped to 120v mains.

I took macro photos of each transistor.  I have the correct ones installed in the correct orientation.

[Paul Birkeland]

Alright, this is helpful info!

So what I can see is that you're presenting 185V to the plates of each 12AU7, and getting a cathode voltage of 1.1V.  This would be consistent with that center 12AU7 sucking down all the available current possible, and not giving the TL431 enough voltage to operate.  On the other hand, the four LED's on that board should be glowing brightly. 

What I would double check first is that you have continuity (~0 Ohms) between every pad labeled G on that board and ground in the amp (the bare buss wire running around the front row of terminal strips is a good ground reference).  Ground passes "through" that board, so you could check continuity from terminal 24 to the ground buss.

Let me know if any of this points out issues.  If not, I have some other tests that you can run.

-PB

[John EH]

.3 Ohms from both sides of the jumper labelled G on the boards to chassis ground. That's good.

[Paul Birkeland]

Alright, so the center shunt reg board is grounded, receiving power, and there is some voltage present at the 12AU7 cathode.

Now we will be interested in the outboard boards, as we really, really want them to draw some current so the center board can work properly.

First of all, we want to see that the outboard 12AU7's are glowing (seems obvious, but just good to check).

Next, a red wire runs to the "A" side on each of the outer green PC boards to the "I" pad.  Measure the voltage here, it should be your ~180V.

A black wire runs to the "B" side on each of the outer green PC boards to the "I" pad.  Measure the voltage here, it should be 0.  Measure the resistance between these pads and ground, it should be nearly 0. (0.3 in your case)

This would confirm that you have voltage coming into that board.  Next, I would want to ensure that the "G" to "G" jumpers are present.

Lastly, if everything above checks out, you can be very suspicious about the LED orientation.

-PB

[John EH]

Alright, so the center shunt reg board is grounded, receiving power, and there is some voltage present at the 12AU7 cathode.

Now we will be interested in the outboard boards, as we really, really want them to draw some current so the center board can work properly.

First of all, we want to see that the outboard 12AU7's are glowing (seems obvious, but just good to check).

Next, a red wire runs to the "A" side on each of the outer green PC boards to the "I" pad.  Measure the voltage here, it should be your ~180V.

A black wire runs to the "B" side on each of the outer green PC boards to the "I" pad.  Measure the voltage here, it should be 0.  Measure the resistance between these pads and ground, it should be nearly 0. (0.3 in your case)

This would confirm that you have voltage coming into that board.  Next, I would want to ensure that the "G" to "G" jumpers are present.

Lastly, if everything above checks out, you can be very suspicious about the LED orientation.

-PB

The 12AU7's are NOT glowing.

Red wires on A on both C4S "I" points - 184V
Black wires on B on both C4S "I" points - 0V

A - "I" to ground = OPEN (this is expected)
B - "I" to ground = .03 ohms

All G to G jumpers installed on all three boards.

John

[Paul Birkeland]

12AU7's are NOT glowing.

Oh, well, that will cause some problems!

There is a terminal strip back by the RCA jacks with a blue capacitor on it, this is responsible for making the tubes glow.  You should see roughly 6V across that blue capacitor, that is a good place to start.

This 6V feed will also be present across tube socket pins 4/5 (they are connected together) and pin 9.  This can be a little tougher to check with a meter, but often times you can peek around and find a broken wire in there.

-PB

[John EH]

12AU7's are NOT glowing.

Oh, well, that will cause some problems!

There is a terminal strip back by the RCA jacks with a blue capacitor on it, this is responsible for making the tubes glow.  You should see roughly 6V across that blue capacitor, that is a good place to start.

This 6V feed will also be present across tube socket pins 4/5 (they are connected together) and pin 9.  This can be a little tougher to check with a meter, but often times you can peek around and find a broken wire in there.

-PB

Paul,

You're the man.  You wouldn't believe it or maybe you would.  The negative wire coming from terminal 1L wasn't broken, wasn't hanging out, just loose inside the terminal.  Reheated it and I got both C4S lit.  The regulator board LED's aren't on but the regulator voltage dropped to 160 and I don't have my 6v on 4 and 9 on the regulator socket so I know it is the jumper added in the kit from reg socket to B socket.  I have to troubleshoot that. 

Will let you know if I achieve sonic success or let you know what my next problem is.  Thanks!

Stupid ground wires.

John

[John EH]

OK I spoke too soon.  I have all tubes lit and still no regulator board LED's lit.

Terminal 15 has 100v

Terminal 31 has 75v so it seems one side is working.

Both 12 and 32 are a little high at 165, and 170 respectively.

Both "K" pads on the regulator board are at 1.9v

John

[Paul Birkeland]

Alright, things are getting better, feel free to post the I/O voltages on the center PC board (when that tube is glowing).

I guess the ~1V that was there was being fed out from the TL431 and the voltage divider.

I think you're pretty close now.

-PB

[John EH]

A side
I - 172v
O - 165v

B side
I - 167v
O - 162v