Eros BUILD HELP NEEDED

[haiku626]

Grainger said to go and study the diagrams so instead of reading the instructions over and over, I looked at the picture of the finished Eros on pg 79....  Okay, I have to admit that I did something really stupid.  I got R2A and R2B inverted which then caused me to also invert R1A and R1B because I used the color of the R2 resistor as a guide.  I removed all of them and placed them in their proper location.
Voltage Readings for the side B PC board are now KReg: .92 s/b 1.00 and OA is at 160 s/b 170vdc.  These two past problems are now history, and the good news is that the left channel now has sound.

The bad news is, and I hate to drive everyone nuts, but now the other (A side) PC board has weird voltages and no sound.  I might have jostled something on the A PC board when removing and reinstalling the resistors on the other B PC board.
Kreg: 5.01 s/b 1.0vdc and Breg: 139 s/b 100vdc.  I tried swapping the tubes and still don't have any sound and the voltage readings stay the same.  

[Grainger49]

Sounds like the same thing.  But were these voltages good to start with? 

If the voltages were good, then it is a loose solder joint.  Start by rewetting the solder pads where the wires are and where the wires land.  You will have to take out the screws to get to everything.

A "rewet" is taking your solder iron, put a little solder on the tip and put it on the joint.  When the joint becomes liquid count 1-2-3 (about two seconds) and remove the solder pen. 

[haiku626]

I rewetted all solder joints on the A side PC board except for the LEDs since they all light up.  Also rewetted all terminals and tube pins where the wires from the board connect. Still no sound on the right channel.

Kreg still out of acceptable range at 4.91vdc s/b 1.00
OB: 139 s/b 100
Breg: 139 s/b 100
OA: 140 s/b 160

Here are the tube pin voltages.  Possibly Grainger, Paul, Noskipallwd, or others can diagnose the readings to guide me. 
Socket C:
1: 143
2: 139
3: 139
4: -
5: -
6: 162
7: 94
8: 95
9: -

Socket A:
1: 139
2: -
3: 5
4: 6
5: -
6: 139
7: -
8: 5
9: -

[Paul Joppa]

OK, the servo (kreg) is not regulating the EF86 voltage. The relevant kreg connects to A3.

That involves the 2N2222, the 174 ohm resistor R3, and the EF86 cathode A3. I assume the EF86 in socket A is lit up, since it has the right filament voltages at pins 4 and 5. It will be difficult to test the voltages on the 2N2222, but that might narrow the field. At least check voltages on the 174 ohm resistor R3, and the correct terminals on the 2N2222.

[haiku626]

Hi Paul,
The 2N222 transistor is oriented properly with the tab toward the middle of the board.  The lead closest to the tab is in the middle hole.
I am not getting a voltage reading from R3 the 175 ohm resistor, and no longer can get its rated resistance reading from it (reads only .2)

[Grainger49]

Haiku

   .  .  .   were these voltages good to start with? 

If the voltages were good, then it is a loose solder joint.  .  .  . 

[haiku626]

Hi Grainger,
Yes, the readings for kreg were good before at 1.21vdc and the R3 resistor did test good at 174.  But now the readings for kreg are 4.91 s/b 1 and R3 is .2 s/b 175.
If I am taking the R3 resistor reading directly from its 2 wire leads on both side of the resistor, would the reading matter if I had a bad solder somewhere?  I thought that I was isolating the meter reading to the resistor only by doing this.

[Paul Joppa]

The 2N2222 may be damaged; its base and emitter are across the 174 ohm resistor. (The earlier grounding problem may have exposed the transistor to too much voltage.)

Of course it's possible that those two leads are just shorted on the board, either by a solder bridge or a stray wire. Bright light and a magnifying glass are in order - and plenty of patience, it's a pain to unscrew the board and get it to where you can see the underside. If you can't locate a short then you'll have to remove the transistor to test it and re-test the resistor. I expect when the transistor is out, the resistor will measure normally, in which case just replace the transistor with a new one. Contact Eileen on Monday to get a replacement.

[haiku626]

Hi Paul,
There was no short on the board for the R3 resistor so I removed 2N2222.  R3 is still giving a .2 reading.  Can you tell me how to test 2N2222.  All the advice that I have been getting is much appreciated.

[Paul Joppa]

That's unexpected! Remove R3 and re-check its resistance - if it is 174 then there's a short on the board, if it's still 0.2 then the resistor is shorted - extremely unusual! - but it would explain the data.

For the transistor, check resistance from base (pin 2) to emitter (pin 1), and base to collector (pin 3). You may have to google "2n2222 datasheet" to identify the pins. Do each check in both directions. They should read very high in one direction, low in the other - a few hundred ohms, not zero - actual value depends on your meter.

[haiku626]

Paul,
R3 removed from the board reads 173.4
2N222
Base to 1: 0
Base to 3: 0
1 to Base: 463.5
3 to base: 459.6
I suppose I have a short on the board; I don't see any readily visible bridges except where they share the same trace.

[Paul Joppa]

Zero seems improbably low, but both junctions seem to rectify - so I'm not quite sure what to think. These readings will be different on different meters, which is a pain.

Check the 174 on the other (working) board (without unsoldering) - if it is also zero, then the zero does not indicate a problem. If it's 174 or close, then replace the 2N2222.

[haiku626]

Hi Paul,
Sorry but the 2N2222 reading should be OL (over limit) not zero for Base to 1 and Base to 3.  Does this change your recommendation to replace the 2N2222?

R3 reading on the good side (left channel) is okay at 173.5.
R3 on the bad side reads 173.4 taken off the board and .2 again when put back in the board even with the 2N2222 removed. If I place the resistor in R3 on the A side of the board it reads 173.4.  

[Paul Joppa]

Yes it does change - the 2N2222 is OK by this test, as is the resistor. There is a short somewhere on the board, or a mis-connection. One end of R3 goes to -reg which is grounded; the other end to the transistor (terminal "r"), to R4, and to terminal "x" - if any of these are grounded, that would be the problem.

If you can't find it, at some point you'd do better to just build and install a new board. Eileen can help with that if necessary.

[haiku626]

Hi Paul,
I have examined the board using a magnifying glass and have reviewed the manual instructions for the board along with comparing the wiring to the good board.  I don't see any possible bridges except where traces are shared at breg and kreg.  Can something at socket D or the shunt regulator PC board affect the readings that I am getting, or is this eliminated from causing the problem that I am experiencing?  I want to make certain that I cover all areas before calling Eileen for a rebuild of the C4S board.