Odd problem playing LPs

[Larpy]

Heater voltage on the PS board is fine.

But I caught a mistake I made reinstalling the board above the 7308: I reversed the wires to OC/OKA and OD/OKB.

Now that I've corrected that, I get these voltages:

IA  218   IB 151
OA 163   OB 144
OC 98     OD 140
OKA 99   OKB 139
OKC 2     OKD -.003

[Paul Birkeland]

If you pull the EF86s and 6922, does that 151V on IB pop up to 220?

[Larpy]

It goes up to 287v.

[Paul Birkeland]

My focus would be on the 12AU7 socket to get that regulator working.  What are the Kreg voltages?

[Larpy]

I put the 7308 back into the socket and measured pins 3 and 8, 147v and 258v respectively.

I then noticed a little smoke rising from the board above that tube and pulled the plug.  Nothing is obviously burned that I can see.

[Paul Birkeland]

You don't want to run the amp with just the 6922 tube installed.  You'd want to run the amp with just the 12AU7 installed in the D socket to check on power supply voltages. 

If you put a 7308 in the D socket instead of a 12AU7, that is going to cause some damage to the Eros for sure.

[Larpy]

No, I never took out the 12AU7.  I removed the 7308 and the EF86s, then put the 7308 back in.

Now I have all 4 tubes installed.  I think I found the cause of the smoke (a tiny solder whisker between legs of a transistor).  Fixed that and now I have:

IA 218  IB  280
OA 163 OB 230
OC 98   OD 53
OKA 99 OKB 59
OKC 2   OKD -.004

[Paul Birkeland]

Which transistor had the solder wiskers?  I would check to be sure you have the appropriate voltages at pins 4/5 of the EF86 on the sketchy channel (should be about 50 and 56V DC).  If that all looks good, then I'd swap in a new 2N2222 transistor on that side.

[Larpy]

Checked all the wires from the 7308 socket and all have continuity and measure correct resistance.  Checked all the wires coming from the board and they all have continuity.

Hard not to credit the demon for returning sevenfold.  At least today I got out of my bathrobe and got dressed before turning on the solder station.  I'll count that as a victory.

[Larpy]

Uh oh, I forget which one it was.  Pretty sure it was one on the left side.  I'll go check to see if I have any spare 2N2222s.

[Larpy]

Never mind. . .

[Paul Birkeland]

I'll order 4 and change them all.

There should only be two in there. 

You'll also want to go back to the D socket board and figure out why you're getting 280V instead of 220V on one side of the HV regulator.  Why this is happening would depend a bit on what your Kreg voltages are. 

[Larpy]

I've been sloppy with my terminology.  The solder whisker involved either a PN4250A or a MJE350.  I do have extra MJE350s.

Should I still replace the 2N2222s?  Replace the PN4250As as well?

[Paul Birkeland]

I would only replace a PN4250 or MJE-350 if you can find a shorted pair of leads with your meter. 

[Larpy]

Which legs do I measure to check for a short?

I inspected the D socket and the grid resistor soldered to pin 7 is a little scorched.  That might account for the smoke I saw.  What would cause that grid resistor to draw too much current (which is what I assume would scorch it)?