Bottlehead Forum

Bottlehead Kits => Eros Phono => Topic started by: PaulG on April 03, 2020, 06:20:34 PM

Title: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 03, 2020, 06:20:34 PM

I just got to page 54 of the EROS instructions where the Shunt Regulator board is installed. 
I have 2 drain wires attached on page 48, but not soldered to the center of D.
If I continue with the installation of the Shunt regulator board, soldering the two drain wires that I attached on page 48 will get a lot more difficult.
I'm working from a set of instructions printed out in 2015.
Is there a reason to leave the drain wires unsoldered?

Thanks for putting up with my OCD!

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 04, 2020, 05:47:51 AM

I would go ahead and solder them.  I don't remember there being anything else that connects to that point.

If you are building a kit with parts that are 5 years old, do be sure to use your meter to test all the LEDs after they are soldered.  They slowly absorb moisture over time and can be damaged from soldering if they are allowed to sit in a humid environment for a few years.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 04, 2020, 03:15:18 PM

Thanks for the answer.  I will go ahead and solder the drains to center D.

The kit was in a bedroom drawer in San Diego so I hope the LEDs are ok.  I guess if any of them fail to light up that is a possible failure point....

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 04, 2020, 03:20:59 PM

To test the LEDS with a meter am I just looking for continuity? or just for all of then to have the same resistance?

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 04, 2020, 03:26:45 PM

Most meters have a diode setting, and one orientation of your probes should be able to light up each LED or at least say "1.57V" on the meter display.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 04, 2020, 06:16:28 PM

I got all 4 of the diodes to light up when I put in the tube and powered up the unit to test shunt regulator voltage.
The red wire from D1 tested a very solid 223.1 with all 4 diodes lit.
The red wire from D6 tested a wavering 110 VDC  The 2 diodes on the B side of the Shunt regulator board lit right away with the ones on the A side lagging about 15 or 25 seconds behind.

I repeated both tests because I hadn't checked the Tube heaters.
D1 was exactly as before 223 VDC and I could see the Tube heaters lit.
D6 tested differently with an immediate surge to 330 VDC and then settled to a solid 139 VDC.  The tube heaters were lit.

I'm going to reread every thread having to do with Shunt Regulators but I would appreciate any thoughts.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 04, 2020, 06:30:52 PM

What are the Kreg voltages?

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 05, 2020, 07:57:44 AM

Thank you for asking but I am afraid I must now reveal exactly how much of a beginner I am. 
I have found the two (A and B) KREG pads. 
Please confirm that the positive probe goes to the +Reg pad on the same end. 
I'm also assuming the board and tube need to be live when I do this.

I have taped off the red leads from D1 and D6 to prevent an accident.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 05, 2020, 09:21:44 AM

Black probe lead to ground, red probe lead to each Kreg pad with the meter set to DC volts.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 06, 2020, 08:47:51 AM

Thank you again for your help, support and patience.

KREG A measures 1.86 VDC
KREG B Measures 6.2 VDC

What is the next step in finding my screwup?

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 06, 2020, 08:55:14 AM

I suspect you have a soldering issue on the C4S board.  Do both halves of the 12BH7 light up?

1.86V on Kreg and 110V on the plate means ~10mA of current, which is insufficient and not what the board is set for.  You can end up with that for these other reasons:

1.  Swapped 2N2222 and 2N2907
2.  Swapped TL431 with MPS4250
3.  Missing board jumper
4.  Poor solder joints on PC board
5.  Black wires from D3/D8 going to the wrong Kreg terminals on the board

-PB

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 06, 2020, 01:01:11 PM

All 4 of the heater rods glow.
I will recheck items 1-5 and report back in the morning. 
Thank you again for your knowledge and especially your patience.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 06, 2020, 01:02:41 PM

I have an Eros 1 in for repairs with some similar issues, so it's all quite fresh right now.

-PB

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 06, 2020, 03:41:05 PM

1. the 2n2907 transistors are on the shunt board version 4.4  in the location from the instructions with the little tab over the outline printed on the board.  They are kind of dull and the 2n2222s on
    the other two boards are still shiny... indicative of something going on inside?
2. The TL431s are in place.
3. All the board jumpers from the instructions appear to be correctly installed.
4.  Looks like time to unmount the PC board and search the other side for the offending solder error
5. Black wires from D3/D8 go to the correct Kreg terminals

I'll let you know if there's any breakthrough.

All the best,

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 06, 2020, 03:42:21 PM

Solder joints on the shunt reg PC board can cause problems like this too.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 09, 2020, 06:52:00 PM

It only took three days for me to get my courage up to dismount the shunt board and check every solder joint and then reinstall. 
I did find some sketchy joints and that I had missed the end of one resistor entirely. 
I just checked the voltages and they are now in spec.  D1 is now 223.0 VDC  and D6 (which was 139 VDC) is now 222.8 VDC.

Thank you again for your wisdom and encouragement.

Have a great weekend.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: Paul Birkeland on April 10, 2020, 05:11:10 AM

I'm glad you got it sorted.  In the Eros 2, we made some adjustments to make it much easier to pop that board off if necessary.

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 11, 2020, 04:13:48 PM

Great news! 
I made it all the way to page 66 of the Eros instructions before finding myself flumoxed again. 
The instructions call for a 1uF 630V Film Capacitor Plus another of the same spec on page 67. 
My kit came with two 1.50 uF 630V Film Capacitors by the same manufacturer with the same appearance.
Is this a point where I should stop and order parts?
Are larger capacitors a running change that occured back in 2015?

Title: Re: When should I have soldered the 2 drain wires at the Center terminal of D?
Post by: PaulG on April 11, 2020, 04:23:49 PM

In the immortal words of Emily Litella, "Never Mind" I just read a post in which Paul Joppa explained the running change that put 1.50 uF 630V Capacitors In my kit rather than the 1.0 uF version in the instructions.  Hope you all having a great weekend.