Voltage test after shut regulator install.

[Tom228]

Hello all.

Slowly getting my new Eros put together and I think I have a voltage issue.

I put the power supply in and the output voltages are where one would expect.  Checking at the 5w resistor, I measured 362v and at the 6v output it was 6.3v.

Got the shunt regulator installed and measured the output voltages (forgive me, I don't have the manual right handy) off of D1 and D6??  at 260v where the manual says it should be 225v.  Is that too high?  The tube glowed right nice and purdy.  Put off a lot of heat, too.

Thanks in advance for your help and time.

 

[Paul Joppa]

Yeah, that's not good. It should be 225 +/- 1 or 2% - it is set by 1% resistors. Best give the tube pin voltages (except 4/5/9, they are the heater which apparently is working fine) - also IA, OA, IB, OB on the reg board. Are all four LEDs lit?

 

[Tom228]

Where would I place the neg lead of my meter when testing the socket voltages?

All 4 LEDs are lit.  One side was slightly dimmer than the other.

The voltages coming off the power supply are fine, according to the manual.  I looked at page 13 and the resistors listed there are in place on my board.  I have verified that the shunt regulator board is in the proper orientation with bA, OB/IB closest to the power supply.

 

[Tom228]

Here are some voltages:

5w resistor - 276v (this was up around 362 when I did the voltage check prior to installing the shunt regulator)
6.3v output - 6.28v
Red lead off of D6 - 272v
Red lead off of D1 - 257v
d7 - 0v
OA - 270v
IA - 273v
OB - 262v
IB - 274v

I'm not very comfortable with getting into the other pins on the socket with the system on.

 

[Paul Birkeland]

What are your Kreg voltages?

Also, do you have the 12BH7 installed?

-PB

 

[Tom228]

Hi Caucasian Blackplate - yes, it is glowing real purdy like and is quite warm.  I can feel the heat coming off of it from 4-6" away.

kreg closest to the power supply board - 1.86v
kreg furthest away from the power supply board - 1.85v

 

[Paul Joppa]

OK, that's useful. The low kreg voltages indicate the tube is trying like crazy to sink enough current to pull the voltage down, but the OA and OB voltages indicate it's not succeeding.

Two possibilities are immediately apparent - either the C4S is generating too much current (are the R1 values correct?) or the C4S output OA and OB are not connected to the tube plates (pins 1 and 6). The latter is why the plate voltages are helpful. You may need to unbolt the PC board and push it out of the way to get those measurements.

 

[Tom228]

Hi Paul.

On the A side R1 is 37.7 and on the B side R1 is 37.5.

Does the orientation of the capacitors (104k) on Cc matter?  The text on mine is facing inward.  Whereas, the pictures in the manual have the text facing outwards.

I have OB going to pin 1 and OA going to pin 6 and have verified that they are indeed connected.  The board is oriented with A on the left and B on the right.

Pin 1: 260v
Pin 2: 0v
Pin 3: 1.87v
Pin 4: 6.28v
Pin 5: 6.28v
Pin 6: 272v
Pin 7: 0v
Pin 8: 1.86v
Pin 9: 0v

 

[Paul Birkeland]

Additionally, if the black wires going to Kreg got switched, this kind of problem would present itself.

 

[Paul Joppa]

The large amount of heat from the 12BH7 suggests it is indeed conducting a lot of current, which is consistent with the measured voltages. If the R1 is correct and the LEDs are lit (meaning R2A and R2B are correct) the I worry the transistors (the large ones, MJE5731A) may be reversed, or have a solder bridge at their connections.

Here's a test, if you can't find anything along the lines either of us Pauls have suggested: Unsolder the black wire at D3, leaving it connected to kreg on the board. Put your meter (use clipleads!) between D3 and the black wire, and set it for 200mADC to measure the actual current. If it reads 23.5mA then the C4S is good; if it reads a lot more then the C4S is delivering way too much current, and something on the board is either mis-wired, fried, or has a bad solder joint. (Or, as is always possible, there is something else I have not thought of that's gone wrong!) This one is a puzzler.

 

[Tom228]

I'll give that a try, Paul.

I've removed the board and inspected it real-close-like to verify there's no solder bridges.  The 2 transistors are facing the proper way, according to the document (that is, their metal sections are pointing towards each other, looking at the other components on the board).

I checked up the solder joints on both R1's and reseated the 104k's to match the orientation shown in the build guide.

Someone remind me to ask for a solder sucker for Christmas.  This wick sucks!  :*)

I will try to get that current measurement ASAP.

 

[Tom228]

Paul - Kreg->D3 = 22mA.

Got it put back together:

d1 - 261v
d6 - 275v

 

[Tom228]

Hi all.

What do I do now?

 

[Paul Birkeland]

I would recommend posting some quick photos of the PC board and socket wiring, so we can look it over.

-PB

 

[Tom228]

Here's some I've taken as the build has progressed.  I'll get a couple more tonight (no FB login is required):

https://sphotos-a.xx.fbcdn.net/hphotos-prn1/1015018_10201814471342721_1260350501_o.jpg
https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-frc1/1026000_10201597415636464_103837924_o.jpg
https://sphotos-b.xx.fbcdn.net/hphotos-ash4/1008730_10201597352074875_316818426_o.jpg

 

[Tom228]

Here's the images from tonight:

http://imgur.com/a/QyjGR

Nice shiny high-res ones

 

[Paul Birkeland]

I'm not seeing the errors that would cause this.

Can you:

1.  Meausre the DC voltage on both sides of the 270 Ohm resistor?

2.  Verify that you have MJE5731A transistors on the board (not TIP50's or anything else)

We'll get this sorted out.

-PB

 

[Tom228]

Hi Caucasian Blackplate.

Thank you for all of your help with this.  While I'm pretty good at following directions and putting stuff together, I'm not great at troubleshooting.  So, all of the help is most appreciated.

When I measure the DC voltage on teh 270 Ohm resister - is that the big 5w one on the power supply?  Do I leave the - probe on the back resistor both times?  Do you want that with or without the shunt regulator attached?

I'll post a picture of the transistors tonight.

 

[Paul Birkeland]

With the regulator attached, place the black probe in the ground post at the front of the chassis plate, then use the red probe to measure the voltage on each side of the 270 Ohm resistor.

-PB

 

[Tom228]

I've got MJE5731AG (AFB43) transistors on the shunt regulator.

Off to re-attach it.