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Old 22nd August 2009, 05:07 AM   #1
TheGimp is offline TheGimp  United States
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Default Calibration of Mercury 1000 tube test set

I've done searches on

Tube & Test & Set & Calibration
Mercury & 1000 & Tube & Test & Set & Calibration
Etc....

Anyone have any suggestions on calibrating a Mercury 1000/2000 test set?

I've got the schematic, user manual, etc.

No calibration info though.

Thanks.

Steven
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Old 22nd August 2009, 01:40 PM   #2
Trout is offline Trout  United States
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Quote:
Originally Posted by TheGimp View Post
I've done searches on

Tube & Test & Set & Calibration
Mercury & 1000 & Tube & Test & Set & Calibration
Etc....

Anyone have any suggestions on calibrating a Mercury 1000/2000 test set?

I've got the schematic, user manual, etc.

No calibration info though.

Thanks.

Steven
I could have swore there was cali info in the manual, if memory serves it requires the use of a specific tube as well. I have that model, I'll check later for the info.
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Old 22nd August 2009, 02:10 PM   #3
Trout is offline Trout  United States
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OK,

I have the Merc 2000. The calibration info is in the user manual.
I made it downloadable since the attachment button on here messes up the size/scan

Mercury 2000 calibration instructions

It does show using a 6BA6 tube during the process, when I bought mine, it still had the original cal tube in the box.
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Old 26th August 2009, 08:26 PM   #4
TheGimp is offline TheGimp  United States
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Thanks.

1000 does not have cal procedure in manual, but I have a late 1000 that is like the 2000 w/o the transistor test circuit.

So, the info should apply.
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Old 29th August 2009, 03:25 AM   #5
TheGimp is offline TheGimp  United States
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I've been trying to go through the cal procedure and it looks like there is something wrong but I'm at a loss as to what.

I've got three 6BA6s that read over 4200Gm to work with, and I can build a test set to bias them and measure the actual GM at data sheet specs if necessary for reference.

The DC Bias is only -3.2V instead of the -5.9 in the schematic. The signal is only 0.68Vrms instead of 1V, unless it is supposed to be 1V peak in which case it is close.


1. Preliminary setup is fine.

2. Zero Cal is fine

3. Meter Sensitivity Cal has the meter going negative and not adjustable.

I checked both diodes (D2 and D3) thinking one might be out and causing an imbalance, but they are fine.

Both lamps B2 and B3 are OK.

Anyone have any suggestions?

tks

Steven
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Old 31st August 2009, 03:18 AM   #6
TheGimp is offline TheGimp  United States
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I found a 270Ohm resistor open (R20), and in the cal procedure the diode is backwards in 3.b

The test set now cal's properly.

I'm getting good readings and good voltages on the pins (using a tube extender with test points), except for tubes with topcaps. No dc on them so I've still got work to go. Strange thing is the Gm shows good on those tubes even though I'm not getting DC on the caps.
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Old 31st August 2009, 06:43 PM   #7
TheGimp is offline TheGimp  United States
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I found a bad tube extender contact was causing problems.

It looks like everything is OK now, except I've got a couple of resistors out of spec.

I got 20 6P1P-EV tubes in the mail this morning. Tested all 20 and they all tested good.

Selector D
Load 90
Socket 6
G - 7
P - 1/2/6/9
Gm 3700** (Low Scale)

Low Gm3900 (2), High Gm 4900(2), The remainder were between 4100 and 4400Gm.

Hopefully this info will help someone else in the future.

Now to design a PP amp with 6P1P-EVs. I'll use 6N2P-3Vs as unity gain phase splitters/drivers. Probably 6SN7s (for low noise) as first amp stage to drive the 6N2P-EVs.

I've got Hammond 1609 transformers on order for the outputs, and a old Stancor power transformer (dual 300V 120ma windings plus 5V and 6.3V) for power.

Steven
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Old 9th December 2010, 12:57 AM   #8
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Hello: I have a Mercury 2000 tube tester too!! I need to find out where I can buy the 500 ma 100 piv silicon rectifier used to calibrate the meter sensitivity. Can you help?? Thanks, Alex
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Old 9th December 2010, 01:25 PM   #9
TheGimp is offline TheGimp  United States
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Since the cal procedure specifies Silicon or Selenium as the rectifier, it is not critical.

I suggest a 1N4002, 3, 4, 5, 6, or 7.

I used a 1N4007 as I have a bunch.
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Old 9th December 2010, 07:49 PM   #10
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I need to open my 2000 and check it out good.
Lately I am getting what I'll call meter float.
No matter what type of tube I check, new production, old tubes, nos and so on the meter never settles in. I get a pretty wide fluctuation in the readings.

Maybe its just line fluctuations?
I still have the original calibration tube that came with the meter, but most certainly the unit is getting up there in age and may need a few parts.
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