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Old 7th September 2011, 01:25 AM   #11
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Quote:
Originally Posted by rknize View Post
What type of 5842 are you using? It's not the Russian one, is it? Those have a different pin-out.
Russ,

I tried with Raytheon and with Ampex.

I have:
B-: 297V
B+: 448V
R16: 5.75v
R17: 0V
R27: 5.79V
R28: 0V
R10: 0V
R21: 0.02V

As a note, both CCS are getting very warm with 5842 in. Does seem to happen without. I checked for possible shorts - seems OK.

I received today 6x new CCS. I will try new ones.

Alain
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Old 7th September 2011, 02:51 AM   #12
Jpeg is offline Jpeg  United States
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Default I thinK I figured it out!

I think I know why your voltages are reading so weird. You have a bad gound. That was the reason why I had so much trouble measuring voltages on my 5842, by chassis ground had come loose, from your readings, I bet $10 you have the same problem. Your chassis needs to be grounded back to the circuit board in addition to the 3rd prong of your outlet. I connected one of the ground wires of my RCA inputs to the chassis and now I have no trouble measuring 5842 voltage from the coupling cap and ground.

I hope this helps.
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Old 7th September 2011, 03:57 AM   #13
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Quote:
Originally Posted by Bola View Post
Russ,

I tried with Raytheon and with Ampex.

I have:
B-: 297V
B+: 448V
R16: 5.75v
R17: 0V
R27: 5.79V
R28: 0V
R10: 0V
R21: 0.02V

As a note, both CCS are getting very warm with 5842 in. Does seem to happen without. I checked for possible shorts - seems OK.

I received today 6x new CCS. I will try new ones.

Alain
B+ and B-: look fine.

R16/R27: if that is the voltage *across* that resistor, it looks fine. The CCS are doing their job. They will get fairly toasty after a while: 448V - 170V = 278V * 12mA = 3.3W. If there is a short, then they have all of B+ across them and will get very hot indeed. You have the CCS heatsinks insulated, right?

R17/R28: these are just gate stoppers for the CCS. Practically no current runs through it. 0V is expected

R10/R21: The voltage *across* this resistor should be around 6V or so.
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Old 7th September 2011, 12:06 PM   #14
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Quote:
Originally Posted by Jpeg View Post
I think I know why your voltages are reading so weird. You have a bad gound. That was the reason why I had so much trouble measuring voltages on my 5842, by chassis ground had come loose, from your readings, I bet $10 you have the same problem. Your chassis needs to be grounded back to the circuit board in addition to the 3rd prong of your outlet. I connected one of the ground wires of my RCA inputs to the chassis and now I have no trouble measuring 5842 voltage from the coupling cap and ground.

I hope this helps.
Jpeg,

I have not grounded the board to ground outlet - I waited to do that when I would do the final assembly with the chassis. Could it be that simple??? Man, I would feel idiot if it is the case, knowing how reference grounding is important!!!

I will try tonight. Thanks you are helpful.
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Old 7th September 2011, 12:13 PM   #15
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Quote:
Originally Posted by rknize View Post
B+ and B-: look fine.

R16/R27: if that is the voltage *across* that resistor, it looks fine. The CCS are doing their job. They will get fairly toasty after a while: 448V - 170V = 278V * 12mA = 3.3W. If there is a short, then they have all of B+ across them and will get very hot indeed. You have the CCS heatsinks insulated, right?

R17/R28: these are just gate stoppers for the CCS. Practically no current runs through it. 0V is expected

R10/R21: The voltage *across* this resistor should be around 6V or so.
Russ,

Do you mean the CSS needs to be insulated from the heat sink? No I did not - I have insulated all the other but not the two CCS, trusting pictures of the Tubelab manual. Do you think it is critical since both (Anode) are connected to B+? Or am I missing something?

Thanks for the helpful info. I really appreciate your support. I own you one!

Alain
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Old 7th September 2011, 03:08 PM   #16
rknize is offline rknize  United States
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Sorry, what I meant was that they need to be insulated from the chassis. If you are using the heat sinks from the parts list and they are not mounted to the chassis at all, then you don't need to insulate them (note that the heatsink will have the full B+ voltage on it).

You don't need an earth ground on the chassis for the amp to work (though it is needed for safety reasons). The PCB has it's own ground that it uses because the amp and power supply are all together. Since your B+/B- measurements make sense, I assume you are using the PCB ground as a reference for your meter.

Just to clarify this one more time: when you place both meter probes on each side of R16/27, you get ~5V. When you ground the meter to the PCB power supply ground and measure both sides of the resistors with the meter, you get 0V on the tube side and 5V on the CCS side? What do you get with no tube in place?
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Old 8th September 2011, 12:46 AM   #17
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Quote:
Originally Posted by rknize View Post
Sorry, what I meant was that they need to be insulated from the chassis. If you are using the heat sinks from the parts list and they are not mounted to the chassis at all, then you don't need to insulate them (note that the heatsink will have the full B+ voltage on it).

You don't need an earth ground on the chassis for the amp to work (though it is needed for safety reasons). The PCB has it's own ground that it uses because the amp and power supply are all together. Since your B+/B- measurements make sense, I assume you are using the PCB ground as a reference for your meter.

Just to clarify this one more time: when you place both meter probes on each side of R16/27, you get ~5V. When you ground the meter to the PCB power supply ground and measure both sides of the resistors with the meter, you get 0V on the tube side and 5V on the CCS side? What do you get with no tube in place?
Ok, here it is:

Without tube (still heat from heatsinks):

Ground to:
R16 tube: 17V, R16 IC: 449V, both sides: 0V
R17 tube: 17V, R17 IC: 17V, both sides: 0V
R27 tube: 17V, R27 IC: 449V, both sides: 0V
R28 tube: 17V, R28 IC: 17V, both sides: 0V
R10 & 32 both sides: 0V

With tubes on (heat from heatsinks):

Ground to:
R16 tube: 6V, R16 IC: 13V, both sides: 6.5V
R17 tube: 6V, R17 IC: 6V, both sides: 0V
R27 tube: 3V, R27 IC: 10V, both sides: 5V
R28 tube: 3V, R28 IC: 3V, both sides: 0V
R10 & 32 both sides: 0V
Ground to tube: 6.6 & 4.25V

I tried for potential poor coupling cap (I rised one leg for both coupling cap) = no change in the data.:

I checked again for potential shorts - nada.

I also grounded the board to the grid - nada.

However, both tube sockets are hooked up through 4 inches of wire (not directly welded to the board). Am I facing oscillations or some weird phenomena?

My next step is to change both ICs. I don`t have a good feeling for the end result but I need to give it a try...

Alain
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Old 8th September 2011, 12:56 AM   #18
Jpeg is offline Jpeg  United States
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It does not need to be grounded to work, but, if you are testing voltage values against the ground, it does need to be gounded. For safety, it should be grounded to the 3rd prong of an outlet, but the ground I am refering to is the return path back to the power supply. (It is kind of confusing) If the black lead of your meter is not connected to a to the return path, you may be 0 readings when if fact there is power. If your chassis is not connected to the board ground somewhere, you should make sure you are connecting your test lead to a good ground connection on the board such as the hole labled GND 2 on the board, near in between C5 and where your inputs hook up.

When you tested your plate votage on your 5842s and you put the red lead of your tester on the coupling capacitor, where did you put your black lead?
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Old 8th September 2011, 01:03 AM   #19
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Originally Posted by Jpeg View Post
It does not need to be grounded to work, but, if you are testing voltage values against the ground, it does need to be gounded. For safety, it should be grounded to the 3rd prong of an outlet, but the ground I am refering to is the return path back to the power supply. (It is kind of confusing) If the black lead of your meter is not connected to a to the return path, you may be 0 readings when if fact there is power. If your chassis is not connected to the board ground somewhere, you should make sure you are connecting your test lead to a good ground connection on the board such as the hole labled GND 2 on the board, near in between C5 and where your inputs hook up.

When you tested your plate votage on your 5842s and you put the red lead of your tester on the coupling capacitor, where did you put your black lead?
JPeg,

I connected the probe to Gnd2 (bottom of the board) - Always did since the begining. The board is on my work bench, not yet in a box
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Old 8th September 2011, 01:11 AM   #20
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I am thinking out loud: If without tube I have a drop of voltage in R16 & R17, it means that I have a leak somewhere, isn`t?
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