Stellar CM1 with FOX 460 MOD and PSU update MOD
« on: August 11, 2017, 02:30:24 PM »
Hello folks~

I've mod the Stellar CM1 (as same as older APEX460) with "FOX 460 MOD  KIT" and "VPS1 PSU  KIT" from MicrophoneParts.com.

I used Tim's CT12 capsule , GE6072a,  AMI T14 with the "FOX 460 KIT".
It worked fine with PSU which was just replaced diodes D5, D6.

After that , I decided to mod the PSU with the "VPS1 PSU KIT" to get more accurate B+ and Heat.
But when I finished and  connected my mic and tested, I got  noise like "Aeeeeeeeeee~" which was followed mic preamp gain value.

The stock PSU was old version without words on transformer ,and  transformer was screwed on PCB with ground wire from power plug.

Can anyone please give me some advice?
« Last Edit: August 11, 2017, 11:02:46 PM by axlreddy »


Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #1 on: August 11, 2017, 09:02:07 PM »
Did you test the voltage of the transformer leads?

I have the TNC acm 1200 and used it for the Matador/Chunger kit. The
transformer in my power supply was attached to the circuit board also.
The transformer  was unmarked and I discovered that the voltage of the
leads were opposite of the transformers in the supplies that Chunger
sells.

If you are experiencing that problem, any 25v capacitors on the 9v
side of the circuit have likely become swollen and the power supply is
running very hot.

Also, you must have drilled holes in the floor of your power supplies
case to mount the transformer, correct?  Did you grind/ sand some of
the paint off from around the hole that you attached the ground wire
to so that you could be sure to get good contact for ground?

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #2 on: August 11, 2017, 10:13:57 PM »
Thanks for reply
I've checked the transformer,  wires were correct, and yes I mounted the transformer to another free hole on chasis with grind paint to make sure that I have grounded(see pic).

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #3 on: August 11, 2017, 10:34:28 PM »
Is the ground cable attached the the case ? It's probably attached to
the other side of the transformer but I can't see that. Though, In the
picture it looks like it loops back to the power plug.

I'm new to this diy electronic stuff so my questions are basic because
that's really all the help I can be. So don't take my simple questions
as condescension.

I've now reached my limit as far as the help I can offer. Hope you figure out the problem if it's not a grounding issue.

Bernard

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #4 on: August 11, 2017, 10:59:21 PM »
Don't say that Bernard.
I'm new here, too.

I've attached  ground to another side of transformer.
But still got same noise.

Thanks for reply then

ln76d

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #5 on: August 12, 2017, 06:23:48 AM »
In chinese PSU mostly are two types of transformers AC: 175V and over 200V.
First one usual works good with change only of zeners, with second one usual you need to reduce voltage with higher value resistors, before zener diodes.
« Last Edit: August 12, 2017, 07:47:42 AM by ln76d »

Gus

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #6 on: August 12, 2017, 07:42:38 AM »
If I understand the question, the adjusted tube microphone worked OK with the stock supply but does not with the new power supply kit.

Did you change the microphone to power supply cable when you changed the PCB?

Do you have a schematic of the new VPS1 PSU KIT power supply circuit? I searched for the kit schematic but only found a picture of the parts.

Passive B+ active B+ regulation?

It is going to be all guesses without a schematic or good pictures of the top and bottom of the PCB.

The stock supplies can be improved with a few parts changes and In76d listed two, there are a few more thing you can do

When I read posts like this I think about what liability is there selling tube voltage power supply kits to the public?

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #7 on: August 12, 2017, 01:59:32 PM »
 On the 7 pin connector in the original supply, pin 7,4, and chassis are bridged together and connected to ground on the xlr connector. 

In your kit all those pins are ground, did your instructions have you bridge those pins together like the original when you replaced the original connectors?

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #8 on: August 12, 2017, 04:12:12 PM »
If I understand the question, the adjusted tube microphone worked OK with the stock supply but does not with the new power supply kit.

Did you change the microphone to power supply cable when you changed the PCB?

Do you have a schematic of the new VPS1 PSU KIT power supply circuit? I searched for the kit schematic but only found a picture of the parts.

Passive B+ active B+ regulation?

It is going to be all guesses without a schematic or good pictures of the top and bottom of the PCB.

The stock supplies can be improved with a few parts changes and In76d listed two, there are a few more thing you can do

When I read posts like this I think about what liability is there selling tube voltage power supply kits to the public?

Cable was same,and I don't have schematic just follow the build guide manual,

Today, I've put the PCB to PSU from my another C12 clone
which was as same as the picture in the VPS1 manual.
(see the picture, transformer with chinese words)
But I still got Hum.
I think the problem may  from PCB

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #9 on: August 12, 2017, 04:21:58 PM »
On the 7 pin connector in the original supply, pin 7,4, and chassis are bridged together and connected to ground on the xlr connector. 

In your kit all those pins are ground, did your instructions have you bridge those pins together like the original when you replaced the original connectors?

The Pin7,4 and chasis and XLR  Pin1 and tab are bridged together as original except one wire from picture
(see the white wire between two red circles,


BTW , my 7pin  XLR cable was soldered below:
Pin 1 = B+
Pin 2 = Heater       - fat wire
Pin 3 = Bias
pin 4 = Polor
pin 5 = audio -
pin 6 = audio +
pin 7 = ground      - fat wire
The pin1,3,4,5,6 will solder with another small wires,
And I've soldered pin7 to the tab of connector's case.


Gus

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #10 on: August 12, 2017, 05:16:20 PM »
Looking at the pictures the soldering does not look good at some connections. It could be the pictures
I don't see any flow thought the holes and other things

Is U51 a LM317 or a LT device?
what is marked on U52?
What are the other transistor or mosfets numbers on the other two larger heatsinks?

Do you know how to work around higher tube voltages with a scope?

« Last Edit: August 12, 2017, 05:25:31 PM by Gus »

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #11 on: August 13, 2017, 12:51:34 AM »
Looking at the pictures the soldering does not look good at some connections. It could be the pictures
I don't see any flow thought the holes and other things

Is U51 a LM317 or a LT device?
what is marked on U52?
What are the other transistor or mosfets numbers on the other two larger heatsinks?

Do you know how to work around higher tube voltages with a scope?

I soldered wires on the back of PCB, and I've checked the continuity point to point, they all passed

U51 is NJM317F (voltage regulator)

U52 is LM329 (voltage reference)

MosFET IRF820 on the left heatsink
LD1084V(voltage regulator) on the right heatsink
(see picture)

I don't know how to  work around higher tube voltages with a scope.
Can you please give me some help?

Regards!


 

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #12 on: August 13, 2017, 04:01:03 AM »
I've read this thread and do the same test,
https://groupdiy.com/index.php?topic=51377.msg830964;topicseen#msg830964
Just like the man who described in thread, noise disappeared immediately when power off.
and sound stayed for a bit.
Problem seems from heater?(am I right?)
What should I suppose to do now?
« Last Edit: August 13, 2017, 04:08:48 AM by axlreddy »

ln76d

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #13 on: August 13, 2017, 07:26:07 AM »
I woould rather look in B+ than heater, but i didn't had that PSU in my hands ;)

Gus

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #14 on: August 13, 2017, 08:23:48 AM »
I soldered wires on the back of PCB, and I've checked the continuity point to point, they all passed

U51 is NJM317F (voltage regulator)

U52 is LM329 (voltage reference)

MosFET IRF820 on the left heatsink
LD1084V(voltage regulator) on the right heatsink
(see picture)

I don't know how to  work around higher tube voltages with a scope.
Can you please give me some help?

Regards!



Found this https://microphone-parts.com/products/tube-mic-power-supply-1

the 1084 is most likely for the heater supply http://www.mouser.com/ds/2/389/stmicroelectronics_cd00003086-330743.pdf
There is a time delay of 4 sec from the MP link look at page 17 of the next link
http://www.ti.com/lit/ds/symlink/lm117.pdf

There is a inductor L30 I wonder what that is for.

The MOSFET is most likely for the B+ supply being a HV part

The 317 does not have a heat sink so it might be used as a voltage reference or a constant current device.

What is the R32 trim  used for?

What is the other trim used for?

It looks like you are not using a temp control iron or if you are the heating is not that good.
What type iron and solder are you using?

I would check all the solder connections.

Is the sound 50,60 100,120 Hz (I Don't know what country) or is the sound higher in frequency?

With a scope this could be as simple as checking the B+ and heater supply for oscillation.
« Last Edit: August 13, 2017, 08:33:28 AM by Gus »

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #15 on: August 13, 2017, 12:39:19 PM »
Found this https://microphone-parts.com/products/tube-mic-power-supply-1

the 1084 is most likely for the heater supply http://www.mouser.com/ds/2/389/stmicroelectronics_cd00003086-330743.pdf
There is a time delay of 4 sec from the MP link look at page 17 of the next link
http://www.ti.com/lit/ds/symlink/lm117.pdf

There is a inductor L30 I wonder what that is for.

The MOSFET is most likely for the B+ supply being a HV part

The 317 does not have a heat sink so it might be used as a voltage reference or a constant current device.

What is the R32 trim  used for?

What is the other trim used for?

It looks like you are not using a temp control iron or if you are the heating is not that good.
What type iron and solder are you using?

I would check all the solder connections.

Is the sound 50,60 100,120 Hz (I Don't know what country) or is the sound higher in frequency?

With a scope this could be as simple as checking the B+ and heater supply for oscillation.

R32 is trimmer to adjust Heater
R54 is also trimmer to adjust B+

I use this to solder, isn't it temp control?
https://img.ruten.com.tw/s1/1/7d/87/11091103199623_682.jpg

Noise is between 200Hz~700Hz(I live in Taiwan).

Today I found the noise disappeared when I turned down Heater by R32  trimmer
But the value of DMM just 5.7V.
I don't think this is normal.

Khron

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #16 on: August 13, 2017, 12:49:27 PM »
Linked photo doesn't work, when clicked; works by copy-paste though.

What DC voltage are you getting before the regulator? And what AC voltage can you measure coming out of the transformer, from the heater winding? Both of these are low enough to be scope-able, by the way.

It's not uncommon for heaters in microphone tubes to be run at lower-than-normal voltages (6.3v usually), for both noise and lifetime reasons.

And some construction tip: use (more) flux, or flux-cored solder; heat up both the solder-pad AND the component leg / wire, and THEN feed some solder into the joint ;)
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #17 on: August 13, 2017, 01:58:08 PM »
Linked photo doesn't work, when clicked; works by copy-paste though.

What DC voltage are you getting before the regulator? And what AC voltage can you measure coming out of the transformer, from the heater winding? Both of these are low enough to be scope-able, by the way.

It's not uncommon for heaters in microphone tubes to be run at lower-than-normal voltages (6.3v usually), for both noise and lifetime reasons.

And some construction tip: use (more) flux, or flux-cored solder; heat up both the solder-pad AND the component leg / wire, and THEN feed some solder into the joint ;)
Thanks for your advice~

I am not really sure about what I understand(forgive me, I'm new here)

I tested DC from transformer yellow wire joint on PCB,the reading was 5.8v, and 99.5v on blue wire.


Khron

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #18 on: August 13, 2017, 02:05:01 PM »
1) Multimeter set to AC voltage, measure between the two yellow wires, ie. red probe on one yellow wire, black probe on the other yellow wire.

2) Multimeter set to DC voltage, black probe on one of the mounting screws, red probe on the left-most pin of the LD1084 (input, when looking from the front of the device); be careful not to slip with the probe, and short out things.

3) Same as 2), but red probe on the metal tab of the LD1084.

I assume the kit included two isolation pads for the two heatsinked components?
Khron's Cave - Electronics - Audio - Teardowns - Mods - Repairs - Projects - Music - Rants - Shenanigans

Re: Stellar CM1 with FOX 460 MOD and PSU update MOD
« Reply #19 on: August 13, 2017, 02:27:36 PM »
1) Multimeter set to AC voltage, measure between the two yellow wires, ie. red probe on one yellow wire, black probe on the other yellow wire.

2) Multimeter set to DC voltage, black probe on one of the mounting screws, red probe on the left-most pin of the LD1084 (input, when looking from the front of the device); be careful not to slip with the probe, and short out things.

3) Same as 2), but red probe on the metal tab of the LD1084.

I assume the kit included two isolation pads for the two heatsinked components?

Thanks a lot , I've done your steps.
1)  9.5V

2) 4.6V

3) 5.9v