Rcherche wiring diagram for Rack SV32SR for Neumann AM32

[salnikov]

Hello to all members.

Following mishandling, I have an electric resistance in burned into my rack SV32SR (Depth Range rack) my Neumann AM32, see the two pictures below:




This burned resistance has the effect of not having to pitch calculation in automatic mode (the needle on the poster is always right).
In "fix" mod, everything works correctly.

A member would he the electronic diagram of the rack? Or if a member knows the value and power of this resistance?

In advance, thank you all for your help.

[Stevie342000]

I have a couple of questions: Why did the resistors fail? Is there another fault which caused the resistors to fail? If yes then you need to resolve that issue as well as replacing the burnt out resistor. The other question is what is all that gunk around the replaced electrolytic capacitor? Is it leaking fluid? Has it failed? I may have a copy of the manual or know where you can get one. Send me a PM.

[andybee]

the brown fluid is glue, to hold the cap in place.
Maybe somebody have a schematic of this unit?
There must be a reason for the burned resistor.

[dubcutter89]

Hi!

Are there EL84 tubes on the unit?
Is one of the resistor legs going to the EL84 (grid or cathode)? Or is it going to psu? connected to the terminal on the back/pitch box? - check with multimeter when machine is OFF.
What was the mishandling? Short circuit in the Pitch box?

It might be a series current limiting resistor or something like that for the breaking current which is controlled by the El84...or something else...sorry I cannot tell for sure.

Here's a pic of an old tube pitch I took, but I don't even see those resistors...sorry

Lukas

[salnikov]

Hello Lukas and thank you for your message.

Or, one of banchesde resitance connects to a tube.
If you wish, I found the pattern of the rack, but I'm too novice to read properly.
Do you want I send you by the MP?

[salnikov]

Hello to members.

So about my problem, I have additional information that could perhaps help people who want to help me:

1.) The two series resistors are not original and therefore not visible in the wiring diagram.

2.) I do not know the reason for the addition of two resistors.

3.) These two series resistors come to connect on one of two large electrochemical capacitors (see photo below).
In the picture I have circled in red.


4.)I measured one of two resistance (which still seems in good condition and is not exploded) and I have about 92 ohms.

What is the usefulness of these two resistors connected to the capacitor?

I hope this information can help and find the solution?

[markrob]

Hi,

Unless and until you get a copy of the schematic, it will be hard to determine why this mod was made or if it should remain in place. Are there any other mods to the electronics? That might explain the need for the resistor. For example, back in the old days selenium rectifiers were often used in tube equipment. These go bad over time and are often replaced with modern silicon rectifiers. When this is done, a series resistor was often added to keep the filtered DC voltage within spec as the older devices had much larger voltage drops as compared with silicon.

Mark

[salnikov]

Hello to all members.

For those who may be an idea to solve this problem, here is the electric Route map of the rack.
I'm sorry, this scheme is not very readable.
I have a better PDF version, please ask me by the PM.

[markrob]

Hi,

Based on the schematic, the picture Lukas posted, and your photo's, there are a number of modifications that were made in this part of the circuit. My advice would be to carefully trace out and document the modifications and try to determine why they were made. Perhaps you could restore to the original specification. The resistors may have burned because they were undersized. More likely, given the age of the mod, something else failed (e.g. one of the filter capacitors) and caused the resistors to fail as well. Do have any means to check the two electrolytic caps for shorts or high leakage current?

Mark

[salnikov]

Hello Mark and thank you for your reply.

So far everything worked.
The two resistors have burned following a essair have connected a frequency inverter to 220V input of the machine.
As soon as I turned on the machine with the inverter, the two resistors have burned.
So if I simply replace the two resistors with new strengths, this can run it or other component also died again?

[dubcutter89]

Markrob is right, first check other parts for right value and working condition.

I assume you wanted to use a 220V inverter because the AM32b turns hot when using 230V ?

I had a look at the scheme - maybe you can check following parts:

-Green Cicle "PSU Capacitors" - I think these are the 2 capacitors in your picture where the modified resistor goes. It might be that your inverter has high frequency noise on the output, for which the first capacitor in the psu looks like a short circuit to ground and therefore the resistor was burned..(mark?)
the other wire from the caps goes on the backside of the unit. I think that there is the inductor of the psu filter...

- check the rectifier and replace if necessary!

- replace resistor (200Ohm?) and try without inverter...carefully!

- green/red circle next to ecc82 tubes: check values, these are also connected direct to the second psu capacitor.

- check all tubes

- it seems to me that the yellow foil(?) capacitors are from the filter, and with some luck there is no problem
(orange/yellow path is where the actual pitch is implemented - the more the el84s conduct the more breaking current flows through the VA62 pitch and decrease the moving speed of the carriage)

please send me the pdf of the schematic: lukasobwaller(())gmx.at

Lukas

[salnikov]

Lukas Hello and thank you for all that information.

I'll try to control everything despite my poor knowledge of electronics ...

Just a auestion, do you think it is possible that the value of the two resistors is burned approximately 92 ohms for each resistor?
If so, do you think I can try to simply replace the two resistors with two new resistors and see if it works again?

[dubcutter89]

As it has been said before: there might be some errors with other parts. It is impossible to judge by looking at a photo...
But if you are lucky then you only have to replace that resistor (or 2) and maybe the capacitors... Please ask somebody who has experience with old electronics for doing this!

Check the 2 capacitors (50uF + 100uF in the schematic) if they are still good (no leakage..). Best would be to replace them!
Insert a new resistor: assuming something like ~100mA current draw for all tubes a 220Ohm resistor will reduce voltage by 0,1*220 = 22Volts. That would make sense to me (but still we don't know why there is modification and why the resistors failed!!!)

P=U*I so the resistor power loss in that case is 2,2 Watt --> use at least a 5 Watt (or 10Watt) resistor !!

Don't use the inverter as it may have caused the failure...

Compare with the other unit (as far as I know the tube pitch is made of 2 units SV32)
I'm sorry, without more detailed information, measurements and a solid reconstruction of the modification it is impossible to give any further advice...

---->>>> PLEASE BE CAREFULL <<<<<----
Tube based electronics are running on high voltage which is very dangerous!!!
Ask a professional electrician for all works to be done!
I'm not responsible for anything that may go wrong!!!!!!
---------------------------------------------------

Lukas

[mossboss]

You have very good information from all the people here, but at most is best guess due to lack of information
The modification has been done for some reason or another by someone who knew what he was doing, that makes it very very hard to decipher the modification from what you have described so far, including the photos, which show the damage
If I where you I would put it back to original condition, at least you will know that it is back to as it was designed, try it out than worry about the modification, it may not even be necessary
At least in this way you can get up and running
Make sure that you check every component and wiring to be exactly the same as the schematics you have, there may be other components associated with this modification, they will need to be removed as well
It is crucial that you check for any other components that may have been used elsewhere
Already mentioned in another post
These units have VERY HIGH voltages involved, so unless you are confident in working with high voltage equipment, it's best you get someone who has experience with vacuum tubes to do the job for you
Very dangerous stuff
Keep us informed
Best