Identifying characteristics of old transformers?
« on: July 23, 2020, 01:21:26 PM »
Hi,
 I have a couple of ATI DA2016-1 Audio Distro amplifiers that I am parting out because it is time to get rid of them. They are really well made but they don't have much monetary value as an appliance, so I am trying to recycle some parts rather than just throw them away.

 I contacted ATI to ask if they had any info about the audio transformers, and they very kindly took the time to reply but they said the units were so old that they no longer had any documentation for the transformers.

 They are line output audio output transformers. My first guess is that they are 600ohm line level with a 1:1 winding.

 is there any way to make some tests that will provide more info? I have a DE-5000 Handheld LCR Meter if that helps.

 Thank you for any help you can offer.

 Thank you!
« Last Edit: July 23, 2020, 01:25:57 PM by trans4funks1 »


scott2000

Re: Identifying characteristics of old transformers?
« Reply #1 on: July 23, 2020, 02:05:27 PM »
Maybe linking the manual and/or specs could get some more clues....

Those are some nice Bourns pots ....

ATI DA2016-1
« Reply #2 on: July 23, 2020, 02:15:23 PM »
specifications for DA2016-1  as published in 1988:
" +22 dBm  transformer outputs "
suggests a 1:1.


ruffrecords

Re: Identifying characteristics of old transformers?
« Reply #3 on: July 23, 2020, 05:37:22 PM »
What is the supply rails?

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

Re: Identifying characteristics of old transformers?
« Reply #4 on: July 23, 2020, 07:42:57 PM »
Hi,
 If I understand the question you are asking about the power supply. I confess it did not occur to me to make measurements before disassembling this afternoon, but the markings on the power supply transformers allowed me to look up their specs.

DPC-20-1200

https://belfuse.com/resources/datasheets/signaltransformer/ds-st-pc-series.pdf

Voltage - Primary    115V, 230V    
Voltage - Secondary (Full Load)    Parallel 10V, Series 20V    
Current - Output (Max)    Parallel 2.4A, Series 1.2A    
Primary Winding(s)    Dual    
Secondary Winding(s)    Dual    
Center Tap    No    
Power - Max    24VA

scott2000

Re: Identifying characteristics of old transformers?
« Reply #5 on: July 23, 2020, 08:58:24 PM »
I think this manual is for a newer version but the theory of operation has some info that may be helpful.. Pretty sure the older ones used the 5533 chips....

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&ved=2ahUKEwjChJv31eTqAhUFh-AKHdTWAdcQFjANegQIBRAB&url=https%3A%2F%2Fwww.atiaudio.com%2Fs%2FDA2016-1.pdf&usg=AOvVaw2B0fxrdK7g5yetoWEy6lxQ

Re: Identifying characteristics of old transformers?
« Reply #6 on: July 23, 2020, 11:01:21 PM »
I don't think I had appreciated the idea of deducing the function of the transformer by looking at the other specs, but now may be able to imagine that...

1) 26dBm output gives some idea of current capacity.

2) The 5533AN op amps have an gain or output capability that may be assumed.

3) The B+ voltage can suggest what sort of gain or output level the op amp stage can make.

4) The TC4051BP 1:8 Analog Multiplier ICs have an output capability that may be assumed.

5) The 5533AN op amps are likely to have been combined with a transformer of some particular input impedance.


The basic operation of the distribution amp is intended to convert a pair of inputs into 8 pairs of outputs so as to interconnect professional audio gear. The utilization context that I am familiar with was in dubbing facilities where VHS tapes were replicated in a room full of rack mounted recorders, each of which required analog audio and analog video to be served from a distribution system. The appliance more or less provided a 1:1 in to out relationship between the input and the each of the multiple outputs. 

I had been thinking in terms of learning to make some tests, so I had not thought much about what I wrote above until considering the replies posted here. I haven't thought through the details so if you have any further comments please share. :-)

If there are some testing procedures that can be learned, I would appreciate any ideas you will share.

Thank you!


scott2000

Re: Identifying characteristics of old transformers?
« Reply #7 on: July 24, 2020, 08:58:42 AM »
this is a pretty good video.....  the measurements start later....

Vacuum Tube Output Transformer Measurements Determining Turns & Impedance Ratio & Matching To Tubes

https://www.youtube.com/watch?v=Yzo3A-NywSs

Re: Identifying characteristics of old transformers?
« Reply #8 on: July 24, 2020, 12:08:47 PM »
Thanks, that was a very helpful video. I like the presenters style of delivery.

Thank you.

Re: Identifying characteristics of old transformers?
« Reply #9 on: July 24, 2020, 07:51:19 PM »
Hi,

 I used the procedure shown in the video to confirm the winding ratio. I started by looking at the circuit board traces to get an idea about the pin out for hot, cold, and ground, and then sent a 1.5vAC 1kHz sine wave signal through the transformer.

 The drawing I have attached illustrates what I found. The 1:1 ratio was the circuit I found in the existing distro amp, while the two 2:1 examples show possible implementations.

 Is there any way to make some estimate of the current capability? Will I have to rely on the assumption that 26dBm is a good estimate?

 Finally, is there any information I can learn with the use of my LCR meter? I bought it for simple testing of capacitors and have wondered if it was useful for use with transformers.

 Thank you!

 
« Last Edit: July 24, 2020, 07:56:24 PM by trans4funks1 »


Re: Identifying characteristics of old transformers?
« Reply #10 on: July 29, 2020, 06:32:41 PM »
FWIW,
  I measured a bunch of the transformers, and they seem to range between 900mH and 1050mH.

  I am not sure what else I can learn about these transformers, but would appreciate the chance to learn.

 Thank you.

rackmonkey

Re: Identifying characteristics of old transformers? New
« Reply #11 on: July 30, 2020, 02:04:38 AM »
Is there any way to make some estimate of the current capability? Will I have to rely on the assumption that 26dBm is a good estimate?
 Thank you!

See the basic setup in the first post here, then perform the inductance vs voltage level test described in the second post.

https://groupdiy.com/index.php?topic=73039.0

Perform that test at the lowest frequency of interest (often, 20 or 30 Hz). Note the voltage when inductance reaches its highest peak, before it starts to drop off.  That’s the roughly the max voltage level you can put through the transformer before gross distortion sets in. From there, Ohm’s law is your friend for rough power estimation.

Alternatively, use a function generator plus a very low distortion, wide bandwidth signal amp or DC amplifier to drive the transformer with the secondary terminated with 10k ohms resistor (or 600 ohms if you intend to connect to vintage equipment). Run that into your audio interface on your computer and use REW or a similar measurement suite to do a real time analysis, again at the lowest frequency of interest. Increase the signal generator level gradually. When the harmonics start to rise significantly, back off on the level a bit until they just fall back off.  Measure the level of that signal and that’s roughly your max voltage you’ll want to put through the transformer. Again, ohm’s law is your friend from there if you want to come up with a power level.

Be sure you run the second test above with the appropriate source impedance for your intended application. A series resistor between the signal amp and the transformer under test is a cheap and simple way to do this.
« Last Edit: July 30, 2020, 02:12:51 AM by rackmonkey »
Whether you think you can or you think you can't, you're probably right.


 

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