A Audio and hi-fi forum. AudioBanter.com

Go Back   Home » AudioBanter.com forum » rec.audio » Pro Audio
Site Map Home Register Authors List Search Today's Posts Mark Forums Read Web Partners

Question About Organ Service Manual Test Procedure



 
 
Thread Tools Display Modes
  #11  
Old January 25th 21, 12:00 AM posted to rec.audio.pro
[email protected]
external usenet poster
 
Posts: 105
Default Question About Organ Service Manual Test Procedure

Mike Rivers wrote:
===============
>
> I think you're over-thinking this. Measurements with your meter will get
> you well into the ballpark. At that point, take on the job of "organ
> technician" and use your ears. If some notes stick out, adjust those so
> they blend in with the rest of the instrument.


** Absolutely.

This Q has been thoroughly over answered.

The OP is being too pedantic for words.

> In the Amphenol VTVM era, we didn't use dBu or dBV, and 0 "dB"
> represented the voltage required to pump 1 milliwatt into a 600 ohm
> load, which is the reference voltage for dBu.
>
> [(0.775 V)^2 / 600 Ω = .001 mW]


** Errr - might be .001 Watts ?


...... Phil

Ads
  #12  
Old January 25th 21, 01:11 AM posted to rec.audio.pro
Mike Rivers[_2_]
external usenet poster
 
Posts: 2,159
Default Question About Organ Service Manual Test Procedure

On 1/24/2021 6:00 PM, wrote:
>> [(0.775 V)^2 / 600 Ω = .001 mW]

> ** Errr - might be .001 Watts ?


Yup. I had milliwatts on the brain.

--
For a good time, call http://mikeriversaudio.wordpress.com
  #13  
Old January 25th 21, 01:16 AM posted to rec.audio.pro
geoff
external usenet poster
 
Posts: 1,771
Default Question About Organ Service Manual Test Procedure

On 25/01/2021 3:04 am, Mike Rivers wrote:
> On 1/24/2021 6:03 AM, Paul Dorman wrote:
>
>> **** I have a standard Digital multimeter.* The test notes go up to
>> A#4, which is 466 Hz, which might be pushing the frequency response of
>> the meter.

>
>> **** The organ stop tabs used are Diapason 8' and Tibia 8'.* I am not
>> sure about the Fourier Transform of these waveforms, but hopefully they
>> are close enough to an ideal sinewave, that the measured RMS value
>> will be close enough.
>>
>> **** But the harmonics of a 466 Hz fundamental, can be far beyond
>> 500 Hz, and hence out of the meter's range.

>
> >****** This test procedure appears to be a simple level-
> > setting adjustment for volume, for the different groups > of stop

> tabs in the organ.* Some measurements are at > the voice coil of the 12"
> speaker, and some are
> > measured at a crossover network.

>
> I think you're over-thinking this. Measurements with your meter will get
> you well into the ballpark. At that point, take on the job of "organ
> technician" and use your ears. If some notes stick out, adjust those so
> they blend in with the rest of the instrument. Not all organs are voiced
> perfectly, so get it close with your meter and then touch it up as needed.
>
>> ***** I just noticed that the service manual mentions that a model
>> 870 Amphenol is an excellent choice for "measuring audio signals
>> as low as -50dB".

>
> That's the kind of multimeter that was the standard bench instrument on
> a radio/tv repair shop. Because measurements often must be made at the
> grid of a tube, the megohms-input impedance of the VTVM, because of the
> tube at the front end, wouldn't load down the signal that's there.
>
> The input impedance of a modern DMM is pretty high, so you shouldn't
> have any problem making measurements either at the speaker terminals or
> the input of the crossover network, even if it's a tube amplifier.
>
> In the Amphenol VTVM era, we didn't use dBu or dBV, and 0 "dB"
> represented the voltage required to pump 1 milliwatt into a 600 ohm
> load, which is the reference voltage for dBu.
>
> [(0.775 V)^2 / 600 Ω = .001 mW]
>
> -50 dBu is about 2.5 mV. If this is a tone wheel organ, you'd find
> voltages in that range coming right off the pickups (I think - I don't
> know for sure), so unless the adjustment procedure involves mechanical
> adjustment of the pickups to adjust the level going into the amplifier
> section, you'll be fine with the sensitivity range of your meter.
>
> Happy tweaking, Mr. Organ Technician.
>
>
>


Here are some organ technicians. Or specialists at least , though mostly
Hammond-centric.

Have got useful info and replacement parts off them in the past for my
C3 and L122 ....

http://www.tonewheelgeneral.com/

geoff

And for those suspicious of the link:
view-source:http://www.tonewheelgeneral.com/
  #14  
Old February 3rd 21, 05:35 AM posted to rec.audio.pro
Paul Dorman
external usenet poster
 
Posts: 56
Default Question About Organ Service Manual Test Procedure

On 1/24/2021 7:04 AM, Mike Rivers wrote:
> On 1/24/2021 6:03 AM, Paul Dorman wrote:
>
>> **** I have a standard Digital multimeter.* The test notes go up to
>> A#4, which is 466 Hz, which might be pushing the frequency response of
>> the meter.

>
>> **** The organ stop tabs used are Diapason 8' and Tibia 8'.* I am not
>> sure about the Fourier Transform of these waveforms, but hopefully they
>> are close enough to an ideal sinewave, that the measured RMS value
>> will be close enough.
>>
>> **** But the harmonics of a 466 Hz fundamental, can be far beyond
>> 500 Hz, and hence out of the meter's range.

>
> >****** This test procedure appears to be a simple level-
> > setting adjustment for volume, for the different groups > of stop

> tabs in the organ.* Some measurements are at > the voice coil of the 12"
> speaker, and some are
> > measured at a crossover network.

>
> I think you're over-thinking this. Measurements with your meter will get
> you well into the ballpark. At that point, take on the job of "organ
> technician" and use your ears. If some notes stick out, adjust those so
> they blend in with the rest of the instrument. Not all organs are voiced
> perfectly, so get it close with your meter and then touch it up as needed.
>
>> ***** I just noticed that the service manual mentions that a model
>> 870 Amphenol is an excellent choice for "measuring audio signals
>> as low as -50dB".

>
> That's the kind of multimeter that was the standard bench instrument on
> a radio/tv repair shop. Because measurements often must be made at the
> grid of a tube, the megohms-input impedance of the VTVM, because of the
> tube at the front end, wouldn't load down the signal that's there.
>
> The input impedance of a modern DMM is pretty high, so you shouldn't
> have any problem making measurements either at the speaker terminals or
> the input of the crossover network, even if it's a tube amplifier.
>
> In the Amphenol VTVM era, we didn't use dBu or dBV, and 0 "dB"
> represented the voltage required to pump 1 milliwatt into a 600 ohm
> load, which is the reference voltage for dBu.
>
> [(0.775 V)^2 / 600 Ω = .001 mW]
>


If we calculate 1 milliWatt into a speaker 8 Ohm load, it will be:

(0.089 Vrms)^2 / 8 Ohms = .001 Watt

And 5dB above that would be .00316 Watts = (0.159 Vrms)^2 / 8 Ohms.

So it's obviously impedance dependent.


> -50 dBu is about 2.5 mV. If this is a tone wheel organ, you'd find
> voltages in that range coming right off the pickups (I think - I don't
> know for sure), so unless the adjustment procedure involves mechanical
> adjustment of the pickups to adjust the level going into the amplifier
> section, you'll be fine with the sensitivity range of your meter.
>
> Happy tweaking, Mr. Organ Technician.
>
>
>


 




Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
FS: QUAD ESL-63 Service Manual, Owner's Manual, + Many Extras bartluff Tech 0 April 30th 06 05:18 PM
FS: QUAD ESL-63 Service Manual, Owner's Manual, + Many Extras bartluff Marketplace 0 April 29th 06 03:18 PM
FS: Manual and Service Manual copies MrMarksMusic Marketplace 2 October 31st 04 01:52 AM
FS: Manual and Service Manual copies MrMarksMusic Pro Audio 0 October 29th 04 10:32 PM
FS: Manual and Service Manual copies MrMarksMusic Tech 0 October 29th 04 10:29 PM


All times are GMT +1. The time now is 11:14 AM.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2021, Jelsoft Enterprises Ltd.
Copyright 2004-2021 AudioBanter.com.
The comments are property of their posters.