Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
Is there a special meter that is used for alignment?

Nick S.,

The meter used is/was an alternating current (AC) meter used to measure the audio signal output. As the various circuits were peaked the audio would increase increasing the reading on the meter. If a radio has automatic volume control (AVC), the negative voltage on the AVC line can be used as an indicator to adjust/peak the radios RF and IF circuit adjustments.

Radiodoc
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:Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
:Is there a special meter that is used for alignment?

We used an AC VTVM for all our alignment jobs, this was sensitive to microphone level (-70 dBm) for all our audio work. It would seem like to me that the AVC and you would be fighting each other, so we would disable the AVC or AGC, whichever you call it, and keep the input low enough not to overload anything. It also seems that listening to the speaker worked just about as well.

Lewis

:Nick S.,
:
:The meter used is/was an alternating current (AC) meter used to measure the audio signal output. As the various circuits were peaked the audio would increase increasing the reading on the meter. If a radio has automatic volume control (AVC), the negative voltage on the AVC line can be used as an indicator to adjust/peak the radios RF and IF circuit adjustments.
:
:Radiodoc
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:
::Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
::Is there a special meter that is used for alignment?

:Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
:Is there a special meter that is used for alignment?

I like using an oscilloscope watching for the max peak-to-peak waveform of the typical 1Khz tone.

.Many BC band recievers have you adj for best output at 1400kc. Trim the Ant/RF/IF for best output and only touch the Osc adj if the dial indicator if off freq. If you have a good ear,trust it as you dont have to get too scientific about this. But if you have a signal generator,freq meter,scope,VOM and can spare some time (and savor the experience),then go with the manufacturers aligment procedure.Run the unit for an hour to get it warmed up. Keep the unit on the bench as it would sit in the cabinet,as if its tipped on its side to access adjustments,the readings can all change when its put right side up. Also if the cabinet is metal,the magnetic fields can all change when the unit is placed back inside it. I have a metal stand made from an old barbeque grill that I can use to raise the unit off the bench and tweak the underside through the bottom of the grill. Adjustments hold pretty still when I'm done. For a visual indicator of signal strength,some units have an 'S'meter to go by,especially communication-type recievers.

:Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
:Is there a special meter that is used for alignment?
Nick: You are correct in that the human ear is a very poor judge of loudness (this is what decibels are all about) and an analog ac voltmeter is probably the best indicator of "peaks". I prefer to use a VTVM set on the AC voltage function and connect it to the plate of the output tube so that the level is very high and easy to read. In fact, my meter is 9 inches and you will be suprised what a difference accurate peaking makes in total set sensitivity. You can use an analog VOM if you use a .1 mf capacitor in series with the meter lead connected to the plate of the output tube for DC isolation. Another technique that works nice is to connect an analog VTVM on its DC function to the AVC line as this monitors the AVC voltage during alignment which is the same thing as watching an S meter or a tuning eye. The amount of AC voltage across the low Z voice coil of a speaker is very low for the ranges of many meters unless you want to turn up the volume and deafen yourself. Good Luck.

A Zenith I want to align recommends using an output meter across the speaker leads. I've not run up on an output meter in years of haunting swap meets. What can I use instead in this instance and still keep it across the speaker leads?

Bill,
Unless I'm missing something here, an old analog VOM (AC scale) or o'scope are good candidates. The continuously moving needle will allow you to peak the audio, whereas a DMM has an update/refresh/sample rate, making minute adjustments impossible. Another option is a VTVM or o'scope on the AVC line.

marv

:A Zenith I want to align recommends using an output meter across the speaker leads. I've not run up on an output meter in years of haunting swap meets. What can I use instead in this instance and still keep it across the speaker leads?

I use a Simpson model 260 for this purpose. Works great. Usually the 2.5v AC scale is all you need for peak readings on the speaker terminals. There are loads of them on eBay. I was lucky enough to find a brand new one sealed in a military box a few years back at a hamfest.
Steve

Nick S.,

There is an Simpson output meter at Triode Electronics on eBay at:

http://cgi.ebay.com/SImpson-Model-427-Output-Voltmeter-0-50V-0-10V-0-2V_W0QQitemZ200115086827QQcmdZViewItem#ebayphotohosting

Radiodoc
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:Seems I always see 'hook up a meter to the voice coil' when doing an alignment (conventional AM receiver) but I have never been successful doing that. Everyone I talk to just listens to the loudest tone by ear, as do I.
:Is there a special meter that is used for alignment?

Not a bad price but the meter glass is cracked. I used a Simpson 269 on 3VAC across the speaker leads and it worked fine.

Bill J.,

I just thought he may want to see one. I have used a Simpson 260 on the ac range. I also have a Weston model 571 output meter I use quite a bit. It was part of USA signal corps I-56 test set. It only measures about 5 x 3.5 x 2.25 inches and doesn't take up much real estate on the work bench.

Radiodoc
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:Not a bad price but the meter glass is cracked. I used a Simpson 269 on 3VAC across the speaker leads and it worked fine.