Help with IG-72 Audio Generator

[Multi-Volti Devices]

Hello:

Thanks for the correction Terry

Murray

-----Original Message-----
From: Terry Perdue <terryp at halcyon.com>
To: Multi-Volti Devices <multi-volti at softhouse.com>;
HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
Date: Saturday, July 03, 1999 12:29 AM
Subject: Re: Re: Help with IG-72 Audio Generator


>Actually, it's not in one of the legs of the bridge; it's part of the
output
>leveling loop. I think that the audio oscillator that was HP's first
product
>was the first to take advantage of an incandescent bulb's resistance vs
>voltage curve in this way.
>
>-----Original Message-----
>From: Multi-Volti Devices <multi-volti at softhouse.com>
>To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
>Date: Friday, July 02, 1999 4:53 PM
>Subject: Re: Help with IG-72 Audio Generator
>
>
>>It may be a Wein bridge oscillator. They almost always use an incandescent
>>lamp in the bridge...weird but true. I don't remember it's purpose, but it
>>definitely will not oscillate with out it...it's a leg of the bridge.
>>
>>You cannot measure a cold tungsten filament's resistance and get much
>>intelligence from the measurement...the resistance is much lower cold than
>>hot...that's why inrush current is 'rough' on incandescent lamps.
>>
>>Murray
>>-----Original Message-----
>>From: Ed Richards <k6uuz at JUNO.COM>
>>To: HEATH at LISTSERV.TEMPE.GOV <HEATH at LISTSERV.TEMPE.GOV>
>>Date: Thursday, July 01, 1999 12:31 PM
>>Subject: Re: Help with IG-72 Audio Generator
>>
>>
>>>Dave;
>>>I am not familiar with that kit, but engineers frequently use a light
>>>bulb for regulation as the resistance of the filament varies greatly with
>>>the current through it. (measure he resistance of a 100 watt bulb and
>>>calculate the wattage according to Ohm's Law! It is not used to emit
>>>light, just regulation. It very well could kill the circuit if open.
>>>Warning! Use only the original number lamp or the circuit may not work
>>>correctly!
>>>Ed Richards
>>>
>>>
>>>On Thu, 1 Jul 1999 07:14:28 -0700 Dave <zommbee at IX.NETCOM.COM> writes:
>>>>Hello Heathniks,
>>>>
>>>>I have an IG-72 I'm trying to get working (without the
>>>>schematic, of course :-)
>>>>
>>>>I've recapped it, replaced 1 bad 6X4, but still not
>>>>getting it back to life.  There is NOT much to this
>>>>thing!  The other tubes test good, and I've tried
>>>>substitution as well.  Still zilch.
>>>>
>>>>But there is a lightbulb on the UNDERSIDE of the
>>>>chassis - 110v 3w with a screw-in base.  It's open
>>>>and I am getting a new one today.  It's different
>>>>from the power light - it's not visible with the case
>>>>on and seems to be just a load of some sort.
>>>>
>>>>What is this bulb used for and if
>>>>it's open, will that stop the unit from oscillating?
>>>>
>>>>Any other ideas on what else could be wrong?
>>>>
>>>>Thanks,
>>>>
>>>>Dave WB7AWK
>>>>http://www.boatanchors.com
>>>>
>>>>Sponsored by the City of Tempe
>>>>
>>>>Listserver Submissions:  heath at listserv.tempe.gov
>>>>Listserver Subscription: listserv at listserv.tempe.gov - "subscribe
>>>>heath 'name' 'call'"
>>>>Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff
>>>>heath"
>>>
>>>Sponsored by the City of Tempe
>>>
>>>Listserver Submissions:  heath at listserv.tempe.gov
>>>Listserver Subscription: listserv at listserv.tempe.gov - "subscribe heath
>>'name' 'call'"
>>>Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff heath"
>>>
>>
>>Sponsored by the City of Tempe
>>
>>Listserver Submissions:  heath at listserv.tempe.gov
>>Listserver Subscription: listserv at listserv.tempe.gov - "subscribe heath
>'name' 'call'"
>>Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff heath"
>

Sponsored by the City of Tempe 

Listserver Submissions:  heath at listserv.tempe.gov
Listserver Subscription: listserv at listserv.tempe.gov - "subscribe heath 'name' 'call'"
Listserver Unsubscribe: listserv at listserv.tempe.gov - -"signoff heath"