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 Post subject: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 8:18 am 
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Location: Toledo, Ohio
Hi guys I am restoring a Saphire 1 AM radio from a 1962 Volkswagen.

According to the Sams Photofact there should be a .22ohm @ 2 Watt resistor on the emitter of the output transistor. The original resistor had obviously burned up and was replaced by a large wire wound or unknown value. The replacement had crumbled into pieces so no idea on the value that was in there.

I have found some .22 @ 2w replacements online but was curious if the composition mattered. There is carbon comp, metal film and wire wound. is there a recommended one for a resistor in this position? Sams has some denotations that state to use a specific part number but nothing else. I figured I would check before purchasing.

Thank you
T

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 8:25 am 
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Dunno about the Volkswagen radios, but Bendix, Ford and Delco mostly used BWF/BWH wirewounds and some open/non-encapsulated wirewounds... The first band is double width on the BWH/BWF resistors to tell you it's a wirewound. Current production is SPF/SPH:

www.farnell.com/datasheets/14314.pdf

Cheers,

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 9:36 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Consider replacing with these,

https://www.ebay.com/itm/5-PCS-0-22-ohm ... SwbqpT7cMq


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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 9:40 am 
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Joined: Jan Mon 25, 2010 7:51 am
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Location: Toledo, Ohio
Omer those are the ones I was actually looking at but was not sure if it should be a wirewound in this instance.

Brian, yes just checked and this radio was manufactured by Bendix. The BWF/BWH is that a flame proof-fused type resistor?

Thanks
T

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 9:59 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
bastardbus wrote:
Omer those are the ones I was actually looking at but was not sure if it should be a wirewound in this instance.

Brian, yes just checked and this radio was manufactured by Bendix. The BWF/BWH is that a flame proof-fused type resistor?

Thanks
T


6V radio?

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 10:00 am 
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Joined: Jan Mon 25, 2010 7:51 am
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Yes 6V auto radio...

I just saw your link on the resistors...DUH! Well it is 4 AM here...LOL

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 10:04 am 
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Joined: Jan Mon 25, 2010 7:51 am
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Saw these but curious about the Wattage Rating on them (see cover of the box in photo).


https://www.ebay.com/itm/1-5-Pack-TRW-BWH-Molded-Wirewound-22-OHM-1-Watt-10-Resistors-NOS/141912596836?hash=item210aa66164:g:MpoAAOSwe7BWzgrI


https://www.ebay.com/itm/5x-IRC-TRW-2W-10-Molded-Wire-Wound-Resistors-BWH-Series-New-Old-Stock/182825297908?hash=item2a913ca7f4:m:mCyG-2I4N5x77OMx3OW1Mwg

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Last edited by bastardbus on Dec Sat 02, 2017 10:11 am, edited 1 time in total.

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 10:10 am 
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Joined: Sep Tue 30, 2014 6:08 am
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Location: The Old Dominion VA 23518
bastardbus wrote:
Yes 6V auto radio...

I just saw your link on the resistors...DUH! Well it is 4 AM here...LOL



And note that the emitter resistor requires a Positive Temperature Coefficient - Those SPF/SPH have a +800ppm Tempco. Bingo !

Domestically, I've always used the BWH resistors - They look like this:

Image

or, for absolute economy, a Noble or Cosmos (brands) ceramic emitter resistor, commonly seen in Stereo gear:

http://www.talonix.com/shop/item.aspx?itemid=8898

I got a BWH assortment offered by Mouser years ago - no .22 left, just the odd stuff now. 78 BWH resistors, all </= 1 ohm, all 2 Watt wirewound, for $12 or so back in 1989.

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 10:13 am 
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bastardbus wrote:


The real goods. 2 Watts in a 1 Watt package - straight from the datasheet. The resistors are ubiquitous in transistor gear - that double wide first color band tells you right away it's a wirewound, and all BWH's are 2 Watt resistors....

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 Post subject: Re: Proper composistion for transistor emitter resistor ?
PostPosted: Dec Sat 02, 2017 10:15 am 
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Joined: Jan Mon 25, 2010 7:51 am
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Location: Toledo, Ohio
Great the wattage rating listed on the one auction was 1 watt and I noticed the rating on the box was by temp. I will grab me some of those. Thanks a bunch!

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