Author Topic: Firestone Air Chief portable record player - Firestone tubes!  (Read 546 times)

MikeNinNH

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I really must remember to take pictures of the players I acquire BEFORE I take them apart.. anyway, over the weekend I snagged a Firestone Air Chief 4-G-23 portable record player.. it's a suitcase design where the turntable drops down on the front and the speakers flip open on the sides (they can be detached too).  It has a Voice of Music 1255 changer. Yeah, I'm young enough to forget that Firestone stores used to sell electronics as well as tires and such...  But the real surprise was on the tube amp - Firestone record player, Firestone tubes! They still work too (yup, another 50EH5 amp, I'm getting real familiar with this tube).  Fixed the bad-filter-capacitor hum yesterday. Got the SAMS folder with the schematics yesterday too from eBay - there were no docs anywhere for this player online anywhere (heck, I can only find a grainy scan of the front picture from the Sams folder online). Some folks no doubt wouldn't need the schematics on this simple, no-preamp-tubed, volume-control-for-each-channel amp, but I'm more comfortable working on electronics with the schematics on-hand.

Still have to decide whether to replace the paper-foil capacitors or not - I don't THINK they're why I can't get the volume real loud using my default iPhone tester - clean out a problem POTS, and need to clean up the V-M changer so it can get past the drop-and-arm-swing without my help spinning the turntable, but not in too bad shape.

EDIT: For some reason one picture is upside down.. but that's okay, because that's how it's installed in the turntable, hanging upside down (when the turntable is opened) from the top of the cabinet. Note they included tube retaining clips on the chassis for this reason.

 

TC Chris

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Re: Firestone Air Chief portable record player - Firestone tubes!
« Reply #1 on: March 31, 2017, 06:29:51 PM »
I think "real loud" is a relative concept.  We have much higher expectations these days.  You've got one tube per channel, so any amp output depends pretty heavily on a cartridge with lots of output to drive those tubes.  And I doubt that it was ever ear-spitting (except for the distortion levels).

Chris Campbell

electra225

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Re: Firestone Air Chief portable record player - Firestone tubes!
« Reply #2 on: March 31, 2017, 07:10:47 PM »
About a watt of output.  The 50EH5 is a "high fidelity" version of a 50C5.  The printing on that one tube looks really Sylvania-ish to me.
If it ain't broke, call me.  I can break it....

MikeNinNH

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Re: Firestone Air Chief portable record player - Firestone tubes!
« Reply #3 on: March 31, 2017, 08:54:46 PM »
In terms of loudness I was comparing it to my other portable project, a Magnavox Holiday portable with an 80-01-00 amp (the schematics are in the download area).  That amp also has two 50EH5's, but there's a 12AX7 pre-amp as well. It's generally more sophisticated than the Firestone's amp (but still much less so than a lot of consoles).  The Firestone amp has a whopping 4 caps in the entire amp, not counting the three power filter caps in the can.  Doesn't get more basic!  I'll have to scan and post the Sams page for it.

Ken Doyle

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Re: Firestone Air Chief portable record player - Firestone tubes!
« Reply #4 on: April 01, 2017, 10:21:54 AM »
A 50EH5 is somewhat more sensitive than a 50C5, in other words, it requires less input to reach full output than a 50C5 does. 

MikeNinNH

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Re: Firestone Air Chief portable record player - Firestone tubes!
« Reply #5 on: April 02, 2017, 09:37:49 AM »
Here's my scan of the SAMS Photofact 674-5 of this player - really, it's the amp (AMP-35).  I guess this should go under the amps section of Downloads? Anyway - the volume POTS are both bad - one creates a nasty hum through a certain range in the middle (contact cleaner didn't help), the other seemed mostly fine (but also had a bit of hum in the middle range) until it seized up on me yesterday (full disclosure - this is a couple of hours after I had cleaned it out with MaxPro Contact Cleaner; I let it dry about 45 minutes before restoring power, still, I guess it could be related).  I ordered a pair of 3Mohm POTS off ebay (meant for Fender amps) to replace them. Meanwhile,I've bypassed the volume POTS (on the schematic the line from the input jacks now goes directly to the 47k resistors on each channel; the POTS have also been disconnected from B-, thus all connections from them are gone). I discovered, once I did that, that both volume, frequency response, and hum reduction vastly improved by connecting the negative lead of the 22uf (replacing the spec 25uf) 25watt cap C2 directly to the chassis (not B-). I'm still puzzling that one out, but now it sounds great! If all I was gonna use this amp for was as an iPod amp I'd be golden!  Of course I'm putting the turntable back in, so I'm replacing the volume POTS.  I plan on restoring the spec circuit setup when I install the new POTS - I think. Or maybe I should consider an alternate wiring that keeps the 22uf cap attached to the chassis? Thoughts?