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can i use this amp?

davestradamu

davestradamu

Swimming in Sound
hello, i came across a motorola sterephonic console with an amp in it. the unit only has a phonograph and it appears to be stereo. it has one 12ax7a and 3 other yet unidentified tubes. the question is:



what do i do with it??? :scratch2:


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happy listening! :music:
 
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Nice copper chassis. :thmbsp: I'm guessing one tube's a rectifier, & one's a 6BQ5 or maybe 6AQ5, but that's tough to guess. SE integrated monoblock, that really wants a brother, I think, though there's nothing wrong with mono by itself. EDIT: It's funny how they'd put the power supply on a seperate chassis, for such a small space /weight saving on the amp itself. (?) 2nd EDIT: Which means that's NOT a rectifier on the amp after all, & it's probably stereo, like you said in the beginning, or rather PP mono, since there's only one OT. ;)
 
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thanks! i am DYING to make this into something!

this might be my entry into DIY! the only tube experience i have is with my chi-fi preamp.

i think i need the theory, or 101 class to get me up to speed on how these guttings work.
 
Thats an odd setup. Do my eyes deceive me or is that an outboard mounted power supply? If that truly is what it is, then you're good. If I'm seeing things, then you might have a hot chassis set. Need the tube numbers to confirm. If the numbers start with 12 and 6, you're good. If its got stuff like a 50c5 or 60fx5 or 35c5, then its a hot chassis.
 
I need to learn the basics of tube amp topology. I do not know what a hot chassis is, truth be told. I am going to need some help here. I will do some reading. Should I get it? Or just more info about its configuration?

Thanks a ton!
 
hot chassis means you can get a big shock from it, just by touching it, or any metal portion of it, big shock!!
 
Somehow I thought that! It hasn't been plugged in for years. If it is a hot chassis I shouldn't get it. I hate my cats sometimes but not that much! I will get the tube types tomorrow!
 
Hot chassis, that is good safety information, I just recently pulled a stereo tube chassis and outboard power supply as mentioned from a old TT and I did not think of that. Professional knowledge is "priceless", lack of could be "lifeless". Scary thought.
 
I thought the hot chassis amps were the ones with no power transformer? :scratch2: I'm fairly sure that's an end-bell on that outboard chassis, so I don't "think" this one's a hot chassis. Someone who knows what they're doing will educate us soon, I bet. :yes:
 
you guys are awesome! tomorrow i will have exact tube specs. i was doing 100 other things at the time, or else i would have done a better job with the pics. after we figure out if this is deadly or not.... i will decide on a use for it... :D

happy listening! :music:
 
the place that has the console was closed today. so i will have more information tomorrow. i am really hoping i can make a nice bedroom system or a headphone amp with this!

thanks for all of your knowledge and expertise!

happy listening! :music:

EDIT:

after doing some digging i have found this:
http://cgi.ebay.com/ws/eBayISAPI.dl...=true&rt=nc&si=Cg3f9BWc5gCiWzjZRSnp9iGfbVc%3D

looks like the 2 tubes in question are 6BM8

looks like i have a shot at making this into something fun! :banana:

or will i shock the crap out of myself with this thing??
 
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davestradamu said:
after doing some digging i have found this:
http://cgi.ebay.com/ws/eBayISAPI.dl...=true&rt=nc&si=Cg3f9BWc5gCiWzjZRSnp9iGfbVc%3D

looks like the 2 tubes in question are 6BM8
:banana:

or will i shock the crap out of myself with this thing??
Click to expand...

It might be a stereo amp, if yours to be has a 2nd OPT under the chassis like the ebay one does. The ebay one I also see 2 ganged pots as well.

Pretty sure that it's not a hot chassis, that power transformer looks big enough to do the heaters and B+ supplies.
 
Interestinger & interestinger. That third pic in the auction shows 2 transformers underneath, not just one. Probably a 3rd (center) channel? One might be a choke, I guess. :scratch2:
 
i will be picking this up today. how can i test this? (other than plugging it in and putting my finger on the copper)

how many watts do ya think this is capable of? 3-5? i would like to pair this with a small pair of efficient bookshelf speakers, provided i can get it working.

thanks for all of your help! real pictures of the amp will come today! i am also trying to figure out a decent case to hold both chassis...

EDIT:

The ad says the console had a VM ceramic cartridge. after reading very little i have gathered that ceramic carts are high output and do not need a separate preamp.(true?) would this mean i could use a line level output device without changing much? also what about RIAA? i would like to use a digital source but i am afraid of hacking this up too much since it will be my first DIY!

you comments are welcome and appreciated!
 
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Second thought. I have a multimeter and will check voltage across the chassis when plugged in. Hopefully this will end up in the DIY section.... :D
 
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A few thoughts:

If it has a radio tuner in it there is going to be a selector switch for tuner or phono, and possibly an aux input. That is where you could feed in your CD or whatever source. And yes the ceramic cart. is a high level output not requiring a phono preamp.

When you get a look inside, find the tube map and make a list of all the tubes and the model #.

Also the amp chassis may have a model number stamped on it somewhere.
 
i've returned home with the amp! here is the skinny

attachment.php


Chassis:

Motorola with a few numbers on them
9 "M" 60 i have gathered is the date

HS-890A seems to be the model# for the amplifier
HS-893A or HS-898A (its smudged) for the power supply

tubes:

EZ80/6V4 in the power supply. (British, rectifier?)
12AX7A preamp (USA)
2x ECL82/6BM8 power (British)

attachment.php


Has 3 transformers on the main chassis

Looks like it is 3 channel? the console had a larger woofer between the L and R.

Tone, Balance and Loudness controls. One input.

attachment.php


attachment.php


THE BAD!!

The unit does not power on and no tubes light up. The phonograph did not spin either. Power supply issue? I took it anyway. Free.

I started tracing the voltage from the outlet and got no farther than the fuse. although it looks ok.

I have been given some great advice and will be checking out the dim bulb tester.

happy listening! :music:

this might be ready for the DIY section...
 

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