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Old 30th November 2009, 02:32 AM   #1
john65b is offline john65b  United States
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Default Motorola 3 channel Tube Amp from Console

Anyone know these Motorola Tube amps? Picked up a Motorola Console from the early 60 the other day. I took a peek inside and saw the tubes, so I got a little enthusiastic...

3 Channel jobbies - 2x fronts and a single bass channel, and a separate Reverb and preamp unit, as well as a tuner.

L/R Front Channels - (4) 6BM8 (ECL82) Push Pull
Bass Channel - (2) 6BQ5 (EL84) with single 12AX7 Push Pull
Reverb - (2) 6BM8 with single 12AX7

Preamp has two 12AX7 - one for preamp stage other for tone control

Tuner looks to be in great condition, but I don't care to do anything with it..although the power tranny looks nice and clean...

Anyway, hooked up the Motorola amp and its preamp (also with tried the amp with a JFET BOZ) on my B&W DM220i and it sounded just OK. I really didn't expect much since its almost 50 years old (build date is 1962)...but it was unlike my Magnavox 6V6 PP from a console I found a while back that sounded incredibly nice right off the bat...

Anyway, anyone with advice to strip the parts and build something new, or mod what I have? Leaning toward building a new amp around PP EL84...

By the way all six 6BM8 (ECL82) say "Made in Great Britain" and have the Mullard Coding:

OG2
BOH

These worth anything?? All test excellent on my Knight 600 tester...
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Old 30th November 2009, 03:03 AM   #2
Fenris is offline Fenris  United States
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Recommend at a minimum replacing the electrolytic caps - guarenteed those are shot. Also, clean the sockets and pots and check the remaining components for values (resistors and caps can drift with age). Depending on the condition of the wires, they may need replacement. And watch the transformers, the potting resin may have degraded with age.
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Old 30th November 2009, 03:26 AM   #3
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That one is ALOT more complex than any of the 3 channel jobbies i've seen.

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Old 13th December 2009, 02:42 AM   #4
john65b is offline john65b  United States
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Been a bit busy, but here are some pics of the amp and preamp. There's also the little VIBRASONIC reverb thingy....
Attached Images
File Type: jpg P1010001.JPG (713.3 KB, 426 views)
File Type: jpg P1010002.JPG (677.5 KB, 385 views)
File Type: jpg P1010003.jpg (608.8 KB, 368 views)
File Type: jpg P1010004.JPG (590.1 KB, 362 views)
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Old 31st May 2010, 10:04 AM   #5
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95% sure this is the very same set-up in my fathers old console, which is sitting in a basement covered with a ton of stuff. Had a single 15 inch driver and something like 2 x 6inch + 2 x 2inch drivers or something. Nearly all open back. Stopped working like 15 years ago.

It always amazed me how this thing shook the house. The Vibrasonic thing was odd to me. I guess you could say it's a reverb of sorts (never liked it personally)

Lots of Christmas music played though it mostly over 35 years. Fond memories.
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Old 31st May 2010, 11:33 AM   #6
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Very cool! I love old console rigs - they had such a style. You guys are really making me want to do something with tubes!

Jim
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Old 10th July 2010, 10:01 PM   #7
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Hi Everyone,Greetings from Jax Fl.I'm new to your site and very glad to be a part of it.I am not sure if I'm doing this properly yet so if not please correct me.I also just aquired an early I think 60s model Motorola 3 channel console and have a few questions I would like to pose.First up ,the #s on this tube amp are HS780b I know very little about this.Mostly wattage rating,also this unit was a record player only,no tuner and I cant find a pre-amp at all. the turntable was pluged directly into the amp.My other question is can I use a much newer pre amp in this inputs or can I just plug a source into these inputs?Any input would be appreciated greatly.I would like to let you all know that I am very new to the world of tube amps and want to learn as much as I can about them.I am however smart enough to have read the postings about how dangerous these things can be and the what to and what not to do's about them.I would also like to say that all that info was very useful and I will probably grow a lot older from having that kind of information available to me.The tubes in this amp are ELC82 and 12AX7s if that helps.All you folks have a great weekend.Thanks for any help you send my way.Rob.
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Old 10th July 2010, 11:02 PM   #8
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Quote:
Originally Posted by robsrockin1 View Post
Hi Everyone,Greetings from Jax Fl.I'm new to your site and very glad to be a part of it.I am not sure if I'm doing this properly yet so if not please correct me.I also just aquired an early I think 60s model Motorola 3 channel console and have a few questions I would like to pose.First up ,the #s on this tube amp are HS780b I know very little about this.Mostly wattage rating,also this unit was a record player only,no tuner and I cant find a pre-amp at all. the turntable was pluged directly into the amp.My other question is can I use a much newer pre amp in this inputs or can I just plug a source into these inputs?Any input would be appreciated greatly.I would like to let you all know that I am very new to the world of tube amps and want to learn as much as I can about them.I am however smart enough to have read the postings about how dangerous these things can be and the what to and what not to do's about them.I would also like to say that all that info was very useful and I will probably grow a lot older from having that kind of information available to me.The tubes in this amp are ELC82 and 12AX7s if that helps.All you folks have a great weekend.Thanks for any help you send my way.Rob.

Rob,

Member Tom Bavis may have the schematic for your unit in his extensive collection. The schematic is necessary to planning a restoration.

That unit employed a ceramic cart. on the TT. You should have no problem in connecting a CDP to the I/Ps. AAMOF, it's likely you will have to attenuate the CDPs O/P.
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Old 11th July 2010, 02:42 PM   #9
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Hi Eli D,This is robert the new guy.I appreciate the information and was wondering how to go about contacting this Tom B that you mentioned?Can you please tell me what CDP means and AAMOF.I dont wish to sound stupid but I do not text and you just went strait over my head.I have to learn things the hard way.I would also like to mention that the TT from this unit seems to be in pretty good shape and is all there,the info I can find is,motorola golden voice.Stamped on the bottom is PS274 and it was built in Gr. Britan.The cabinet from this piece was beyond help so it has been salvaged.My point is that if any of you are trying to restore one of these consoles this TT is yours.I have no need for it at all and just dont want to toss it out.If this can help one of you out figure the best way to get it to yourself and I will box it up and hand it to the shipper that has come to get it.Have a good day folks and again Thanks for your help.Robert.
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Old 11th July 2010, 05:12 PM   #10
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AAMOF = as a matter of fact. CDP = compact disc player.

The TT was probably made by BSR, but might have been made by Garrard.
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