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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Jul Fri 13, 2018 11:37 am 
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1 amp slow blow.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Jul Sun 15, 2018 3:38 am 
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i figured that would be a good value.

steve


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sat 04, 2018 2:41 pm 
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my plan as of 10:00 this morning is to tear down the turntable and restore it, then a weekend of professional baseball down in Altoona for two days.

i'll need that and a confession booth after the TT restoration :x .

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sat 04, 2018 3:40 pm 
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The biggest limitation of a tube amplifier is the size and quality of the output transformer. Evidently, Motorola spent more money there.

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sat 04, 2018 6:16 pm 
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they spent some money then. it sounds fantastic.

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sat 04, 2018 6:37 pm 
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Tim Tress wrote:
The biggest limitation of a tube amplifier is the size and quality of the output transformer. Evidently, Motorola spent more money there.


They pretty much had to far as their three channel consoles go in order for the bass driver to actually produce good bass.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 05, 2018 5:05 am 
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turntable restoration did not go well.

someone was at it before b/c the big gear wheel that the platter turns was extremely tough to turn.

the grease froze up everywhere which caused it to not work. the double-decker idler is ground down with shards of rubber all over the top of the motor assembly.

of course, some backyard teknishiunn or should i say "makanik" took the TT apart to relubricate. the master mechanic lost springs, screws, a few other parts I think, and just bastardized the thing.

for now, I shined the turntable up and placed it back into the cabinet, where it will set until find another one, which really does not matter to me if I do or don't.

I'm using it with tuner and a soundcard input and enjoying it that way for now.

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 05, 2018 4:59 pm 
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Contact Gary stork
https://www.thevoiceofmusic.com

He might be able to help you.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 05, 2018 10:50 pm 
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Hey DR,

If you REALLY want to talk about cooked 6BQ5, let's talk about SHERWOOD. My Sherwood S1000II that I use for my center channel has 4, runs them at about 450 per tube, and I'm lucky get 2 years out of a quad.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Mon 06, 2018 4:24 am 
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yikes on those values :shock: .

did you ever calculate the static dissapation via cathode current, plate voltage, and some maths ?

i'm curious to know what it may be.

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Mon 06, 2018 4:28 am 
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Dutch Rabbit wrote:
yikes on those values :shock: .

did you ever calculate the static dissapation via cathode current, plate voltage, and some maths ?

i'm curious to know what it may be.

steve


Plate voltage is 450. Sorry I should have put that in. Haven't tried to calculate anything else. I will tell you that amp outperforms even my DJ amps at 120 watts


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Mon 06, 2018 1:52 pm 
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Interesting reading here on the 6BQ5. If one is concerned about the high voltages or dissipation, how about using a 7189? Of course, one has to be sure that the tube socket is wired properly since the 7189A has some internal pin connections that the 6BQ5 may not.

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Mon 06, 2018 7:47 pm 
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Motorola used a few different turntables over the years. Could you post a picture of yours here? I have at least one spare, if I have something that'll work for you I'd be happy to send it your way for little more than the cost of shipping.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Tue 07, 2018 2:35 am 
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Don Cavey wrote:
Interesting reading here on the 6BQ5. If one is concerned about the high voltages or dissipation, how about using a 7189? Of course, one has to be sure that the tube socket is wired properly since the 7189A has some internal pin connections that the 6BQ5 may not.


amp originally ran 7189 but those are $$$$.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Tue 07, 2018 3:31 am 
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this fisher had a pair of 6BQ5 tubes in it.

it peaked 35 watts with music program, kid anyone not. these poor little tubes were like two little charred hot dogs standing up on a metal serving tray.

i felt so sorry for them.

here is the thread and there are pics of the tubes somewhere in it.

when the project began on page 1, it certainly did NOT end as planned on page 3, but man o man, am i happy. it is a daily driver and sounds just so classic and wonderful.

viewtopic.php?f=13&t=304362

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Fri 10, 2018 9:25 pm 
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well,

after using this, I have found out that the tweeter is really bright and sort of piercing.

when I disconnected it and allowed the mids to just play with the woofer, the set sounded much better and not so tiring on the ears.

I padded down just the tweeter in each cabinet so its amplitude is just a bit above the two mids.

the set sounds even better. it is nice and crisp with detailed highs that are not at all overbearing and ear irritating.

I can crank it up now without the HF bothering the eardrums so the bass just pounds.

dad came down to the shop today with me. he even said that it was just too sharp and "treble-ley" as he put it.

I am extremely happy. even dad is too :) .

I would say that the tweeter was cut down 50% from its original volume and now balances with the midrange and bass drivers.

excellent :!:

steve


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 12, 2018 4:10 am 
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DR,

As a matter of fact, those JJ tubes are about the only ones my Sherwood doesn't immediately incinerate. That amp destroyed a matched pair of what was good GE oval plate 6BQ5, took about four months.


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 12, 2018 4:57 am 
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that is good to know about the JJ.

of the very few new production tubes that i have ever used, JJ seemed to be very good.

i used a pair of 6L6gc JJs in a scott amplifier and these two pairs in this motorola amplifier.

yea, i have the good NOS and used good american tubes, but they will be in storage since the price of them are going out of sight.

notice the price of 5U4gb and the 6BQ5 tubes lately ?? holy smoke, only a few years ago, i bought 15 NOS 5U4 for a mere 20 bucks plus shipping. i also bought nice sized amazon box of used good ones at a fest for $10. about 10 years ago, i bought a pile of the soviet rugged 6n14-p/n or something like that for $20. that's not happening anymore.

steve

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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Sun 12, 2018 11:45 am 
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Dutch Rabbit wrote:
that is good to know about the JJ.

of the very few new production tubes that i have ever used, JJ seemed to be very good.

i used a pair of 6L6gc JJs in a scott amplifier and these two pairs in this motorola amplifier.

yea, i have the good NOS and used good american tubes, but they will be in storage since the price of them are going out of sight.

notice the price of 5U4gb and the 6BQ5 tubes lately ?? holy smoke, only a few years ago, i bought 15 NOS 5U4 for a mere 20 bucks plus shipping. i also bought nice sized amazon box of used good ones at a fest for $10. about 10 years ago, i bought a pile of the soviet rugged 6n14-p/n or something like that for $20. that's not happening anymore.

steve

especially because I like to use these on my Packard Bell, (the amp is visible)

https://www.ebay.com/itm/GE-5U4-GB-Vacu ... itleDesc=0


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 Post subject: Re: Motorola SK14M HiFi Stereo Questions
PostPosted: Aug Thu 16, 2018 5:14 am 
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other than the turntable being there for looks, I am extremely happy with the way this turned out.

someday I might find a TT for it, but I'm not really interested in doing so right now. I would rarely use it anyway. I have it hooked up to my shop's computer playing my 7k playlist. I will do the same by hooking it up to the baseband audio wall jacks that is part of my whole house speaker system when I load it up and take it to my home.

I am quite impressed with the JJ 6BQ5 tubes.

also, I'm very glad that I attenuated the tweeter. it was so shrill, sharp, overbearing, and bright. it is now matched in amplitude with the woofer and mids in each cabinet. the front baffle now sounds well balanced without the screaming tweeter. I can now crank it up to hear the booming bass and to not have my eardrums pierced out with shrill treble.

it sounds fantastic.

here are the final pics.

steve


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