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Cavalier is right. Especially with the two cables connected to the amp, but not the tank--two antennae there.
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04-29-2016 03:54 PM
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You might want to try that same test again making sure that all lights, TV, Washing machine etc... are switched off. In my case I noticed that when the dining room's dimmer is on downstairs, my Polytone in the room upstairs also does a particular kind of hum.
Last edited by Zack; 04-29-2016 at 04:14 PM.
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I have gone ahead and re-installed the reverb tank and reconnected everything.
Originally Posted by Greentone
I have my amp(s) in a cabinet here at work so I can close the doors and all seems... normal... So I took the amp out of the cabinet and plugged it into a different power source and the pulsing stopped.
At least this is something external to the amp!
Otherwise, I'm totally wowed by the sound of this amp. I should make a clip just to see if I can capture the sound it generates from my two Gibsons.
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Whoa! New NAD. I bought a six channel Polytone MiniBrute PA for my son to use as a keyboard amp. The price was right. I have owned a three channel Mini Brute PA for years and love it. Derned. I am sorry I am giving this one away. It is the best sounding Polytone (into my MB III cab) I have ever played.
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Still works:
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Hammertone
that was Polytone's big bass amp in the day. It is on the cover of my Polytone owner's manual.
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Do you have an actual, printed/bound manual? All I've ever seen is a couple of rather poorly photo-copied sheets of instructions.
I'd love to get an actual Polytone manual.
I'm kind of a manual geek... I just love actually following instructions to learn how to do stuff.
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Yes, I have an actual, glossy, bound Polytone owner's manual from the early 80s.
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Some of the cool Polytone paraphernalia that Gumina supplied to dealers back in the day included autographed 8X10 glossy photos of Joe Pass endorsing Polytone, and Ray Brown doing the same. I think there were also glossies of George Benson and Herb Ellis.
I have the Joe Pass and Ray Brown glossy photos somewhere around here. Keith Murch probably has a drawer full of them.
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Hi folks, finally found a tech to have a look at my amp at about 40 mns drive away. But in fact, traffic is so horrid that it took a whole hour.
He himself found it impossible to date to get his hands on a schema and is still looking. The good news is that the amp is in top condition. The speaker's fine, which I'm relieved about as it'd be next to impossible to find the same.
The control were tested and they're fine , delivering good ranges of modulation. The only stuff that needs definite attention is the jack input for the guitar lead. He's going to check the whole circuit, etc... & I shld get it back on The 05/05.
I feel so much better now!
Sent from my VF-895N using Tapatalk
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Found that site in case it can be of any help.
Quite a list of polytone schematics.
Polytone Schematics
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For the record, here are the pics i took when i changed the caps in my polytone.
It's a 86 and not a 83, i remembered a bad date. Which goes with the description that was given earlier (mid knob, colored tolex)
hope someone finds it interesting
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That's interesting, Zack. Yours is the first '86 I've seen with black diamond Tolex. Transitional amp--it has the mid-range like the smooth black Tolex amps. Nice amp.
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it Greentone was reacting to my pics, then it's not that much of a hear scratcher, since mine is actually not a black diamond tolex amp, but a red tolex amp. which corresponds to your description i think: 4) fourth series ('85-'90?)--black, grained Tolex covering; black grill cloth--not foam; plastic "P" Polytone logo on lower left of grill; first amps to have "mid" knob; with, i guess a kind of special edition ugly-as-hell red tolex thing? Originally Posted by Greentone
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Hi everybody! I discovered this forum a number of years ago, and I've learned all kinds of valuable information from it, but this is my first time actually posting. I've got a bit of a problem with an old Polytone that I recently acquired, and I'm hoping that some of you will have the sort of expertise that could help me fix it.
I got a Polytone MiniBrute IV (15" speaker with reverb) a couple of weeks ago. This is either a late 70s or early 80s model, I think, with a red concentric distortion knob on the volume pot and a velvet covering with a foam grille. Anyways, it was working great for a while, then last night at a gig I got very little output, some consistent volume modulation, and a very unpleasant sort of distortion on what little sound there was.
As a bit of backstory, I was returning from a gig the other day and heard something hit the pavement, and when I checked it was one of the screws from the bottom of the amp (holding the power section chassis). I replaced it and tightened the other screws, but did not try the amp again until the next day, when I noticed this volume issue. Perhaps that loose screw caused the problem, I don't know. I did open up the cabinet upon returning home yesterday, and did not notice any obvious problems, e.g. loose wires or obviously fried components, and the power section of the amp is again securely mounted to the cabinet. I'm at a loss, as I'm no electronics expert, but if anybody has advice before I go through a lengthy tech-search, I would greatly appreciate hearing it! Thanks.
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Greentone will likely be along soon w/ a possible answer, he's the resident Polytone guru.
yesterday I picked up a Mini Brute IV from the 70's like yours.
I had another Polytone a few years ago that had the same issue you describe except the loose screw.
never did figure it out and sold it as is.
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Greentone here...but maybe not to the rescue. I'm trying to figure out how the screw fell out of the amp. Screws that hold the preamp in place (top of the cabinet) are, IIRC, screwed through the cabinet from the outside. However, the hold down screws for the power amp (bottom of the cabinet), again IIRC, are screwed to the cabinet from the inside, no?
If one came loose, it would have to migrate all the way out a jack hole. Do you think that is what happened?
Meanwhile, I suspect that there is something else going on in your amp. First: are you sure that you didn't accidentally turn on the red distortion concentric knob? I believe it's designed to work in one of three ways: (1) red knob off, black volume knob set to volume desired = clean sound; (2) both knobs on, set to volume desired = gritty, edge of distortion sound; (3) just the red knob on, set to _desired??_ volume, black volume off = completely useless, distorted sound...sounds like a bag of bees. Polytone thought they were "keeping up with the times," I suppose, but this distortion is about as hip as your grandmother pole dancing.
If the red knob was, in fact, off, then there is something amiss with the amp. I have a Polytone MBIII in my shop right now--though not on the bench--that has a low volume with distortion. Could be a similar deal. When I get a chance to look at it I'll give you a heads up. There's several things that could be wrong, but the good news is that there is sound coming from the amp. That's generally easier and less expensive to work with than when there isn't any sound.
GT
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I have the same amp and have occasionally had this issue, although not recently. Most of the times it was the distortion knob - I couldn't pinpoint what was causing it but turning it rapidly back and forth and making sure it was actually off fixed it. Rarely I would get the same kind of sound issue and had to pump the volume (not silently, with a signal coming through) - like turn the volume from minimum to maximum a few times - and the sound would come back to normal, albeit loudly, while the volume was cranked. Not too scientific of an answer but hope it helps.
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Ah, thank you everyone! I'm still having the problem, but I went through a couple of troubleshooting steps:
First, I can attest that the distortion knob is not the problem. It was the first thing I check at the gig, and following rio's advice did nothing to alleviate the problem. In fact, the distortion circuit seems to be functioning with no problem (aside from having the same volume issue). I can also report that the bass knob appears to be acting almost like a volume control; with the knob rolled off there is even less volume, and when raised near the maximum end of the sweep it drastically increases the volume, without alleviating the distortion. Additionally, the amp cuts out for a second after volume-spiking from this treatment.
Greentone, I could be mistaken about the function of the screw that fell out, as that was pure conjecture on my part, but it is one of four such screws in the bottom of the cabinet, screwed in from the outside. Regarding, the red knob, it functioned exactly as you describe prior to this problem, although with the caveat that it couldn't be nearly as hip as the hip my grandmother would throw out while pole dancing.
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Those do sound like the power amp hold down screws...I just didn't recall them being external.
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Buying a 1985 Polytone MB IV this Saturday. $150 supposedly in "fantastic" condition.
Never played thru one and would like help dailing in a great Jim Hall, Peter Bernstein tone.
Playing on a Godin Kingpin II, heavy round wounds, thick pick.
Any help from you Polytone veterans would be great.
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$150?
quite the deal!
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Okay. I have a couple of MB IV amps. First, set the volume half-way up, regardless of whether or not you are going to play softer than that--control the volume from your guitar.
Second, set the slide switch on the middle position, neither "dark" nor "brite." The middle position gives you the sound that most jazz guys use.
There are two inputs. I don't know how hot the Godin pickup is. If it is any less hot than a Gibson humbucker, use the high input.
Don't use too much reverb--the reverb on the Polytone isn't _that_ great sounding. I'd advise going with a setting of about 9:00 o'clock to 10:00 o'clock.
Vis-a-vis the tone stack, keep the distortion control completely off. It is one of the great suck-o knobs of all time. Now, try bass on 10:00 o'clock. Put the treble on whatever suits you. I find that on a Gibson-type archtop that ends up being about 1:00 o'clock or so. If the amp was made truly in the mid-80s it will have a mid control. Set that about 12:00 o'clock. You should be good to go.
Control the overall "tone" from your guitar by rolling the tone control back to suit your ears.
I just looked at all of my Polytones and the tone stacks are more or less what I just reported above. The amps sound great.
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$150 is an awesome deal. I picked up my mid-70's MBIV about a month ago from a Forum member for $300, and felt like I got a good deal.
I have been tinkering with the settings on mine (including this morning based on this post), and currently set the bass knob straight up at 12:00, treble at around 9:00 (no mid-knob). I also keep the "dark/bright" switch on "dark," rather than the middle position as Greentone does. To me it really shifts the amp into that smokier sounding jazz mode -- could be function of the guitar itself (a thinner bodied Campellone).
I've used both the hi and lo input jacks. Even with the lo input, I find I can't turn it up past 9:00 - 10:00 without getting yelled at. (I keep the guitar volume at about 1/2 - 3/4.)
Agree that the distortion knob is not useful -- played around with it one day, then clicked it into off position and haven't turned it back on. The reverb is OK, but I mostly keep it off and use a pedal. I live in an old, old house with wide board plank floors, and if you get anywhere near the amp with the reverb on it sounds like a shelf full of dishes crashing. Also, when turned up, feedback begins to occur -- no idea why (microphonic something or other?). Easier and better sounding just to use a pedal.
Good luck and hope it turns out to be everything you're hoping for.
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I have a theory: the distortion on Polytone amps is there to discourage players from using distorted tone...
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