Polytone Mini Brute IV

**bmw2002** · 01-13-2017, 11:48 AM

Originally Posted by lawson-stone

I have a theory: the distortion on Polytone amps is there to discourage players from using distorted tone...

I was under the impression Polytone started off as accordion-centric amps, and later found favor in the guitar world. In any event, would love to hear an accordion version of In-A-Gadda-Da-Vida.

**Greentone** · 01-13-2017, 04:50 PM

Yes, Polytone was founded by a jazz accordionist who also made bass, guitar, and keyboard amps.

**Cunamara** · 01-13-2017, 07:25 PM

Apparently the Minibrute came about at the request of Joe Pass, who wanted a small light amp that approximated the tone of a Fender Twin Reverb.

**mrcee** · 01-13-2017, 08:58 PM

Originally Posted by Greentone

Yes, Polytone was founded by a jazz accordionist who also made bass, guitar, and keyboard amps.

Jazz accordionist Tommy Gumina

**TimPeak** · 01-14-2017, 01:31 PM

Update: the amp wasn't the one in the craigslist ad.

The guy was 70 years old and said the amp has sat in his closet. I plugged it in and BOOM!

The volume on the master was off and my guitar vol was off. Just a loud booming noise.

The seller said it must be dust in the input so the signal is blocked. ????

I've played in blown heads before, but I've never heard anything like this before.

Didn't buy it....but...the damn thing looked brand new! It also had a mid dail. It looked exactly like this one:

polytone.htm

What would you do? Lowball for $50 and take it to the shop, or just forget it?

Still can't get over how new it looked.

**lawson-stone** · 01-14-2017, 01:35 PM

$50... I'd buy it for parts or even restoration if it wasn't too badly damaged. Could just be a problem with the distortion channel.

**bmw2002** · 01-14-2017, 01:44 PM

If you have a regular or recommended amp tech, perhaps give him/her a call first and get a "it'll likely cost you at least $x00 to get it up and running again."

My instructor has an early '80s one that he just had revamped and I think he spent around $150 or just getting it in good shape -- and it worked before that (no booms).

If it's great cosmetic shape, it might be worth it to take a chance.

**wintermoon** · 01-14-2017, 02:11 PM

offer him $50, if he says no ask if he'll meet you 1/2 way @ $75.
even if its something major you can still sell it later and easily get your money back.
btw isn't that a 90s model? Greentone would know.

**TimPeak** · 01-14-2017, 02:43 PM

Seller accepted my offer of $80. Picking up tomorrow morning. Wish me luck.

**TimPeak** · 01-15-2017, 04:08 PM

$80 later (plus a can of Deoxit Contact Cleaner) I have an amazing sounding amp. I've been chasing tone for a long time. I'm hooked.

Turned out to be a PT MB IV circa 12/1995 with 15".

Sprayed contact cleaner in the pots and on my jacks. Inserted and let it stew for an hour. Voila. Like new.

Anyone wanna buy a brand new Roland Blues Cube Hot?

**Greentone** · 01-15-2017, 04:56 PM

TimPeak,

Glad you worked it out. What a find! I also have a mid-90s MiniBrute like yours, although it's a III. (no reverb) Not only does the amp sound great, it's built like a tank. This amp gets gigged about twice a week, or so, and has been for at least the last 20 years without fail. It has been used for guitar (solid body and archtop), electric bass, and upright bass, and keyboard chores. Both I and my son just throw it in the car and go.

Unless anyone has a supply of red kryptonite I don't think there's any likelihood that this amplifier can be killed.

I think you have found your amp. Enjoy.

**Greentone** · 01-15-2017, 09:43 PM

Here's my Polytone MiniBrute III (mid-90s version) at a gig. I played the gig with my son. He used the MBIII and played a Gibson L-6S guitar into it. I played my '68 Stratocaster into one of my 5e3 Deluxe amps.

Polytone Mini Brute IV-polytone-minibrute-iii-jpg

Polytone Mini Brute IV-polytone-minibrute-iii-jpg

**MisterNL** · 03-05-2017, 06:02 PM

Hi. I'm trying to bring new life to the MBIII bass amp I bought in 1980. It needs a speaker upgrade, since the original was poorly replaced back then.

What are the impedance requirements? Internal at 8 ohms, with the potential for another 8 ohm external resulting in combined 4 ohms?

Any specific recommendations?

Thanks for your help. This seems like the most knowledgeable polytone info source.

Norm

**r_cc_c** · 03-05-2017, 11:39 PM

I only know of two types of 12" speakers for MBII (not III)

Eminence 121124a. This is a OEM model which Eminence does not sale in retail.

And more recently

Polytone branded 12" speaker with big magnet which is made in China.

Both are 4 ohm.

**Stringswinger** · 03-06-2017, 12:08 AM

Polytone speakers were 3 and 4 ohm depending on model and are no longer available. You can use 8 ohm speakers (and will suffer some power loss) or use one of the available 4 ohm speakers as a replacement.

**BigDaddyLoveHandles** · 03-06-2017, 01:48 AM

Speaking of 4ohm speakers, does anyone have an opinion in Warehouse Speakers? I know their models are available in 4, 8 and 16 ohms.

**vintagelove** · 03-06-2017, 09:39 AM

Originally Posted by BigDaddyLoveHandles

Speaking of 4ohm speakers, does anyone have an opinion in Warehouse Speakers? I know their models are available in 4, 8 and 16 ohms.

Im very big on WGS speakers, haven't heard one I think is bad yet, prefer them to celestion in many cases.

**Greentone** · 03-06-2017, 04:21 PM

Which covering do you have on your MBIII? (I ask because it makes a difference in the speaker.) Do you have the one that is covered in felt, or the one that is covered in black, diamond-patterned Tolex? The felt-covered MBIII usually has a 3-ohm CTS speaker; the Tolex covered one has a 3-ohm Eminence speaker. Both speakers are 15" units. Both sound excellent in the amps. The difference is that each fits in the cabinet slightly differently. The Eminence won't just smoothly fit into the holes for the CTS and vice versa.

I have a 70s an 80s and a 90s unit. Each is a bit different from the other. All three sound outstanding.

You _can_ replace with 8-ohm speakers, but the amp really sounds best with a 3 or 4-ohm unit. It _works_ the amp.

**EarlBrother** · 03-08-2017, 05:49 AM

Watson i have the same Polytone but no problems had it since the 1980s.It has low miles on it.But i am gonna start using it more.Hope you found the problem and better yet a way to fix it.I did discover one(this has nothing to do with your issue)day that turning my amp toward the wall got me the tone this thing is known for.That is in my practice room.Havent played it out doing that wonder if would have same results any way.Hope you find the answer.E

**Tcaron20** · 03-23-2017, 09:36 PM

My mini brute has sat unused for a few years but with my recent adventure into Jazz and a new archtop I hoped to give it a new life. Unfortunately the reverb stopped working, probably an easy fix, but more troubling is that as I post it the volume fades and sound starts to distort.

Any ideas? Out of all my amps the Polytone sounds the best with the archtop.

Thanks,
tom

**Greentone** · 03-24-2017, 08:29 AM

Twist the distortion and the volume knob each fully back and forth about twenty times.

**Tcaron20** · 03-24-2017, 08:34 AM

Would component cleaner shot into the volume and distortion knobs help?
Your suggestion is interesting because the distortion does not work either.

thanks

tom

**GNAPPI** · 03-24-2017, 09:55 AM

I've never been in the innards of a Polytone, but intermittent problems in SS electronics can be solved. They're better than hard errors.

In the order of most likely causes...

1. Volume pot internal issues. Clean with a quality contact cleaner or replace the pot.

2. Cold Solder. Touching up solder / reflowing connections on the PCB's starting on the pre-amp and power supply sections. Cold solder causes the same symptoms as #3 and other than scraping off the resist etch the repair is the same.

3. PCB cracks. Usually occur around large devices like caps. See image below.

4. Heat sinks. When heat sinks are made, they either drill or punch the mounting hole and little aluminum extrusions will keep the transistor from seating on the sink. When heat sink grease is applied initially it closes the gap, but over years the grease dries, or migrates and an air gap is left between the sink and device. Unscrewing the device, scraping the extrusion and re-applying heat sink grease is the repair. See image below.

4. "Fretting" corrosion on tinned lead connectors. Re-seating connectors, re-flowing solder on connector pins, or removing connectors totally and soldering interface wires between PCB's directly. Peavey has had this issue.

5. Loose speaker terminals. Solder or re-tension the connectors.

6. Defective interface wires between PCB's. Replace wires or see #4 for other solutions.

Polytone Mini Brute IV-pcb_crack-jpg

**Tcaron20** · 03-24-2017, 12:31 PM

Hey Gary,

Thanks man! Moved the volume and distortion knob 20 times with component cleaner, left it one for an hour and it seems to be fixed. Too early to be sure, not ready to gig with it yet. Hate to loose this amp, sounds too good with my Jazz guitars.

Distortion does not work but it is pretty bad anyway, never use it.

did the same with reverb know and it too came back. I want to put a 3 spring in it but am looking for advice as to what screws to remove to get to it. Hate to Take changes that I ruin something else?

Thanks,

tom