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Old 05-05-2008, 11:25 AM   #1
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Polytone MiniBrute II assistance needed!

Got this li'l freak on repair.Symptoms:
1.The original loudspeker is missing (some cheap OEM instead).
2.The reverb doesn't work properly,as the reverb pot is turned clockwise there's an increasing "shhhh" noise coming out.However,the reverb tank is intact (just measured it).
3.The owner complaints that the amp is heating excessively.I ran it on the bench on moderate volume without the back pannel and nothing of the sort.I didn't get out yet the driver/output stage circuit as it's placed on the bottom of the combo and I hate touching that mineral wool inside the box but I saw two big,old electrolytics in a very poor state (surely,amongst others,this amp needs a full recap job as all the electrolytics are "originals").
And now,the issues:
1.The front pannel logo says "Mini-Brute II" but the back pannel plate says "model Mini/Teeny Brute 90 Watts Serial No. P-6202".What model am I dealing with?
2.No matter what about the above,I did find some Polytone schemos here:
http://www.murchmusic.com/polytoneserviceinfo.htm
but nothing looks like the amp I have on the bench.The most confusing thing is that on the schemos I see 4558s,071,LM358 and 301 IC's but on the amps' PCB there are (from left to right) LM301,LM1303N,LM301,TBA231,TBA231.
Does anybody have a valid schematic for this amp?I'm kinda lost,please help!
3.What might be the most appropriate replacement driver for this amp,assuming that the owner wants to keep "that specific Polytone's voicing"?
There are some rumours that the original,4 Ohms' Polytone's driver is (or was,for that instance) some kind of Eminence.Any thoughts?
Thank you!
Regards,
Attached Images
File Type: jpg Polytone Minibrute II pre detail 02.jpg (415.4 KB, 77 views)
File Type: jpg Polytone Minibrute II pre detail 03.jpg (473.7 KB, 59 views)
File Type: jpg Polytone Minibrute II pre detail 05.jpg (281.7 KB, 56 views)
File Type: jpg Polytone Minibrute II pre detail 06.jpg (483.6 KB, 69 views)
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Old 05-06-2008, 01:35 AM   #2
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I have some older schematics, not sure how well they will scan. Have you contacted Polytone and asked?

http://www.polytoneamps.com/

All the drivers I have seen in them have been Eminence. I think of these in terms of PA systems. Like a keyboard amp, so a full range speaker rather than a guitar speaker.

I don't have a problem with the insulation, it hasn't got into my skin so far. But some disposable plastic or rubber gloves would work.
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Old 05-07-2008, 09:10 AM   #3
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Hey Enzo,
Thanks for your comments!
Quote:
Originally Posted by Enzo View Post
Have you contacted Polytone and asked?
http://www.polytoneamps.com/
No chance.They have no e-mail address and a phone call is out of question from where I live due to outrageous local fees.
Besides,I read some Polytone users' comments about the poor customers' service over the phone (something related to an old lady/secretary unwilling to cooperate)...not necessary true,but I'm not in the mood to spend big $$ on a trans-oceanic phone call just to get some evasive reply.
Quote:
Originally Posted by Enzo View Post
I have some older schematics, not sure how well they will scan.
If I'm not asking too much and when you got some time for it,please try scanning those schemos and post them somewhere (or send them by mail)...TIA!
Quote:
Originally Posted by Enzo View Post
All the drivers I have seen in them have been Eminence. I think of these in terms of PA systems. Like a keyboard amp, so a full range speaker rather than a guitar speaker.
Very useful info,thank you!
Quote:
Originally Posted by Enzo View Post
I don't have a problem with the insulation, it hasn't got into my skin so far. But some disposable plastic or rubber gloves would work.
I'm some kind of a "Terminator" myself (I have very resistant hands' skin on a wide variety of textures and chemicals,with no side effects whatsoever)...but not on the mineral wool,wich gives me some noticeable irritation.Wearing rubber gloves does solve this problem but I'm kinda "old school",always prefer working with bare hands.
Regards,
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Old 12-31-2009, 10:55 AM   #4
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Any luck with your reverb ssssh issue (#2)? I've got the same thing...THANKS!
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