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Polytone Taurus Elite - Some assistance, please?

Started by WimWalther, July 28, 2023, 01:41:15 PM

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WimWalther

This is a new-to-me Polytone TE, made in 1997. First thing, I can't find a schematic that's specific to the model. In fact, the one I'm using doesn't even show the power amp or the speaker wiring. What I've found is available here:

https://drive.google.com/drive/folders/1OrH3eF8Fvftk0LxFIvtqVoZEsBE7Gi6k

My PA uses the MJ802 / MJ4502 outputs and may match one of the 110W drawings in the above folder.

One other question: The footswitch is missing. Does it use latching or momentary switches? (I'm assuming the former..). Anyone have a spare?

Oh, also, please take a look at the photos.  See the flying resistor? The caps too small for the clamps, shimmed up with foam tape? The general ratty wiring? Has someone modded it, or are these all "stock features"?

Thanks in advance, more to come as time permits.

WimWalther

#1
Oh this is lovely.

I tried to unplug the spade connectors from the 15" driver so I can make a power measurement of the amp, and the black "board" that holds the lugs popped right off the frame.

So now I need to remove all of the spades, and remove the driver to fix the terminal board.. which probably means removing the power amp as well. Cripes.

And this, because some Chinese guy couldn't properly set an aluminum rivet!

WimWalther

Got all that taken care of. Well.. almost. It seems that the terminal lugs on the no-name driver are some weird intermediate size: 0.205" aka 5.2mm. None of the 3 standard size connectors will fit - either too small, or they fall off. So now I get to deal with that idiocy.

Btw, the PA is rated at 125W.. and while it makes 135W at hard clipping, it maxes out at 80W clean.

Is this normal for SS gear? Am I talking to myself here?

phatt

Hi wim, first up, Does the Amp work as per normal?
For that era the Foot switch is likely a latching type.
Use what you have or use an open plug and bridge the terminals you will soon work out if it's latching or not.
I have no idea about the flying resistor, hard to tell what it's connected to??
As for the Caps padding, Yes often done when they run out of parts.
As I've never seen these amps, looks like it's a budget brand so could be factory layout.
(I've seen worse from Early Roland amps)

Re Speaker issue,, why not use the original spades?

80Watts clean from 130 Watt rig is par for most gear,, Sand or Glass

Phil.

WimWalther

I have almost no experience with instrument amps, and this particular amp is new-to-me. IOW, I don't know what's normal for it.

Can't reuse the old terminals as some idiot (...) threw them away!

I've concluded that the driver may be a replacement. The flying resistor is in series with the vol pot for the tweeter horns. It's a 50R 5W part that acts as a hard limit to prevent burn-out. Mfr's DS for the tweeters calls for 30R, but I guess 50R is close enough. Guess the new driver didn't have a place to mount this resistor?

The FS is definitely the latching type. I bought an original off ebay, it's on the way. Needs the actual switches replaced.. theyre on the way as well.

I don't believe that Polytone was a budget amp.. but I haven't found any MSRP info yet.

Thanks!

WimWalther

#5
Re: Polytone MSRP

Glenn Murch at Murch Music up in Canadia recalls that back in the late 90s the mid-line Polytone Mini Brute II retailed around $900 (CAD, I assume?) The MB II is a single channel amp with a single 15" driver.

Based on that price of $900, the top-line Taurus Elite (3 discrete channels, pair of piezo horns, Hammond spring reverb, "modulator" Leslie effect circuit) would have been well above - perhaps around CAD$1200-1400? Fyi, the USD :: CAD exchange rate was about 1:1.4 in 1997.

Doesnt sound like a "budget" or "bargain" model to me.. but my knowledge of late 90s amp prices is weak at best.

Tassieviking

They are usually very clean sounding amplifiers as they were aimed at Jass Guitarists more then anything else. They are known to clearly reproduce the sound of the guitar and not "colour" the tone, something that most other styles are looking for.
The are also good with other instruments where you want the clean true sound to come through the speaker.
Acordians, mouth organs and piano etc used them when amplification was needed as well.
Its just a case of the right tool for the job.
There are no stupid questions.
There are only stupid mistakes.

Tassieviking

There are no stupid questions.
There are only stupid mistakes.

WimWalther

#8
Hey, thanks for posting those. What I'd like to see now is a cabinet wiring schematic.. but I've so far been unable to find one.

Quick question: The amp uses a pair of Motorola KSN-1005A piezo tweeters, wired parallel. The mfg data sheet specifies a 30R series resistor to prevent burnout at high volumes. But since it has a parallel set, should this value drop to 15R? Or I suppose each tweeter could have its own 30R part?

FYI, as received the amp had a single 50R part in series with the parallel pair. This looks like a later (sloppy!) mod that was done when the 15" driver was changed.. or at least I think it was changed, as the soldering is really amateurish.

Tassieviking

#9
Quote from: WimWalther on August 19, 2023, 08:48:19 PMThe amp uses a pair of Motorola KSN-1005A piezo tweeters

The amp should have an Ampeg custom 15" speaker or an EVM-15L speaker,if there are any tweeters in it they would have been added by someone at a later date.

If it sounds good, leave the 50 ohm resistor in there, two tweeters would likely be too loud with a lower resistance to them.


Thinking of the wrong amp, must stop posting at 5am and get more sleep.
There are no stupid questions.
There are only stupid mistakes.

WimWalther

#10
The driver turns out to be an Eminence 15" made in late 1997. I'm now assuming it's the original part. The codes from it are:

15504 15504 4OHM
  67-97320056 G2

The two tweeters are definitely original, all TE models have them. The 50R series resistor is just a "hi-limit" part to prevent burnout. It wasn't properly installed, really appears just scabbed-on by some hack.

I'm debating replacing it with a 20R, as that's closer to the datasheet spec.. haven't really decided yet, might try both values.

There is also a separate Volume control just for the tweets, it's a 25K pot in series with the tweets + 50R hi-limit. So no worry about too much tweeter level.

Tassieviking

I would only replace the resistor if the amp is not sounding right, if you have enough highs coming out then leave it.(Maybe clean up the mess a little bit)
If you do decide to change it then you might need a higher wattage for the resistors you put in, and then you also have to make sure that the L-Pad can manage the higher load as well.
I am presuming the pot you mentioned is a L-Pad or a wirewound high power potentiometer that controls the tweeters.

The 50R resistor might have been a late change in the factory or it could have been performed as an upgrade or recall from the factory but performed at the local service center.(back of the local music shop).
There are no stupid questions.
There are only stupid mistakes.

WimWalther

Turns out that the 50R was intermittent open, and the reason the horns weren't running. Stupid thing measured fine on the bench but acted like 1-2M under load. Now it's gone, the horns work, and there's a 20R 5W in its place.