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Author Topic: Polytone Taurus Elite amp low volume no schematic!  (Read 21876 times)

DrGonz78

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #15 on: July 29, 2013, 02:01:39 AM »
You can also rely on fileden.com for upload of these files, as it is a simple to use file server site.
“A person who never made a mistake never tried anything new.” -Albert Einstein

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #16 on: July 29, 2013, 06:02:43 AM »
i have been trying for 4 1/2 hours to load the photos i took.i tried to goto fileden.com and i can't even connect with the site to start an account. i also tried photobucket with no results.it's 5:58am and i'm going to bed. i'll try again in the morning.maybe it isn't yahoo friendly.maybe its because the photos are in documents and settiongs administrator.i really don't know. it should take under a minute to do this and it is really a hair puller. anyone else have any ideas on uploading these ,so they can be viewed by others that the pictures may help. i did see one fellow asking where a wire went on the same amp. my picture might show him. it was an older post ,but who knows he might still need the info...ed!

DrGonz78

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #17 on: July 29, 2013, 06:18:10 AM »
yeah dude go sleep at that point!! I hate when crap like that happens, as it is like the World Wide Web is against you!! Don't worry man it all works in the end... or so I was told too  :trouble
“A person who never made a mistake never tried anything new.” -Albert Einstein

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #18 on: July 30, 2013, 03:03:41 AM »
lets see if this works! i cut and pasted the browser into this post....ed!


http://s1093.photobucket.com/user/edwardeffect1/library/#/user/edwardeffect1/library/POLYTONE%20TAURUS%20ELITE?sort=3&page=1&_suid=1375167601484007348028784194593

going to put the amp back together today to do more testing.thanks for your patience.it's 3:15am and i woke up thinking how to make this post so eveyone could view the pictures i took.i do my best thinking in my sleep.when i try to learn a guitar song i play it before i go to bed.then i end up playing the song back in my head during sleeping.it works...ed
« Last Edit: July 30, 2013, 03:17:47 AM by EDWARDEFFECT1 »

DrGonz78

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #19 on: July 30, 2013, 04:28:06 AM »
Well it is good to have the pictures online so everyone has an idea to see the Rat's nest we are working on here. I love Polytone amps but looking inside of them it is always a wonder how they sound so good... I follow all the advice given thus far from Juan and others... However looking at the pics I have to question what caused the browning of the circuit board here... Did you inspect the traces on this part and test the mylar film cap for any damage?

“A person who never made a mistake never tried anything new.” -Albert Einstein

Roly

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #20 on: July 30, 2013, 05:52:32 AM »
Can you find good main power rails, like +/-40 volts?

Can you find good preamp supply rails, like +/-15 volts?

Have you tried injecting a signal into Fx Return?  What happened?
If you say theory and practice don't agree you haven't applied enough theory.

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #21 on: July 30, 2013, 12:47:38 PM »
tried a cascio keyboard thru the effects return.amp has the same low volume.about the same as going thru the input of any of the three channels.the brown in the picture of the mylar cap is solder rosin. the cap climbs to .809k in circuit..it probably is good,it probably is reacting to other components in the circuit.without a print who knows.as for the rail voltages i don't know how i can take any readings off the transfromer board side of the circuit.it has 2 short wired connectors (moldex connectors) to get any voltage readings off that area i would need to have  2 or 3 ft jumper connectors with modex connectors. i believe the odds are high for it to be a preamp problem as there are 3 channels and for all to be bad would be not likely. if i had a huge volume gain thru the effects return i would say lets look at the preamp circuit ,but thats not the case.any ideas?...thanks...ed!!
« Last Edit: July 30, 2013, 05:33:56 PM by EDWARDEFFECT1 »

DrGonz78

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #22 on: July 30, 2013, 07:47:54 PM »
Here is the power schematic for a mini-brute and I am pretty sure they are very close. Look on the board for where the transformer plugs into the power board. Should be easy to start checking for voltages around caps too. Look at the regulators to provide other various voltages to the preamp...

P.S. I could not find the thread where I got these pics... I searched but could not find it... Thanks to that poster for these pics and schematics.

Double P.S. The 378B looks more like it here it is...
« Last Edit: July 30, 2013, 08:10:15 PM by DrGonz78 »
“A person who never made a mistake never tried anything new.” -Albert Einstein

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #23 on: July 30, 2013, 08:40:37 PM »
i can check the parts on the board ,but i need to extend the wires that go to the connectors as they are only about 2-3 inches long.i can't turn the board upside down to get at the board with this situation to measure anything with the power on due to this situation..i measured all the capacitors. transistors were checked with a diode test on my fluke 87iii meter and a radio shack diode tester and they all tested good.all resistors and diodes were also good.solder joints looked good.both 50volt 8200uf capacitors were checked and measured good on my sencore ca55 capacitor checker which tests caps under a load.if i had 4 molex connectors of the right size and gender i could extend the wires and check everthing.i'm sure that is what they did at polytone when they were in business....ed!!

J M Fahey

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #24 on: July 31, 2013, 12:27:04 AM »
That amplifier is crazy, it's a mess .

Quite probably it was kludged to use some surplus stock.

The channel PCBS are CRAZY: they look like "all inside one big PCB" jobs, with power amp and PSU together with the preamp ... and they filled only the preamp holes, leaving 80% of each board empty .... CRAZY.

That said, you were LUCKY because they used a "known" power amp, the exact same that DrGonz posted <3)

The only (unimportant) difference is tha the "official" one uses a dual transistor while the one to repair has 2 separate TO92 ones.

I suspect the Power amp works, that you have a connectors problem or something, but to check it, feed 1 or 2 V RMS 1KHz into what's labelled as "input" or "R1" into the official schematic.

Load the amp with 8 ohms (we don't want maximum power yet but to see how it behaves), scope it, and start raising input signal until output starts clipping, then back a little to *almost* clean.

I want to check whether we have a real sensitivity/power problem or not.

I guess not, but let's confirm.

And such problems are best solved in a *functional* way, checking how *systems* actually behave, compared to what's expected, not measuring part by part.

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #25 on: August 07, 2013, 11:57:03 AM »
sorry Juan!
  i worked on my car the other day and one of my knees has been hurting since.had to carry the amp down stairs to the basement where my funtion generator and scope are.that is why i am posting this so late,sorry!! i'm not sure what i have to do here. i have the signal generator on 1khz with a sine wave and i just switch between the voltage scale and the time scale on the scope and with the signal generator and scope clips attached to each other i get a sine wave on the scope.when i clip onto a 1/4" input jack with the signal generator and attach the ground lead of the scope to a speaker terminal and probe the other speaker terminal i don't get anything on the scope. it's probably me. i switch the scope thru different voltage scales and time periods with no result.....i really need help with the scope. i tried to calibrate it by touching the calibrate with the test probe and tried to make a connection with the ground connector on the scope and when i turn the calibration dial i see little difference.guess i need some tutoring with this .its a b&k scope....ed!!

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #26 on: August 08, 2013, 04:30:36 PM »
thanks for the schematic dr gonz78.the schematic number pa378b is the right schematic.the output tansistors are listed that i have mj4502 and mj802.i will try to check things out for you again juan.i goofed up i carried the unit back upstairs to get the transistor numbers off the transistors and i noticed i forgot to hook up the rca cable to the output board, so i didn't have a preamp signal going to the output which = no scope pattern.i screwed up sorry. i will redo the check for you later tonight....thanks...ed!
« Last Edit: August 08, 2013, 04:32:12 PM by EDWARDEFFECT1 »

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #27 on: August 08, 2013, 08:27:27 PM »
i have a B&K 2120b scope (30mhz) and a Tenma 721005 work station.i set the scope @ 2v and the time @ .2 and when i touch the cables from the tenma with a sine wave and 1khz signal the scope give me a great looking pattern.i attached the clips from the signal generator to a 1/4 inch plug and plugged it into the input of the amp.i tried going across the speaker with the ground and probe.i get nothing.no difference with the volume and master volume controls.i unplugged the rca jack coming from the preamp i am guessing and get no change there either(just the straight line on the scope) going from ground (the outside of the plug and probing the tip ..going to try to get voltage readings with my fluke from the base and emitter of the mj4502 and the mj802 output transistors.By the way my friend that called polytone got a call from Diane today. he happened to be not home,so he is going to call them back tomorrow.if i get ahold of a print for this monster i'll try to pass it on to the rest of the ss guitar site if possible...ed!

Roly

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #28 on: August 09, 2013, 11:12:36 AM »
Try working forward from the back of the input socket, reducing the sensitivity of the CRO as you go stage by stage.

But first...

Quote from: Roly
Can you find good main power rails, like +/-33 volts?

Can you find good preamp supply rails, like +/-15 volts?

If you say theory and practice don't agree you haven't applied enough theory.

EDWARDEFFECT1

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Re: Polytone Taurus Elite amp low volume no schematic!
« Reply #29 on: August 09, 2013, 04:49:33 PM »
hey gang! i had a heck of a time getting the alligator clips on to the emitter of the transistors.i got +36vdc on the MJ4502 and -36vdc on the MJ802,so i have no power supply problem. i am guessing what i am getting from the amp is all shes got.i'm thinking that it is overated by polytone.unless there is say 10 volts on the 15volt supply for the preamp.i mentioned earlier that the trace was cut at the opto isolator which is right after the large probably 3amp diodes on the first preamp board.i don't know if it was cut at the factory or someone cut it by accident.don't know if i fix the trace will i get smoke. who knows without a print.my buddy called diane back today and got the answering machine.looks like Roly wins this round.no answer from Ploytone....not counting on getting a print for the preamp section..thanks for the power supply print. it was right.i'll try to get a voltage reading off one of the voltage regulators legs and see if i get 15vdc supply voltage......ed
« Last Edit: August 09, 2013, 08:46:27 PM by EDWARDEFFECT1 »