Polytone Taurus Elite amp low volume no schematic!

[EDWARDEFFECT1]

i have a polytone taurus elite amp that has low volume on all 3 channels.the speaker test good with a 9v battery test. the output transistors test good.all parts on the board attached to the power transformer test good.solder joints look good.need a schematic if anyone has one available.channel 3 volume control was broken. i need to relace it.i believe it measures 250k.on the channel 1 board i checked the diodes ,capacitors and resistors and they test good.they are located behind the pilot light.any help appreciated....ed!!

[EDWARDEFFECT1]

just did some searching on the net and found out this is a keyboard amp.i was trying a guitar thru the amp and the volume is low.i'm sure it will be louder running a line signal thru it ,but i'm sure it won't be 140 watt loud as listed in the broshure on the amp...still can't find a schematic anywhere?

[Roly]

I found these, the first may be some sort of general help;

http://www.murchmusic.com/polytoneserviceinfo.htm

...but I also found a number of comments from very dissatisfied customers - brand new amp with fault, won't repair, won't send circuit, etc.  This story alone suggests that asking Polytone direct will be a waste of time.  With this sort of company techs need to do tracings of every one of their amps they encounter and publish them free on the web.

Crisp piccies seem in order.

[EDWARDEFFECT1]

hooked up a keyboard to the amp and it is low in volume on all 3 channels with the volume and master volume controls full up.if i let it run for about 3 or 4 minutes it starts making a clicking sound that is in perfect rhytum like a metronome. sometimes i can hold a key down and the volume will jump up to full volume for a split second if i pick the right key to hold.i have all the reverb and modulation knobs turned all the way off.i am getting close to finding the problem.may be a heat issue ic,transistor or something. will have to try the pinkie test.  thanks....ed!

[EDWARDEFFECT1]

polytone has not answered me back about my request for a schematic.i see a polytone taurus 2 channel amp schematic for $20.00 which is different than the polytone taurus elite keyboard amp i have.guess i can't even buy one on the net...i'll check your site out you sent... thanks Roly.....ed!

[Enzo]

Try calling them on the phone.   Emails can be ignored, at least talking to someone, they will tell you outright that they will or will not send schematics.

[Roly]

I won't be holding my breath.

http://www.gearslutz.com/board/geekslutz-forum/580867-source-polytone-amp-schematics.html

They have the absolute worst customer service I have ever dealt with. my Polytone mini brute ii was purchased brand new and had immediate problems right out of the box. I contacted Polytone to see if they can fix it. The lady there (Diana) flat out said no we are way too busy and refered me to a place in NJ (Danny's amp repair). I then asked if I can please have a schematic so I can have one on hand cause I am going to search out a local tech. she was very difficult about giving me one but finally took my fax and email. 4 days later I still have no schematic. I left them 3 polite messages in the mean time. I have not heard a peep back. Really upsetting. I purchased the amp new (came without a single document, and no warrenty info), they will not repair it, and they don't even have the courtiosy return my call or fax over a piece of paper. It's almost like she enjoys making my life difficult.

{this has to be one of the worst non-service stories I've ever heard - they wouldn't back up a brand new amp?}


Meh.  Don't sweat the circuit; get in there and have a look and see what you've got (post pix), then we'll just do a bit of technishing and fix it, eh?  Five'll get ya ten it's just a blown output stage.

[EDWARDEFFECT1]

i have already called and i had a friend call and he told them to call him as he wanted to buy from them.all you get is an answering machine.guess what no call back to either of us.maybe i'll have someone else call as three times might be the charm.ha! ha!...i think Roly has tried this before.guess i'm s.o.l.

[Roly]

An answering machine is not a sign of a customer-focused dynamic company giving the player's needs a high priority.  Why am I not surprised?

Nah; "You never find just one roach in a kitchen".  After reading a number of negative posts with no balancing or offsetting posts, you get the general impression.  I mean, have a look at this and ask yourself if this is a company you would be keen to do business with.

On one hand I'd say persist with them, expecting nothing, just to prove the point; but on the other, time to dust off the camera and multimeter, and trace out the circuit...

[EDWARDEFFECT1]

found a cracked solder joint on an electrolytic resoldered and got rid of the clicking sound.it was on the master volume board .047uf i believe.i noticed all three of the preamp boards have the same circuit board with different configurations.just have low power now.i have a trace that goes to an opto-isolator that has been cut.not sure if it came from the factory or it is part of my problem.without a schematic who knows! if i take a reading with my meter on dc from the transistor case to ground is get -.0032 on one side and .0012 on the other.not sure ,but shouldn't it be +15vdc on the npn transistor and - 15vdc on the pnp.guessing i have a voltage problem in the 15vdc circuit.any thoughts appreciated....ed

[DrGonz78]

Why not add some pics to this thread. For one I would like to see a pic of the power supply circuit. It helps to have these pics of the amp out here online for all to see later down the road too. I think we need to start at the power supply and work out the voltage readings through the amp. Lets figure out where on the circuit they create the lower 15v rails (i.e. dropping resistors).

[Roly]

sometimes i can hold a key down and the volume will jump up to full volume for a split second
...
a heat issue ic,transistor or something

That sounds more like an intermittent contact/connection.  Solid state devices don't just fix themselves if presented with the right frequency.

Method 1 is is guess, randomly replace parts, and get nowhere.

Method 2 is to methodically and logically trace signals and voltages until the cause of the problem is located, then fix it.

Polytone Taurus Elite, front panel;



A couple of tests that suggest themselves are to take a signal from he Preamp Out socket to another amp and see if that sounds normal.

Similarly to take the Fx Send of another amp and inject it into Effects Loop Input and see if a clean high power output can be obtained.  That way we will have some sort of idea when end of the amp we should be looking at, preamp or main amp.  Also the old trick of linking Fx Out and In with a known good lead.

I must comment that I don't find the control layout on this amp very intuitive.

Inside, the first port of call should be the power supply to confirm voltages for the preamps and output stage (and a cap with a value of 0.047uF is very unlikely to be an electrolytic).

[J M Fahey]

Please do all this and post results:
1) put >master< volume on 10.
2) in all channels, put all 3 tone controls in >5< , dark/bright switch on center position, volume on >0<
3) put all reverb controls, both channel and master, on >0<
4) put all >modulator< controls on >0< , clicking >speed< off.
5) put a known good plug/plug cable from Effects >out< to >in< , and set both >gain< controls to >5< .
6) inject 200mV RMS @ 400Hz to 1KHz in channel 1 input.
Scope speaker output and raise >volume 1< slowly until speaker output starts clipping, then lower a little until it *almost* cleans up.
Measure and post AC voltage here.

[EDWARDEFFECT1]

drgonz78, i took pictures for you and the rest of the guys on the site as i had the whole preamp master volume assembly out and the output power transformer.i have tried to upload photos before and had problems. i'll try to send them if someone can dirrect me in what to do...thanks. i have the pictures on my computer to forward what next....ed!!

i took 13 pictures!

[EDWARDEFFECT1]

i just tried loading the photos to photobucket as that is what i was told to do last time. i still could log in ,but had no luck uploading the pictures...help!!

i'll put the amp back together once i upload the pictures and try to get to my signal generator and scope and see if i can do what you have requested JM.......ed!