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Amplifier Discussion / speaker load/load box
« on: November 20, 2013, 12:06:40 AM »
whats the scoop on speaker loads? you need a speaker load for all tube amps and for some solid state amps,but not all! how do you determine what solid state amps need a load before powering up for testing and what solid state amps don't....thanks!!

i pulled all the ic's and still no +15v.all were in sockets thank god!i found a solder bridge between a black ground wire and the positve of the circuit. it has been corrected.the big short is gone,but apparently i still have one to find. i found 2 capacitors with bad solder joints and fixed them with buss wire as i think the trace was loose or missing(coudln't solder,so i followed the trace to the next component and buss wired the lead to the next component).all fixed now!i took the preamp board outside to get really good look in  natural light and looked it over with a fine tooth comb.i found a solder bridge on the one board and opened it up hoping that was my short to no avail.when i turn the unit on the +15v reads 11vdc then diminishes to 3vdc.still something drawing voltage from my supply.when turning the amp on there is a loud squeal.when we hooked a guitar to the input it had a loud guitar sound and squeal for about 4 seconds then nothing no squeal due to lowered voltage.....ed

the -15v regulator is slightly warm and at proper voltage.the +15v reads .003vdc and gets hot to the touch.going to do a pinkie test on the op amps as dr gonz metioned and see what i get.i removed 2 op amps from the reverb board as there was a capacitor arcing due to a bad solder joint.thought that an op amp might of got fried ,so i removed them from circuit and it had no effect on the regulator to the pinkie test. was outside fixing a broken brake line and bleeding brakes. back to the amp....ed

thanks Dr Gonz for posting schematics.all diodes on the board with the 15v supply regulators test good with a diode test. both 24v supply rails are present.when i do the pinkie test on the regulators.the new regulator i installed is getting hot to the touch.something must be loading it down.getting .003v output from how to find the shorted part that is doing this?i have tested all the capacitors with a capacitor meter and also checked across the leads of the caps on low ohms of my fluke for shorts and i haven't found anything.also tested a transitor on the board and it is good also.there is a trace cut near a opto- isolator.i believe it was done at the factory and it doesn't seem to be in the same part of the circuit as my the amp previously did work with this same condition.just didn't seem to have 130watts.previously i found 2 wires detached from the unit.a black wire on the regulator board and a purple wire in the reverb board. they have been repaired.that is all i have for now. open for any ideas for testing for the short.guess it could be on any of the board with the 15+v supply.thats alot of parts to check.might not be on the supply board ,but may be on another board in a later part of the circuit.tough to test do to layout of boards all sandwiched together vertically.

got the schematic from poly tone.i have to figure out how to downsize it.i found out that i have the - 15v supply ,but lost the +15v supply. if i touch the regulator it gets hot.something is loading it down.i have the +24volts at pin 1 of the pnp regulator.any suggestions on locating the short that is loading down the regulator.i only get .003volts going to the ic socket of the +15v.the -15v is present. i replaced the regulator and got the same how to find the part that is shorted and loading down the circuit.Roly,enzo,and juan ,i am going to leave my e-mail adress.if you want a copy of the schematic i will send one to you (polytone taurus elite).i have the power supply and another print with everthing else.the only problem is the print and the circuit board numbers don't match as they use the same circuit board for all three channels,but it does allow you to go part by part thru the!!

i am supposed to get a schematic from polytone from Diane. it is supposed to be in the mail.i tried the effects loop with my traynor 20 watt tube amp and got very low volume using the traynor as a preamp and the polytone as a power amp and also got low volume with the polytone as a preamp and the traynor as a power amp.the only thing i question is that the polytone has what is called a main it a preamp out,speaker out,power amp out.need a manual that identifies what it is.maybe thats why i didn't get volume using the polytone as a power i hooked the traynor send  into the effects return of the polytone.i don't have the volume i had previously.i am guessing i might of not hooked up a connector before putting the two back boards on the amp again. i thought i plugged everthing in ,but now i/m not sure.i've lost my patience with this thing and i am going to wait till i get the schematic to renew my interest in this thing...Ed!!

got a call from Polytone and a e-mail that said they were sending me a schematic usps.will let you all know if i get it. diane seemed to be very nice on my answering machine. seemed like a nice lady judging by her voice.I tested one of the regulators on the 1st preamp board and i got -15vdc.I didn't find the +15vdc yet. i powered up the amp and ran a chord from the Polytone send to a traynor 20 watt amps return and the volume is low.must be a preamp problem.i need to verify the output section the same way as the volume is lower than what i had previously.if i get the schematic. i can use my signal tracer and check the ic's ect for signal starting at the inputs...

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 buddy called diane back today and got the answering machine.looks like Roly wins this 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

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 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!

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!

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!!

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!!

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 probably is good,it probably is reacting to other components in the circuit.without a print who for the rail voltages i don't know how i can take any readings off the transfromer board side of the 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!!

lets see if this works! i cut and pasted the browser into this post....ed!

going to put the amp back together today to do more testing.thanks for your'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 works...ed

i have been trying for 4 1/2 hours to load the photos i took.i tried to goto and i can't even connect with the site to start an account. i also tried photobucket with no'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!

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