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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 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 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!!

Amplifier Discussion / marshall 6100 100 watt anniversary amp head
« on: June 04, 2013, 01:04:41 AM »
i have a marshall 6100 30th anniversary amp head it is purple. i believe it is a 1992 model. i can't find a good shematic for it that is ledgible and clear for what i need to repair.i have 500+ vols dc on pin 5 of the power tubes.any ideas? i believe it is supposed to have -50vdc on this pin for the bias.500+ volts on the grid is really bad. any thought or ideas appreciated.i am guessing it might have a bad coupling cap between do i test it as all the connections are under the main board of the power tubes. i also get .010 ohms in both directions on the 2 large diodes on the power supply board.i replaced the diodes with new ones and i still get 0.010 ohms across them in both directions testing on the diode scale of my meter.the 2 diodes were good out of this low reading in both directions an indication that there is a short farther down the circuit....thanks...ed!

hi i know this is a solid state site,but i also know there are some good techs here.i have a fender deluxe reverb reissue that blew a fuse. one or the power tubes was shorted.i put new tubes in it and tried to rebias it using a weber bias rite meter.the amp will bias then when you wait about a minute the bias starts going up a tenth at a time.then you keep turning the bias down till there is no more adjustment.there are 2 dcv test points on the print-34vdc(reads -35vdc) and -49vdc (reads 50vdc).the voltages are perfect and they stay rock solid on there readings. the bias probe is good as i just did a couple amps with it with no problem.also to prove it i let the amp run for about 3-4 minutes and finally the tube with the higher bias red plated,so i shut it down right away.the bias is affecting both tubes as the current keeps counting up a tenth at a time on them.all the components on the circuit test good.i also changed the 2 electrolytic s with no difference.the voltages do show no problem with the bias circuit.there are no cathode caps on pin 8 of the 6v6 power tubes.both cathodes are tied to ground.this one is a hair puller.lets see who has the answer to this tough problem?....thanks....ed i will try to attach schematic...thanks...ed! page 5 is the right schematic...

Amplifier Discussion / shorted kustom 400 watt bass head
« on: October 15, 2011, 05:21:12 AM »
i have a kustom 400 watt bass amp one of the newer china blew the 8amp fuse and a npn output chip.i replaced the bridge rectifier also.i replaced the parts and plugged it in with a homeade current limiter with a 100 watt bulb.the bulb is staying bright so i have a short in the amp. what is the best way to find it.if it is with an ohmeter what readings should i look for.are there any other ways to test for a short.variac? oscilloscope do you do it .....thanks...ed

Amplifier Discussion / johnson j150 millennium pico fuses blowing
« on: September 21, 2011, 09:53:13 AM »
i have a johnson 150 millenniium 2x12 combo amp and it keeps blowing the 2 pico fuses(f1 and f2).i have no 32v supply and no +12 or -12 supply voltage coming off the power board. everthing checks out good on the supply board and there appears to be no shorted output chips,or shorted capacitors. i also checked the main board too and found nothing.any help appreciated. i have the + / - 5v supply and the b+ supply.thanks...ed

does anyone know where i can get a schematic for a marshall mb-450h amp head.i put a signal in the input and get a signal at the speaker that is controllable by the volume controls on the amp.when i hook up a guitar and speaker i get nothing.

Amplifier Discussion / mesa boogie m6 carbine schematic
« on: June 28, 2011, 03:58:15 AM »
where can i get a schematic for this amp. it powers up but no sound. i found 2 bulged  47uf capacitors and replaced them along with 2 bad ic.i have signal to the output board  jumper wire now but nothing after that...thanks...

Amplifier Discussion / what is signal tracing the enzo way?
« on: June 04, 2011, 09:06:09 PM »
i noticed in a post someone recommended using the send outlet of the effects loop to run a signal into the input or return  jack of the effects loop of another amp.if the amp was playing right the preamp would be good on the amp in test. if it didn't get proper sound it was recommended to do the enzo signal tracing test....what is this test....thanks...i use a mfj injector/ works excellant in testing ic's,output chips,and signal tracing the amp itself.i just fixed a alto powered monitor and i had signal on the output chips output ,but it was really low in volume. when i touched the input jack where i input the signal for the signal tracer it was also extremely low in volume. i thought i had a low battery in the tracer. when i unplugged the input jack with the injector leads still hooked up and touched the positive side of the jack the signal was loud as it usually is when testing. something was loading the circuit. i got my ohmeter out and found 4 shorted zenier diodes.i replaced them and bingo got a loud signal all the way to the output chip.the alto is back and running.could you explain enzo's system of testing...thanks...ed

Amplifier Discussion / line 6 flextone 111xl voltage regulator
« on: June 04, 2011, 04:19:18 PM »
does anyone know the value of u1 voltage regulator.i believe it is a lm1086.all the regulator voltages are marked on the circuit board except u1...thanks...ed!!

i believe i read a previous posting somewhere about checking ac voltages on the chip.i have an do you do it?i know all output chips are different,but there must be some simularities in  the testing proceedure!

Amplifier Discussion / hartke gt-60 amp hums...
« on: February 21, 2011, 09:59:13 AM »
i have a hartke gt-60 that hums on both the clean and dirty channels. it is predominately on the clean channel. awhile ago i remounted the reverb tank away from the power supply as it must of been made on a monday.the tank was mounted dirrectly over the transformer.the hum is alot less than before,but still not where it should be.any ideas?  i have an oscilloscope,but am new to using it. i tested the capacitors and all i get is a dc pattern that is the same on both the negative and positve terminals.i put brand new 2200uf caps in and they read the same.i thought i should get different patterns on opposite sides of the electrolytics.any ideas on learning to use my can i find the hum with the scope?....any help appreciated. i think this amp had design issues.i notice they have a red and black power wires running across the entire board hooking up on the opposite end. bad engineering...thanks.....ed

Amplifier Discussion / walter woods pilot light.
« on: December 05, 2010, 10:05:21 AM »
i have 166.3 vollts dc on one terminal of the light and -163 dc on the other. the light is 125volt ac.any ideas. i must have something leaking dc into it. there are no identifiers for dirrection with the caps.i have replaced all the large capacitors and the bridge rectifier with a 1000volt 25 amp part. the amp works fine,but no pilot light.i have another post with pictures of the circuit board if it helps....thank any help apreciated......ed

Amplifier Discussion / walter woods electracoustic amp won't power up.
« on: October 25, 2010, 07:54:43 PM »
got a electracoustic amp that wont power up.from the power transformer the leads go to a 1k resistor that is enclosed in a gold anodized heat sink( which reads.999k).then it goes into a red square item (c&k u21 rectifier?)that has 2 grounded legs on the bottom and then there are 4 more  legs,but one leg is missing.where can i get this part and does anyone have a schematic so i can figure out where the 4th leg goes.the fuse is good.i haven't got into any voltage checks yet...thanks...ed

Amplifier Discussion / ideas on fixing damaged circuit board traces
« on: October 20, 2010, 08:43:53 PM »
looking for ideas on fixing circuit board traces.what glue would you use for glueing a physically good trace that is loose from the circuit board ,but is in good shape otherwise?what fixes do you recommend for broken traces.(examples:buss wire,.030wire)  how do the circuit trace pens work?is it to high of a temperture that causes traces to get broken and removed from the board?any other ideas?jump in!!!thanks....ed

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