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Need Schematic for Randall guitar amplifier RG80

I have a burned resistor that I cannot read the color codes on and need to find the value for it. It is in the driver section left of the TIP 31? transistor that I also suspect is bad since all the voltages are wrong and the capacitors might be leaking causing bias problems.

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Posted on Jan 02, 2017

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bolinlamar
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SOURCE: Crate GX-20M burned resistor + popped cap values?

go to
http://www.crateamps.com/support/index.php
you may find what you are looking for there.

Posted on Aug 20, 2009

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SOURCE: Searching for a schematic diagram for a Marshall

Try this:

http://www.schematicconnection.com/store/asp/prodtype.asp?prodtype=195


Posted on Apr 01, 2010

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SOURCE: Ineed a schematic for a Guitar Research Amplifier

Here is a link, unfortunately it requires a different viewer than Adobe but you can find the special viewer although the viewer may not be a free program.

http://elektrotanya.com/orange_ad-30r_sch.djvu/download.html

Posted on Jan 22, 2011

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1 Answer

Where can I download the schematic diagram of zed 22fx?


all resistors are banded with different colors and each band has a specific value
band colors range from black , purple, orange yellow dark green blue red grey and white and color diagrams and values can be found on the net or from shops like Jaycar
however if you want a schematic diagram if you go google and type in schematic diagram for zed 22fx you may be lucky enough to find a pdf version down load
if such a diagram is unavailable unsolder yours and take it to the shop and have it identified and they will have spares for sale

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Where will I find a schematic with wattage values for all the resistors


Use this in Google to fine manuals and schematics:
Epiphone junior amplifier manual Google zoeken
Most resistors are 1/4 watt, unless something is added in the schematic.
You also can deduce the wastage, because for every size is a wattage, or the other way around.
When you are not sure, and it fits, use a bigger resistor. The same resistance (ohm) but a higher wattage is no problem as long as it fits in the housing.

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Need Schematics for Mackie C300 Speaker


Do you have the existing resistor, Larry? Is it crisped up, or can you still read the colored bands? Those colored bands are a color code indicating its resistance - if you can read them off here, we can tell you what its resistance is.

As to wattage... that's something we could at least estimate from size & shape, weighted a little by speaker wattage rating (that resistor should never see as much wattage as the rating).

Last... if we knew for sure what every other component is (from its printed labeling), we could reconstruct the schematic and calculate that resistor's value. Reverse-engineering a crossover designs is far from being rocket surgery. 8)

I offer these as alternative approaches; it may be near-impossible or impossible to get that schematic.

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1 Answer

I have a burnt resistor on a V55hd head. It is near one of the powertubes. Need to know how to calculate the value for replacement, and know if there is some sort of resistor type that will be more heat...


Usually the amplifier will have "symmetry" and there will be matching resistors near the other power tubes that you can get the value from. This is PROBABLY a screen resistor for the tube and values are often around 470 ohms or so but I could not find a schematic. These USUALLY don't fail unless a tube has shorted. Heat sinks are NOT used. The best resistors for the purpose are "wire wound" ones and of a suitable wattage rating. Sometimes we put ceramic beads on the leads to raise the resistors off the board to allow air circulation. Occasionally solder will break and the arcing at the leads adds to the heat. If you trace where the resistor goes by pin number of the tube and the type of the tube that would help me to help you... trace a matching tube to the same pin and you will likely find a matching resistor. Note that some power resistors DO change color a bit after they get hot in use, but if they char or the coating falls off that is a failure.

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1 Answer

I need to know the value of the Resistor "R1" in


Let us use a bit of logic to resolve this... I have an Axiom but it would be a lot of screws to take out to get to the part... so let us think about this. The resistor value starts with a "1" and we know it is 5% tolerance (gold). we know the resistor burnt up with likely 5 volts on it... Value could be 1000 ohms, however the voltages present (12 volts max) would NOT have burned up a resistor of 1000 ohms. The USB area is mostly 5 volts and across 100 ohms is only a quarter watt... not enough to really burn up a resistor... First thing is to MEASURE that the resistor s open... in spite of being burned, it MAY still be OK... these resistors now usually either open or remain close to their value. The resistor ALSO may be a fusible resistor intended to act as a fuse... Is the resistor open or not? is it near a resistance with a "1" as the first digit? If it is not open I suspect it is not all of the problem. In that case, look for a burned circuit trace on the board. If it is open, then MEASURE the voltage across the resistor with the power applied. If you find 5 volts, then it MIGHT be a 10 ohm used to limit the USB current to 500ma. Get back to me with your findings... I have unraveled many of these things...

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1 Answer

I have a RH50 T amplifier, it had a bit of a bumpy car ride to band practise the other day and now when i play through it, it will make a permanent buzzing noise on the clean channel that gets 70% worse on...


You may have damaged the variable resistors (the volume controls), you can purchase replacements from a local Electronics store (if UK based try Tandy). Otherwise have you checked the speaker itself for damage? You may have split the speaker which will need to be replaced.

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I want to know what is the resistance value R32 - marshall g15rCD 15 watts


The value of r32 on the g15r cd amp is 10 Ohms 1/4 watt Brown-Black-Black

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