Discussion in 'Amps & Cabs' started by RVA, Nov 14, 2015.
OK, thank you.
RVA, Our house currents can vary from between approx 115 to 125 volts so transformers can yield higher or lower readings depending on what the house/venue etc outlet tests at. This is why people use a variac and a multimeter to precisely set the amount of volts the trans is getting and take readings off that. These are the volts that go thru the power cord and go to the "120 V AC" leads
On that Fender tranny, 67, what did you find that caused it to fail? I saw you say a shorted tube. Were there other things that caused the tube to short?
I used a Fluke meter very similar to 67plexi's. I had the power on and standby off. I checked in the 2 pin connector for each of the wire colors above. I checked the yellow wires 2x and verified my readings each time. I even flipped the negative and positive probes to each side.
I am going to have a funeral for my dear old friend, then harness it's organs (tubes and cab with 18" speaker.) for a suitable donor. That you for helping me get closure on this and saving me from paying for a costly diagnosis.
Not sure what you mean here RVA, are you giving up?
In that case...
I'm sending you my sincere sympathy to you in regards to your dear old friend... bon voyage...
That seems to be 67plexi's recommendation, as finding the problem requires a point by point diagnosis.
Your Peavey is a combo not a head, right?
Combo. It has a very nice 12" speaker. I will experiment with it as a cab.
It is ALIVE!!! (Frankenstein reference)
This is a rather bad ass combination!
Use this voltage chart when testing a amp
What is the row of B's for?
The B+ is your dropping string B+1= high voltage from power transformer secondary leads to first filter capacitor +
then a 3-5 watt resistor to B+2 then the next filter capacitor + and so on. If B+1= 500VDC do you want 500VDC on your first preamp tube
I don't think so more like 185-200VDC the dropping string is how this is done. B+1 & B+2 are hidden behind the large black filter capacitors
B+3 is the green wire from the filter board to the phase Inverter B+4 is the next green wire to the overdrive channel B+5 is the 3rd green wire
to the first input preamp tube.
This is a gut shot of MEGA-PLX you can see the 10 watt 6000 ohm resistor on the filter board.
not trying to brag but this is one of the best sounding amps ever. JTM-45 PT 1968 Marshall plexi OPT.
Another good video from Mr Carlson
The last video I posted shows a trick for removing those blobs of hot melt glue.
What are those little boards that are on the sides of the chassis, next to the guitar input jacks for?
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