65 Deluxe reverb reissue Power transformer problem
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65 Deluxe reverb reissue Power transformer problem
I have a DRRI with a blown tranny. I thought it was caused by a shorted rectifier. Did not blow either fuse. I put 120V to Primary and do not get any voltages from secondary. I replaced the power transformer, rectifier tube and the 5 large filter caps. Amp came on worked and sounded great for about two hours, Then the transformer blew again. I'm back where I started. Can't see any other problems. bad resistors, shorts, etc. HELP!!!
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Stevem
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Re: 65 Deluxe reverb reissue Power transformer problem
First off the fact that the original PT went south by going open is why the fuse did not blow if it's the right amperage slow blow type as called for, but that being said it's odd that it opened and died and did not fail by shorting.
Now you state the the replacement PT failed, did this one not blow the fuse also?
Now you state the the replacement PT failed, did this one not blow the fuse also?
When I die, I want to go like my Grandfather did, peacefully in his sleep.
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: 65 Deluxe reverb reissue Power transformer problem
What's the failure mode ?
Open primary ? HT secondary ?
Ohm out the windings, and identify a pattern.
Please make sure the caps are discharged !
rd
Open primary ? HT secondary ?
Ohm out the windings, and identify a pattern.
Please make sure the caps are discharged !
rd
Re: 65 Deluxe reverb reissue Power transformer problem
Test power tubes
Tom
Don't let that smoke out!
Don't let that smoke out!
Re: 65 Deluxe reverb reissue Power transformer problem
Many Fender amps have different transformers depending on what country the amp is sold in and what safety regulations have to be met. Some of these have internal thermal fuses that will open if the transformer gets too hot. What country are you in? What is the mains voltage and frequency?
If you are playing very loudly with lots of distortion on a hot stage with a low mains frequency, that is a torture test for a transformer.
If you are playing very loudly with lots of distortion on a hot stage with a low mains frequency, that is a torture test for a transformer.
Last edited by LOUDthud on Wed Jul 16, 2014 8:34 pm, edited 1 time in total.
Re: 65 Deluxe reverb reissue Power transformer problem
Sorry, I am new here and didn"t realize i had posted on two different post. I am in the US. 120V 60hz. I completely unhooked the transformer and connected 120 to the black and white primary wires. i have no voltage coming out of any kind. i have a new transfomer ordered and when i put it in i am going to replace all tubes and rebias and see what happens
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beasleybodyshop
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Re: 65 Deluxe reverb reissue Power transformer problem
You should make/buy a light bulb limiter - there is a sticky here in one of the forums on TAG.
Pull all the tubes from your amp, hook up the transformer (use a schematic/layout if you need to) and power it on with the limiter. If it lights up bright and stays that way with NO tubes in the amp and you have it wired properly, then there is some kind of serious problem.
Does sound like a shorted power tube if you havent changed or swapped those out during your transformer debacle.
Pull all the tubes from your amp, hook up the transformer (use a schematic/layout if you need to) and power it on with the limiter. If it lights up bright and stays that way with NO tubes in the amp and you have it wired properly, then there is some kind of serious problem.
Does sound like a shorted power tube if you havent changed or swapped those out during your transformer debacle.
"It's like what Lenin said... you look for the person who will benefit, and, uh, uh..."
Re: 65 Deluxe reverb reissue Power transformer problem
The thing usually causes PTs (that have otherwise been properly designed for the load that the amp produces) to overheat and blow, is a point in the circuit that causes too much current to be drawn across the PT (from Pr: to Sec:).
Remember that current x voltage = power, and that therefore, too-much power (which is manifested in the form of heat/smoke/fire) at a given voltage, is the product of too-much current draw. (The Mains fuse is supposed to blow before fire starts, and this is an indication of too-high-a-current-draw)
You have to find the cause of the excessive current draw. This will typically be where supply voltage is being dumped straight to ground - thereby putting excessive loading on the PT.
It could be a shorted tube.
It could be a shorted filter cap.
It could be a B+ wire contacting the ground return directly at some point in the circuit where its not supposed to be.
It could be carbonisation between pins on a bad tube socket
Now you know the basic theory, you must use your powers of deduction to find the fault.
Looks for clues like cooked/burned supply resistors - a tell-tale sign of excessive current being drawn though the resistor in a way that exceeds the resistor's designed power-handling rating
Be careful working with high voltages.
Remember that current x voltage = power, and that therefore, too-much power (which is manifested in the form of heat/smoke/fire) at a given voltage, is the product of too-much current draw. (The Mains fuse is supposed to blow before fire starts, and this is an indication of too-high-a-current-draw)
You have to find the cause of the excessive current draw. This will typically be where supply voltage is being dumped straight to ground - thereby putting excessive loading on the PT.
It could be a shorted tube.
It could be a shorted filter cap.
It could be a B+ wire contacting the ground return directly at some point in the circuit where its not supposed to be.
It could be carbonisation between pins on a bad tube socket
Now you know the basic theory, you must use your powers of deduction to find the fault.
Looks for clues like cooked/burned supply resistors - a tell-tale sign of excessive current being drawn though the resistor in a way that exceeds the resistor's designed power-handling rating
Be careful working with high voltages.
He who dies with the most tubes... wins
Re: 65 Deluxe reverb reissue Power transformer problem
OK, Now i have installed new Fender Transformer, new filter caps, all new tubes. Amp come on works good But, Using my TAD bias probe I am reading 150 mA at the power tubes. Way too hot. any suggestions
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martin manning
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Re: 65 Deluxe reverb reissue Power transformer problem
Remove the power tubes and measure the voltage from pin 5 to ground to see if you have any negative voltage there. We're you able to bias the output tubes the last time around?
Re: 65 Deluxe reverb reissue Power transformer problem
no voltage pos or neg at pin 5. I did not try to bias first time. it had original tubes and i thought rectifier shorted tranny so i just replaced the rectifier tube.
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martin manning
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Re: 65 Deluxe reverb reissue Power transformer problem
Start at the bias supply tap on the PT and look for AC voltage. Then see if there is DC after the bias supply rectifier. I'm guessing the most likely failure point is the rectifier itself.