1974X died.....(but lives again!)

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Buc McMaster
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1974X died.....(but lives again!)

Post by Buc McMaster »

....suddenly and completely. Checked fuse....okay. Replaced the rectifier and it came to life once more.......for about three minutes and it went silent again. I intend to deliver it to an amp shop later this week but do any of you have experience with such a failure? What might I expect at the repair shop?

It's a 2004 model, new preamp and power tubes installed about a week ago.
Last edited by Buc McMaster on Wed 08/17/22 7:17 am, edited 1 time in total.
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Bieworm
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Re: 1974X died.....

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Buc McMaster wrote:
Tue 08/02/22 6:49 pm
....suddenly and completely. Checked fuse....okay. Replaced the rectifier and it came to life once more.......for about three minutes and it went silent again. I intend to deliver it to an amp shop later this week but do any of you have experience with such a failure? What might I expect at the repair shop?

It's a 2004 model, new preamp and power tubes installed about a week ago.
Hard to say.. but I do know the original transformers fail often. Marshall usually sends a replacement transformer in those cases. But I think you need an official tech to support that procedure.
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Buc McMaster
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Re: 1974X died.....

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I was trained as a radio repair tech in the USAF in the 1970s but I'll admit to not having had much motivation at the time and I certainly did not pursue the field after leaving the military....perishable skills......complete idiot electronically speaking. That said, intuition tells me that a bad transformer would not have been provoked to work with a new rectifier.......if the transformer is blown, it's over, new rectifier be damned.....yes? Would the amp have worked short-term as it did with a new rectifier if it was a blown transformer?
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Re: 1974X died.....

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Maybe the new rectifier tube is a lemon?
I had a new JJ fail instantly . Stay away from JJ
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Buc McMaster
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Re: 1974X died.....

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Maybe so.....the new one I plugged in was an NOS Mullard.....could have been bad. But still the question: if the transformer was blown would the rectifier replacement have revived the amp for a brief time? Or, if the transformer is in fact blown, would the amp have remained silent? I'm thinking the transformer is okay and the problem is elsewhere, but as I said, I have no skills in this arena....hence my question.
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Re: 1974X died.....

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There could be a failing winding in the transformer that reveiles itself when enough current is being drawn. But that would be onlu a few seconds.. not minutes. And the fuse should blow from the excess current draw.
Does the amp turn on with all tubes removed?
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Buc McMaster
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Re: 1974X died.....

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So......the tech called today about the apparently injured 1974X....

It did have a broken leg cap in the tremolo circuit....sussed and fixed. Apparently the real issue was mechanical: someone had installed extra washers on the outside of the tremolo input jacks such that a guitar cord male tip only made intermittent contact. What?! I cannot imagine why this may have been done. And, having been informed of this, I do recall that I had used a curly guitar cord for the first couple of weeks of ownership and had switched to a different straight cord the day it began to act up, leading me to believe the cords interacted differently with the input jacks. Sheesh.
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Re: 1974X died.....(but lives again!)

Post by Buc McMaster »

Retrieved the Marshall from the amp shop yesterday and it is as expected....rippin' and roaring' once again. Had me concerned for a bit.....all's well that ends well.
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