Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Tone Junkie on May 14, 2020, 05:14:27 am
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Great amp super clean channel. went with a James tonestack on both the clean and overdrive channel. Did a solid state CF on both . For some reason having trouble with the dumble style effects loop usually works right out of the gate . Have sound into and out of the first stage but when it goes thru the 1.8K resistor no sound . Changed the resistor no help. other than that great sounding amp didn't use the 5879 tube messed with the bloom a bit but still a great sounding overdrive .
Thanks Bill
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Have sound into and out of the first stage but when it goes thru the 1.8K resistor no sound
Not sure what this means? 1st stage of preamp? 1st stage of FX?
It would have sure helped IF you had posted an accurate schematic of the amp in it's current state?
So, my response is going to be based on the assumption that the entire amp works fine except the FX loop. In other words, the clean and overdrive channel are functioning properly.
* see the attached trouble shooting ideas and try those and then try the suggestions below:
1) Check voltages on fx
2) check send and return jacks
3) check pots
4) quadruple check your wiring & check for continuity
With respect,Tubenit
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How close is this to what you have in your D'Mars? Can you edit this to what you actually have? I've attached an editable ExpressSCH version for you.
Can you provide an accurate schematic of the amp in it's current state, please?
With respect, Tubenit
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Tubnit see in V3a on the schematic you put up were it comes out of #3 on the tube and then runs into a 1.8k resistor. Then branches of to the send pot. for the effects loop. With my signal tracer I can listen to the signal going into V3a and coming out of pin number #3, stronger as it should be. But on the other side of the 1.8k resistor no signal.That schematic is pretty close other than the tone stack on the overdrive side is after the solid state CF after the second stage.
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Tubnit bunch of good ideas will check the 27k being grounded first. Thanks Bill
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Good call on the 27K resistor. might be bad, reading no resistance in circuit, But stranger still reading as an open short to ground thru the resistor. I was tired last night and needed a fresh eyes on this . Will change it out when I get home from work. thank you
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But stranger still reading as an open short to ground thru the resistor.
Open short to ground??? What does that mean? How is that displayed on your meter?
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Open short to ground???
I'm thinking he means it doesn't have continuity to ground??
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Sorry guys i misspoke ,Trying to hurry out the door to work . Kids talking to me at the same time. With my tester it showed continuaty strait thru the resistor which it shouldn't do .when i measured the resistance it didn't register,usually in circuit it might show the wrong resistance because of other factors but always shows something . So im going to change that out when i get home .Thanks Bill
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Got it. I had used a 5 lug terminal strip in a couple places . This one mounted in the middle which made that lug grounded. Tied my whole circuit to grounded lug which stopped the sound right there. LOL
Thanks Guys PS amp sounds fantastic cant wait to crank her up tomorrow.
Will put some pictures up when I get her in the 1x12 cab.
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You're not the first person to tie a circuit by mistake to a terminal ground lug. :icon_biggrin:
Anything that you're willing to share in the way of photos, schematic, sound clips or specific critique of tone would be valued. :thumbsup:
With respect, Tubenit