Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: stringbender.dk on September 19, 2016, 03:47:34 am
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Hi!
I'm from Denmark.
I buyed a super reverb amp kit from Tube amp doctor two years ago.
I got a tech to make it for me. I wanted him to do three mods in it.
1. convert the tremolo from photocell to tube tremolo(bias)
2. wired it to run a 12" speaker instead of 4X10"
3. make a "tweed mod" in the normal channel, and connect the tremolo to the normal channel...
I found the layout and diagrams for the tremolo mod here on hoffman amps webpage and gave them to him.
But he had many troubles with the tremolo. and he could not make the tweed mod. he used a lot of time (money) to make the amp.
But when it finally worked, I wasn't happy with the intensity in the tremolo. it could not be deep enough.
Can we do something to make it go deeper, I asked him. He soldered some capacitors in the tremolo circuit. and it worked...
but now after a year, the tremolo doesn't work anymore. I could make it work in the first place if I pulled the V5 tube out and put it in again. but if I switched the tremolo off and on again, then it wouldn't work again....
I have tried new tubes in V5 and some new output tubes. but it won't work anymore...
Have you seen the same thing in your amps?
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I suppose you haven't a schematic to show us ....
Franco
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The intensity of the tremolo in the Hoffman bias vary circuit is dependant on the bias setting for the power tubes. You will have to compromise between strong tremolo and your 'correct' bias. This is more noticeable with 6L6 tubes than 6V6 tubes.
You can replace the 4.7K and 25µF cap on the oscillator tube cathode with a red LED to increase the intensity of the tremolo.
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Did you look in ARCHIVES for the tremolo mods? Lots of useful info there.
http://el34world.com/Forum/index.php?topic=604.0 (http://el34world.com/Forum/index.php?topic=604.0)
With respect, Tubenit
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thank you for your answers :)
So, Sluckey, could a tech adjust the bias "normal, if he do the mod you just suggest, or does the bias still be cold for increasing the intensity?
Sluckey: "You can replace the 4.7K and 25µF cap on the oscillator tube cathode with a red LED to increase the intensity of the tremolo."
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Just try it and see.
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how big an LED should I buy?
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5mm RED rated for 1.7v to 2v @ 20mA. Connect LED cathode to ground. Don't get any current hungry jumbos. If it doesn't blink then it's hooked up backwards or it's too big.
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thank you :) is it really that simply?
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just one more question :)
The tremolo circuit should still be wired like the "hoffman way", right?
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The tremolo circuit should still be wired like the "hoffman way", right?
I'd say ya, but might get over-ruled. I believe it's an easy way of boosting tube gain, for a stronger trem signal out.
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do you mean it will hurt the tube?
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The tremolo circuit should still be wired like the "hoffman way", right?
Yes.
This mod will not hurt any tubes.
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would this LED do the trick?
http://www.musikding.de/LED-5mm-red (http://www.musikding.de/LED-5mm-red)
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yes
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Hi again, I've found this in a old thread.... is this the way the LED should be wired in the tremolo circuit?
Is there any diagram or layout for the mod?
it's just so I can show a tech what I'm talking about... :)
Sorry to bring back an old thread.
But I just finished modding my 2 channel AB763 Hoffman Deluxe with 2 - 6V6's
I played with the mods here looking for a full rich swampy trem that the Brownfaces and Blackfaces I've owned were lacking IMO.
The best trem I've ever heard in person is from my 57 Tremolux and after implementing the mods here, I feel this amp leaves it for dead,
I'm going to say , the richest/fullest swampy Trem I've heard :worthy1: thanks for the insight folks
I ended up with
V5 - Pin 2 - 0.02uf
V5 - Pin 3 - LED to Ground
V5 - Pin 8 - 220K and the 0.1 cap off that resistor to ground I changed to 0.05uf
I tried a few different tubes and found a really nice one
Thanks for the tips folks , Awesome mods