Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Effects => Topic started by: Medman on October 03, 2012, 02:09:10 am
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Hi, I have built a 6G15 reverb from Hoffman site. When I tried it the signal comes through unmolested. Their is a change when you adjust the tone and if you thump the tank you can here the springs rattle. I noticed their is a resistor across the input to groung on the scematic and I can not find any other scematic with this on it. HELP Please, this is my first undertaking on a build in many years and don't want to crash and burn :worthy1:. Many thanks . Medman
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Their is a change when you adjust the tone and if you thump the tank you can here the springs rattle.
Hi Medman, and welcome!
That means that the reverb recovery stage is working, so it should be the preamp to verb drive stages that's the problem.
This part of the 6G15 is basically a champ amp but instead of driving a speaker it's driving the verb tank.
If your sure all the tubes are known to be good than you probably have something miswired or a cold solder joint, you'll find it. Are you sure all the heaters are lighting up? Turn on the verb unit and turn off the lights in the room to be sure.
Could you post all the voltages for each tubes pins and all the B+ PSU nodes?
Divide and conquer, try this, hook up a speaker (8 ohm) to the verb output jack that goes to the verb tanks input instead of the tank. Plug in a guitar and see if you get any sound. It won't be loud but you should be able to hear it easily.
I noticed their is a resistor across the input to ground on the schematic and I can not find any other schematic with this on it.
Do you mean the guitar input tube stages grid? There is a 1M across the input jacks hot/grid to ground.
There is a 220K added on Doug's that Fender left out on the verb recovery stage that is needed. It goes across the verb tanks return jacks hot/grid to ground. If that R is not there and the verb tank is disconnected while the units on that triode will go into runaway and melt.
Here's a copy of my schemo drawing that I built for the 6G15. You can see where/how that R is added. (I also added a couple of 10K grid stoppers that you can leave out.)
Brad :icon_biggrin:
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Thanks for help. This site is GREAT for us novice builders... Thanks again, and my God bless you and yours, will post results...medman :think1: :icon_biggrin:
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Took your advice went through and checked soder joints also added a wire to ground close to power input, not works GREAT, thanks for inspiration.Now a cabinet is next on agenda, don't know what I did but it worked, Have you ever built a revibe? Thanks again. Medman :laugh: :icon_biggrin:
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I ment to say working GREAR, Thanks :icon_biggrin:
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Glad you got it working.
No, I havn't built a revibe. Look in Dougs tube amp library of information for info and pictures on how to build one.
Here's the link;
http://www.el34world.com/schematics.htm (http://www.el34world.com/schematics.htm)
Brad :icon_biggrin: