Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on January 22, 2013, 08:43:19 pm
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This is my attempt to try and make the 5D6 Bassman Layout. I am 99.9% certain of the circuit after looking at 30+ pics of all resistors,coupling caps,cathode,feedback,tonestack,PI,bias,etc.
If you spot anything that is different on your 5D6 Bassman if you are lucky enough to own one Please chime in here
I see 1K brown,black,red 1K input grid resistors
Hold on i have to redo another layout. This isnt right
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I see 1K brown,black,red 1K input grid resistors
Not possible because that would look like a short given the guitar's 250k volume pot and ~6k pickup impedance.
I never saw a tweed Fender with less than 1MΩ; when grid leak biasing was used, the resistor after the cap would be several-megs.
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Ok :think1:
Edit: No confirmed voltages
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Sketch look very nice .
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Well i think i was wrong about the transformers being the same as the 5D6A. Just cant find real good resolution pics of the bias area
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Can anyone confirm the absence of the 220Kr between the treble and bass pots wipers. I dont think there was one. All pics available dont show clear views of stock 5D6 amps. This is driving me mad. Im already crazy so im 90% there. I cant see very good these days. You have to save and blow up the picture to see it better
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I'm pretty sure I see a resistor with some red paint on it and spagetti tubing on the leads.
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I'm pretty sure I see a resistor with some red paint on it and spagetti tubing on the leads.
I'll be damed! You have good eyes there my friend. Now i feel better. You made my day. Thanks a mill Steve :icon_biggrin: :worthy1:
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Did you review the pics on Steelguitar forum?
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Apparently chassis 035 P/T did not have a bias tap.
Thanks for the work and the great eyes.
Unless I am wrong, I believe Doug's 5F6a board could be used to make a 5d6 clone. In Plexi's honor, we should call it a 5D6c. Therefore submit the layout to the forum, (5d6 clone).
From what I can tell no one, and I mean no one has posted a schemetic or layout. Kudos Plexi :worthy1:
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Yes drgonzonm i did see that one pic with no bias tap. But i have seen others with the tap. Really one heck of an amplifier to try and document. My collector friend says that the specs on the 5D6 are all over the place between the November-DL & December-DK and visa versa. I think just owning one would be enough to satisfy even the most picky conisouer. I also think the fact that the 5D6 & 5D6A both use dual rectifiers is pretty awesome for the time period. Like HBP said in an earlier postin,you could remove one 5U4G for a little guitar sag. You have the best of both worlds using 2 for strong bass and one for guitar sag. Though i think we can all agree that these were and are better guitar amps. The OT is different i have found for the 5D6 vs the 5D6A. Possably power transformer specs to but i dont suspect so. Different PT pics do show all cloth PT wire vs 5D6A half cloth,half plastic coated. Call it the 5D6HF (Hoffman Forum)
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Apparently chassis 035 P/T did not have a bias tap.
if you need a bias tap you van easely have one using 'high " voltage secondary , like some Marshall did on some amp
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The comment regarding the bias from an HT secondary, was the method documented on chassis 035.
It is my understanding that the DK and DL designation on the 6D's signified different months of manufacturing plus design differences and the DL became the E6.
I made comment previously on this thread that the D6Fa board could be a possible source for a 6D, remembering that the diode application is different and the PI's are different. Cathodyne on the 6D and LTP on the 6F's
Plexi your modesty is showing.
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This pics shows where they dissconected the selenium rectifier and got a bias tap from one of the 5Y3's. Ran a wire from the 5Y3 to a 100K resistor with diode and 6800r. I had to google modesty. Modesty = a 5D6 in my possesion. Fat chance that will ever happen. Abbracabara! Ding,ding!
It didnt work :dontknow:
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This pics shows where they dissconected the selenium rectifier and got a bias tap from one of the 5Y3's. Ran a wire from the 5Y3 to a 100K resistor with diode and 6800r. I had to google modesty. Modesty = a 5D6 in my possesion. Fat chance that will ever happen. Abbracabara! Ding,ding!
It didnt work :dontknow:
I was referring to suggesting that the work you did, be called a 5D6HF. When you send the schematic and layout to be saved, at least add the following plexi50 et. al.
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Oh ok drgonzonm. The only thing left for me to do is to take all the voltage readings with a 5Y3 in it. I have not had the time to go and post those 5Y3 and all preamp voltages. Getting ready to finish the Deluxe 5E3. Good idea
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there is a ground missing on the bias supply... 25uF 25V (+) & 68K should be grounded.
--pete
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Thanks for noticing that Pete.
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V2 12AY7 [2nd bottle from right] should have 1 & 7 strapped and not 2 & 7.
--pete
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schematic attached. please check for errors.
--pete