Blackface Deluxe non-reverb servicing

Ronno25

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The 220k resistors and series caps are somewhat bizarre. I just looked at a lot of circuit pics on reverb.com and can't find anything that has them.
 

Ten Over

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You might be able to attach a solder lug to the chassis using the hole that the Death Cap used to go through before you removed it. That way you don't have to drill a new hole for the dedicated mains ground. How ever you connect the mains ground to the chassis, make sure that wire is long enough that it would be the last power cord wire to tear loose in the event that you are swinging the amp around by the power cord.
 

slider313

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What are these resistors I've circled? They don't seem to be leading anywhere and they aren't on the schematic so far as I can tell.

They look to be 100k plate load resistors.

1662325518401.png
 
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David Barnett

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They are 220k. I checked again and they are connected to the point between the series treble caps you mentioned.

View attachment 1024588

Do the red lines drawn correctly? The point where the three resistors come together in each group is the power supply node. If the red lines go to the far ends of the 220K resistors instead, this would be an RC network across the plate resistor. What's the value of the yellow ceramic caps?

Screen Shot 2022-09-04 at 10.09.21 AM.png


And if what I've drawn is incorrect, where do those ends of the resistors go?


My AA763 Deluxe amp is from September 1963 and doesn't have these. Your amp is either a very early, almost prototype Blackface amp, or has been modified. What's the serial number stamped on the back of the chassis? Mine, for example, is "A00468".
 
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Wally

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but the imprinted serial number is 1964
If that serial,number falls in the number range that sits at the end of 1963 and the beginning of 1964, I would call the amp a 1963 based on the ink stamp date on the chassis…unless that decode is in the the last week of the year, maybe. Those serial number charts are good for all of the year except that transition from the end of 9ne to the beginning of the next. The authors of the articles “Dating Fender Amps” admit to this vagueness on the cusp of the year.
 

schmee

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It seems I have seen those 'mid placed' resistors before for some reason, but I'll be damned if I could remember where.... or truly if!
 

Wally

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Maybe to add the actual model number would be a good idea .....
It is true that prior to the BF era Fender schematic numbers were in fact model numbers as well as dating codes for the circuit. That model correlation went away for many models when they started the BF era. There is a date code for the circuit, but many schematics share the same codes among different models…especially in the BF era.
 

Ronno25

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Do the red lines drawn correctly? The point where the three resistors come together in each group is the power supply node. If the red lines go to the far ends of the 220K resistors instead, this would be an RC network across the plate resistor. What's the value of the yellow ceramic caps?

View attachment 1024694

And if what I've drawn is incorrect, where do those ends of the resistors go?
You are correct. My apologies guys that previous drawing I posted is wrong. David Barnett's in post #27 is correct.
 
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Paul G.

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I can't, for the life of me, figure out what those resistors (the ones between the plate load resistors) are doing.
 

Wally

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Serial number impressed into chassis is A 00658.

PT 606325
Choke 606312
OPT 606314
That number is on the cusp for BF non-verb Deluxe amps. I would date that amp to 1963 unless I found other date codes that established that it was a very early 1964.

The 220k ohm resistors are interesting. They appear to be original From what I can see. ????
 

Lowerleftcoast

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I am in suspense.
Use your meter to find where the 220k resistors are connected. Perhaps the junction of the two caps (500pF and 250pF?) in series? Are they connected to anything at all?
 

Wally

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That's what I figured. So then it forms a second order high pass filter.

One cap is 500pF, what is the other cap?

Would this hi pass filter reduce frequencies below the cutoff point while passing frequencies above the cutoff point? If so, then I can understand why one rarely sees this circuit in a Bf/SF Fender, neh???? New one for me…..I have an amp I need to open up for a look-see. Same non-verb circuit but built before this one was.
 

Ronno25

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I am in suspense.
Use your meter to find where the 220k resistors are connected. Perhaps the junction of the two caps (500pF and 250pF?) in series? Are they connected to anything at all?
 

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