Caps in series??

[Enzo]

I am still troubled by this over the wire thing.

You say the wire in question is under the part board. Are you telling us the 350pf cap is sitting on top of the board right where the wire goes under it? Is the 350pf cap soldered to the ends of the wire? Or is the cap simply sitting above where the wire goes? If that is the case, there is no relation between cap and wire, other than they are physically near each other. Regardless, all that matters is what are the two ends of the added cap soldered to?

Looking at the layout, I see the curving dotted line for the hidden wire. If one end of the 350 is soldered to the end of the 250, and the other end to the eyelet at the end of the 0.1uf, then it seems the 350 is parallel the treble pot. Please clarify.

it would help to either photo the thing, or at least describe it using different words.

[J M Fahey]

Every time I read this I am more and more worried, and no,

Thanks I got my answer

does NOT apply because nobody actually answered, because nobody understood your question to begin with.

Or at some point *thought* they understood (me included) but your later answers confuse the things even more.
So far the unanswered questions are:

1) is the 350pF cap soldered to anything or is just, say, glued there, on the top of the board
The "dotted line" does not help me because it is under the board, as unconnected as if it were on the Moon.

2) IF soldered, where to?
We need pictures showing that, plus a layout hand edited by you, showing the cap and its connections (or lack of them).

3) FYI , you are referring to a LAYOUT , not a SCHEMATIC.

Just to make Life easier, here they are, download one, edit in Paint or whatever showing the cap , its legs, position and wiring (if any)

[Chuck H]

Photos are irrelevant at this point because DB put the cap back where he THOUGHT it was after Gerald Weber attempted to restore the amp and managed to flip the OT leads wrong !?!?!?!?

No point continuing. We're lucky the amp works at all at this point. Whatever the old mod, mojo, as used by Hendrix thing is long buried a lack of documentation. The most to be hoped for now that GW has undone the differences is to keep the amp as stock. Distinctly NOT as Hendrix used it (with some sort of circuit that involved a 350pf cap).

Cheers

[J M Fahey]

Sorry but pictures are *still* needed, per the description not sure whether the cap was soldered somewhere, glued to the top or some other way of mounting.

Also not sure about the cap orientation.

Nor on what side of the board it actually was.

Unless you can answer all that with certainty.

[Enzo]

I'd like to follow along a bit longer, because the forum relies upon communication, and I fear it was breaking down here.

[dumbassbob]

Every time I read this I am more and more worried, and no, does NOT apply because nobody actually answered, because nobody understood your question to begin with.

Or at some point *thought* they understood (me included) but your later answers confuse the things even more.
So far the unanswered questions are:

1) is the 350pF cap soldered to anything or is just, say, glued there, on the top of the board
The "dotted line" does not help me because it is under the board, as unconnected as if it were on the Moon.

2) IF soldered, where to?
We need pictures showing that, plus a layout hand edited by you, showing the cap and its connections (or lack of them).

3) FYI , you are referring to a LAYOUT , not a SCHEMATIC.

Just to make Life easier, here they are, download one, edit in Paint or whatever showing the cap , its legs, position and wiring (if any)

see where the 100k plate and slope resistor are At that point where the dotted line is going under the board..There is a 350pf dommino cap going over that wire to the 250pf The wire under is connected ..So all I wanted to know is if was doubleing the voltage or is it doing nothing since both the wire and the cap are connected...Also on My board there is a 250K resistor from point D in the middle of the 2 plate resistors going to that other.047 on both channels Thanks for posting the schematic

[J M Fahey]

see where the 100k plate and slope resistor are At that point where the dotted line is going under the board..There is a 350pf dommino cap going over that wire to the 250pf

"Going over" tells me NOTHING .
Do you understand what I'm saying?
DRAW where is that cap connected to and if possible post a PICTURE , not a VERBAL DESCRIPTION which nobody here understands.

The wire under is connected

Connected to WHAT?
Is it connected to the : domino cap" ?
HOW?
DRAW the connection and add a picture, just in case your drawing is incomplete.

..So all I wanted to know is if was doubleing the voltage or is it doing nothing since both the wire and the cap are connected...

We are not seeing any connection , nor the cap.

Also on My board there is a 250K resistor from point D in the middle of the 2 plate resistors going to that other.047 on both channels

Please DRAW what you are saying.
We are trying to help you, we DO NOT have the amp before our eyes, in our benches, we must RELY on your verbal descriptions only, which are incomplete or poor.

Thanks for posting the schematic

You're welcome

[Enzo]

OK< nothing is changing any voltages. Adding a cap in this area will only potentially change the frequencies in the tone circuit a bit.

However, I am with Juan. Where the part sits doesn't mean anything. We need to know where each end of the new cap is soldered to.

Look at the layout image above just as it shows on the screen. The 250pf cap is soldered to two eyelets, one at each end. The lower end has the dotted line to another eyelet where two 100k resistors are soldered. So one end of your 350 must be soldered somewhere. Is it at either of the eyelets where that short dotted line connects? In other words is one end of it soldered either to the lower end of the 250 or to the joint of the two 100k? And is the other end of the 350 soldered to the eyelet at the top end of the 250? That would put it in parallel with the 250, making the treble cap 600pf instead of 250pf, and that will shift the tone control down to upper mids a little more.

If the 350 is soldered to other points, then we need to know just where.

[Chuck H]

In a previous thread about this amp with other, equally ambiguous circuit descriptions 52Bill proposed an alternative tone stack that Fender is supposed to have experimented with on some amps. By DB's description of the series treble caps and the extra 250k resistor in the circuit I think there may be something to this. It would also explain why the original, "as originally purchased by Bob" tone has never been restored. Now that the amp has been rewired, and fussed with, rewired again and fussed with repeatedly it's IMPOSSIBLE to know what the original circuit actually was and the likely incorrect re installation of the 350pf cap by Bob after the GW rewire absolutely doesn't matter. Learning about the added cap in the circuit as it is gets Bob nowhere because the circuit is different now than when the cap was used in the amp before. Take out the damn cap, it doesn't apply anymore and is being used out of context no matter where it is/was.

I'll speculate that the ORIGINAL incarnation of the amp MAY have been with the original treble circuit series cap having been replaced by the 350pf and the 220k resistor having been replaced by a 250k that is now also being used out if context with the circuit as it exists now. Possibly the 250k and "that other .047" cap is a "reverb on both channels mod" too.

Bob, does the amp have reverb on both channels?

Anyway, it's ALL speculation now that the amp is in it's fourth or fifth incarnation with no accurate documentation of how the circuit was previously wired and Bob's tacked in "I think it was here.?." circuits. Blah, blah, blah...

Here's my vote. It's the experimental circuit that Bill posted with a text note I added:

[Leo_Gnardo]

In a previous thread about this amp with other, equally ambiguous circuit descriptions 52Bill proposed an alternative tone stack that Fender is supposed to have experimented with on some amps.

Thanks Chuck for finding 52Bill's diagram. I remember that thread, and that I'd run across a ? '63 Tremolux head with that same rarely seen experimental EQ stack. Which helped unravel the mystery to which we have returned. A re read of that thread (please please please post the link) may re solve the re asked questions we are re beating around the bush. Again. Interminably. Ad nauseum. Domino caps and all. No disrespect meant to you DAB, but I'm sure we covered it there. Find it, read & it may save us all a lot of key flapping & head scratching. The useful answers came about post #100 or so the last time this historical folklorical Bandmaster was in the MEF spotlight.

[J M Fahey]

Well, there might be something there, but the added 220k resistor *should* have the other end connected to real ground, rather than to a +350V line.
In theory both are "audio ground" , but real/chassis ground is safer, better, and has no ripple

[dumbassbob]

Every time I read this I am more and more worried, and no, does NOT apply because nobody actually answered, because nobody understood your question to begin with.

Or at some point *thought* they understood (me included) but your later answers confuse the things even more.
So far the unanswered questions are:

1) is the 350pF cap soldered to anything or is just, say, glued there, on the top of the board
The "dotted line" does not help me because it is under the board, as unconnected as if it were on the Moon.

2) IF soldered, where to?
We need pictures showing that, plus a layout hand edited by you, showing the cap and its connections (or lack of them).

3) FYI , you are referring to a LAYOUT , not a SCHEMATIC.

Just to make Life easier, here they are, download one, edit in Paint or whatever showing the cap , its legs, position and wiring (if any)

On The LAYOUT look at the 100K plate (R)that goes to Pin #1 there is a black dot then you see the dash marks going to the black dot at the 250 cap..Someone 45 yrs ago soldered a 350 PF Domino cap.So BOTH the under the board wire And the 350PF cap Are BOTH (piggyback) going to the 250PF cap..All I wanted to know is if made the voltage higher Or if the 350pf cap would be canceled.Someone here already said it did..Thats why I said "I got my answer...

[dumbassbob]

In a previous thread about this amp with other, equally ambiguous circuit descriptions 52Bill proposed an alternative tone stack that Fender is supposed to have experimented with on some amps. By DB's description of the series treble caps and the extra 250k resistor in the circuit I think there may be something to this. It would also explain why the original, "as originally purchased by Bob" tone has never been restored. Now that the amp has been rewired, and fussed with, rewired again and fussed with repeatedly it's IMPOSSIBLE to know what the original circuit actually was and the likely incorrect re installation of the 350pf cap by Bob after the GW rewire absolutely doesn't matter. Learning about the added cap in the circuit as it is gets Bob nowhere because the circuit is different now than when the cap was used in the amp before. Take out the damn cap, it doesn't apply anymore and is being used out of context no matter where it is/was.

I'll speculate that the ORIGINAL incarnation of the amp MAY have been with the original treble circuit series cap having been replaced by the 350pf and the 220k resistor having been replaced by a 250k that is now also being used out if context with the circuit as it exists now. Possibly the 250k and "that other .047" cap is a "reverb on both channels mod" too.

Bob, does the amp have reverb on both channels?

Anyway, it's ALL speculation now that the amp is in it's fourth or fifth incarnation with no accurate documentation of how the circuit was previously wired and Bob's tacked in "I think it was here.?." circuits. Blah, blah, blah...

Here's my vote. It's the experimental circuit that Bill posted with a text note I added:

Thanks for posting the schematic...Yes that is where the 350pf is ,But the Under the board wire going to the 250pf is also still connected,So that would put the wire and the 350pf in Parallel(right?)and then in Series with the 250pf

[Enzo]

SImple test: measure resistance end to end of the 350pf. If there is zero ohms, then the wire is still shorting it.

[Tom Phillips]

SImple test: measure resistance end to end of the 350pf. If there is zero ohms, then the wire is still shorting it.

The test Enzo describes is really important because it will tell you about that part of the circuit that is in your amp now. The diagram shows how the amp was designed to be built over 50 years ago. Furthermore, the diagram doesn't even show the rare tone stack configuration that your amp originally had. That tells us that we can't take anything as pure truth. We need to investigate and test. It's important to distinguish between the modified condition of the circuit and the old service information because there is no guarantee that any particular sections of the amp will match. Ya can't be two places at the same time and you can't base your final diagnosis on a dashed line shown on a diagram.

If you read zero resistance across the 350pF cap that implies that the wire is still connected under the board. If so then the cap is shorted out and will have no effect on circuit operation. There is, of course a small possibility that the 350pF cap has failed in a shorted condition but, jez, it's gonna be really difficult to get through this if we don't get the basic evidence sorted out. If your not convinced then remove the 350pF cap and measure the resistance between the eyelets again.

I will add that it is relatively easy to remove or change the wires under an old style Fender parts board. It is often done on purpose when doing custom mods and sometimes the wires are disconnected by accident when doing work on the board. That causes all mannor of confusion and problems.

For those who are interested the old discussions about this amp are here http://music-electronics-forum.com/t34032/ (With photos)
and here http://music-electronics-forum.com/t34782/

Tom