Caps in series??

[dumbassbob]

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

thanks Tom for finding my old post with the pictures of my amp..That 220k plate resistor was factory.. Only mod was the domino cap that someone stuck on piggyback to the wire...

[Chuck H]

sigh.?....

The amp went to Gerald Weber for??? By the time DAB got it back from Gerald (over two years later) DAB had a bag full of pulled caps and an amp that was rewired as per the BF schem and had the 350pf cap circuit removed! When DAB got the amp back it was missing it's secret sauce and he attempted to restore it by putting the 350pf domino cap back in where it seemed to be before he sent it to Gerald.

Everyone read this twice if necessary. The 350pf cap and it's placement in the current amp is utterly arbitrary.

[g1]

I don't think anything is possible here without pictures.

[J M Fahey]

thanks Tom for finding my old post with the pictures of my amp..That 220k plate resistor was factory.. Only mod was the domino cap that someone stuck on piggyback to the wire...

What the HELL does that mean?
"Stuck on" means NOTHING !!!!!
Where the heck is it soldered.

I see a picture from above showing a "domino cap" soldered from a 100k resistor end to an intermediate eyelet and a small ceramic (can't read it fully) from said eyelet to the next one upwards.

The original layout shows a wire bridge/jumper (dotted, meaning it's invisible under the board) joining the mid and lower eyelets, very probably because ceramic cap legs were not long enough or to protect it from vibration.

Now IT SEEMS (no confirmation after some 100 maddening wasted posts) that the wire bridge is still there and dumbassbob soldered the Domino cap across the wire, shorting it, OR he pulled the jumper and the domino cap is NOT shorted.
WE CAN NOT GET THAT SIMPLE QUESTION ANSWERED.

Is this a bad joke?

Do not post or answer ANYTHING until this very simple and crucial question is ANSWERED by dumbassbob:

Measure resistance across the domino cap, is it shorted or not?

YES or NO?

[J M Fahey]

thanks Tom for finding my old post with the pictures of my amp..That 220k plate resistor was factory.. Only mod was the domino cap that someone stuck on piggyback to the wire...

What the HELL does that mean?
"Stuck on" means NOTHING !!!!!
Where the heck is it soldered.

I see a picture from above showing a "domino cap" soldered from a 100k resistor end to an intermediate eyelet and a small ceramic (can't read it fully) from said eyelet to the next one upwards.

The original layout shows a wire bridge/jumper (dotted, meaning it's invisible under the board) joining the mid and lower eyelets, very probably because ceramic cap legs were not long enough or to protect it from vibration.

Now IT SEEMS (no confirmation after some 100 maddening wasted posts) that the wire bridge is still there and dumbassbob soldered the Domino cap across the wire, shorting it, OR he pulled the jumper and the domino cap is NOT shorted.
WE CAN NOT GET THAT SIMPLE QUESTION ANSWERED.

Is this a bad joke?

Do not post or answer ANYTHING until this very simple and crucial question is ANSWERED by dumbassbob:

Measure resistance across the domino cap, is it shorted or not?

YES or NO?

[Chuck H]

What pictures? Bob mentioned the thread with pictures and Juan seems to be looking at a picture now, but I don't see any pictures in the link or the links on the link.?.

EDIT: Never mind. I only saw the lower link in Toms post and didn't realize there was another.

[J M Fahey]

Hi chuck, I was looking at this:


Of course, it's 5 screens away, other members have to hunt for this, simply because dumbassbob is too lazy, careless or rough enough to do it.

I for one won't answer a single comma until dumbassbob clears this mess, by answering YES IT's SHORTED or NO.

Each can do as he pleases, after all Masochism IS a human trait.

I suggest watching Roman Polanski's latest film/movie , a true Masterpiece:

La Vénus à la fourrure (2013) - IMDb

Venus in Fur Trailer (Theatrical Trailer) - IMDb

Venus in Fur Trailer (International Version) - IMDb

[J M Fahey]

Forum special feature: automatic double post.
Oh well.

[Enzo]

Thanks Juan, geez, if we had had that photo in post #1, we could have saved going back and forth for 30 posts.

[g1]

I have no idea whether that picture represents the current state or some previous state.

[J M Fahey]

Thank Tom who did the digging , I just copypasted .

[52 Bill]

I don't know why, but I just re-read that entire post. Leo Gnardo asked if the open end of the 220K resistor was connected to the point where the two caps met. Bob said the resistance reading was zero between the two points. That led me to create the schematic that I posted. I had never seen this circuitry before in real life or on paper.

This was based upon the information that was culled from the more than 100 posts in that old thread. If in fact the jumper that is normally installed on these boards is wired across the domino cap and that there is also a jumper from the end of the 220K resistor to the end of the 250pf cap then the plate resistor value would be altered and the domino cap would be bypassed.

I wish that someone with technical skills could actually check this amp out and finally answer the question about the added circuitry. For whatever reason Bob doesn't know how to or doesn't want to answer even straightforward questions about it. Maybe Leo Gnardo can remember who owns the Tremolux that he fixed in the past and can track it down to get the real scoop.

[Leo_Gnardo]

Maybe Leo Gnardo can remember who owns the Tremolux that he fixed in the past and can track it down to get the real scoop.

To the best of my recollection the circuit was as you posted Nov 2013, 52 Bill. And extra points for making it look just like a Fender schemo with your photoshop skills, sure had me fooled then amused. Chuck posted it for our convenience with the name "maybestack" in #24 of this thread. To get the owner of that Tremolux happy I simply did without the extra bits and let the normal tonestack be what we're used to.

By coincidence I saw the T'lux owner for the first time in @ 17 years last Wednesday. His studio is 35 miles away, sorry not going there to peer inside the amp again, and I'm sure he's not going to bring it here. What was obvious, Fender put in extra eyelets for the extra caps so it was no accident they were there. A tone experiment that came & went like a shooting star, if you blinked you missed it. DAB's bandmaster is a rare "living example" of that dead-end design. If the "maybestack" is what made the amp sound special, and you like it, I have no problem with that. And it's bound to be different from those made before and after.

- - - - - - -

Juan, "Venus in fur trailer" sounds like something from way up north Canada where you might find a trailer full of fur: "We carry fox, wolf, badger, wolverine, ermine, fisher, mink, weasel, beaver, elk, wapiti, moose, even skunk. Hey whatever you want, we got it in Venus and Nanook's fur trailer! Just follow the northern lights, point your mukluks thisaway and don't mind the snow. Don't forget we're open all night from September thru June."

[52 Bill]

Part of the continuing mystery/misdirection is that in a later thread (about popping noise) Bob mentions removing the extra 220K resistors. Which ones? I don't know.

[J M Fahey]

For whatever reason Bob doesn't know how to or doesn't want to answer even straightforward questions about it.

The main point here is that some old stagehand or night guardian at the ????? Theater or something wanted to get rid of some old beaten "house amp" , and the local pawnshop wouldn't pay more than $50 for it ... if that much ..... so just in case he started telling some unbelievable story about it to anybody he approached, to try and add some value to it.
Guess who fell for it ... hook, line and sinker?
Yes, "XXXXXXXXXX" ...... who else?

And that gullible buyer who must remain unnamed has been agonizing since, including throwing thousands of hare earned dollars into the fire, molesting everybody who falls in his trap, trying to recover the Mojo which was never there to begin with.

What Mojo anyway?
Old Fender amps sound killer on their own, without help of any fairy dust or harebrained Mods.