Caps in series??

[Dave H]

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

DAB said "It sounds fine" in post #1 and the smoke has stayed inside for 45 years so why worry about it?

What is with that unconnected wire at the top right of the picture?

[Tom Phillips]

...What is with that unconnected wire at the top right of the picture?

Looks like a shielded wire was added for the input signal and the stock wire was just disconnected and left hanging.
Tom

[J M Fahey]

Looks like a shielded wire was added for the input signal and the stock wire was just disconnected and left hanging.
Tom

Of course, pulling the old now unused wires would have pulled some of their attached Mojo with them, so just in case better leave them there.

Notice that we still don't have the resistance across the Domino cap measurement.

Just in case, I'm not holding my breath.

[Chuck H]

Ok... Everyone hold off with "IT'S ALL SPECULATION!" because it doesn't matter. DAB has almost NEVER taken a measurement or done a test as requested. Expecting otherwise or getting upset about it is the equivalent of getting mad about water being wet. So speculation is, and shall remain, all that's going to happen.

I've been re reading the old threads regarding this amp and I think I've got a bead on what's happened and even how DAB can get the mojo back! (It's all speculation though )

I'll be using the timeline of events and inserting my own SPECULATION about how this amps story played out. It may go a little long, but please hang in there.

DAB's amp started to sound and perform poorly (probably due to old electrolytic caps).
Under the hood he found that one of the "extra" 220k resistors was cracked.
DAB started working on the amp and that didn't fix the sound. In fact it made it worse.
DAB sent the amp to Gerald Weber, who "fixed" the amp. But now the amp sounded dull and bad.
DAB sent the amp back to GW. By the time GW and DAB were finished, DAB had a bag of parts, the amp had been "restored" to a stock BF circuit and had the power supply electrolytics replaced.
The amp still sounded bad and had other problems so DAB sent the amp to a different tech. Skip.
Skip cleaned up the marginal work done by GW and returned the amp to DAB. But now the amp was unstable. It was discovered that the OT leads had been reversed at some point. This was corrected and the amp sounded pretty good, but still not the same as it did by DAB's memory.
In an attempt to restore the mojo DAB reinstalled the domino caps. But now they were across jumper leads installed when the amp was wired as a BF circuit. So the domino caps are doing nothing.

I don't know if DAB reinstalled the "extra" 220k resistors in some circuit configuration he THOUGHT they may have used. DAB said he thought they terminated at the downstream side of the .047 coupling caps for the tones tack recovery stage. Obviously this is wrong because Fender wouldn't install a coupling cap and the then bypass HV to the downstream side. That makes no sense at all. Even if the circuit ISN'T stock and someone other than Fender installed those extra eyelets and 220k resistors, I seriously doubt someone savvy and conscientious enough to add eyelets would be so ignorant of circuits. So the amp wasn't wired that way. Same with the domino caps. They wouldn't have originally been installed across a jumper. Whether DAB has the domino caps wired that way now I don't know. Whether he has the extra 220k resistors applying HV to the downstream side of the coupling caps I don't know either. These things have been hinted at. DAB has been saying what he thinks the circuits are, but not revealing how they got that way and not confirming with tests.

So I speculate...

The original circuit was using the circuit proposed by 52Bill and Leo. That is, the domino caps were in series with the stock treble caps and the extra 220k resistors were wired from the junction of the caps to the HV node. NOW... Since the amp started sounding bad DAB opened it and found the cracked 220k resistor. I now think the amps tonal problems were age related and had nothing to do with the cracked 220k resistor. In fact I think that 220k resistor WAS ALWAYS CRACKED and this is why the amp has never been restored to it's original, as purchased by DAB, tone. Why?!? Because when Gerald Weber first fixed the amp it sounded dull and wrong. That is what I would expect from the experimental circuit proposed by 52Bill and Leo. And when the amp was made to BF specs it sounded too bright and harsh to DAB. That, I suspect, was the actual tone of the stock BF circuit. So what circuit was actually in there???????

Since one of the extra 220k resistors was cracked (perhaps since DAB purchased the amp), the two caps were no longer part of the 220k circuit but simply in series. The treble circuit cap value in this circumstance is 145.8pf. I SPECULATE that if DAB removes the 220k resistors, the domino caps AND the 250pf stock treble caps and simply puts 150pf caps in the treble circuits that the amp will sound as DAB remembers. Or very, very close.

The lack of documentation and cooperation on DAB's part along with other speculations from posters that haven't followed the amps history has confused the issue greatly. I'll wager six craft beer PNW that I have this exactly right.

[Chuck H]

This would be the intended experimental circuit:


This would be how DAB was actually using it:


This would be how GW rewired it:


This would be how DAB may have it wired now:


This is how it should be rewired:

[Chuck H]

I'll offer this...

To avoid any further misinterpretation and miswiring by DAB, confusion here on the forum and just because I'm so confident in my theory I will look over DAB's amp, touch up whatever it needs and rewire it to the proposed circuit FOR FREE if DAB will prepay shipping.

[dumbassbob]

Thank you Chuck thats a nice offer,yes #4 is how DAB has it,with the domino caps ..I took the (2) 220k resistors out (why did Fender do this?)...All I wanted to know is if the Domino caps are doing anything. Good or Bad...The amp was cleaned up by skip simmons He only charged me the shipping(after being totally ripped off by amp guru G,webber over $1500.00 11/2 yrs)...I asked him if the domino caps didn't hurt anything,to leave them in, I don't know why I guess thats why I am DAB.... I seem to always start trouble here I do not mean to...I am a pretty good guitar player,and I build my own LH guitars...Thanks again

[DrGonz78]

I seem to always start trouble here I do not mean to...I am a pretty good guitar player,and I build my own LH guitars...Thanks again

Well all the threads have been very entertaining at the least. If you ask for help and someone says use your meter to test resistance on a part, then do it. Confirm if the cap is series or parallel and move on.

[dumbassbob]

Thank you Chuck thats a nice offer,yes #4 is how DAB has it,with the domino caps ..I took the (2) 220k resistors out (why did Fender do this?)...All I wanted to know is if the Domino caps are doing anything. Good or Bad...The amp was cleaned up by skip simmons He only charged me the shipping(after being totally ripped off by amp guru G,webber over $1500.00 11/2 yrs)...I asked him if the domino caps didn't hurt anything,to leave them in, I don't know why I guess thats why I am DAB.... I seem to always start trouble here I do not mean to...I am a pretty good guitar player,and I build my own LH guitars...Thanks again

I forgot..I bought this amp in 1971 from the Hbowl...I only looked inside of it to put my name and parents phone number under a small piece duct tape.. I did keep good RCA tubes in it and not overdrive it on 10..Then in 1989 it was stolen by this prick,it went to NYC...In 2003 My mom said someone named Mannys called for me..I got it back..So I do not remember if it had the domino caps or not,same with the plate wire reversed,But GWeber never found any of this ,all he did was shotgun the all the Blue caps THATS Why it didn't sound good,that a a bad ground wire that was coroded.

[Chuck H]

Bob... Just test for the jumper. If there IS a jumper under the cap (which I expect there is since you seem to be sure there is). Just pull the jumpers and leave the domino caps. Actually, this should only be done on the channel you found the cracked 220k resistor on. The other channel should be restored to the experimental circuit. This is very likely how you were playing the amp for years before it was stolen. I base this on the tonal reports by you along a time line of the amps history here. Plenty of room for error. But I do know that nothing else seems to have been the right formula!!! Don't worry about the Astron caps unless some read way off spec. Even then there is no way to know where the off spec cap was installed before GW pulled it. As long as you have decent film caps in there it's all good.

The point is to recreate what you originally had. Which "I" believe was a cracked 220k resistor that was failing to complete the experimental Fender circuit. And in that case you had just straight up series capacitors equal to 145.8pf instead of the stock 250pf treble cap.

I think the domino caps were always in there and not installed post theft. They're too old to be part of a mod some dink whistle attempted. Maybe they weren't part of the original Fender circuit, but they were probably in the amp when you originally owned it.

[The Dude]

If you ask for help and someone says use your meter to test resistance on a part, then do it. Confirm if the cap is series or parallel and move on.

A-frickin-men! A few seconds with a meter vs. 1/2 hour of writing posts. For shit sake! Reading this thread is testing the lock on my "impolite gate".

[J M Fahey]

I forgot..I bought this amp in 1971 from the Hbowl...I only looked inside of it to put my name and parents phone number under a small piece duct tape.. I did keep good RCA tubes in it and not overdrive it on 10..Then in 1989 it was stolen by this prick,it went to NYC...In 2003 My mom said someone named Mannys called for me..I got it back..So I do not remember if it had the domino caps or not,same with the plate wire reversed,But GWeber never found any of this ,all he did was shotgun the all the Blue caps THATS Why it didn't sound good,that a a bad ground wire that was coroded.

WHO cares about this?
Did anybody ask?
JUST MEASURE THE FUCKING DOMINO CAP RESISTANCE

[J M Fahey]

Bob... Just test for the jumper. If there IS a jumper under the cap

Way too late for that.
The question,of course, will never be answered, because that would end this lonely afternoons filling thread, and then, what will DAB do with his empty life?

But you came to the rescue, offered him some 20 alternate possibilities, which will give DAB stuff for at least 200 extra posts, either here or on alternate threads.
Fun filled !!!!!!!!!!!!!!!!

Since none of the new possibilities will be fully confirmed or denied, each of them *can* split in extra juicy subthreads, such as colour, vintage, smell, texture, magnetism, humidity, weight, temperature, etc. of each 220k resistor, Domino (as a table game) compared to Chess, Go and Mah Jong , and so on, forever.

This is very likely how you were playing the amp for years before it was stolen.

How would you know?

But I do know that nothing else seems to have been the right formula!!!

Neither this will
We are "solving" a mojo and fairy dust problem here, not a Tech one.

Even then there is no way to know where the off spec cap was installed before GW pulled it.

True. That comment can also be applied to each and all of DAB's comments: no way to know.

The point is to recreate what you originally had.

How?

Which "I" believe was a cracked 220k resistor that was failing to complete the experimental Fender circuit.

Which Fender experimental circuit?
How would you know there was one in there?
The amp pictures exactly match the standard eyeletted board shown in the official layout, with the unique exception that pictures show a so called domino cap (noob/tyro name, I'd call it 350pF and couldn't care less about its packaging) soldered to eyelets which were always there, originally carrying a short jumper wire, and where some modder might have added an extra 350pF cap, and he might or might not have remembered to pull the jumper wire.

Which brings us back .... again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again to the unsolvable question: is the 350pF cap ("Domino to its friends) shorted with a jumper or not?
Now a long and entertaining story in 47 chapters will follow, where DAB tells us all about his childhood dog Snooky, all the tricks he played and how he misses it, or a detailed description, minute by minute, of the trip he made to GW's shop, or something equally unrelated.

And in that case you had just straight up series capacitors equal to 145.8pf instead of the stock 250pf treble cap.

How would you know?

I think the domino caps were always in there and not installed post theft.

How would you know?

They're too old to be part of a mod some dink whistle attempted.

So what
I have somewhere a couple old PA amps chock full of them.
If I were modding and didn't have some value, I'd happily pull one from such donors, any day of the week.

Maybe they weren't part of the original Fender circuit, but they were probably in the amp when you originally owned it.

How would you know?

[dumbassbob]

Got the Measurements

I first measured with black prob to ground and red to domino cap on Ohms Got DL...Them I put red prob on the 250cap it read on the normal channel 285.5Kohms ON the Tremolo channel it read 250.8k ohm..So the Domino caps do not do anything...I tried to see where the 220 plate resistors went to under the board I used the contuinty and it goes to the 250 cap..I will put one of the 220(R) back in and see how it sounds...The Amp works great..All preamp tubes are RCA,but I only have one worn out pair of RCA 6L6GC,so I am useing Tung Sol 6L6gcThey do not have as much kick as the RCA,but I like more than JJ's...Why did Fender put the extra 220 plate (R) in anyway? Both Transformers are dated Sept 1963...DAB

[Chuck H]

Way too late for that.
The question,of course, will never be answered, because that would end this lonely afternoons filling thread, and then, what will DAB do with his empty life?

But you came to the rescue, offered him some 20 alternate possibilities, which will give DAB stuff for at least 200 extra posts, either here or on alternate threads.
Fun filled !!!!!!!!!!!!!!!!

Since none of the new possibilities will be fully confirmed or denied, each of them *can* split in extra juicy subthreads, such as colour, vintage, smell, texture, magnetism, humidity, weight, temperature, etc. of each 220k resistor, Domino (as a table game) compared to Chess, Go and Mah Jong , and so on, forever.


How would you know?


Neither this will
We are "solving" a mojo and fairy dust problem here, not a Tech one.

True. That comment can also be applied to each and all of DAB's comments: no way to know.

How?

Which Fender experimental circuit?
How would you know there was one in there?
The amp pictures exactly match the standard eyeletted board shown in the official layout, with the unique exception that pictures show a so called domino cap (noob/tyro name, I'd call it 350pF and couldn't care less about its packaging) soldered to eyelets which were always there, originally carrying a short jumper wire, and where some modder might have added an extra 350pF cap, and he might or might not have remembered to pull the jumper wire.

Which brings us back .... again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and againand again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again and again to the unsolvable question: is the 350pF cap ("Domino to its friends) shorted with a jumper or not?
Now a long and entertaining story in 47 chapters will follow, where DAB tells us all about his childhood dog Snooky, all the tricks he played and how he misses it, or a detailed description, minute by minute, of the trip he made to GW's shop, or something equally unrelated.

How would you know?

How would you know?

So what
I have somewhere a couple old PA amps chock full of them.
If I were modding and didn't have some value, I'd happily pull one from such donors, any day of the week.

How would you know?

Dayam Juan!?! That's some "S" to reply to. I'll sum it up simply and just say that I have followed this amps history here and I believe Bob has been humble, possibly a bit accurate, with his SN , and I don't think, as you seem to, that he is insincere. A pain in the a$$ maybe, but not an evil troll. If you take this position and read through ALL THE POSTS ABOUT THIS AMP (and there are several) you would probably come to the same conclusions I have. I know you're just frustrated and don't have patience or time for mediocrity (and justly so since you da man). That's why I'm not taking the multiple quotes followed by "How would you know?" offensively. I don't know anything. It's just my theory based on research and character interpretation. I'm sorry you're having a such a problem with that. I hope you won't trouble with it further in this light and I'll see you on the next thread