New Fender "type" amp build suggestions

[JMPGuitars]

All 3 preamp tubes were bad… brand new JJ’s!!!

Shocking.

[foreverstrung]

When looking at your earlier pics I see some potential noise issues with the reverb circuit. (but hook up the tank te eliminate lots of noise already!)
- the wire from the return RCA jack to the grid of the recovery triode should be shielded wire and as short as possible.
- the green and black wires from the reverb transformer to the reverb input RCA jack are preferably flat to the chassis bottom. Certainly not flying. Don't forget that the reverb circuit in an amp is one of the most sensitive and potentially noisy parts of the amp.

Is this a bit better?

[JMPGuitars]

Get the reverb wires away from the heater wires! ...and twist them.

[foreverstrung]

Get the reverb wires away from the heater wires! ...and twist them.

I can't move them too far away from each other as they cross each other and both are spose to stay flat to the chassis. I don't have enough slack now to twist them. I'd have to splice an extension. Do you think soldering an extension and then twisting would make for a better outcome then leaving them as is?
Thx
Dave

[foreverstrung]

What path do you suggest I follow with the scope? I really don't understand most of what I see with my scope. I'm mostly concentrated on just seeing good sine waves. When I don't, I don't know if there's something there or I'm just wasting time. I'd really like to be able to follow a path to help pinpoint areas of concern.
Thx
Dave

[Bieworm]

Did you try my tube advice? This is crucial!
Also.. zip tie the black and green reverb wires so they are tight together. Make the curve the other way (left) and try to tuck away the heater wires more to the corner of the chassis

[foreverstrung]

Did you try my tube advice? This is crucial!
Also.. zip tie the black and green reverb wires so they are tight together. Make the curve the other way (left) and try to tuck away the heater wires more to the corner of the chassis

Yes. I’ve replaced all of the preamp tubes. Dressed out that reverb area as suggested. I even had an extra 12at7
When I plug in the guitar, I get nothing musical being produced. MV is producing an unlovely sound. Reverb still too is putting out an unwanted sound.
I’ll take a break and then come back and put fresh eyes on all my connections. Double check coupling caps.
With the scope on it I get good sine-waves to V1, after that, all waves I pick up at the way to the speaker are distorted.
Looking for that “ah ha!” moment sometime soon.

[foreverstrung]

Ah ha! Some success. I found a major omission. Now I’m cranking out some sound. Lots of gain. I’d like some clean sound too.
Also unwanted sound out of the master volume. Not overwhelming, but it needs to be eliminated.
Reverb is the worst noise right now. It’s unusable like this.
I’ve found about a half dozen mistakes since I started troubleshooting. That’s not counting what you guys pointed out.
Very happy I got to here.
I can’t eliminate having fried something too.
Thx
Dave

[Bieworm]

Dave.. I see a lot going on in the images.

Wiring Layout:
- Too much unnecessary long runs of wire all over the place
- Parallel wire runs should be avoided (look at the cathode and plate wires of V1B for example)
- Wires should be flush with the chassis bottom. Now you have a lot of potential antennas introducing
picked up noise into the circuit
- Wires should be at a decent distance from each other. If not possible they should cross at 90° angles
- The heater wiring is really terribly done

Soldering:
- Try to avoid soldering wires or components into the turret holes. It’s not to be underestimated how
often those kind of connections aren’t making proper contact and introduce noise problems.
- When soldering a wire there should always be a hook connection. I see at the output jacks that there
are solid wires going straight through the hole/eye without mechanical connection. Bad strategy…
- Don’t trust solder joints of wires and leads that were made on a ground buss. I always pull on the
connection while soldering until the solder solidifies.

Methodology:
- The way you do the cathode cap/resistor on the (by the way waaayyy overdimensioned) preamp
cathodes is raising questions. Are those caps coated with an insulating layer? In case of conduction the
2 cathodes of V1 will be connected to each other through the contact between the resistor lead and
the housing of the caps. Those caps touch each other too. Bad strategy anyhow. My advice would be
to use smaller caps and make a bridge with the resistor on the cap leads. Try to get some offset
between both parts in the process. Might electronically be just fine when the resistor and cap touch
one another, but in a combo you could get vibration noise and it would be a shame that this would be
the source. Sometimes signal carrying caps can translate this vibration into audible hash..
- Don’t use beefy solid wire to make a connection from turret hole to turret hole.
- Get rid of that wire you have there for any future use! If it was my amp I would do all jumpers from
tube sockets to the board all over again with wire that is easy to manipulate (pre tinned PTFE or cloth
wire). And I would definitely do the heater wiring all over again.

About the excess gain.. that's why I put a 12AY7 in V1. I run my amp between 1 and 2 before getting OD starts to engage.
Sorry for the long winded post and don't take things personal. This is only advice, given with the best intents. You'll get it fixed man!!

[foreverstrung]

Get rid of that wire you have there for any future use! If it was my amp I would do all jumpers from
tube sockets to the board all over again with wire that is easy to manipulate (pre tinned PTFE or cloth
wire). And I would definitely do the heater wiring all over again.

About the excess gain.. that's why I put a 12AY7 in V1. I run my amp between 1 and 2 before getting OD starts to engage.
Sorry for the long winded post and don't take things personal. This is only advice, given with the best intents. You'll get it fixed man!!

I hated using this wire. I asked before I started about this wire. I bought a bunch of this 1-2 years ago and had it on hand. I really wish I hadn’t used it. It’s so difficult to dress out.
I also figured going in the top of the turret was problematic but the trade off was overloading the turret.
I appreciate all of that message. I needed to hear it. I’m going to replace all of the wire. I’m really kind of OCD about how all of this is viable let alone mechanically.
I’ve got cloth wire and PTFE wire on hand. Not enough of either to do the entire amp, but maybe enough to rewire the tube sockets and new heater wires.
Next time I’ll order double turrets.
I may just order some new wire and double turrets. If I do, it might be a minute before my next post
Again, I really appreciate all of the feedback

[JMPGuitars]

I use the PTFE exclusively for amps (but I would try the Tefzel, it is supposed to be very good quality wire - that doesn't necesarilly mean easy to work with). Bieworm's advice is good, but don't be afraid to leave short leads above the chassis to create distance from wires that shouldn't be close to each other.

For example, you don't want anything touching your heater wires. It's better to create a good amount of distance (within reason) between the reverb wire, and heater wire. Personally, I wouldn't have mounted the reverb tank connection near the heater wires at all. Reverb circuits can be a PITA to build, and adding extra noise sources won't help the process of cleaning it up.

Thanks,
Josh

[foreverstrung]

Good stuff. Thanks.
I’ve ordered some new wire. PTFE. 25uF caps too that I’ll bridge like Biworm suggested. ( notice the pic of the 2.2k resistor that got fried sitting right alongside of one of these 25uF E caps)
Some other things to help dial this in as well.
I’ve removed all of the heater wires and just about everything else from the sockets.
I also moved the turret board over, (away) from the tube sockets.
I also removed the radial 22uF 450v cap and replaced it with an axial so that it lays flat as possible so that I could use 3/4” standoffs. (I had to use 1/2” with the radial E cap).
I’m actually quite relieved and very much looking forward to rewiring all of this especially now that I’ve moved this turret board over.
I’ll rewire the output jacks too. I might change out the cliff jacks for the old school Fender full contact jacks.
I’ll also remove and reset most, if not all, of my connection into the turret holes throughout. I’ve ordered some double stack turrets if I’m worried about over piling on any one turret
Thanks again.
I’ll keep this thread updated.

[JMPGuitars]

Keeping your output jacks isolated from the chassis (the Cliff plastic jacks) are less likely to cause noise issues than full metal jacks.

If you can move the reverb jacks away from the heaters, that would be good. You might have some room now that you moved the board. Be careful about stray metal bits if you have to drill new holes.

That slightly fried resistor also tells you there was a bigger issue around there. To mark it like that, there has to be way too much heat for too long. Those CMF resistors don't play around. A cheaper resistor could have exploded...popped.

[Bieworm]

Dave.. this is a very important question: do you have a ground connection on the RCA jacks of the reverb? Cuz if there isn't you have the following problems:
- 1 there is no grid load to ground of the reverb driver tube via the dwell pot
- 2 there is no grid load to ground on the recovery tube via the 220k resistor on the jack
--> I don't see any wires to ground, nor do I have the impression the jacks are grounded on the chassis.

I know there is no ground wire drawn on my layout, but the schematic clearly states they should have a ground reference. My jacks are considered to make a ground connection right there where they are bolted to the chassis. That is how Leo Fender did it. Now, sometimes you can get away with grounding the jacks directly with their body to the chassis, but sometimes this turns out too noisy and you have to isolate the jacks from the chassis and make ground connections to the negative side of the cathode resistor of that part of the circuit.
Me thinks that is the culprit of that noise you had, and it also fried that cathode resistor. You might have to replace the tubes as well.

Look closely at this picture. The jacks are grounded directly to the chassis.
viewtopic.php?p=258282#p258282

[foreverstrung]

If you can move the reverb jacks away from the heaters, that would be good. You might have some room now that you moved the board. Be careful about stray metal bits if you have to drill new holes.

I’ll do that. I’d have to move them to the top/bottom of the chassis and then plug those back panel ports professionally so that it doesn’t look ghetto but I definitely do want as quiet as possible reverb.

Dave.. this is a very important question: do you have a ground connection on the RCA jacks of the reverb? Cuz if there isn't you have the following problems:
- 1 there is no grid load to ground of the reverb driver tube via the dwell pot
- 2 there is no grid load to ground on the recovery tube via the 220k resistor on the jack
--> I don't see any wires to ground, nor do I have the impression the jacks are grounded on the chassis.

I am not grounded properly. Great catch.
I ordered these new E caps and wire express so hopefully I can get this back together sooner.
I feel much more confident with these changes and your help.
Thx
Dave

[foreverstrung]

Question:
What is the significance of, if any, that the .1uF cap off of the volume wiper is red-ish in color and the other .1uF coupling caps everywhere else is yellow?

[JMPGuitars]

I would assume the little red caps are WIMA radial caps, and the yellow caps look like Mallory type axial caps.

[Bieworm]

Correct. I use the panasonic red caps for smaller spots.

[foreverstrung]

Good stuff. I used the Mallory because it’s what I had but I just slightly elevated it so I could dress it out nicely. I’ve reset it from the other pics I’ve sent as I’m resetting and reworking much if this project.
This PTFE wire is extremely so much easier to work with. Very happy to be using it.
I rewired most all of the pot work too.
I’m relocating the RCA jacks for the reverb to the flat of the chassis but I’m waiting to connect all of the tube sockets considering the best location.
Dave

[Bieworm]

Good stuff. I used the Mallory because it’s what I had but I just slightly elevated it so I could dress it out nicely. I’ve reset it from the other pics I’ve sent as I’m resetting and reworking much if this project.
This PTFE wire is extremely so much easier to work with. Very happy to be using it.
I rewired most all of the pot work too.
I’m relocating the RCA jacks for the reverb to the flat of the chassis but I’m waiting to connect all of the tube sockets considering the best location.
Dave

Doesn't matter what type of cap you use. As long as it's the right value + voltage rating and decent quality you're fine. All in all it's just a matter of aesthetics. I just don't like things being able to move around inside the chassis.