Fender Dlx Rev build- last Q b4 fire-up.

[Chuck H]

Great! Here's a couple of notes that will hopefully help the process along...

The bias winding on your power transformer is not independent. It's a "tap" on the HV winding. That means that as your HV reduces with greater current (as it will) your bias tap voltage will also reduce. Adjusting may seem a little wonky while this is happening. You may even need to alter the bias circuit again. with a resistor smaller than 22k.

The schematic indicates -37V of bias. I expect your plate volts to be a bit higher than the schematic and so I would expect your bias voltage to be a bit higher too. This is necessary to keep the tubes happy at the higher plate voltage. But all tubes are different so don't be so concerned about actual bias voltage as bias current. We needed to correct the bias voltage to achieve the correct current, but the current is really the important thing.

So, since your plate volts will drop some as you increase current you will need to use the plate voltage number that is present with whatever you read for current on those cathode resistors. Remember that the mV reading across those resistors is analogous to the current through the tube. Current times voltage is watts. Shoot for about 8 watts.

The amp will likely be much more powerful sounding than you've experienced so far. Don't be afraid

[Sea Chief]

.. so Im gonna tack on a 10k instead yes?

Now, the Q is whether this rogue 22k was added after (looks not: as its exactly same looking, size, brown body even band spacing fwiw as R50, also a 22k), and more importantly does 22k mean it was strangling the ammount of current available? Am I thinking right-?

[Chuck H]

ChuckH. ive noticed s'thing odd. On the pdf R59 is a 10k. On my board it seems to be 22k.. and is indeed the same colour bands as the one I have ready to tack on (red/ red/ orange/ gold).. and also it measures (albeit in situ) 21.5k.

A HA! I thought that could be the case, but I didn't warn against it because things were already too complicated. So... Either replace it with a 10k or just tack the 22k across it as specified and you'll be very close to the stock circuit.

[Chuck H]

.. so Im gonna tack on a 10k instead yes?

Now, the Q is whether this rogue 22k was added after (looks not: as its exactly same looking, size, brown body even band spacing fwiw as R50, also a 22k), and more importantly does 22k mean it was strangling the ammount of current available? Am I thinking right-?

It's hard to know why the R59 value is different from the schematic.

The resistor wasn't strangling current, really. It was limiting the bias adjustment. No significant current happens in the bias circuit, but it does "tell" the tube what current to pass. So rather than strangle current that resistor value is telling the tube to strangle itself, sort of.

[Sea Chief]

It's hard to know why the R59 value is different from the schematic.

The resistor wasn't strangling current, really. It was limiting the bias adjustment. No significant current happens in the bias circuit, but it does "tell" the tube what current to pass. So rather than strangle current that resistor value is telling the tube to strangle itself, sort of.

Ok 22k tacked on (to 22k) now measuring 10.8k. The schematic is from 1993, my board 2002.. maybe thats the reason different. But could it possibly be a mistake- do you think?

[Sea Chief]

Right.. at pin 5 of V8 (amp on/ tubes in/ stby not flipped up so amp not fully on) I now get a range of -60V to -30V rotating th bias pot fully one way to fully t'other.

Well thats better is it not?

[Sea Chief]

Ok now then..

Measuring across V8 I now can get -20mV! the bias pot Id say is about -36V, so I had to dial the pot "~most of the way" over twds the -32V max. Is that ok?

[Tom Phillips]

Ok now then..

Measuring across V8 I now can get -20mV! the bias pot Id say is about -36V, so I had to dial the pot "~most of the way" over twds the -32V max. Is that ok?

That's OK.
Now measure the plate voltage at 6V6 Pin 3, multiply by 0.020 and post the results.

And I presume you meant "measuring across the 1 Ohm resistor. Not V8"

[Sea Chief]

Yep doing as you typed- learning as I go/ great.

8.5!

So thats 8.5 watts then, and something along the lines of "that makes ~60% of 14(? where does that fig come from) dissipation". Whatever dissipation is. So I guess thats not, surely, my DR is actually a 8.5w amp? (b b but its should be 22w? maybe Im not on board with this).

Anyway Im very pleased.

So the last Q of mine is; is 8.5 an expected figure?

[Tom Phillips]

8.5!... So thats 8.5 watts then, and something along the lines of "that makes ~60% of 14(? where does that fig come from) dissipation". Whatever dissipation is. So I guess thats not, surely, my DR is actually a 8.5w amp? (b b but its should be 22w? maybe Im not on board with this).
Anyway Im very pleased.
So the last Q of mine is; is 8.5 an expected figure?

8.5W is an "acceptable figure." You are good to go if both tubes are within ~15% of each other.
8.5W is the idle dissipation within the tube. The output power measurement is another thing and requires a signal generator, a dummy load and an oscilloscope to do properly.

In post #113 you indicated that you just wanted to be told what to do but didn't want to learn the theory. If that's not correct and you do want to learn how and why these circuits function then we can go back to my post #111 and take it from there.
So the question is "Do you want to be Sea Chief" or just be a "Sea Cadette?"

[Chuck H]

I know you didn't measure 8.5V on pin 3 of one of the 6V6 sockets. I think we're interested in where your plate voltage came out?

And...

How's the trem working now?

[Sea Chief]

I know you didn't measure 8.5V on pin 3 of one of the 6V6 sockets. I think we're interested in where your plate voltage came out?

And...

How's the trem working now?

Well I wasnt expecting this at all..

The amp sounds exactly the same- very flat. Not an iota of difference. Not much fendery about it: I have to turn bass to 0, treb to 10 with the sg to get anything nearing normal tone (Tbh Im fed-up with the pickups in this sg faded- they sound like thick mud/ barely any highs even get through unless bass is dialed out totally, and treb maxed).

EDIT: The tremolo s the same/ weak, but now has a really annoying quiet dud-dud-dud twice a second in the background. Constantly. And the reverb's feedback is even worse- I cant turn past 4 w'out feedbacking, & its noisy with the tremolo.

Also theres now a quiet, but distinct annoying ON sound (cant explain) whereby before it was quiet. After all this work today- Ive actually made it worse!

[Chuck H]

After all this work today- Ive actually made it worse!

I disagree. If the amp doesn't work when producing correct wattage with more correct HV that is new things that need fixing. Some of what you describe, like the reverb feedback being worse now and an audible "on" sound, could be a direct result of the amp producing correct power. Getting the basic amp working properly is absolutely the first step. Then the peripherals like reverb, trem troubleshooting noise/hum, etc. So, like it or not, you're on the right track.

WHAT IS YOUR PLATE VOLTAGE NOW?

[Sea Chief]

Sorry I thought I posted it up..

Better at 425V. (So why does the amp sound flat/ as dead as before?)

[Chuck H]

It was implied by your 8.5W idle figure but I wanted to see it in print. That's much better.

Your amp isn't only capable of that 8.5W. For one thing that is only one tube. So it would be 17W by that reasoning. But that's still not accurate. That is how many watts the amp is making just sitting there. That's why it's called "idle". Your amp will make more power when conducting a signal.

We're not sure why it sounds as dead as before. There are still things wrong with the amp though so reserve judgment for now in the interest of your sanity

A good question now might be: What did that guitars clean tone sound like plugged into a different amp? Better? What amp?

Unplug the reverb pan output and turn up the reverb knob. Does it still feedback?

Remember I mentioned that pan location within a head cabinet can be tricky. Unbolt the pan and scotch it around, even turn it. Whatever it takes to find a quiet spot. Then mount it so it stays there. If scootching the pan around doesn't affect the noise level you may have a ground problem causing the noise.

Check trem voltages against the schematic.

Report findings.